Treatment of arsenic-bearing beneficiation wastewater by oxidation-coagulation process

In order to process arsenic-containing beneficiation wastewater from a tungsten mine, the oxidation-ferric salts coagulation method was put forward to overcome the demerits of conventional ferric salts coagulation process for arsenic removal. H2O2 and NaClO as oxidants were selected to investigate the effects of arsenic removed. The result showed that: on the basis of the same arsenic precipitation conditions by ferric salts, pH was about 7.55, the dose of ferric chloride was 453.33 mg·L-1 (nFe/nAs=3.0), the coagulation reaction time was 25 min, the dose of PAM was 40 mg·L-1, the optimum conditions for pre-oxidation of H2O2 was pH 5.50~7.50, oxidation reaction of 25 min, H2O2 dose of 950 mg·L-1. Arsenic-containing beneficiation wastewater firstly treated by pre-oxidation of H2O2, then by coagulation, after 60 min precipitation, the concentration of arsenic in effluent water was about 0.302 mg·L-1, removal rate of arsenic reached 99.28%. The optimum conditions for pre-oxidation of NaClO was pH 6.00~8.00, oxidation reaction of 25 min, H2O2 dose of 1500 mg·L-1. Arsenic-containing beneficiation wastewater was firstly treated by pre-oxidation of NaClO, then by coagulation. After 60 min precipitation, the concentration of arsenic in effluent water was 0.437 mg·L-1, removal rate of arsenic reached 99.0%. Through the comparative analysis, H2O2 was the best oxidant.