【作者】 窦爱春；

【导师】 杨天足；

【作者基本信息】 中南大学 ， 冶金工程， 2012， 博士

【摘要】 我国存在大量高碱性脉石型复杂低品位氧化锌矿,采用直接酸浸工艺很难经济有效地处理该类矿物,为此,国内外大量科研工作者针对性地开发了氨浸及碱浸工艺,利用配合物的形成在碱性体系选择性浸锌,避免了碱性脉石的大量溶出,取得了较好的效果。但氨浸和碱浸工艺所选择的配体仅局限在NH3、Cl-、OH-,一定程度上限制了选择性浸出体系的发展,因此,本文提出选择合适配体、开发新的选择性浸出体系处理此类复杂低品位氧化锌矿,以期为此类矿物的处理提供新的思路。论文的主要研究内容与结论如下：(1)对利用配合物形成浸出有价金属过程中配体选择问题进行研究,得出了评判配体L对金属离子M配合能力强弱的依据,并由此确定了“粗选-精选”两步选择配体的方法。以此法选定亚氨基二乙酸根离子(Ida2-)为配体,且所选配体ida2-对菱锌矿、水锌矿、硅锌矿、异极矿及红锌矿中Zn(Ⅱ)均有较强的配合溶解能力,对低品位氧化锌矿中脉石类杂质Ca、Mg、Fe及Si具有较好的选择性,由此提出了碱性亚氨基二乙酸盐体系处理低品位氧化锌矿方案。(2)298K,6<pH≤12时,分别以ZnCO3、Zn5(OH)6(CO3)2、Zn3(OH)4CO3·H2O、ZnO为平衡固相研究了Zn2+-Ida2--CO32--H2O体系平衡热力学,并对Zn2+-Ida2-CO32-H2O体系固相转变规律及固相稳定区域进行分析。研究表明,Zn2+-Ida2--CO32--H2O体系中存在平衡固相转变情况,体系中固相ZnC03、Zn5(OH)6(C03)2和ZnO可在一定区域内稳定存在,随pH值升高,体系平衡固相将由ZnCO3转变为Zn5(OH)6(C03)2,最后转变为ZnO；不同平衡固相的Zn2+-ida2-_CO32-H2O体系中锌溶解特性差异较大,单一平衡固相的Zn2+-Ida2--CO32--H2O体系不足以表征Zn(Ⅱ)在ida2--H2O体系中的溶解过程。根据Zn2+-Ida2--C032--H20体系固相转变时锌溶解度变化,提出了从Zn2+-Ida2-C0O二-H2O体系浸出液中沉锌的方案,调酸沉锌：加酸使体系pH<8,可使Zn2+以ZnCO3形式沉淀；调碱沉锌,加碱使体系pH>11,可使Zn2+以ZnO形式沉淀。(3)研究了Ida2-H2O体系浸出低品位氧化锌矿的工艺过程,研究表明,温度、pH值对锌浸出效果及杂质溶出情况影响较大,确定了最佳浸出工艺条件：配体总浓度0.9mol·L-1、温度70℃、pH值8、反应时间4h、液固比5：1。在最佳工艺条件下,锌浸出率保持在76%以上,Ca、Mg、Fe、Si在浸出液中含量分别在340mg·L-1、6mg·L-1、16mg·L-1、25mg·L-1左右,由此说明,Ida2--H20体系对矿物中脉石类杂质具有较高的选择性。(4)提出采用“沉锌-沉钙-再浸出”工艺处理低浓度含锌浸出液,低浓度含锌浸出液直接用CaO调碱沉锌使Zn2+以ZnO沉淀形式加以回收,回收锌后的浸出液经CO2调酸沉钙脱除沉锌过程中积累的大量钙离子使浸出剂得以再生,再生浸出剂可返回浸矿。研究表明,温度、沉锌终点pH值及反应陈化时间对CaO沉锌效果均有较大影响；温度对CO2调酸沉钙过程影响较大。确定了CaO调碱沉锌最佳工艺条件：温度85℃、沉锌终点pH值10、反应陈化时间60min；CO2调酸沉钙最佳工艺条件：温度70℃、沉钙终点pH值8、CO2流量0.2L/min。浸出液按上述条件经“沉锌-沉钙-再浸出”工艺循环5次,沉锌率均高于90%,沉钙率均高于93%,锌浸出率均高于75%,沉钙过程所得粗氧化锌中平均锌、铅品位分别为60.07%、3.84%,沉钙过程所得碳酸钙纯度达97%以上。(5)采用pH电位法测定了25℃、40℃、55℃、70℃下的ida2-加质子常数以及ida2--Zn2+配离子稳定常数,分析了温度对Zn2+-ida2--H2O配合物体系的影响,结果表明,ida2-加质子作用及Ida2-与Zn2+配合作用均随体系温度升高而减弱。结合所测热力学数据,通过理论计算,分析了温度对Zn2+-Ida2--CO32--H2O体系Zn(Ⅱ)溶解及沉淀过程影响,结果表明,由于温度对Ida2-加质子作用及Ida2-与zn2+配合作用的影响,Zn2+-ida2--C032--H20体系锌溶解度随温度升高而下降,且随着体系温度升高,锌溶解度与pH的变化关系曲线(曲面)图规律性地向pH值减小的方向移动。更多还原

【Abstract】 There is a large amount of low grade refractory zinc oxide ore exiting in our country, in which the gangue is alkaline. It is very difficult to treat this kind of resource economically and efficiently by acid leaching. In order to extract zinc and avoid the alkali gangue being dissolved from this kind of zinc oxide ore, the method of ammonia leaching and alkaline leaching had been studied widely due to the correspond lixivants can complex with Zn(Ⅱ) and the results revealed that it’s available to extract zinc selectively by ammonia leaching and alkaline leaching processes. However, it is to some extent restricted the development of separating Zn selectively from low grade zinc oxide ore, because of the ligand used in the above two complex-leaching processes are only NH3, Cl-and OH-. Therefore, the object of this work is to select and develop new ligands for zinc selective leaching from this low grade refractory zinc oxide ore, which will provide a new idea for the zinc hydrometallurgy process. The main contents and conclusions were drawn as follow:(1) Ligand selection for complex-leaching valuable metals in alkaline system was investigated, which indicated evaluation rules of the binding capacity of ligand (L) with metallic ion (M). Thus, a two-stage ligand selection method composed of a primary selection and a critical selection was determined. The applications of this method showed that iminodiacetate (Ida2-) can be used as a complex agent for complex-leaching smithsonite (ZnCO3). Moreover, the ligand selected (Ida2-) also had large binding capacity with Zn(Ⅱ) of willemite (Zn2SiO4), hemimorphite (Zn4Si2O7(OH)2·H2O), hydrozincite (Zn5(OH)6(CO3)2) and zincite (ZnO). More importantly, impurities such as Ca, Mg, Fe and Si which were abundant in low grade zinc oxide ore can not be dissolved in alkaline iminodiacetate aqueous solution, it’s said that Ida2-had high selectivity with impurities of quasi-gangue during leaching process. Through these results, the scheme for treating low grade zinc oxide ore in alkaline iminodiacetate aqueous solution was proposed.(2) Thermodynamics of Zn2+-Ida2--CO32--H2O system with different equilibrium solid phases including ZnCO3, Zn5(OH)6(CO3)2, Zn3(OH)4CO3·H2O and ZnO were studied respectively at298K of pH value6-12. Subsequently, the equilibrium solid phase converting rules and its stable area of all the above probable solid phases in Zn2+-Ida2--C032--H2O system were determined. The results showed that ZnCO3, Zn5(OH)6(CO3)2and ZnO can exist stably as the equilibrium solid phase in a certain area in Zn2+-Ida2--CO32--H2O system, while Zn3(OH)4CO3·H2O can not. In Zn2+-Ida2--CO32--H2O system, the equilibrium solid phase can converted from ZnCO3into Zn5(OH)6(CO3)2and finally into ZnO with the increase of pH. It is inadequate to characterize the dissolution process of Zn(Ⅱ) in alkaline iminodiacetate aqueous solution by using the thermodynamics results of Zn2+-Ida2--CO32--H2O system with only a single equilibrium solid phase, for there is great difference of dissolution characteristics among the different equilibrium solid phases. Ideas for Zn2+precipitation from leaching liquor were proposed by means of the solubility of Zn(II) changes while equilibrium solid phase converted in Zn2+-Ida2--CO32--H2O system. Zn2+would be precipitated as ZnCO3when the pH of Zn2+-Ida2--CO32---H2O system was below8by adding with acid, and adding with alkali to adjust the system of pH>11, Zn2+would be precipitated as ZnO.(3) The process of leaching low grade zinc oxide ore in Ida2--H2O system was investigated. It showed that temperature and pH had great effect on Zn(Ⅱ) extraction and the dissolution of impurities. The optimum conditions for leaching low grade zinc oxide ore were determined as follows, total concentration of Ida2-0.9mol·L-1, temperature70℃, pH=8, liquid to solid ratio5:1and leaching time4h. As a result, the extractions of Zn are above76%, concentration of impurities Ca, Mg, Fe and Si are about340mg·L-1,6mg·L-1,16mg·L-1and25mg·L-1respectively in leaching liquor. It’s certained that the Ida2--H2O system had high selectivity with impurities of quasi-gangue.(4) The process of "Zn2+precipitation-Ca2+precipitation-releaching" was adopted to treat the leaching liquor with low concentration of Zn2+, in which CaO was directly added to adjust the alkalinity and make Zn2+be precipitated as ZnO for recovery. Then the acidity of the residual solution was adjusted by CO2to remove the accumulated Ca2+as CaCO3, and the lixiviant can be regenerated simultaneously for recycling use. It showed that the recovery of Zn was influenced by the factors of temperature, the final pH value and aging time of precipitation, while the precipitation of Ca was affected by temperature. The optimal conditions for Zn2+precipitation were determined as follows:temperature of85℃, final pH of10and aging time of60min. And the optimal conditions for Ca2+precipitation were as follows:temperature of70℃, final pH of8and flow rate of CO2gas of0.2L/min. The results show that when leaching liquor is treated under above optimal conditions for5times cycle operation, the precipitations of and Ca are over90%and93%respectively, and the extractions of Zn by releaching with regenerated lixiviant are above75%. ZnO obtained from Zn2+precipitation process contains60.07%Zn and3.84%Pb (average value), while CaCO3obtained from Ca2+precipitation process has purity more than97%.(5) The pH potentiometry was used to determine the protonation constants of Ida2-and stability constants of Ida2" with Zn2+at different temperature (25℃,40℃,55℃,70℃), and the effect of temperature on Zn2+-Ida2--H2O complex medium was investigated subsequently. The results show that the protonation of Ida2-with H+and the complexation of Ida2-with Zn2+become weaker and weaker as the temperature increase. According to the thermodynamic data determined, the effect of temperature on dissolution and precipitation processes of Zn(Ⅱ) in Zn2+-Ida2--CO32--H2O systems were analyzed by theoretical calculation. The results show that the solubility of Zn(Ⅱ) in Zn2+-Ida2--CO32--H2O system declines with the increase of temperature, and the graphs of the solubility of Zn(Ⅱ) against pH on which the solubility of Zn(Ⅱ) curves move ruly with the increase of temperature to the direction of the decrease of pH value. The reason for causing these two phenomena is both due to the effect of temperature on the protonation of Ida2-with and the complexation of Ida2-with Zn2+更多还原