Treatment Of Steel Pickling Waste Liquor By Electrochemical Synthesis Of Magnetite

The steel pickling waste liquor has serious pollution and great harm,so how to recover it as resources has become a big problem in steel industry.In view of high content of Fe2+ ions in the steel pickling waste liquor,a new method of electrochemical synthesis of magnetite(Fe3O4)is proposed in this study:a part of Fe2+ ions are electrochemically oxidized to form Fe3+ ions,then Fe3O4 can be formed under suitable conditions.In the experiment,the removal effect of total iron(TFe)in the steel pickling waste liquor was taken as the index,the effect of reaction conditions was investigated,the reaction process was optimized,and the reaction mechanism was explored.This study can provide effective technical reference for the resource recovery of steel pickling waste liquor.The experimental results are as follows:(1)The effects of initial pH,reaction temperature(T),electrode spacing(d),current density(J)and reaction time(t)were investigated by single factor experiment.The preliminary technological conditions were as follows:pH=9,T=30℃,d=1cm,j=20mA/cm2 and t=40min,residual TFe=2.23 mg/L,and the removal rate was 99.98%.(2)Response surface design method was used to optimize pH,t,J and t.The model obtained by analyzing data with design expert 8.0.6 was very significant,and pH had the most significant effect on TFe removal.The optimum reaction conditions were pH=9,T=35℃,J=20.07 mA/cm2 and t=30 min.When the concentration of TFe in the influent was 10 g/L,the residual TFe=0.28 mg/L,the removal rate was more than 99.99%,and the product has strong magnetism.(3)Under the optimal reaction conditions,the effect of TFe concentration in influent liquor was investigated.When the concentrations of TFe in the influent were 1～20 g/L,the TFe removal rates were more than 99.8%,and the residual TFe were less than 10 mg/L;when the concentrations of TFe in the influent were 20～50 g/L,the TFe removal rates were more than or equal to 97.85%.(4)Under the optimal reaction conditions,the removal effect of heavy metal ions was investigated.When the concentrations of nickel were 2.5～50 mg/L,the removal rates of TFe were more than 99.9%,and the removal rates of nickel were more than 90%;when the concentrations of manganese were 10～100 mg/L,the removal rates of TFe were more than 99.99%,and the removal rates of manganese were more than 99%;when the concentrations of chromium were 2～40 mg/L,the removal rates of TFe were more than 99.9%,and the removal rates of chromium were more than 99.5%.(5)The results of XRD,XPS and Raman analysis showed that the product was Fe3O4 with high purity and a small amount of γ-Fe2O3.