Preparation Of Copper Powder From Industrial Crude Copper Sulfate By Electrowinning And Application Research Of New Corrosion Inhibitor

Copper powders play vital role in modern industry, because it is not only one of the fundamental materials in powder metallurgy industry, but also has the largest production and comsumption in the non-ferrous metal powders in China. With the crude copper sulfate as the raw material, the preparation of copper powder by electrowinning has the advantages including low cost, short process, wide application of the product, and so on. However, in the actural process, using crude copper sulfate as raw materials will directly make the impurities such as As, Sb, Bi, etc. higher than the standard in the production of copper powder by electrowinning. In the meantime, the quality of the anode used in the electrowinning will directly affect the content of Pb in the copper powders, which is now Pb-Ca-Sn in use in factory. The aims of the present study were focused on the preparation processes, the modification of materials, the structural characterization and the electrochemical properties of copper powders.In this paper, the impurities removal from the crude copper sulfate was carried out by oxidation-neutralization-precipitation method and oxidation-neutralization-flocculation method, respectively. The results show that:In the oxidation-neutralization-precipitation process, the optimum removal conditions were obtained as follows:the removal efficiencies of As, Sb, Bi and Fe reach98.03%,42.97%,35.36%and89.42%, respectively by controlling60g/L of Cu2+concentration, mFe/mAs=13.5,2ml/L of30%H2O2, pH=4.0with5min of oxidation time; In the oxidation-neutralization-flocculation process, the optimum removal conditions were obtained as follows:the removal efficiencies of As, Sb, Bi and Fe reach94.17%,45.95%,88.64%and98.83%, respectively, by controlling60g/L of Cu2+concentration,3ml of aggregating agent,20ml/L of30%H2O2, pH=3.8with10min of oxidation time and1h for reaction time.The effects of compositions of electrolyte and process conditions on the current efficiency and product performance were investigated. The results show that the increases of Cu2+concentration, electrolyte temperature, scraping time and unlike electrode distances improve the current efficiency. The increase of high current density, high H2SO4 concentration and low Cu2+concentration was beneficial to obtain small particle size powders. Meanwhile, cell voltage was reduced by increasing Cu2+concentration, H2SO4concentration, electrolyte temperature. The optimum conditions were determined as follows:15g/L of Cu2+concentration,140g/L of H2SO4concentration,1800A/m2of current density,35℃of electrolyte temperature,30min of scraping time,14L/h of circulation flow and4.5cm of eletrode distance, respectively. Under the optimum conditions, the adaptability of impurities removal method were demonstrated, and high quality copper powders with normal distribution of particle size and dendritic shape were successfully obtained. All indexes could meet the national standard of FTD2.In order to seek for the insoluble anode with low anode potential and corrosion rate, this paper studied the electrochemistry performance of Pb-Ag-Ca, Pb-Sn-Ca, Pb-Sn-Sr, Pb-Sn-Sb-Ag, Pb-Sb by CP-Chronopotentiometry, Cyclic Voltammetry(CV), Corrosion Rate and Linear Sweep Valtammetry(LSV). Among these anodes, Pb-Ag-Ca alloy was prior to other alloy anode with lowest stable anode potential and corrosion rate for industry application of preparing copper powder under large current density.Corrosion inhibitor A was used to be as anti-oxidation firstly. Both A and B have the similar structure and corrosion inhibiting mechanism, which is the formation of polymeric compound film on copper powder surface. However, inhibitor A is more hydrophobic and effective than inhibitor B, which is due to the additional CH3group in inhibitor A compared to inhibitor B. The oxidation process was obviously superior to corrosion inhibitor B, and cheaper than B, non-toxic, non-polluting. And the product could completely replace B as electrolytic copper powder of gas phase inhibitors. The best condition was concentration of0.75%o per dosage of corrosion inhibitor A at normal temperature after placing three days.The continuous engineering-oriented experiment of electrowinning copper was carried out and the technological parameters were determined.30kg of crude copper sulfate were added into the solution approximately to120L. By controlling adding1/40total solution volume of H2O2, Fe/As=13.5and adjusting the solution final pH to3.8with NaOH, the removal efficiencies of As, Sb, Bi and Fe could reach98.08%,85.29%,97.83%, and76.09%, respectively. And then, the optimum technological parameters of electro winning copper were as follows:12-14g/L of concentration of copper ions,135-140g/L of concentration of sulphuric acid,1600-1800A/m2of current density,32-35℃of work temperature,32-30min of scraping powder cycle,30-40L/h of circulation flow,5.5cm of electrode distance. After the impurity removal, the content of As, Sb, Bi, Fe, Pb and other impurities in electrowinning copper powder prepared from copper sulfate solution was greatly reduced. All indexes can meet the national standard of FTD2.