Research On Purification And Recycling Of Copper Electrolyte With High-concentration Arsenic

In the process of copper electrolytic impurities such as arsenic, antimony and bismuth are dissolved into copper electrolyte.The quality of cathode copper is influenced by the impurities. In order to obtain qualified cathode copper, the impurities of arsenic, antimony and bismuth must be removed. The purification of high arsenic decopperizing electrolyte, recycling of purified solutions and the preparation process of refined nickel sulfate from crude nickel sulfate are researched in this work.Reduction and purification of denickelized electrolyte by SO2show that the removal rates of As and Sb decrease with ventilation temperature increasing, but increase with ventilation time and reaction time increasing. The removal rates of As and Sb could reach64.78%and56.99%when SO2flow rate is100ml·min-1, reaction temperature is21℃, ventilation time is2h, standing time is5d and dilution factor is1.2. The content of As2O3of the purifying residue is91.85%.Recovery of arsenic and nickel from two-stage decopperizing electrolysis is investigated. When the SO2flow rate is60mL·min-1, the ventilation time is90minutes, the standing time is90minutes, the reaction temperature is60℃and the H2SO4concentration is253g·L-1the reduction rate of As(V) is up to94.54%. As2O3could be obtained from reduced decopperizing electrolysis crystallized at20℃, and crude nickel sulfate could be crystallized from foregoing mother liquor at-20℃When the volume ratio of the reduced solution to the evaporated solution is0.62, the removal rates of As, Sb and Ni are90.5%,25.38%and56.58%, respectively.High quality nickel sulfate for electroplate industry is prepared from crude nickel sulfate by precipitation process and precipitation-extraction process separately. The optimal conditions for sulfide precipitation in the process of precipitation are concluded as follows:reaction temperature is10℃, reaction time is1.5h, initial pH is1.46and the excess coefficient of added Na2S is1.1. The suitable factors of oxidation-precipitation are as follows, that reaction temperature is60℃, reaction time is1h, final pH is3.0and the excess coefficient of added H2O2is1.0. There are suitable conditions of fluorination that reaction temperature is70℃, reaction time is1.5h, the pH value at reaction end is4.5-5.0and the excess coefficient of added NaF is2.3. The removal rates of Cu, Fe, As, Ca and Mg can be99.82%,99.52%,99.66%,99.63%and99.14%, respectively. The Na content of nickel sulfate prepared by precipitation process is4.85%.The optimum conditions of oxidation-precipitation method and fluorination method in the precipitation-extraction process are same with precipitation process. P204is used for Cu and Zn extraction. When the extraction pH is4.5, the extractant concentration in the organic phase is20%, the O/A is1:5, the stage number is3, the extraction time is lmin, and delamination time is10min, the content of Zn in the raffinate is too limit to detect, and content of Cu is less than0.002g·L-1. The equilibrium pH for separation of Ni and Na is above7.5. Ni and Na loaded organic phase is washed by pure nickel sulfate solution which contain Ni23.28g·L-1in a continuous, four-stage counter-current mixer-settler system, and purified nickel sulfate solution could be prepared by scrubbed of washed organic phase using4N diluted sulfuric acid. Emerald NiSO4·6H2O crystal produced with purified nickel sulfate solution can reach the national standard of first rate product used for plating.The appearance and chemical composition of cathode coppers are both fit to the national standards (GB/T467-1997) when the purified decopperizing electrolyte is returned to electrolysis system. Experiment is carried out when the current density is235A·cm-2, the concentration of Sb decreases from0.492g·L-1to0.441g·L-1and the concentration of Bi decreases from0.341g·L-1to0.234g·L-1during one electrolyzing period. When the current density is305A·cm-2and the other parameters are constant, the concentration of Sb decreases from0.411g·L-1to0.375g·L-1and the concentration of Bi decreases from0.201g·L-1to0.125g·L-1.