Research Of Leaching Nickel And Cobalt From Waste Residues Of Manganese Sulfate Purified Solution

Cobalt and nickel are widely used in aviation, spaceflight, machinery manufacturing, electrical instrument and chemical industries as well. Hence, these are considered as strategic resources. As the lack of cobalt and niekel resources in China, cobalt and nickel are produced mostly through the dominated mineral pyrometallurgy, but cobalt and nickel mineral resources good for pyrometallurgy has gradually dry up. Therefore, the hydrometallurgy of cobalt and nickel secondary resources has great practical significance. Dimethyldithiocarbamate precipitation is a secondary resource containing nickel and cobalt, which was formed by adding sodium dimethyldithiocarbamate to purify the manganese sulfate solution of pyrolusite reductive leaching process. The study on leaching technology of extraction of nickel and cobalt from dimethyldithiocarbamate precipitation was investigated using nitric acid and sodium nitrate as oxidants respectively in dilute sulfuric acid medium in this paper. And study on leaching kinetics of Co was investigated. More details were described as follows:In leaching technology of Co and Ni using nitric acid, the single factor experiment design was planned to study the effect of nitric acid concentration, leaching temperature, sulphric acid concentration and leaching time on the Co and Ni leaching efficiencies. The results showed that under the conditions of nitric acid concentration1.16mol-L-1, leaching temperature45℃, sulphric acid concentration1.47mol-L-1and leaching time30min the leaching efficiencies were98.0%for Co and95.0%for Ni, respectively. And the growth rate of Ni was faster than that of Co. Using single factor experiment as the foundation, the extraction rate of Co for response value, central composite design of response surface methodology was designed for sulfuric acid-nitric acid system, fitting the quadric polynomial model. The results showed that the linear effects and the quadratic effects of nitric acid concentration, sulfuric acid concentration, leaching temperature, leaching time on leaching efficiencies were significant. The interactions between nitric acid and sulfuric acid, nitric acid and leaching temperature, sulfuric acid and leaching temperature were significant, respectively. The optimal condition was obtained:nitric acid concentration1.36mol·L-1, sulfuric acid1.31mol-L-1, leaching temperature44.2℃, leaching time26.8min, the leaching efficiency of Co could reach98.0%.Similarly, in leaching technology of Co and Ni using sodium nitrate, the single factor experiment design was planned to study on the effect of sodium nitrate concentration, leaching temperature, sulphric acid concentration and leaching time on the Co and Ni leaching efficiencies. The results showed the leaching efficiencies were96.0%for Co and94.0%for Ni, respectively, under the conditions of sodium nitrate concentration0.41mol-L-1, leaching temperature50℃, sulphric acid concentration1.84mol·L-1and leaching time3h. And Ni was leached before Co in the experiment. Using single factor experiment as the foundation, the Co extraction rate for response value, central composite design of response surface methodology was designed for sulfuric acid-sodium nitrate system, fitting the quadric polynomial model. The results showed that the linear effects and the quadratic effects of sodium nitrate concentration, sulfuric acid concentration, leaching temperature, leaching time on leaching efficiencies were significant. The interactions between sulfuric acid concentration and sodium nitrate concentration or leaching temperature were singnificant, respectively. The optimal condition was obtained:sodium nitrate concentration0.46mol·L-1, sulfuric acid1.81mol·L-1, leaching temperature51.2℃, leaching time2.5h, the leaching efficiency of Co could reach96.0%.Leaching kinetics of Co in the sulfuric acid-sodium nitrate system, the Avrami equation(n=1) was used to describe the leaching process. The results showed the leaching process was controlled by the chemical reaction, the apparent activation energy was117.5kJ·mol-1, and the apparent activation order were1.69and2.08for sodium nitrate and sulfuric acid, respectively. The macro-kinetic equation was as follows:...