Study on leaching treatment of titanium gypsum with oxalic acid
Although the acid leaching of titanium gypsum with sulfuric acid can effectively leach iron impurities,it is easy to cause the phase transformation of gypsum,which has great influence on the environment and high process risk.Based on this,oxalic acid was used instead of sulfuric acid to leach titanium gypsum for iron impurities.The influences of leaching temperature,leaching time,mass fraction of oxalic acid and ratio of liquid to solid on the leaching effect of iron were investi-gated.The results showed that the diffusion process was the main process in oxalic acid leaching,and temperature and time were the main influencing factors.Under the conditions of leaching time of 110 min,leaching temperature of 90℃,mass fraction of oxalic acid of 6%and liquid-solid mass ratio of 8,the leaching rate of iron by oxalic acid reached 84%.Combined with FT-IR,XRD and SEM characterization results,it was found that the iron impurities in the titanium gypsum were ad-sorbed on the surface of the gypsum crystal in a flocculating manner.Appropriate amount of oxalic acid could effectively re-move iron impurities in titanium gypsum,and excessive oxalic acid would cause partial dissolution of gypsum and the forma-tion of calcium oxalate on the crystal surface,which affected the crystal morphology.Oxalic acid leaching treatment of tita-nium gypsum could effectively remove iron impurities in titanium gypsum,which was an environmentally friendly and effec-tive iron removal process.The experimental results could provide reference for the study of iron removal of titanium gypsum.
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