Cr(Ⅵ) reduction by ferrous sulfate in PHREEQC program

  Both experimentation and modeling were done to study the chemical reduction process of Cr(Ⅵ) by Fe(Ⅱ). Effect of pH, reductant dosage and coexisting anions were investigated, to help elucidate the mechanisms of the experimental results by PHREEQC. It was found that Fe(Ⅱ) reduction of Cr(Ⅵ) to Cr(Ⅲ) resulted in better removal effect at alkaline pH, with a mass ratioof FeSO4·7H2O/Cr- at 80. Under such conditions, there moval process was more economical and effective. There asonis that different reaction conditions affected the formation and saturation index (SI) of chromium compounds. A large number of anions coexisting round water, but Cl- exerts negligible effect on Cr(Ⅵ) reduction. But Cl- could form unstable complexes with Cr(Ⅲ). SiO2-3 tend edtoin hibit the process at acidic neutral pH values,but promote the process at alkaline pH,different forms were obtained at varied pH values.