【作者】 陈永明；

【导师】 唐谟堂； 杨声海；

【作者基本信息】 中南大学 ， 有色金属冶金， 2009， 博士

【摘要】 为有效利用硫化锌精矿中的铁资源,避免铁渣堆存对生态环境的污染,并简化现有铁矾渣提铟流程,提高铟的直收率,消除低浓度SO₂烟气排放危害,本论文提出了盐酸体系中炼锌废渣湿法提铟及铁资源有效利用的新工艺。首先对盐酸体系中铟锌提取、铁黄制备以及铁矾渣碱分解等过程进行了系统而深入的理论分析,详细阐明其热力学原理和动力学规律。采用双平衡法详细讨论了Zn（Ⅱ）-Fe（Ⅲ）-NH₃-CO₃^2--C1-H₂O体系铁酸锌前驱体共沉淀过程中,[Zn]T、[Fe]T、[NH₃]T、[CO₃^2-]T、pH之间的平衡关系,确定了Zn²⁺、Fe³⁺离子共沉淀的最佳pH范围为6.3<pH<7.3。在理论分析的基础上,对炼锌渣的热酸浸出、浸出液还原与净化、TBP萃取铟锌等过程进行了工艺研究。结果表明,在温度90℃、时间2h～4h、M_HC1/M_Theory=1.5～2.5、液固比L/S-（3～5）:1的条件下,炼锌渣中Zn、Fe、In的浸出率均达95%以上。向热酸浸出液中加入磁黄铁矿或硫化锌精矿进行还原浸出。以磁黄铁矿为还原剂时,在W_pyrrhotite/W_Theory=1.4、温度90℃、时间2h、磁黄铁矿粒度为0.088mm～0.106mm的优化条件下,Fe³⁺的还原率高达96.30%,As³⁺、Sb³⁺脱除率分别为67.7%和24.77%;采用硫化锌精矿为还原剂时,在温度90℃、时间3h、硫化锌精矿粒度45μm、W_ZnS/W_Theory=1.1的最佳条件下,Fe³⁺平均还原率为96.62%,Zn、Fe、In平均浸出率分别为93.89%,94.46%和97.89%。在温度50℃、时间25min、铁粉用量为1.6倍理论量的最优条件下添加铁粉置换除杂,Cu²⁺、Pb²⁺、Cd²⁺的脱除率分别为99.90%、32%和17%,In的损失率<1%。所得净化液在水相酸度1.5mol·L^-1、有机相组成70%TBP+30%磺化煤油、相比O/A=1.5:1、室温、振荡及静置时间均为10min、3级逆流萃取的最佳条件下同时萃取铟锌,In、Zn、Sn的萃取率均>99%,Fe²⁺萃取率<1%,由此实现Fe与Zn、In的有效分离。在相比O:A=3:1、3级逆流反萃、室温、振荡及静置时间均为5min的最佳条件下,纯水反萃负载有机相,In、Zn反萃率分别为99%和60%-90%,而Sn的反萃率则<3%。常温下锌板置换反萃液中In³⁺可产出海绵铟和纯ZnCl₂溶液,铟置换率>99%。以净化后的FeCl₂萃余液为原料,加入2mol·L^-1NH₄HCO₃溶液中和沉淀制取Fe（OH）₂+FeC03悬浮液,再通入空气氧化反应产出铁黄。整个氧化过程遵循“溶解电离.氧化沉淀”反应机制,分为晶核形成和晶体生长两个阶段,均为相界面的氧化反应控制,其活化能分别为127.26kJ·mol^-1和237.86kJ·mol^-1。氧化温度、空气流量和体系初始pH值均对氧化速率有显著影响。所得的氧化铁产物均为晶型规整的针形或纺锤形α-FeOOH晶粒聚集成的圆球。FeCl₂萃余液经H₂O₂氧化后,在有机相组成80%TBP+20%磺化煤油、水相酸度3.5mol·L^-1、相比O/A=3:1、相接触时间5min、室温的工艺条件下单级萃铁,平均萃铁率达99.69%;再在相比O/A=1.5:1、相接触时间3min、三级逆流反萃、室温的条件下纯水反萃,铁的平均反萃率为97.3%。所得纯FeCl₃纯溶液与ZnCl₂按n_Zn:n_Fe=1:2混合均匀,总金属离子浓度为0.3mol·L^-1,加入0.5mol·L^-1的NH₄HCO₃溶液作为沉淀剂,采用化学共沉淀法在温度50℃、M（NH₄HCO₃）:M_Theory=1.2:1、搅拌速度600r·min^-1～850r·min^-1、添加剂为十六烷基三甲基溴化铵的工艺条件下制备铁酸锌前驱体。Zn²⁺、Fe₃₊离子基本按理论配比均匀沉淀,两者的液计平均沉淀率分别为Zn99.83%和Fe 99.92%。所得前驱体为单一、分散的球形粒子,平均粒径为100nm～120nm,锌铁摩尔比为n_Zn:n_Fe=0.999:2。根据热重-差热分析结果,在500℃～700℃温度下煅烧前驱体,得到晶型规整、形貌单一、粒径分布窄的铁酸锌粉体。但煅烧温度的上升加剧了粉体的团聚,最佳煅烧温度为500℃,所得铁酸锌粉体平均粒径为150nm左右。提出了“NaOH分解-盐酸还原浸出-TBP萃取铟锌”的含铟铁矾渣湿法处理流程。在NaOH体系中分解铁矾渣,产出Na₂SO₄溶液和含In、Zn铁渣。前者经净化除杂、浓缩结晶回收芒硝后返回分解工序;后者则纳入盐酸体系选择性浸出和TBP萃取In、Zn,浸出渣经磁选富集后作为炼铁原料。对铁矾渣碱分解和分解渣HCl浸出进行了工艺研究,结果表明,在W_NaoH:W_铁矾渣=0.3814:1、温度60℃、液固比2:1、时间2h的最优条件下,铁矾渣分解率高达98.03%,As的浸出率为83.36%,In、Cu、Pb、Cd、Ag、Zn、Sb、Sn等杂质绝大部留于分解渣。DSC-TGA热分析和XRD衍射分析结果表明,铁矾渣碱分解过程中,铁主要以Fe₃O₄形式入渣。分解渣中Fe、In、Zn的含量分别为38.81%、0.23%和12.89%,采用HCl在温度40℃、液固比7:1、反应时间2h、M_Hcl/M_Theory=1.8的最优条件下浸出,In、Zn、Cu、Cd、As、Sn、Sb、Pb、Ag的渣计浸出率分别为98.26%、99.35%、98.79%、98.93%、76.27%、68.50%、80.12%、64.82%和60.80%。分解渣中89.25%的Fe留于浸出渣中,浸出渣Fe含量高达52.48%,经磁选富集和除杂后可作为炼铁原料。盐酸体系中炼锌废渣湿法提取铟、锌及制备铁黄、铁酸锌新工艺实现了铁渣和低浓度SO₂烟气的零排放,In和Zn的直收率大幅提高。原料中的铁可以铁黄、铁酸锌、铁红、铁精矿等多种形式得到有效利用,消除了铁渣排放对生态环境的污染。本工艺可有效处理传统湿法炼锌提铟流程产出的含铟、锌的浸出渣和铁矾渣,对我国储量丰富的高铁铟闪锌矿资源的开发利用也具有重要意义。更多还原

【Abstract】 Aimed at value-added utilization of iron resource in sphalerite concentrate and complete elimination of environmental pollution caused by waste ferric residue heaping,a new process for indium extraction and iron resource utilization in HCl medium was proposed in present dissertation. Adopting this process for jarosite residue treatment,the recovery flow sheet of indium and zinc can be simplified obviously,and the extraction ratio of valuable metals is enhanced consequently.Simultaneously,low concentration of SO₂ offgas emission is prohibited.Thermodynamic and kinetic analysis on the In & Zn solvent extraction,ferric yellow preparation and alkaline decomposition of jarosite residue was systematically carried out,respectively. Adopting double equilibrium method,the equilibrium relationship among [Zn]_T,[Fe]_T,[NH₃]_T,[CO₃^2-]_T and pH was also discussed in detail during zinc ferrite precursor preparation in Zn（Ⅱ）-Fe（Ⅲ）-NH₃-CO₃^2--Cl^--H₂O system.The optimum pH value for Zn²⁺,Fe³⁺ co-precipitation was determined as 6.3＜pH＜7.3.Using zinc hydrometallurgical residue as raw material,technical studies on HCl hot-acid leaching,pregnant solution reduction and purification,In & Zn solvent extraction with tributyl phosphate（TBP） was carried out, respectively.The experimental results show that the leaching ratio of Zn,Fe and In is higher than 95%under the following conditions:90℃, M_HCl/M_Theory＝1.5～2.5,2h～4h,L/S ratio（3～5）:1.Adopting pyrrhotite as reductive reagent,Fe³⁺ ion in hot-acid leaching solution is reduced to Fe²⁺ with reduction ratio of 96.30%under the following conditions: W_pyrrhotite/W_Theory＝1.4,90℃,2h,pyrrhotite particle size 0.088mm～0.106mm. And the removing ratio of As³⁺,Sb³⁺ is 67.70%and 24.77%,respectively. Using sphalerite concentrate as reductive reagent,the optimum conditions was obtained as follow:90℃,2h,ZnS concentrate particle size 45μm, W_ZnS/W_Theory＝1.1.Under above optimum conditions,the leaching ratio of Zn, Fe and In is 93.89%,94.46%and 97.89%,respectively,and the reduction ratio of Fe³⁺ is 96.62%.Iron powder cementation was.conducted at 50℃for 25min. The removing ratio of Cu²⁺,Pb²⁺ and Cd²⁺ is 99.90%,32%,and 17%, respectively,when the addition of iron powder is 1.4 times of theoretical amount.And the loss ratio of indium is lower than 1%.Zn²⁺ and In³⁺ in purificatory solution were simultaneously solvent extracted with 70% TBP+30%sulfated kerosene under the following conditions:room temperature,agitation time 10rain,phase ratio O/A＝1.51,acid concentration of water phase 1.5mol·L^-1.After three-stage of countercurrent solvent extraction,the extraction ratio of Zn,In and Sn is larger than 99%, respectively,and that of Fe²⁺ is lower than 1%.Consequently,iron is completely separated from zinc and indium chloride solution.Zn²⁺ and In³⁺ in loaded organic phase was stripped by distilled water at ambient temperature for 5min with phase ratio of O/A＝3:1.After three-stage of countercurrent solvent extraction,the stripping ratio of In and Zn is 99%and 60～90%, respectively,and that of Sn is lower than 3%.Zinc plate was added into stripping solution to produce sponge indium and purificatory ZnCl₂ solution. The cementation ratio of In³⁺ is higher than 99%.Purifatory FeCl₂ solution and 2mol·L^-1 NH₄HCO₃ was added drop by drop into reaction vessel to prepare Fe（OH）₂+FeCO₃ suspension,which was subsequently oxidated by air to produce ferric yellow.The oxidation of Fe（OH）₂+FeCO₃ suspension follows“dissolving ionization-oxidative precipitation”mechanism,and whole course can be divided into nucleation period and crystal growth that controlled by oxidative reaction on interface. The activation energy of nucleation and crystal growth is 127.26kJ·mol^-1and 237.86kJ·mo1^-1,respectively.Temperature,air flow and initial pH value has remarkable influences on the oxidation rate of Fe（OH）₂+FeCO₃ suspension. The morphology of ferric yellow obtained is a sphere aggregated by needle or spindleα-FeOOH particles.FeCl₂ raffinate was firstly oxidated by H₂O₂,and one-stage of solvent extraction of obtained FeCl₃ solution was carried out under the following conditions:room temperature,agitation time 5min,organic phase composition 80%TBP+30%sulfated kerosene,phase ration O/A＝3:1,acid concentration of water phase 3.5mol·L^-1.The extraction ratio of Fe³⁺ is 99.69%.Fe³⁺ ion in loaded organic phase was stripped by distilled water at ambient temperature for 3min with phase ratio of O/A＝1.5:1.After three-stage of countercurrent solvent extraction,the stripping ratio of Fe is 97.30%.Using FeCl₃ stripping solution and purificatory ZnCl₂ solution as raw material,zinc ferrite precursor was obtained with co-precipitation method under the following conditions:50℃,60min,n_Zn:n_Fe＝1:2,C₁6H₃3（CH₃）₃NBr as radditive,C_ZnCl2+FeCl3＝0.3mol·L^-1, M₍NH₄CO₃:M_Theory＝1.2:1,C₍NH₄CO₃＝0.5mo·L^-1.The results show that Zn²⁺ and Fe³⁺ are co-precipitated with theoretical ratio,and the precipitation ratio of Zn²⁺,Fe³⁺ is 99.83%and 99.92%,respectively.Zinc ferrite precursor obtained is a single,dispersive sphere with average particle size of 100nm～120nm.The Zn/Fe molar ratio of precursor is 0.999:2.According to DSC-TGA analysis results,the precursor was calcined at 500℃～700℃to obtain well crystallized zinc ferrite powder with narrow particle size distribution.The aggregation of zinc ferrite particle enhances with calcine temperature increasing,and the optimum temperature is determined as 500℃.The average particle size of zinc ferrite sample obtained at 500℃is about 150nm.A new hydrometallurgical process for indium extraction from jarosite residue was also proposed in this dissertation.Jarosite residue was firstly decomposed in NaOH medium to produce Na₂SO₄ solution and iron residue bearing indium.Na₂SO₄ solution was concentrated and then refrigerated crystallization to recover mirabilite after arsenic removal,mother liquid was recycled to alkaline decomposition operation.After selective leaching of In and Zn with dilute hydrochloric acid,the magnetic separation of leached residue was carried out to produce iron concentrates that used as raw material in iron smelting.Indium and zinc in pregnant solution were simultaneously solvent extracted by TBP as former mentioned.Technical studies on the alkaline decomposition ofjarosite and HCI leaching of decomposition residue were carried out.Obtained results show that the decomposition ratio of ammonium jarosite can reach 98.03%under the following optimum conditions: W_NaOH/W_Jarosite＝0.3814:1,60℃,liquid-solid ratio 2:1,2h.Impurity elements like Zn,In,Cu,Cd,Pb,Sb,Sn and Ag,are left in residue,while 83.36%of As is leached into pregnant solution in presence of AsO₄^3-.DSC-TGA thermal analysis and XRD characterization results demonstrate that Fe is precipitated in form of Fe₃O₄ during alkaline decomposition.The content of Fe,In and Zn in decomposition residue is 38.81%,0.23%and 12.89%,respectively.After selective leaching with dilute HCl,the leaching ratio of In,Zn,Cu,Cd,As,Sn, Sb,Pb and Ag is 98.26%,99.35%,98.79%,98.93%,76.27%,68.50%,80.12%, 64.82%and 60.80%,respectively,under the following optimum conditions: 40℃,liquid-solid ratio 7:1,2h,M_HCl/M_Theory＝1.8.89.25%of Fe is left in leached residue,and the content of Fe is 52.48%.After magnetic separation and impurities removal,iron concentrate obtained can be used as raw material for iron smelting.In conclusion,the present process proposed for indium extraction and iron resource value-added utilization in HCl medium can achieve zero emission of ferric residue and SO₂ off-gas.The recovery flow sheet of indium and zinc is simple and flexible,and the direct recovery ratio of valuable metal like In,Zn is enhanced dramatically.Iron resource in raw material is value-added utilization in form of zinc ferrite,ferric yellow and iron concentrate.The environmental pollution caused by ferric residues heaping is originally prohibited.The present process has extensive application in the treatment of zinc leached residue and jarosite.Furthermore,tt is significant in the exploitation of sphalerite concentrate bearing high iron and indium.更多还原