Acid Leaching Experiments And Mechanism Research For Blast Furnace Sludge With Low Grade Zinc

Gas sludge is a kind of solid waste which is produced by the process of iron and steel smelting.It is also a kind of valuable resource with abundant valuable elements such as iron,carbon,zinc.In this paper.The total iron content of the gas mud is 29.45%,the zinc content is 8.64%,and the carbon content is 16.63%.Zinc-bearing minerals are mainly red-zinc,sphalerite,zinc-iron ore,etc.Ironbearing minerals are mainly hematite,magnetite,it also contains carbon and a small amount of nickel stone,zeolite and other silicon acid minerals.After the pretreatment of removing iron by magnetic and carbon by flotation experiment.The grade of iron and carbon concentrates was 54.15% and 65.49%,respectively.The zinc concentrate with the grade of 13.39% and the recovery rate of 85.71% was obtained.The optimum leaching conditions were determined as follows: When the acidity was 0.5mol/L,the liquid-to-solid ratio was 6:1,the reaction time was 30 min,the stirring speed was 300r/min,at room temperature,the leaching time was 30 min,The final zinc leaching rate can reach at 96.30% and iron leaching rate was 7.88%.Based on the design principle of Design-Expert 8.0 and Box-Behnken response surface,the multiple quadratic regression equations of sulfuric acid concentration,liquidsolid ratio,reaction time and the interaction between zinc and iron leaching rate were established,and the results were analyzed and demonstrated by ANOVA analysis.The chemical element analysis,XRD analysis and SEM-EDS and energy spectrum analysis of the raw materials and leaching slag showed that the zinc-bearing raw materials were well leached.It can be inferred that the leaching system of the leaching of raw materials is more obvious,and the actual leaching test results is in line.The process of sulfuric acid leaching under low pressure and normal pressure was in accordance with the Avrami kinetic model,the grain parameters was 0.1604.The apparent activation energy was10.02 k J/mol,which indicated that the leaching process was controlled by diffusion.Therefore,the leaching efficiency should be further enhanced.According to the basic principle of thermodynamics,the feasibility of sulfuric acid zinc leaching and the stable region required for purification and electrodeposition of leaching solution were verified theoretically by plotting the ?-p H dominant region map and solubility diagram of different systems.