铜阳极泥分铜液高效分离稀散金属碲

Efficient Separation of Rare Metal Tellurium in Copper-Rich Solution from Copper Anode Slime

以铜阳极泥硫酸化焙烧-酸浸脱铜所得分铜液为研究对象,采用原位还原制得高活性、细微粒海绵铜作为还原剂,在线高效沉淀分离稀散元素碲、协同去除部分有害元素砷,考察了反应温度、反应时间、还原剂过量系数、搅拌速度和氧化剂加入量等因素对碲、砷沉淀率的影响。结果表明,在反应温度95℃、反应时间2 h、还原剂过量系数3、搅拌速度250 r·min^(-1)和未添加氧化剂的优化条件下,碲的沉淀率达85.02%,砷的沉淀率为19.18%。还原渣的主要成分为Cu,Te,As和Se,含量分别为45.93%,15.34%,4.61%和2.69%(质量分数),贵金属Au,Ag,Pt和Pd的总含量为211.0 g·t^(-1),X射线衍射(XRD)分析表明产物的主要物相组成为Cu_(2-x)Te和FeAsO_(4),此外还出现了Te和Cu的衍射峰。该工艺过程简单、环境友好、成本低廉,对分铜液的综合利用具有一定理论价值和实际意义。

Copper anode slime was vital secondary source that contains many metals with high value,such as gold,silver,platinum,palladium,selenium and tellurium. It was usually used as an important raw material to extract rare and precious metals and also attract considerable attention by metallurgical industry. The treatment process of copper anode slime mainly included pyrometallurgy,hydrometallurgy and combination of pyro and hydrometallurgy. However,no matter which treatment process was adopted,the copper-rich solution containing valuable elements of tellurium,gold,platinum and palladium would be obtained in the metallurgical process. How to efficiently recover rare and precious metals from the copper-rich solution had become an urgent problem in metallurgical industry.Relationship diagrams between the forms of Te(Ⅳ),As(V),As(Ⅲ)and pH value were respectively drawn by calculation according to the thermodynamic data,and the speciation of Te(Ⅳ),As(V)and As(Ⅲ)in the copper-rich solution were analyzed. Based on the Nernst equation,the actual electrode potentials of important metal ions in the copper-rich solution were calculated. High-activity and fine-particle sponge copper was obtained by in-situ reduction method,which was used as a reducing reagent to effectively precipitate rare metal of tellurium and remove part of the harmful element of arsenic from the copper-rich solution. The reaction mechanism of insitu reduction was studied by depicting the potential-pH diagram of the Te-H2O system according to thermodynamic calculation. The effects of various factors on the precipitation efficiency of Te,As and precious metals of Au,Pt and Pd were investigated referring to the precipitation efficiency of Te. Amplification experiments were carried out under the optimal conditions,and the chemical composition and the crystal structures of the reduction residue were analyzed by X-ray fluorescence spectrometry(XRF)and X-ray diffraction(XRD),respectively. The results of thermodynamic analysis showed that Te(Ⅳ),As(Ⅴ)and As(Ⅲ)respectively existed as the forms of HTeO2+·H2O,H3AsO_(4) and H3AsO3 in the copper-rich solution,of which the fractions could be reached as high as about 100%.The results of electrochemical analysis illustrated that the reduction order of ions coexisting in the copper-rich solution are[Au(Cl)4]-,[Pt(Cl)6]2-,HTeO2+,[Pd(Cl)4]2-,H3AsO_(4),Cu2+and HAsO2. The potential-pH diagram of the Te-H2O system showed that Cu2+could be reduced to generate fine-particle sponge copper,which was used to reduce HTeO2+to Cu2Te. Fe2+produced by reduction reaction,through oxidation,could react with H3AsO_(4) to form FeAsO_(4). The precipitation efficiency of Te significantly increased from 10.77% to 83.72% with the rise of reaction temperature from 55 to 95 ℃. A high temperature could effectively promote the precipitation reaction of FeAsO_(4) toward positive reaction,so the precipitation efficiency of As gradually increased from 8.74% to 20.17%. As reaction time prolonging,the precipitation efficiency of Te and As gradually increased. The dynamic equilibrium of the precipitation of Te and As reached at 2 h,and the precipitation efficiency of Te and As were 83.72% and 20.17%,respectively. With the rise of reductant excess coefficient,ions with high actual electrode potential preferentially reduced,such as[Au(Cl)4]-,[Pt(Cl)6]2-,[Pd(Cl)4]2-and H3AsO_(4). As the reductant excess coefficient further increasing,fine-particle sponge copper was produced to reduce Te(Ⅳ)to Cu2Te,causing the precipitation efficiency of Te increasing gradually. Because As(Ⅴ)was preferentially reduced to As(Ⅲ)instead of As,the precipitation efficiency of As first decreased and then increased. As the stirring speed improving,Te precipitation efficiency gradually dropped from 78.84% to 69.08% and the precipitation efficiency of As gradually increased from 18.79% to 28.20%,indicating that the precipitation reaction of As might be controlled by diffusion. Under the condition of high acidity and oxidant added,Te could be oxidized back to the solution,which made Te precipitation efficiency first decrease and then increase. The precipitation efficiency of As significantly increased as a result of oxidation of Fe2+and HAsO2 in the solution to obtain FeAsO_(4). The optimal conditions were selected as follows:reaction temperature of 95 ℃,reaction time of 2 h,the reductant excess coefficient of 3,stirring speed of 250 r·min^(-1) and no oxidant addition. In the amplification experiments,85.02% Te and 19.18% As were precipitated. The main components of the reduction residue were Cu,Te,As and Se,with the corresponding contents of 45.93%,15.34%,4.61% and 2.69%,respectively,and the total contents of precious metals of Au,Pt and Pd were 211.0 g·t^(-1). XRD pattern showed that the main phases of the residue were Cu_(2-x)Te and FeAsO_(4). In addition,the typical diffraction peaks of Te and Cu were also observed.