Theresearch On High-efficiency Leaching Of Chromite And Preparation Pross Of Chrome Metal

Chromium salt production occupies an important position in the national economy,meanwhile it has a wide range of applications in chemical,material,metallurgical and other industries.The chromium salt industry is an important basic raw material industry for the national economy.However,the traditional chromium salt preparation process has the problems of low chromium leaching rate and serious pollution of chromium slag,which brings serious harm to the ecological environment and human health that would severely limit the healthy development of the chromium salt industry.Establishing an efficient and clean production process of chromium salt to prevent pollution from the production source is of great significance for the realization of clean production of chromium salts.Chromite sulfuric acid leaching process is a green and clean chromium salt preparation process,but this process has lots of problems such as low leaching rate and difficulty in separating ferrochromium.Exploiting new effective methods to achieve clean and efficient acid leaching of chromite and reduce resource waste benefits the development of clean preparation process of chromium salt products and has the guiding significance for chromium salt industry.In this paper,the acid leaching process and kinetic mechanism of manganese dioxide oxide chromite were studied,and efficient chromite leaching with acidic was realized.The phenomenon of slurry potential oscillation during chromite leaching was found.Theprocess and dynamic mechanism of electric filed enhanced acid leaching of chromite were study.The high efficiency leaching of chromite with electric field enhanced acid without oxidant was realized in this study.A process flow for preparing chromium by electrolysis of chromite is proposed,which effectively solves the problem of Cr（VI）pollution.The main results of this paper are as follows:（1）The acidic leaching process of chromite with manganese dioxide as oxidant was studied,and the technological conditions and kinetic mechanism of the leaching process were analyzed.The results showed that the leaching rate of chromium reached 99%,when the leaching temperature was 130°C,the concentration of sulfuric acid was 60-wt%,the mass ratio of manganese/chromite was 0.18,the leaching time was 180min,and the mass ratio of solid to liquid was 1/8..Through kinetic analysis,it can be seen that in the process of sulfuric acid leaching of chromite,the reaction kinetic equation is 1-（1-X）1/3=kt,and the apparent activation energy is 27.87KJ·mol^-1.Surface chemical reaction rate step controls the overall reaction rate.Slurry potential oscillation behavior during chromite leaching process was found,and the amplitude period of oscillation evolution process was analyzed,and the correlation between oscillation period,amplitude and leaching rate was analyzed.（2）Using electric field as the strengthening method of acid leaching of chromite,the sulfuric acid leaching of chromite without oxidant was studied.The results showed that the leaching rate of chromium can reach 95.6%,and the leaching rate of iron is 58%,when the leaching temperature was 120°C,the acid concentration was 60-wt%,the leaching time was 300 min,and the solid-liquid ratio was 1/8.the current density was 40m A/cm2,The leaching process of electric field enhanced chromite is controlled by the surface chemical reaction rate,and the apparent activation energy is 13.08KJ·mol^-1.The potential oscillation behavior of the pulp during the leaching process under the enhanced control of the electric field was analyzed,and the potential oscillation behavior under the electric field and without the electric field was comparatively studied.（3）Taking the leaching solution after acid leaching of chromite as the research object,the effect of the addition amount of iron remover（potassium ferrocyanide）and the p H of the solution on the separation of ferrochromium in the iron blue precipitation experiment was studied.The results showed that the iron blue precipitation method could achieve the effective separation of ferrochromium ions,and the phases of the obtained samples wereall iron blue precipitated Fe₄[Fe（CN）₆]₃.The electrolysis process for preparing metallic chromium was studied,and the influence of process conditions on the current efficiency and unit power consumption during the electrolysis process was investigated.The optimal electrolysis process conditions obtained in the researches were:reaction temperature 40℃,current density 11.42A/dm²,catholyte p H value 2.4,while the current efficiency was15.83%.There was no Cr（Ⅵ）pollution in each step of the chromite electrolysis to prepare metallic chromium,which effectively solves the problem of Cr（Ⅵ）pollution in the production of chromium salts.