leaching behavior of zinc from crude zinc oxide dust in

Leaching behavior of zinc from crude zinc oxide dust in ammonia leaching

JIANG Tao(姜涛)1 MENG Fei-yu(蒙飞宇)1 2 GAO Wei(高伟)1 ZENG Yan(曾艳)1 SU Huan-huan(苏欢欢)1

LI Qian(李骞)1 XU Bin(徐斌)1 YANG Yong-bin(杨永斌)1 ZHONG Qiang(钟强)1

1 School of Minerals Processing and Bioengineering Central South University Changsha 410083 China2 Pelletizing Plant of Panzhihua Gangcheng Group Co Ltd Panzhihua 617000 China

copy Central South University Press and Springer-Verlag GmbH Germany part of Springer Nature 2021

Abstract Zinc extraction from crude zinc oxide (CZO) is beneficial to the full utilization of secondary resources andenvironmental protection In this paper a systematic investigation was carried out to study the leaching behavior of CZOby using ammonia-ammonium carbonate solution It was found that the maximum leaching rate of zinc from CZO dustwas 957 under the conditions of [Zn]T [NH3]T [CO3

2minus] =1 700 175 liquid to solid ratio 5 1 leaching temperature30 degC and leaching time 60 min Compared with pure zinc oxide (PZO) leaching the CZO leaching required longer timeand more leaching agents which is caused by the Cd2+ Pb2+ and other metal cationic impurities in CZO The metalcationic impurities dissolved in the leaching solution and combined with ammonium to form complexes consumingleaching agents and affecting zinc leaching

Key words crude zinc oxide dust ammonia leaching leaching behavior metal cationic impurities

Cite this article as JIANG Tao MENG Fei-yu GAO Wei ZENG Yan SU Huan-huan LI Qian XU Bin YANG Yong-bin ZHONG Qiang Leaching behavior of zinc from crude zinc oxide dust in ammonia leaching [J] Journal of CentralSouth University 2021 28(9) 2711minus2723 DOI httpsdoiorg101007s11771-021-4803-x

1 Introduction

At present 30 of the zinc resources in theworld are derived from secondary zinc resourcesCrude zinc oxide (CZO) is a kind of zinc-bearingsecondary resource obtained by reductivevolatilization of zinc-bearing wastes in thepyrometallurgical process It is the intermediateproduct in the zinc recycling process and can beused to further prepare electrolytic zinc or activezinc oxide It is usually generated in steel plant

lead-zinc plant and metallurgical industries such asgalvanizing casting smelting and scrap recyclingetc [1] CZO mainly comes from the zinc-containingdust from steelworks zinc oxide plants and lead andzinc smelters The dust particle size usually rangesfrom 01 to 100 μm [2] The composition of CZO iscomplex and it contains a lot of valuable elementssuch as Zn Sn Pb Cd A typical composition ofCZO dust was 194 Zn 246 Fe 45 Pb042 Cu 01 Cd 22 Mn 12 Mg 04 Ca03 Cr 14 Si and 68 Cl [3] Therefore theresearch on the recycling of CZO is not only

DOI httpsdoiorg101007s11771-021-4803-x

Foundation item Project(2020YFC1909805) supported by the National Key Research and Development Program of China Projects(51504293 51574284) supported by the National Natural Science Foundation of China Project (2018-GX-A7)supported by Qinghai Provincial Major Scientific and Technological Special Project of China Project (2020SK2125)supported by the Key Research and Development Program of Hunan Province China Project(CSUZC202129)supported by Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University China

Received date 2021-03-12 Accepted date 2021-09-27Corresponding author YANG Yong-bin PhD Professor E-mail ybyangcsu126com ORCID httpsorcidorg0000-0003-0238-0230

ZHONG Qiang PhD Associated Professor E-mail zhongqiang2008csu163 com ORCID httpsorcid org0000-0002-6198-4627

J Cent South Univ (2021) 28 2711－2723

J Cent South Univ (2021) 28 2711－2723

beneficial to the comprehensive utilization ofsecondary zinc resources but also conducive to theenvironmental protection and thus has significanteconomic and social benefits

CZO is usually prepared for high-purity ZnOby using pyrometallurgical and hydrometallurgicalmethods Hydrometallurgical processes arecommonly more economical and efficient thanpyrometallurgical methods which are very energyintensive and environmentally unfriendly [1]Various leaching agents have been used in thehydrometallurgical processes for zinc extractionfrom CZO among which sulfuric acid andammoniaammonium have been most extensivelyinvestigated [2] However during sulfuric acidleaching the impurities in CZO materials like FeCu Cd Mg Ni are dissolved resulting in thecomplexity of subsequent purification and impurityremoval process Therefore a number of researcherswere devoted themselves to ammoniaammoniumleaching This method was featured by moresuitable selective and economical for CZOmaterials especially those containing high contentsof varieties of impurities BLANCO et al [3]examined the leaching of Zn-containing residueusing ammonium carbonate-ammonia solution aslixiviant and inferred that there was a first orderrelationship among Zn recovery yields (gt95)temperature pH and solid concentration Someresearchers have adapted ammoniacal leaching torecover zinc from zinc-containing materials andthe zinc extractions were all over 90 undertheir optimum conditions [4minus 6] HALLI et al [7]investigated the leaching of Zn Cr Fe Mn and Pbfrom EAF dust using 16 different leaching media atdifferent concentrations It was found that ammoniaoutperformed both sodium and potassium hydroxidein terms of zinc selectivity The studies on thethermodynamic variation rules for Zn(II) -NH3-Cl-H2O showed that Zn(NH3)4

2+ was the predominantspecies under weak alkaline condition and therewere three solid phases (Zn(OH)16Cl04 Zn(NH3)2Cl2Zn(OH)2) appearing in neutral zone [8 9] Inaddition they also found that the zinc solubilitydepended on the concentration of total zinctotal ammonia and total chloride RecentlyWILLIAMSON et al [10] have researched the metalleaching potential from several primary and

secondary zinc-containing materials by ammoniacalleaching The results indicated that under thecondition of 1 molL total ammonia very highselectivity (gt97 against iron) of copper and zincwas obtained

Some studies have found that a few cationicimpurities were still dissolved into ammoniaammonium solution by forming complexes withammonium ion such as Cu Pb Fe and Cd [7 11minus13] HARVEY [14] also reviewed that theimpurities such as lead iron manganese cadmiumand calcium would be partially dissolved intosolution during ammonia leaching of zinc oxidewhich would affect the leaching process of zincoxide MENG et al [15] reviewed and discussed thesolubility and complexation ability of variousmetals with ammonia They found that thesolubilities of ammines of Mn and Fe were usuallypractically low in aqueous solution while Cd couldform stable compounds with ammonia Thereforethe leaching behavior of CZO was different fromthat of pure zinc oxide due to complexes formed byammonium and cationic impurities However theresearch on leaching behavior of zinc and impurityelements with ammonia-ammonium bicarbonatefrom CZO dust is insufficient The controllability ofthis leaching process is not strong The effects ofimpurities on ammonia-ammonium bicarbonateleaching of zinc have not been studied clearly Inaddition the quantity relationship among the maincomponents (ie the concentration of zinc ammoniaand carbonate) in the system and the impact ofvarious factors have been not adequatelyresearched For instance the effects of zinc-ammonia and ammonia-carbonate ratio on ammonia-ammonium bicarbonate leaching of zinc were rarelystudied Therefore research on the leachingbehaviors of CZO dust in ammonia-ammoniumbicarbonate solutions is of great importance foroptimization better controllability and reducedwastes of the process

The main purpose of this work is to explore theleaching behavior of CZO dust and the effect ofcationic impurity elements on the ammonia-ammonium bicarbonate leaching of zinc In thisconnection a comparative study on the leachingbehavior of PZO and CZO was included Theoptimized conditions were identified covering the

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experimental parameters of ammonia-carbonateratio time temperature total ammoniaconcentration liquid to solid ratio (LS) and stirringspeed In addition the difference between leachingcharacteristics of PZO and CZO was also explainedwith experiments and theoretical calculation

2 Experimental

21 Materials and reagentsThe CZO raw material was a zinc-rich dust

supplied by a plant in Longyan China X-ray

fluorescence (XRF) analysis for CZO dust was

performed by using a Panalytical Axios-Max

spectrometer and the results are given in Table 1

The pure zinc oxide powder used in this study was

an analytical reagent and provided by Guangzhou

Luyuan Chemical and Glass Instrument Co Ltd

China All the chemical reagents used in this study

including ammonia solution and ammonium

bicarbonate were of analytical grade Distilled water

was used throughout all the experiments

22 CharacterizationThe phase of CZO dust sample was detected by

X-ray diffraction (XRD) using a Rigaku Smartlabautomatic powder diffractometer with a graphitemonochromator The XRD pattern is shown inFigure 1 indicating that zincite (ZnO) basic leadchloride (PbOHCl) and manganese oxide (MnO)were identified as the main mineral phase Thepercentage of each phase of Zn was determined witha proprietary but widely accepted analyticalprocedure developed by Changsha ResearchInstitute of Mining and Metallurgy Co Ltd As thechemical phase analysis in Table 2 presented9145 of Zn was in the form of zinc oxide and inaddition a small amount of zinc sulfide and water-soluble zinc were also contained

The particle morphology of CZO dust was

detected by scanning electron microscope (SEMMIA3 TESCAN) As shown in Figure 2 theparticles of the CZO dust had various shapesincluding hexagon lamellar and cube In additionthe aggregation of dust particles was not obvious

The particle size distribution was detected bylaser particle sizer and the results are shown inFigure 3 It can be seen that the particle sizes ofPZO powders are smaller than 15 μm and theiraverage particle size was 42 μm CZO dust wascoarser than PZO powder and it had particles lessthan 90 μm The average particle size of CZO dustwas 277 μm

Table 1 Chemical composition analysis of main elementsin CZO dust (wt)

Zn

5121

Al

017

Mn

008

Cd

021

Fe

293

O

2537

Pb

611

Cl

967

Si

016

K

360

Figure 1 XRD pattern of crude zinc oxide (CZO) dustsample

Table 2 Chemical phase composition of Zn in CZO dust(wt)

Item

Content

Distribution

Water-soluble zinc

316

617

Zincoxide

4683

9145

Zincsulfide

112

219

Zincferrite

010

019

Totalzinc

5121

100

Figure 2 SEM image of CZO dust

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23 Leaching procedureLeaching experiments were performed in a

three-necked flask in a thermostatically controlledwater bath equipped with a mechanical agitator Atthe beginning of each test a certain amount ofsample was first taken into the flask Then mixturesof ammonia and ammonium bicarbonate solutionwas prepared according to the experimentalrequirements and then transferred into the flask Theformed pulp was agitated at a constant speed of300minus500 rmin under 20minus55 degC When the reactionwas complete the leaching solution and residuewere obtained by filtration The leaching residuewas dried weighed and packed in vacuum bags forfurther analysis The concentrations of metal ionswere detected by inductively coupled plasma-optical emission spectrometer (ICP-OES PS-6Baird) The Zn recovery (ηZn) was calculatedaccording to the following equation

ηZn =CZn times V

M times WZn

times 100 (1)

where CZn V M and WZn represent the Znconcentration of leachate (molL) the total volumeof leachate (L) the mass of the CZO dust (g) andthe content of zinc in the dust (wt) respectively

The experiments under each condition wererepeated three times and the errors are all within15 So the leaching rate are given only inaverage

24 Reaction mechanismThe coordination of zinc ions with ammonium

is detailed in the reactions Eqs (2) to (8)

NH3 + H2O rarr NH4OH rarr NH+4 + OH- (2)

NH+4 + OH- rarr NH3 + H2O (3)

ZnO + H2O rarr Zn2 + + 2OH- (4)

ZnO + ( x - 1)H2O rarr Zn (OH ) 2 - xx + ( x - 2)H+ (5)

ZnO + yNH3 + H2O rarr Zn ( NH3) y2 + + 2OH- (6)

NH4HCO3 rarr NH+4 + CO2 -

3 + H+ (7)

Zn ( NH3)2 +4 + CO2 -

3 rarr Zn ( NH3) 4CO3 (8)

The main reaction of zinc oxide in ammonia-ammonium bicarbonate leaching is

ZnO + NH4HCO3 + 3NH3 rarr Zn ( NH3) 4CO3 + H2O

(9)

In the process of ammonia leaching zinc oxidedissolves due to the formation of Zn (Π) -ammoniacomplex ion where zinc is predominantly present asZn (NH3)4

2+ ions

3 Results and discussion

31 Thermodynamic calculationThe EhminuspH diagram of the Zn-NH3-H2O system

was constructed using the software of HSCChemistry 60 for Windows As shown in Figure 4a wide stability region of Zn(NH3)4

2+ exists in thepH range of 69minus132 It also can be seen from thefigure that with the increase of pH thepredominance specie of zinc changes from Zn2+ tozinc-ammonia complex In addition the lowest

Figure 3 Particle size distribution of materials

Figure 4 EhminuspH diagram for ZnminusNH3minusH2O system at 25 degC and 01 MPa (Conditions 2 molL [Zn2+ ] 9 molL[NH3NH4

+])

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potential for the conversion of Zn2+ into Zn isminus075 V The conversion of Zn(NH3)4

2+ to Zn occursat lower potential of minus111 V which means that Zn(NH3)4

2+ is thermodynamically more stable It can bededuced that in terms of thermodynamics therecovery of zinc by ammonia leaching may befeasible

32 Ammonia-ammonium bicarbonate leachingbehavior

In this paper [NH3]T represents the totalconcentration of initial ammonia and ammoniumbicarbonate [CO3

2minus]T represents the totalconcentration of initial carbonate [NH3]T [CO3

2minus]T

represents the molar ratio of the total ammonia tothe total carbonate [Zn]T [CO3

2minus]T represents themolar ratio of the total zinc to carbonate321 Zinc extraction from PZO

The effects of reaction conditions on PZOleaching are presented in Figure 5 As shown inFigure 5(a) the zinc leaching ratio of PZOpowders increased rapidly with the increaseof [NH3]T [CO3

2minus]T Especially in the range of20minus30 the leaching ratio increased from 9039to 984 Further increasing the value of[NH3]T [CO3

2minus]T to 4 1 the leaching ratio of PZOpowder reached 991 and then it remainedessentially constant Therefore the appropriate[NH3]T [CO3

2- ]T=4 1 was determined as the optimalcondition in the experiment

As Figure 5(b) displayed apparently theleaching of PZO powder was very fast and 961of zinc was extracted within 10 min When leachingtime increased to 20 min nearly complete zincextraction (999) was achieved and then theleaching percentage reached a plateau

As shown in Figure 5(c) the results showedthat temperature had little effect on the zincextraction of the PZO powder The leaching ratio ofzinc in PZO powder increased with an increase inthe leaching temperature until 30 degC and then italmost remained unchanged

Figure 5(d) shows that the leaching ratio ofzinc increased with the increasing initial ammoniaconcentration and zinc leaching rate was typicallyfound to be fast in the initial period However itwas also found that the leaching ratio of zincremained almost constant over 92 molL which

indicates that the zinc oxide had been completelydissolved with increasing [NH3]T up to 92 molLSo it was suitable to select [NH3]T =92 molL forPZO leaching In this case [Zn]T[NH3]T was 1375and [Zn]T[NH3]T[CO3

2minus]T was 1375094As indicated in Figure 5(e) liquid-to-solid

ratio exerted a significant effect on the zincextraction When liquid-to-solid ratio was in therange of 3 minus 5 the zinc leaching ratio from PZOpowder was rapidly increased from 663 to 999and then it basically kept steady Therefore themost appropriate liquid-to-solid ratio was 5

In Figure 5(f) we can see that the zinc leachingratio of PZO powders increased from 959 to999 and then it kept constant Therefore thestirring speed of 400 rmin was beneficial for theextraction of zinc

Based on the above experiment results theappropriate reaction conditions for PZO leachingwere as follows [Zn]T[NH3]T [CO3

2minus]T=1375094time 20 min temperature 30 oC liquid-to-solid ratio5 and stirring speed 400 rmin322 Zinc extraction from CZO

The effects of reaction conditions on CZOleaching are shown in Figure 6 The experimentresults in Figure 6(a) indicate that the zinc leachingratio from CZO dust increased rapidly with theincrease of [NH3]T [CO3

2minus]T Especially in the rangeof 20minus30 the leaching ratio increased from 884to 940 Compared with PZO leaching in Figure 5(a) the reaction rate of CZO leaching was slowerFurther increasing the value of [NH3]T[CO3

2minus]T to 41 the leaching ratio of CZO dust reached 954and then it remained essentially constant Thereforethe [NH3]T [CO3

2minus]T=4 1 was determined as theoptimal condition in the experiment

Figure 6(b) shows that the zinc extractionefficiency was only 748 in 10 min Then itincreased to 954 with the increase of time to60 min and tended to be steady after 60 min At thebeginning of the reaction the zinc content in thedust was at a high level reacting with a largeamount of ammonia and carbonate ions So the rateof reaction was very rapid and the leaching ratioincreased obviously With prolonging reaction timethe zinc content in the samples decreased graduallyand thus the reaction rate decreased Hence thesuitable reaction time of CZO was 60 min

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As indicated in Figure 6(c) the effect of

temperature on the zinc extraction from CZO dust

was clearly visible The leaching ratio of zinc in

CZO dust increased with an increase in the leaching

temperature until 30 degC Due to the rising of

temperature molecular motion intensified and thus

more leaching reagent molecules collided with zinc

particles and reactions occurred In addition mass

transfer co-efficient and reaction constant were

improved with increasing temperature [16] which

Figure 5 Effects of (a) [NH3]T[CO32minus]T ([Zn]T[CO3

2minus]T=11 60 min 25 degC LS=5 450 rmin) (b) time ([Zn]T[CO32minus]T=

11 [NH3]T[CO32minus]T=41 25 degC LS=5 450 rmin) (c) temperature ([Zn]T[CO3

2minus]T=11 20 min [NH3]T[CO32minus]T=41

LS=5 450 rmin) (d) [NH3]T ([NH3]T[CO32minus]T=41 20 min 30 degC LS=5 450 rmin) (e) LS ([Zn]T[NH3]T[CO3

2minus]T =1375094 20 min 30 degC 450 rmin) and (f) stirring speed ([Zn]T[NH3]T[CO3

2minus]T=1375094 20 min 30 degC LS=5)on PZO leaching

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also promoted the dissolution of zinc However

when the reaction temperature increased from 30 degC

to 45 degC zinc leaching ratio decreased slightly The

reason could be explained that the increase of

temperature caused the rapid evaporation of NH3

and CO2 and the decrease of ammonia and

carbonate concentrations in the solution which

reduced stability of zinc-ammonia complex [17 18]






2minus]T=1700175 60 min 30 degC 450 rmin) and (f) stirring speed ([Zn]T[NH3]T[CO3

2minus]T=1700175 60 min 30 degC LS=5)on CZO leaching

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From the above the optimal leachingtemperature was 30 oC and the leaching ratio ofzinc from CZO dust was 957

As shown in Figure 6(d) the initial totalammonia concentration had an obvious effect on theCZO dust leaching however the leaching rate wasslow compared with PZO leaching When totalammonia concentration increased from 74 molL to1088 molL the Zn leaching rtio increased from906 to 957 When [NH3]T was more than 1088molL the leaching ratio had a minor decreaseTable 3 displays the effect of [NH3]T on zincleaching and residue yield (the mass ratio ofresidue CZO dust sample) Contrary to the changesof leaching ratio the residue yield of CZO dust wasincreased first and then slightly dropped with [NH3]T

increasing When [NH3]T equaled 1088 molL theresidue yield reached the minimum Thereforethe optimum [NH3]T was 1088 molL for CZOleaching Under this condition [Zn]T[NH3]T was 17and [Zn]T [NH3]T [CO3

2minus]T was calculated to be1700175

From Figure 6(e) the zinc leaching ratio fromCZO dust was significantly increased with anincrease of liquid-to-solid ratio until it reached themaximum at 5 and then it basically remainedunchanged Therefore the most appropriate liquid-to-solid ratio was 5

As Figure 6(f) displayed the impact trend ofstirring speed was analogous with that of [NH3]T inFigure 6(d) Zinc leaching arrived at its highestpoint at stirring speed of 400 rmin After that zincleaching ratio kept constant

From the above optimal reaction conditionswere established as follows [Zn]T[NH3]T[CO3

2-]T=1700175 time 60 min temperature 30 degC liquid-to-solid ratio 5 and stirring speed 400 rminCompared with PZO leaching CZO dust leachingrequired longer time and more reagents Moreoverthe zinc leaching ratio of CZO dust was alsosignificantly lower than that of PZO powder Thismay be due to the presence of impurity elementssuch as Fe Cd Pb Mn in the CZO dust These

impurity elements can react with ammonia to formcomplex ions [19] and thus enter the leachate As aresult CZO leaching required more leachingreagents and the zinc leaching ratio was inferior tothat of PZO

In addition from Figure 5(b) we can see thatthe leaching rate of zinc from PZO powder is fastbefore 20 min and the leaching ratio andaverage leaching rate are respectively 996 and498 per min After that the extraction reactionreaches equilibrium As indicated in Figure 6(b)similar to PZO leaching the leaching rate of zincfrom CZO dust is fast before 20 min and itsleaching ratio and average leaching rate arerespectively 839 and 419 minminus1 Then itbecomes slow and the leaching ratio and averageleaching rate decrease to 954 and 029 minminus1respectively After 60 min leaching reaction of zincreaches equilibrium It shows that the leaching rateof zinc from PZO powder was quicker than thatfrom CZO dust and the reason may be theimpurities contained in the dust

CZO dust leaching at higher solid content andhigher reagent levels was conducted under theoptimal conditions established above The result isshown in Figure 7 As can be seen from this figurethe zinc leaching ratio decreased slightly from957 to 952 when the dust addition increasedfrom 20 g to 200 g This means that at higher dustcontent and higher reagent levels zinc leachabilityfrom CZO dust still can maintain at optimal levels

33 Effect of impurities on ammonia leaching ofPZOIt can be seen from Table 2 that the contents of

zinc sulfide and zinc ferrite were only 112 and010 separately which respectively accounted for219 and 019 of the total zinc content HUANGet al [20] found that ZnS in the ore was difficult tobe leached in ammonium leaching systemHARVEY[14] reviewed that zinc sulfide (ZnS)willemite (Zn2SiO4) ferrite (ZnFe2O4) zinc spinel(ZnAl2O4) ferrous-zincite complexes ((Zn Fe)O)

Table 3 Effect of [NH3]T on zinc leaching of CZO dust

[NH3]T(mol∙Lminus1)

Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

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etc did not dissolve in ammonium carbonatesolution From the experimental results of CZO dustleaching the maximum zinc leaching ratio fromCZO dust was 957 With the exception of theinsoluble zinc sulfide and zinc ferriteapproximately 2 of zinc in the dust in the form ofzinc oxide still has not been leached As can be seenin Table 1 the contents of impurity elements MnFe Pb and Cd were respectively 008 293611 and 021 Therefore the total content ofimpurity elements reached 933 These impuritieswould partly dissolve into solution affecting theleaching of zinc331 Leaching behaviors

The chemical compositions of the leachedsolution obtained from CZO dust leaching at theoptimal conditions are shown in Table 4 FromTable 4 we can see that impurities cadmium leadmanganese and iron were dissolved into thesolution and their dissolution percentages wereseparately 478 129 319 and 27 Theconcentrations of zinc cadmium lead manganeseand iron in the CZO leaching solution were712424 3394 13661 700 and 1204 mgLrespectively

The effects of cadmium lead manganese and

iron on the leaching of zinc were studied Accordingto the proportion of impurities in CZO dust theimpurities were added into the PZO powder Theimpurities Fe Mn Cd and Pb were added in theforms of Fe2O3 MnO CdO and PbO respectivelyand the impurities were added at the same time ineach test The experiments were carried out at theconditions of [Zn] [NH3]T [CO3

2minus] =1 375 09420 min 30 deg C liquid-to-solid ratio 5 and stirringspeed 450 rmin The results are presented inFigure 8

Figure 8 shows that the coexistence of cationicimpurities had an inhibitory effect on the leachingof PZO With the increase of the total amount ofimpurities the leaching ratio of PZO powderdecreased gradually When the impurity contentincreased to 10 of the solid amount zinc leachingratio decreased from 999 to 963 This decreaseof zinc leaching ratio was consistent with thoseobtained from PZO leaching and CZO dust leachingexperiments Continuing to increase the impuritycontent to 40 zinc leaching ratio reduced to919 These results indicated that the impurities inthe CZO dust would influence the leaching of zinc332 Equilibrium equations of Zn and Cd in NH3-

NH4HCO3-H2O systemFrom Table 4 we can see that the leaching

ratio of Cd was high (up to 478) Therefore thetheoretical analysis for leaching behaviors of Zn andCd was studied The ammonia leaching solution of

Figure 7 Result of CZO dust leaching at higher solidcontent and higher reagent levels

Table 4 Chemical composition of main elements in CZOleaching solution

Element

Concentration(mg∙Lminus1)

Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957

Figure 8 Effect of total impurity content on PZOleaching ([Zn] [NH3]T [CO3

2minus] =1 375 094 20 mintemperature 30 degC liquid-to-solid ratio 5 stirring speed450 rmin )

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zinc is a complex coordination complexationsystem which contains a variety of ions In order tosimplify the calculation Only zinc oxide aninsoluble substance in the process of zincammonium coordination is considered In additionthe concentrations of unstable complexes of zincincluding Zn(HCO3)

+ and Zn(HCO3)2(aq) are very

low which also can be ignored All of thethermodynamic calculations were calculated at298 K

The dissolution equilibrium of zinc andcadmium in the ammonia system also existed Zincand cadmium in ammonia-ammonium bicarbonatecould react with NH3 or OHminus and the reactions weregiven below

Me2 + + iNH3 rarr Me ( NH3) i2 + (10)

Me2 + + jOH- rarr Me (OH ) j2 - j (11)

Here Me represents Zn or Cd The species ofzinc and cadmium in the ammonia-ammoniumbicarbonate system include Me2+ Me(NH3)i

2+ Me(OH)j

2minusj NH3(aq) NH4+ H+ OHminus etc [6 21] The

concentrations of these ions or complexes can berepresented by the following general formula (12)according to the computerized exponential method[22 23]

R = exp ( A + BpH + C ln [ NH3 (aq ) ]) (12)

where R represents the mole concentration of everyions or species A is the constant obtained by thereaction equilibrium equation B is the product ofln10 and the gained or lost protons number of thecomplex and C means the coordination number ofammonia The stability constants andthermodynamic data of ammonia complexes wereextracted from the chemical software HSCLangford Chemical Manual 16th Edition (L) [24]and Physical Chemistry Manual [25] According tothe thermodynamic data and chemical reactionequation the values of A B and C can be calculatedas listed in Table 5 Therefore the concentration ofeach species can also be calculated

In addition based on the theorems of the massand the charge conservation as well as thesimultaneous equilibrium principle the sumconcentration of zinc ammonia and carbonate canbe expressed as Eqs (13)minus(16)

The concentration relationship of totalcadmium total ammonia and total carbonate in the

NH3-NH4HCO3-H2O system are also established as

follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)

Table 5 Exponential constant of calculation of each ion

Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq

] + eacuteeumlNH4HCO

3( )aqugraveucirc (18)

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

where [Zn2+ ]T [Cd2+ ]T and [CO32minus]T respectively

represent the concentration of total zinc ions totalcadmium ions and total carbonate ions [NH3]T is thetotal concentration of ammonia and ammonium inthe solution [NH3(aq)] [Me2+ ] and [CO3

2minus] representthe concentration of free ammonia free metal ionand free carbonate ions i and j represent thecomplex numbers of ammonia and hydroxiderespectively In Eqs (13)minus (16) or Eqs (17)minus (20)there were six variables of [NH3(aq)] [Me2+]T [NH3]T[CO3

2minus] [CO32minus]T and pH If two of them were given

other four variables could be obtained from theabove simultaneous equations by the computationprogram MATLAB333 Equilibrium concentrations of Zn and Cd in

NH3-NH4HCO3-H2O systemThe effects of different ammonia and

ammonium bicarbonate on the dissolution of zincand cadmium were investigated under the premiseof maintaining the total carbon concentration Thecalculated results are shown in Figure 9

From Figure 9(a) the leaching behavior of

cadmium and zinc in ammonia-ammoniumbicarbonate system was nearly the same withvariation of [NH3]T [CO3

2minus]T When [NH3]T [CO32minus]T

increased from 1 to 4 the concentration of zinc andcadmium increased rapidly Then further increaseof [NH3]T [CO3

2minus]T has little effect on zinc andcadmium leaching Therefore the optimum [NH3]T[CO3

2minus]T for zinc and cadmium leaching was 4which was consistent with the result of previousexperiments Figure 12(b) indicates the effect of[NH3]T on the dissolved concentration of zinc andcadmium at the condition of [NH3]T [CO3

2minus]T=4 Itcan be seen from Figure 9(b) that with the increaseof [NH3]T the leaching of zinc and cadmiumincreased linearly and the dissolution characteristicof them in the ammonia leaching system was almostthe same The equilibrium solubility of cadmium

Figure 9 Dissolution behavior of zinc and cadmium inammonia-ammonium bicarbonate system (a) Effect of[NH3]T [CO3

2minus]T ratio on [Me2+ ]T in the solution(b) Variation of metal equilibrium concentration with theincrease of [NH3]T

2721

J Cent South Univ (2021) 28 2711－2723

was slightly lower than that of zinc but it was alsostrong in ammonia-ammonium bicarbonate system

4 Conclusions

1) The suitable [Zn]T [NH3]T [CO32minus]T for PZO

leaching was 1 375 094 and that for CZO dustleaching was 1 700 175 Compared with PZOleaching CZO leaching consumed more leachingagents For PZO 999 of zinc leaching ratio wasachieved under the optimal leaching conditions oftime 20 min temperature 30 degC liquid to solid ratio5 1 and stirring speed 400 rmin While for CZOdust 957 of zinc was extracted in a longer timeof 60 min

2) The lower zinc dissolution for CZO dustleaching is likely attributed to the small quantities ofinsoluble zinc sulfide and zinc iron spinel in thedust that are recalcitrant to ammonium carbonateleaching In addition metal cationic impurities inCZO dust presented also an adverse effect on theleaching rate of zinc

3) The results of thermodynamic calculationsindicated that the leaching behaviors of Cd2+ andZn2+ in ammonia-ammonium bicarbonate systemwith variation of [NH3]T [CO3

2minus]T and [NH3]T arenearly the same

ContributorsZHONG Qiang and YANG Yong-bin provided

the concept and edited the draft of manuscriptJIANG Tao and MENG Fei-yu wrote the first draftof the manuscript GAO Wei ZENG Yan and SUHuan-huan conducted the literature review andanalyzed the measured data XU Bin and LI Qianedited the draft of manuscript All authors replied toreviewers1049011 comments and revised the final version

Conflict of interestThe authors declare that they have no known

competing financial interests or personalrelationships that could have appeared to influencethe work reported in this paper

References

[1] SADEGHI S M VANPETEGHEM G NETO I F FSOARES H M V M Selective leaching of Zn from spent

alkaline batteries using environmentally friendly approaches

[J] Waste Management 2017 60 696minus705 DOI 101016j

wasman201612002[2] KAYA M HUSSAINI S KURSUNOGLU S Critical review

on secondary zinc resources and their recycling technologies

[J] Hydrometallurgy 2020 195 105362 DOI 101016jhydromet2020105362

[3] BLANCO L ZAPATA V GARCIA D Statistical analysis of

laboratory results of Zn wastes leaching [J]

Hydrometallurgy 1999 54 41minus48 DOI 101016S0304-386X(99)00057-2

[4] MIKI T CHAIRAKSA-FUJIMOTO R MARUYAMA K

NAGASAKA T Hydrometallurgical extraction of zinc from

CaO treated EAF dust in ammonium chloride solution [J]

Journal of Hazardous Materials 2016 302 90 minus 96 DOI101016jjhazmat201509020

[5] FENG Lin-yong YANG Xian-wan SHEN Qing-feng XU

Ming-li JIN Bin-jie Pelletizing and alkaline leaching of

powdery low grade zinc oxide ores [J] Hydrometallurgy

2007 89 305minus310 DOI 101016jhydromet200708002[6] RAO Shuai YANG Tian-zu ZHANG Du-chao LIU Wei-

feng CHEN Lin HAO Zhan-dong XIAO Qing-kai WEN

Jian-feng Leaching of low grade zinc oxide ores in NH4Clndash

NH3 solutions with nitrilotriacetic acid as complexing agents

[J] Hydrometallurgy 2015 158 101minus106 DOI 101016jhydromet201510013

[7] HALLI P HAMUYUNI J REVITZER H LUNDSTROM M

Selection of leaching media for metal dissolution from

electric arc furnace dust [J] Journal of Cleaner Production

2017 164 265minus276 DOI 101016jjclepro201706212[8] DING Zhi-ying CHEN Qi-yuan YIN Zhou-lan LIU Kui

Predominance diagrams for Zn(II) minusNH3 minusClminus minusH2O system

[J] Transactions of Nonferrous Metals Society of China

2013 23 832minus840 DOI 101016S1003-6326(13)62536-4[9] CAO Hua-zhen ZHANG Ze-feng WU Lian-kui ZHENG

Guo-qu A novel approach of preparing ZnO from

ammoniacal leaching solution with high chlorine levels

based on thermodynamic analysis [J] Hydrometallurgy

2017 171 306minus311 DOI 101016jhydromet201706005[10] WILLIAMSON A J VERBRUGGEN F RICO V

BERGMANS J HENNEBEL T Selective leaching of copper

and zinc from primary ores and secondary mineral residues

using biogenic ammonia [J] Journal of Hazardous Materials

2020 403 123842 DOI 101016jjhazmat2020123842[11] SUN Z H I XIAO Y SIETSMA J AGTERHUIS H VISSER

G YANG Y S Lective copper recovery from complex

mixtures of end-of-life electronic products with ammonia-based solution [J] Hydrometallurgy 2015 152 91minus99 DOI10 1016jhydromet201412013

[12] LADWIG W K Impacts of pH and ammonia on the leaching

of Cu(II) and Cd(II) from coal fly ash [J] Chemosphere

2006 64(11) 1892 minus 1898 DOI 101016j chemosphere

200601041[13] YIN Sheng-hua WANG Lei-ming EUGIE K CHEN Xun

YAN Rong-fu AN K ZHANG Lei WU Ai-xiang Copperbioleaching in China Review and prospect [J] Minerals

2018 8 32 DOI 103390min8020032[14] HARVEY T GThe hydrometallurgical extraction of zinc by

ammonium carbonate a review of the schnabel process [J]

Mineral Processing amp Extractive Metallurgy Review 2006

2722

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27 231minus279 DOI 10108008827500600815271[15] MENG Xing-hui KENNETH H The principles and

applications of ammonia leaching of metalsmdashA Review [J]Mineral Processing and Extractive Metallurgy Review 199616(1) 23minus61 DOI 10108008827509608914128

[16] LIAO Ya-long ZHOU Juan HUANG Fei-rong WANG Yi-yang Leaching kinetics of calcification roasting calcinatefrom multimetallic sulfide copper concentrate containinghigh content of lead and iron [J] Separation amp PurificationTechnology 2015 149 190 minus 196 DOI 101016j seppur201505042

[17] REICHLE R A MCCURDY K G HEPLER L G Zinchydroxide Solubility product and hydroxy-complex stabilityconstants from 125 minus 75 deg C [J] Canadian Journal ofChemistry 2011 53 3841minus3845 DOI 101139v75-556

[18] ANTREKOWITSCH J ANTREKOWITSCH HHydrometallurgically recovering zinc from electric arcfurnace dusts [J] JOM 2001 53 26 minus 28 DOI 01007s11837-001-0008-9

[19] HARVAY T G The hydrometallurgical extraction of zinc byammonium carbonate A review of the Schnabel process [J]Mineral Processing And Extractive Metallurgy Review2006 27 231minus279 DOI 10108008827500600815271

[20] HUANG Ping ZHAN yuan LAN Zi-ping Experiment studyon NH3-NH4Cl-H2O systen leaching of zinc oxide ore [J]

Materials Review 2016 30(S2) 469minus473 DOI CNKISUNCLDB02016-S2-104 (in Chinese)

[21] LIU Ji-dong SU Jia-lin LV Jian-hua ZHEN Song-zhangLIU Guo-cheng Thermodynamic analysis on system of ZnO-NH3-NH4HCO3-H2O in process of zinc oxide leaching [J]Inorganic Chemical Industry 2015 47(1) 30 minus 33 (inChinese)

[22] YANG Shen-hai TANG Mo-tang Thermodynamics of Zn(II)-NH3-NH4Cl-H2O system [J] Transactions of NonferrousMetals Society of China 2000 10(6) 830minus833 DOI CNKISUNZYSY02000-06-029

[23] TANG Mo-tang LU Junle YUAN Yan-shen YAN De-sheng HE Qing-pu On the ammoniation-complex equilibriain the system of Zn(lI) -NH3- (NH4)2SO4-H2O [J] Journal ofCentral South Institute of Mining and Metallurgy 199425 701minus705 DOI CNKI SUN ZNGD 01994-06-007 (inChinese)

[24] SPEIGHT J G Lange 1049011 s handbook of chemistry [M] 16thEdition Amarica McGRAW-HILL 2004 DOI 1010801042691900 8953291

[25] YAO Yun-bin XIE Tao GAO Min Physical chemistrymanual [M] Shanghai Shanghai Science and TechnologyPress 1985 (in Chinese)

(Edited by YANG Hua)

次氧化锌烟尘氨浸锌的浸出行为

摘要摘要从次氧化锌烟尘中回收锌有利于二次资源充分利用和环境保护本文采用氨水-碳酸氢铵溶液作

为浸取剂从次氧化锌烟尘浸取锌系统研究了该体系中锌的浸出行为研究结果表明在[Zn]T[NH3]T[CO3

2minus]T=19624液固比 51浸出温度 30 degC浸出时间 60 min 的条件下锌的浸出率最大为

957而对照样纯氧化锌在[Zn]T[NH3]T[CO32minus]T=1700175浸出时间为 20 min时锌的浸出率达

999次氧化锌烟尘浸出需更长的时间和更多的浸出剂其主要原因是烟尘中Cd2+Pb2+等金属阳离

子杂质溶解于溶液中与铵结合形成配合物消耗了浸出剂影响了锌的浸出

关键词关键词次氧化锌烟尘氨浸出浸出行为金属阳离子杂质

中文导读中文导读

2723

J Cent South Univ (2021) 28 2711－2723

beneficial to the comprehensive utilization ofsecondary zinc resources but also conducive to theenvironmental protection and thus has significanteconomic and social benefits

CZO is usually prepared for high-purity ZnOby using pyrometallurgical and hydrometallurgicalmethods Hydrometallurgical processes arecommonly more economical and efficient thanpyrometallurgical methods which are very energyintensive and environmentally unfriendly [1]Various leaching agents have been used in thehydrometallurgical processes for zinc extractionfrom CZO among which sulfuric acid andammoniaammonium have been most extensivelyinvestigated [2] However during sulfuric acidleaching the impurities in CZO materials like FeCu Cd Mg Ni are dissolved resulting in thecomplexity of subsequent purification and impurityremoval process Therefore a number of researcherswere devoted themselves to ammoniaammoniumleaching This method was featured by moresuitable selective and economical for CZOmaterials especially those containing high contentsof varieties of impurities BLANCO et al [3]examined the leaching of Zn-containing residueusing ammonium carbonate-ammonia solution aslixiviant and inferred that there was a first orderrelationship among Zn recovery yields (gt95)temperature pH and solid concentration Someresearchers have adapted ammoniacal leaching torecover zinc from zinc-containing materials andthe zinc extractions were all over 90 undertheir optimum conditions [4minus 6] HALLI et al [7]investigated the leaching of Zn Cr Fe Mn and Pbfrom EAF dust using 16 different leaching media atdifferent concentrations It was found that ammoniaoutperformed both sodium and potassium hydroxidein terms of zinc selectivity The studies on thethermodynamic variation rules for Zn(II) -NH3-Cl-H2O showed that Zn(NH3)4

2+ was the predominantspecies under weak alkaline condition and therewere three solid phases (Zn(OH)16Cl04 Zn(NH3)2Cl2Zn(OH)2) appearing in neutral zone [8 9] Inaddition they also found that the zinc solubilitydepended on the concentration of total zinctotal ammonia and total chloride RecentlyWILLIAMSON et al [10] have researched the metalleaching potential from several primary and

secondary zinc-containing materials by ammoniacalleaching The results indicated that under thecondition of 1 molL total ammonia very highselectivity (gt97 against iron) of copper and zincwas obtained

Some studies have found that a few cationicimpurities were still dissolved into ammoniaammonium solution by forming complexes withammonium ion such as Cu Pb Fe and Cd [7 11minus13] HARVEY [14] also reviewed that theimpurities such as lead iron manganese cadmiumand calcium would be partially dissolved intosolution during ammonia leaching of zinc oxidewhich would affect the leaching process of zincoxide MENG et al [15] reviewed and discussed thesolubility and complexation ability of variousmetals with ammonia They found that thesolubilities of ammines of Mn and Fe were usuallypractically low in aqueous solution while Cd couldform stable compounds with ammonia Thereforethe leaching behavior of CZO was different fromthat of pure zinc oxide due to complexes formed byammonium and cationic impurities However theresearch on leaching behavior of zinc and impurityelements with ammonia-ammonium bicarbonatefrom CZO dust is insufficient The controllability ofthis leaching process is not strong The effects ofimpurities on ammonia-ammonium bicarbonateleaching of zinc have not been studied clearly Inaddition the quantity relationship among the maincomponents (ie the concentration of zinc ammoniaand carbonate) in the system and the impact ofvarious factors have been not adequatelyresearched For instance the effects of zinc-ammonia and ammonia-carbonate ratio on ammonia-ammonium bicarbonate leaching of zinc were rarelystudied Therefore research on the leachingbehaviors of CZO dust in ammonia-ammoniumbicarbonate solutions is of great importance foroptimization better controllability and reducedwastes of the process

The main purpose of this work is to explore theleaching behavior of CZO dust and the effect ofcationic impurity elements on the ammonia-ammonium bicarbonate leaching of zinc In thisconnection a comparative study on the leachingbehavior of PZO and CZO was included Theoptimized conditions were identified covering the

2712

J Cent South Univ (2021) 28 2711－2723


2 Experimental



















Zn

5121

Al

017

Mn

008

Cd

021

Fe

293

O

2537

Pb

611

Cl

967

Si

016

K

360



Item

Content

Distribution

Water-soluble zinc

316

617

Zincoxide

4683

9145

Zincsulfide

112

219

Zincferrite

010

019

Totalzinc

5121

100


2713

J Cent South Univ (2021) 28 2711－2723



ηZn =CZn times V

M times WZn

times 100 (1)











3 + H+ (7)

Zn ( NH3)2 +4 + CO2 -




(9)


2+ ions







+])

2714

J Cent South Univ (2021) 28 2711－2723







2minus]T





















2715

J Cent South Univ (2021) 28 2711－2723


















2716

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723


2 Experimental



















Zn

5121

Al

017

Mn

008

Cd

021

Fe

293

O

2537

Pb

611

Cl

967

Si

016

K

360



Item

Content

Distribution

Water-soluble zinc

316

617

Zincoxide

4683

9145

Zincsulfide

112

219

Zincferrite

010

019

Totalzinc

5121

100


2713

J Cent South Univ (2021) 28 2711－2723



ηZn =CZn times V

M times WZn

times 100 (1)











3 + H+ (7)

Zn ( NH3)2 +4 + CO2 -




(9)


2+ ions







+])

2714

J Cent South Univ (2021) 28 2711－2723







2minus]T





















2715

J Cent South Univ (2021) 28 2711－2723


















2716

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723



ηZn =CZn times V

M times WZn

times 100 (1)











3 + H+ (7)

Zn ( NH3)2 +4 + CO2 -




(9)


2+ ions







+])

2714

J Cent South Univ (2021) 28 2711－2723







2minus]T





















2715

J Cent South Univ (2021) 28 2711－2723


















2716

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723







2minus]T





















2715

J Cent South Univ (2021) 28 2711－2723


















2716

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723


















2716

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723
















2717

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723
















Leaching ratio

Residue yield

740

9062

2148

855

9181

2119

920

9282

1977

980

9368

1925

1088

9570

1815

1166

9535

1841

1244

9550

1837

2718

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723











Element


Leaching ratio

Cd

3394

478

Pb

13661

129

Mn

700

319

Fe

1204

27

Zn

712424

957



2719

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723





Me2 + + iNH3 rarr Me ( NH3) i2 + (10)



2+ Me(OH)j








follows

[ Zn2 +] T = [Zn2 + ] +sumi = 1

4

[ Zn ( NH3)2 +i ] +

sumj = 1

4

[ Zn (OH ) 2 - jj ] + [HZnO2 -

2 ] + [ZnO2 -2 ] +

[ZnHCO+3 ] (13)

[ NH3] T = [ NH3] aq + [ NH+4 ] +sum

i = 1

4

i [ Zn ( NH3)2 +i ] +

[ NH4HCO3] + 2 [ ( NH4) 2CO3] (14 )

[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO3] +

[ NH4HCO3] +[ ( NH4) 2CO3] + [ Zn (HCO3)+]

(15)


Species

Zn2+

Zn(NH3)2+

Zn(NH3)22+

Zn(NH3)32+

Zn(NH3)42+

ZnO22minus

Cd2+

Cd(NH3)2+

Cd(NH3)22+

Cd(NH3)32+

Cd(NH3)42+

Cd(NH3)52+

Cd(NH3)62+

OHminus

Zn(OH)+

Zn(OH)2(aq)

Zn(OH)3minus

Zn(OH)42minus

ZnHCO3+

HZnO2minus

Cd(OH)+

Cd(OH)2(aq)

Cd(OH)3minus

Cd(OH)42minus

Cd2(OH)3+

Cd4(OH)44+

NH4+

H+

A

2653

3176

3706

4251

4628

-6906

317625

380267

430472

463175

487586

510662

442217

minus32370

477

minus3796

minus3956

minus6890

4812

minus3964

89628

minus149884

minus412426

minus695695

429822

554267

21427

0

B

minus4606

minus4606

minus4606

minus4606

minus4606

4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

minus4606

2303

minus2303

0

2303

4606

minus6912

2303

minus2303

0

2303

4606

minus6909

minus9212

minus2303

minus2303

C

0

1

2

3

4

0

0

1

2

3

4

5

6

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

2720

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723

2 [ Zn2 +] + 2sumi = 1

4

[ Zn ( NH3)2 +i ] + [ Zn (OH )+] +

[ H+] +[NH+4 ] + [ZnHCO+

3 ] = 2[CO2 -3 ] +

[OH- ] +[ HCO-3] + [ HZnO-

2] + 2 [ ZnO2 -2 ] +

2 [ Zn (HO) 2 -4 ] +[ Zn (OH ) -

3 ] (16)

[ Cd2 +] T = [ Cd2 +] +sumi = 1

6

[ Cd ( NH3)2 +i ] +

sumj = 1

4

[ Cd (OH ) 2 - jj ] + 2 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] (17)

[ NH3] T = [ NH+4 ] + [ NH

3( )aq] +sum

i = 1

6

i [ Cd ( NH3)2 +i ] +

2 [ ( NH4) 2CO3( )aq



[ CO2 -3 ] T = [ CO2 -

3 ] + [ HCO-3] + [ H2CO

3( )aq] +

[ ( NH4) 2CO3( )aq



2 [ Cd2 +] + 2sumi = 1

6

[ Cd ( NH3)2 +i ] + 3 [ Cd2 (OH )3 +] +

4 [ Cd4 (OH ) 4 +4 ] + [ NH+

4 ] + [ H+] =

2 [ CO2 -3 ] + [ HCO-

3] + [ OH-] + [ Cd (OH ) -3] +

2 [ Cd (OH ) 2 -4 ] (20 )

















2721

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723


4 Conclusions










References















































2722

J Cent South Univ (2021) 28 2711－2723
























2723

J Cent South Univ (2021) 28 2711－2723
























2723

leaching behavior of zinc from crude zinc oxide dust in

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