【作者】 李玉虎；

【导师】 赵中伟； 刘志宏；

【作者基本信息】 中南大学 ， 有色金属冶金， 2012， 博士

【摘要】 由于砷及其化合物的挥发性,其通常富集于各类冶炼烟尘中。除了含有大量的砷,冶炼烟尘中还含有数量可观的有价金属。因此,有色冶金高砷烟尘中砷的脱除与固化,是消除“砷害”,实现资源循环利用的重要途径。本文研究了ISP炼锌工艺中最具代表性的含砷烟尘—高砷次氧化锌中砷的脱除与固化,其研究结果对其它含砷烟尘的处理也具有一定的指导意义。本论文的主要研究内容及结果撮要介绍如下。1、系统研究了ISP次氧化锌中砷的物相。根据次氧化锌中砷的物相形态,次氧化锌可分为三种类型：Ⅰ型成分为锌高铅低,砷主要物相为As2O3; Ⅱ型成分也是锌高铅低,但砷的主要物相为亚砷酸锌；Ⅲ型铅含量偏高,锌含量相对较低,砷主要以砷酸铅物相存在。造成次氧化锌多样性的原因是生产气氛的波动,而引起生产气氛波动的原因除了工艺技术以外,原料成分的波动不容忽视。2、提出了碱性体系选择性浸出脱砷—催化作用下As(Ⅲ)空气氧化—石灰沉砷—砷酸钙渣水泥固化的原则工艺,并从热力学及溶液平衡的角度,对各步工序进行了理论分析。由主要物相的溶解组分log C-pH图判断,利用碱性浸出体系均可实现三种类型次氧化锌中砷的选择性浸出,并且S2-的引入将有助于强化浸出体系的选择性,促进砷的浸出。从热力学上判断,空气氧化As(Ⅲ)是可行的,而可用于As(Ⅲ)氧化的锰化合物有：MnO4-、MnO2、MnOOH、Mn3O4。对As(Ⅲ)氧化过程吉布自由能影响最大的是反应体系的pH。石灰沉砷的产物主要取决于反应体系的终点pH,随着pH的增加,沉砷产物主要由CaHAsO4·H2O向Ca3(AsO4)2和Ca5(AsO4)3OH转变。就含砷溶液的净化深度及砷酸钙渣的稳定性而言,Ca5(AsO4)3OH均是最佳的选择。3、开展了三种类型次氧化锌中选择性浸出脱砷研究。对于Ⅰ型、Ⅱ型次氧化锌采用NaOH-H2O浸出体系可达到较好的脱砷效果,其砷浸出率可分别达84%、68%以上,而铅、锌的浸出率均小于1%；而对于Ⅲ型次氧化锌采用NaOH-Na2S-H2O浸出体系较为合适,在最优条件下,砷浸出率可达73%,同时,铅、锌的浸出率分别为0.4%和0.8%。4、分别开展了双氧水、空气及催化空气氧化As(Ⅲ)的工艺研究。对于本文所得浸出含砷浸出液,采用理论耗量1.2倍的双氧水,可实现As(Ⅲ)的完全氧化,但成本相对较高。空气氧化效率较低,氧化8h,仅有22.3%As(Ⅲ)氧化成五价砷。高锰酸钾对溶液中的As(Ⅲ)具有超计量氧化的特性,该特性源于其还原产物(MnxOy)对As(Ⅲ)的空气催化氧化效应。利用这一催化效应,可有效改善空气氧化As(Ⅲ)效率。控制反应体系在pH为13、砷锰摩尔比为21：1、空气流量0.2m3/h条件下反应5h可使溶液中的As(Ⅲ)完全氧化。5、石灰沉砷效果受温度、pH和Ca/As摩尔比的影响十分显著。含砷溶液未经氧化而直接采用石灰沉砷工艺时,在最佳条件下,沉砷率仅为67%左右；在pH为12,温度95℃,Ca/As摩尔比3：1条件下反应2h,氧化后液沉砷率可达99.5%,所得砷钙渣中的砷主要以晶态的Ca5(AsO4)3OH形式存在。沉砷过程中,浸出液中的铅、锌离子也会发生沉淀。对高铅、锌浸出液采用酸化-石灰沉砷工艺,利用浸出液中残余的硫离子选择性沉淀铅、锌离子,可避免浸出液中铅、锌离子在石灰沉砷过程中发生沉淀。6、砷酸钙渣热处理工艺不仅可使非晶或低晶含砷物相转变为晶态的砷酸钙,还可促使砷酸钙颗粒长大、致密化,从而提升砷酸钙渣的稳定性。高铅、锌砷酸钙渣在热处理过程后,Ca5(AsO4)3(OH)成为唯一的含砷物相,而含铅物相由Pb5(AsO4)3(OH)转化为以Ca2PbO4、PbO2。砷酸钙渣水泥固化效果除了与水泥配比有密切关系外,还与砷酸钙渣自身状况有较大影响。砷酸钙渣中残余的游离砷和碱对固砷效果有负面作用,因此,沉砷结束后需对其进行洗涤。将沉砷渣洗涤、干燥后,800℃下煅烧1h,在水泥/砷酸钙渣配比为3：1条件下固化,所得固化块稳定性采用HJ/T300-2007的方法评价,其浸出液中砷含量仅为1.5mg/L,可完全满足GB508.1-2007的要求。更多还原

【Abstract】 Smelting dusts contain appreciable metal values and a large amount of arsenic due to its volatilization. To recover the metal values from smelting dusts, it is necessarily important to eliminate arsenic pollution by removal and solidification of arsenic. Focused on the representative arsenic bearing dust of Imperial Smelting Process(ISP) in zinc metallurgy, the removal and solidification of arsenic from secondary zinc oxide are investigated in this paper and the findings also benefit for treatment of other arsenic bearing smelting dust. The main experimental results are as follows:1. The chemical phase of arsenic in secondary zinc oxide from the production site was systematically characterized. Based on the results, secondary zinc oxide can be classified into three types:Type Ⅰ with As2O3as the main phase of arsenic in comparison to type Ⅱ with zinc arsenite (Zn(AsO2)2) and type Ⅲ with lead arsenate (Pb(As2O6, Pb4As2O9)). The main reason of the diversity of secondary zinc oxide is fluctuation of production atmosphere, which could be caused by the operational condition or the composition change of raw materials.2. Based on thermodynamic analysis of equilibrium solution, a principle process including selective alkaline leaching, catalytic oxidation of As(Ⅲ), arsenic precipitation and cement solidification was proposed. Arsenic in the three types secondary oxide could be selectively leached out in alkaline leaching system. The addition of S2-not only improved the leaching of arsenic, but also reduced the loss of metal values. The oxidation of arsenic could be thermodynamically accomplished by different oxidants, such as air, MnO4-, MnO2, MnOOH and Mn3O4. The pH value had a significant effect on arsenic oxidation. The products of arsenic precipitation with lime varied according to the terminal pH of solution system. The precipitates were converted into Ca3(AsO4)2and Ca5(AsO4)3OH from CaHAsO4·H2O with the increase of pH value, and Ca5(AsO4)3OH should be the optimal precipitate in terms of the removal of As and the stability of calcium arsenate. 3. The results of arsenic leaching from three types of secondary zinc oxide revealed that the leaching of As reached84%and68%in NaOH-H2O leach system for type Ⅰ and type Ⅱ secondary zinc oxide, respectively, and the leaching of Zn and Pd were both less than1%. For the treatment of type Ⅲ secondary zinc oxide, it is suitable to employ NaOH-Na2S-H2O system to leach out more than73%of As and less than0.8%of Zn and0.4%of Pb.4. The results of oxidation of As(Ⅲ) by hydrogen peroxide, air and air with catalyst showed that As(Ⅲ) in the leach solution could be completely oxidized to As(Ⅴ) using1.2times of the stoichiometric amount of hydrogen peroxide with higher cost. Only22.3%of As(Ⅲ) was oxidized to As(V) by air even in8h. Due to the effect of super stoichiometric oxidation to As(Ⅲ) by the catalysis of manganese oxide on the air oxidation of As(Ⅲ), potassium permanganate could be used to remarkably improve the oxidation efficiency of As(Ⅲ) by air. By blowing0.2m3/h air at As/Mn mole ratio of21and pH of13, As(Ⅲ) could be completely oxidized in5h at40℃.5. Arsenic precipitation with lime was greatly influenced by temperature, pH and Ca/As mole ratio. The removal of arsenic from oxidized solution reached99.5%with a Ca/As mole ratio of3at pH12and95℃in2h in comparison to that of67%without As oxidation, and arsenic was mainly precipitated as Ca5(AsO4)3OH. To minimize the formation of lead and zinc arsenate in lime precipitation, the S2-could be used to selectively precipitate Zn and Pb after the pH adjustment of solution to12.6. It not only converted amorphous or low crystalline arsenic species to the high crystalline arsenate calcium by calcinations process, but also promoted the particle to grow and densify, which improved the stability of arsenate calcium. Ca5(AsO4)3(OH) was the only arsenic precipitate in arsenate calcium with high contents of lead and zinc after calcination. Pb5(AsO4)3(OH) existed in precipitate was decomposed into Ca2Pb04and PbO2. It is important to wash precipitate after arsenic precipitation to eliminate remaining arsenic and alkali. The resultant precipitate was then calcined and solidified with a cement/arsenate calcium mass ratio of3. The obtained solid meets the standard of GB508.1-2007according to the analytical method of HJ/T300-2007, leaving only1.5mg/L of As in the leachate.更多还原