Abstract:Stainless steel pickling liquor is usually neutralized by lime, which produces a large amount of hazardous solid waste (calcium sulfate slag). Gradient separation of targeted components in stainless steel pickling liquor, regeneration of nitric acid by sulfuric acid and coupling synthesis calcium sulfate whiskers with high aspect ratio were studied. Effects of factors on experimental results during fluoride ion removal in high acid environment, gradient separation of valuable metals, and acid regeneration were systematically investigated. Morphology of calcium sulfate whiskers synthesized by coupling reaction in acid regeneration was analyzed by SEM to determine the optimum technological conditions of each process. The results show that fluoride ion removal rate under high acid environment is 97% above, precipitation rate of iron, nickel and chromium is all 99.9% above. Nitric acid is efficiently regenerated and calcium sulfate whiskers are synthesized by coupling reaction. Regeneration rate of nitric acid is 95% above and concentration of nitric acid regenerated exceeds 143 g/L. A reliable and stable new technology to treat stainless steel pickling wastewater is provided.