Fundermental Research Of Iron Precipitation Using Magnetic Flocculation In Zinc Hydrometallurgy

Iron precipitation from solutions is of great importance to most hydrometallurgical treatment of leaching solutions. However the existing iron precipitation methods have many defects such as slow settling velocity, long aging time, poor filterability, non-comprehensive utilization of residues and serious environmental problems. This paper proposed a new process "removing iron from leaching solution using magnetic fluid". In this paper a series of systematic researches about magnetic fluid were conducted based on some knowledge and findings of aqueous chemical behavior and hydrolysis mechanism of ferric iron. First, Fe2(SO4)3solution containing5.6g·L-1ferric iron serves as the object of research to study the mechanism of iron precipitation. Then magnetic fluid process was applied to removing iron from zinc-leaching solution. Further analyses with X-ray diffraction(XRD), Environmental scanning electron microscopy(ESEM), atomic emission spectrometer(AES), pertentiometic titration and dynamic potential test provided a fundamental understanding of the new technology and mechanism, which provided strong theoretical support for the applying of magenetic fluid to iron precipitation from leaching solutions.Pertentiometic titration analysis of ferric iron demenstrated that the hysrolysis and precipitation of ferric iron experienced three processes. Firstly, simple hydrolysate formed. Secondly, simple hydrolysis got together to form cation with high polymerization degree. Thirdly, with the transformation of interior structure cation nucleated, assembled and grew to form various precipitates.Fe2(SO4)3solution serves the object of iron precipitation research using magnetic fluid, and the result showed that temperature and pH influenced the growth process of hydrolysate and the optimum condition was pH2-3and80-90℃. Natural crystal seed was similar to the hydrolysate and can provide growth points for the hydrolysate. Carboxymethyl starch sodium could neutralize the positive charge of the particle surface and contributed to the agglomeration of fine particles. XRD and SEM analysis provided a fundamental understanding of iron precipitation that iron hydrolysate solidly absorbed to the surface of modified crystal seed which created favorable conditions for iron removing.Magnetic fluid was applied to iron removing from zinc-leaching solution. Under the condition of80-90℃,pH2-3,20g·L-1modified seed and1-1.5h reacting time, the precipitate settled repidly within2-3minutes and the clarified liquor contained less than10mg·L-1ferric ion. Iron grade of the residues was above55%after washing and roasting, which created favorable conditions for comprehensive utilization.Not only magnetic fluid can removing iron efficiently, but also the residues contains more iron and less impurities. In conclusion, magnetic fluid is suitable to removing iron from zinc-leaching solution.