【作者】 彭映林；

【导师】 陈文汨； 郑雅杰；

【作者基本信息】 中南大学 ， 冶金工程， 2013， 博士

【摘要】 摘要：铜电解液净化工业生产广泛采用诱导法脱铜脱杂,该法能耗高、产生剧毒砷化氢气体及大量黑铜粉。本文形成了梯度电流密度调控脱铜、价态调控脱砷的铜电解液净化工艺,该工艺可显著提高铜电解液电积过程合格阴极铜的产出率,大大减少黑铜粉的产生,并能直接从中回收得到As203产品,有效克服了诱导脱铜脱杂法的不足。通过铜沉积电化学机理研究揭示了电积深度脱铜机理。采用S02还原铜电解液中As(V),调节As(V)和AsT的物质的量之比为0.4,同时调节Sb(V)与SbT的物质的量之比为0.4,蒸发浓缩使蒸发前后溶液体积比为2.5,10℃下冷却结晶后,Cu、As、Sb和Bi脱除率分别达到82%、62%、55%和85%,XRD分析表明净化渣为CuSO4·5H20和As203。净化渣经溶解、过滤后,得到三氧化二砷和硫酸铜溶液。硫酸铜溶液经双氧水氧化、Na2CO3溶液调节pH为3.7、蒸发结晶,得到的硫酸铜晶体中CuSO4·5H2O含量达98.8%。根据砷价态调控规律调整电解液中AsT和As(Ⅲ)浓度分别为10.00g/L和5.00g/L,在电流密度为235A/m2、电解液温度为65℃下电解168h,电解液中AsT、Sb和Bi的质量浓度分别下降2.9%、35%和18.18%。在电解过程中,As(Ⅲ)不断被氧化,其氧化反应符合一级反应动力学规律。采用电流密度调控分段电积可以实现铜电解液中铜与砷的分离。铜电解液中Cu.As.Sb.Bi和H28O4浓度分别为49.51g/L.10.75g/L.0.369g/L.0.299g/L和181g/L,一段电积脱铜电流密度为200A/m2,添加剂(骨胶：明胶：硫脲质量比为6：4：5)用量为40mg/L,电解液循环速度为10mL/min,电解液温度为55℃,Cu2+浓度从49.51g/L降至29.99g/L时,得到A级阴极铜；二段电积脱铜调节电流密度为100A/m2,电解液温度为65℃,Cu2+浓度从29.99g/L降至8.94g/L时,得到1号标准阴极铜；三段电积脱铜电流密度为100A/m2, Cu2+浓度从8.94g/L降至1.69g/L时,阴极产物主要为黑铜泥。铜电解液中Cu、As、Sb和Bi总的脱除率分别为96.59%、21.30%、25.20%和75.58%。采用8O2还原,使深度脱铜液中As(V)转化为As(III),蒸发浓缩使蒸发前溶液与结晶后溶液体积比为2.65,在15℃冷却结晶脱砷,过滤得到As203晶体,脱砷后液再经-20℃冷冻结晶得到粗硫酸镍。As和Ni总的脱除率分别为90.5%和56.58%。将As203加入电解液中维持As(Ⅲ)浓度为4.84g/L,电解液温度为65℃,在235A/m2电流密度下电解168h后,Sb浓度从0.48g/L下降至0.40g/L, Bi浓度从0.45g/L下降至0.34g/L。将脱镍液返回电解系统,电解液温度为65℃,在235A/m2电流密度下电解154h后,Sb浓度从0.492g/L下降至0.441g/L, Bi浓度从0.341g/L下降至0.234g/L；在305A/m2电流密度下电解123h后,Sb浓度从0.411g/L下降至0.375g/L, Bi浓度从0.336g/L下降至0.232g/L。所得阴极铜质量均达到A级阴极铜标准(GB/T467-2010)。当Cu2+为2.5g/L和H2SO4为250g/L时,铜电解液中铜电沉积过程是Cue2++e→Cu+为速度控制步骤的不可逆电极过程,铜电沉积过程无表面转化反应,受电化学极化和浓差极化混合控制,阴极过程表观传递系数α为0.49,阳极过程表观传递系数α为1.42,控制步骤化学计量数为1,阴极反应级数为1；阳极反应级数为O。其阴极沉积动力学方程为：在Cu2+为2.5g/L和H2SO4为250g/L的电解液体系中,As(Ⅴ)和As(Ⅲ)对铜电沉积过程均具有去极化作用,均使阴极过程的峰电流密度增大。电解液中存在As(V)时,循环伏安曲线阴极分支上只出现-个阴极还原峰,使铜电沉积的峰电位负移；电解液中存在As(Ⅲ)时,循环伏安曲线阴极分支上出现两个阴极还原峰,均无氧化峰。As(V)和As(Ⅲ)存在时,电极过程均受电化学和浓差极化混合控制。沉积物中砷含量随阴极电极电位的降低而增加,在Cu2+为2.5g/L、H2SO4为250g/L和As(V)为10g/L的电解液中,当阴极电位为-0.2V vs.SCE时,阴极产物主要为Cu和Cu20；当阴极电位为-0.43V vs.SCE时,阴极产物主要为Cu3As、Cu2O和Cu5As2;当阴极电位为-0.6Vvs.SCE时,阴极上主要析出H2和AsH3气体。结果表明,在As(V)存在下,控制电流密度电积,可以实现铜电解液中铜与砷的分离。更多还原

【Abstract】 Abstract:The technology of removing copper and impurities by induction method is widely used for purifying copper electrolyte in industrial production, the method presents many disadvantages, such as high energy consumption, forming toxic arsine gas and producing a lot of black copper. In the paper, the new copper electrolyte purification process of decopperization by gradient current density-adjustment and dearsenication by valence-adjustment was proposed to solve these problems. The process can markedly increase the output ratio of cathode copper during copper electrowinning, and greatly reduce the black copper and recover As2O3from copper electrolyte. The electrodepositing mechanism of copper in Cu-depleted electrolyte was investigated to reveal the copper removal mechanism.Arsenic(V) in copper electrolyte was reduced to arsenic(Ⅲ) with the aid of sulfur dioxide, and n(As(V))/n(ATT) was adjusted to0.4, as well as n(Sb(V))/n(SbT), the resultant electrolyte was subject to concentrate and the ratio of initial volume and final volume was2.5time, then the electrolyte was cooled to10℃to crystallize, the removal rates of Cu, As, Sb and Bi are82%,62%,55%and85%respectively, the purifying residue includes CuSO4·5H2O and As2O3. When the purifying residue was dissolved in water, As2O3residue and copper sulfate solution were obtained respectively after filtering. The CuSO4-5H2O content is98.8%when the copper sulfate solution was purified through oxidation by H2O2, adjusting pH by Na2CO3and evaporative crystallization.Adjusting the concentrations of AsT and As(Ⅲ) to10.00g/L and5.00g/L,respectively according to the rule of arsenic valence-adjustment, after copper electrolysis carried out with current density235A/m2at65℃for168h, the concentrations of AsT, Sb and Bi were decreased2.9%,35%and18.18%, respectively. In the process of copper electrolysis, As(Ⅲ) was gradually oxidized, and the oxidation process is applicable to the first order kinetic model.The copper and arsenic in copper electrolyte were separated by multiple stage electrowinning of current density adjustment. When the Cu, As, Sb, Bi and H2SO4in the electrolyte were49.51g/L,10.75g/L,0.369g/L,0.299g/L and181g/L, respectively, the high-purity copper cathode is prepared in the first electrowinning under the conditions that current density of200A/m2, additive(with mass ratio of bone glue:gelatin: thiourea of6:4:5) dosage of40mg/L, electrolyte circulation rate of10mL/min, electrolytic temperature of55℃and Cu concentration in the electrolyte decreased from49.51g/L to29.99g/L. By adjusting the current density to100A/m2and the electrolyte temperature to65℃, when the Cu concentration decreased from29.99g/L to8.94g/L, the copper cathode(Cu-CATH-2) is prepared in the second electrowinning. In the third electrowinning with current density of100A/m2, when the Cu concentration decreased from8.94g/L to1.69g/L, the main product is black sludge. The removal rates of Cu, As, Sb and Bi are96.59%,21.30%,25.20%and75.58%, respectively.The As(V) in the Cu-depeleted electrolyte was reduced to As(III) by SO2, then the resultant solution was subjected to evaporation concentration, when the volume ratio of the reduced solution to the crystallized solution was2.65, and the concentration solution was cooled to15℃to crystallize, As2O3is obtained after filtering, then the arsenic removing solution was cooled to-20℃to crystallize and crude NiSO4is obtained. The removal rates of As, Sb and Ni are90.5%,25.38%and56.58%, respectively.By adding As2O3into the electrolyte to maintain As(III) concentration at about4.84g/L, after copper electrolysis carried out with current density235A/m2at65℃for168h, the Sb concentration decreased from0.48g/L to0.40g/L, and the Bi concentration decreased from0.45g/L to0.34g/L. Nickel removal solution was returned to electrolysis system, after copper electrolysis carried out with current density235A/m2at65℃for154h, the Sb concentration decreased from0.492g/L to0.441g/L, and the Bi concentration decreased from0.341g/L to0.234g/L, after copper electrolysis carried out with current density305A/m2for123h, the Sb concentration decreased from0.411g/L to0.375g/L, and the Bi concentration decreased from0.336g/L to0.232g/L. The quality of all the copper cathodes reaches to the Chinese standard of A grade of copper cathode (GB/T467-2010).For the electrodeposition of copper from solutions of2.5g/L Cu2++250g/L H2SO4, the reaction Cu2++e->Cu+is the rate controlling step, and which is an irreversible charge transfer reaction. There is no surface conversion in the cathodic process. The electrode reaction is controlled by both of the electrochemical and concentration polarization. The values of the apparent transfer coefficient for cathodic process (a) and anodic process(a) are0.49and1.42, respectively. The chemical measurement number for the rate controlling step, v equals1approximately. The orders of the cathodic and anodic processes are1and0, respectively. The kinetics equation of copper electrodeposition is shown as follows:When Cu2+concentration is2.5g/L and H2SO4is250g/L in the electrolyte, both As(V) and As(Ⅲ) have a depolarization effect on the process of copper deposition and increase its peak current density. When As(V) exists in the electrolyte, only one reduction peak is observed in the cyclic voltammogram, and As(V) makes the peak potential of copper deposition shift to more negative value, while when As(Ⅲ) exists in the electrolyte, two reduction peaks are observed, and oxidation peak is not observed in the presence of As(V) and As(Ⅲ).The electrode reaction is controlled by both of the electrochemical and concentration polarization.The As content in the deposit increases with the decrease of cathodic potential. In the electrolyte with Cu2+of2.5g/L, H2SO4of250g/L and As(V) of10g/L, when the cathode potential is-0.2V vs.SCE, the deposit contains Cu and Cu2O, while the deposit forms at-0.43V vs.SCE contains Cu3As, Cu2O and Cu5As2. When the cathode potential is-0.6V vs.SCE, H2and AsH3are produced. The results show that the copper and arsenic in copper electrolyte contaning As(V) can be separated by multiple stage electrowinning of current density adjustment.更多还原