Effect Of Microwave Roasting And Muffle Furnace Firing On Indium Leaching Rate Of Indium Dust

Indium mainly exists in minerals and their metallurgical products andbyproducts as sulfides and sulfates with multiple valence states. The process ofdesulphurizing roasting and acid leaching is an effective method of raising therecovery rate of indium. Microwave, with its advantages of quick, selective, uniformheating and high thermal efficiency, is used to roast samples and can raise theleaching rate of metals during leaching process. Microwave roasting used inextracting indium has been rarely reported. In this thesis, three processing methods,muffle furnace roasting and acid leaching, microwave roasting and acid leaching,sulfuric acid direct leaching, were used to study and analyze the leaching rate ofindium from smoke dust. Visible spectrophotometry was used to measure the contentof indium after acid leaching. The detailed experimental contents were as follows:(1)The reaction conditions required for the complexation reaction betweenindium ion and color developing agent (PE) were explored, including the amountand pH value of NaAc-HAc buffer solution, the amount of sensitizer CTAB, theorder of adding reagent and measuring wavelength. The stabilized time andcomplex-ratio of the two component complex system were also measured.(2) Orthogonal experiments of extracting indium by microwave roasting andmuffle furnace roasting were utilized separately. The experimental results werecompared with that by sulfuric acid direct leaching. The effects of the three methodson the leaching rate of indium from smoke dust were investigated.(3) Under the optimized conditions of the single factor experiment[λ=572nm,4ml NaAc-HAc buffer solution (pH=5.0),1.2ml of phenylfluorone (PE),3ml ofsensitizer(CTAB microemulsion)], reagents were added in the order of In3+â†'NaAc-HAc buffer solutionâ†'PEâ†'CTAB microemulsion to measure the content ofindium in smoke dust.(4) By comparing, it was shown that roasting indium sample before acidleaching can actually raise the leaching rate of indium, resulting from desulfurization and denitrification at high temperature. The indium leaching rate by microwaveroasting sample was higher than that by muffle furnace roasting. The optimalorthogonal experimental conditions of microwave roasting plus acid leachingtechnology were determined, i.e. microwave roasting at800oC for90min, acidleaching condition: sulfuric acid concentration25vol%, liquid/solid ratio1:4,5h.The leaching rate of indium from smoke dust reached85.2%.