Removal Of Antimony In Water By Electrochemical

It was investigated for removal of antimony （Ⅲ） and antimony （Ⅴ） contaminant in water by electrocoagulation process. The effects of influencing factors on the removal efficiency of antimony were investigated including current density, initial pH value, different coexisting ions and ventilation with nitrogen. The results indicated that the final concentration of antimony （Ⅲ） and antimony （Ⅴ） was lower than 5.0 μg/L and 28.1 μg/L after electrolysis of 30 minutes in the initial concentration of 1 mg/L, showing that the removal efficiency of antimony （Ⅲ） was significantly better than antimony （Ⅴ）. The current density and initial pH value had small effects on antimony （Ⅲ） removal; however, increasing the current density significantly improved the removal efficiency of antimony （Ⅴ）. The antimony （Ⅴ） removal efficiency was highest when the initial pH value was 4.5. The existence of Mg²⁺and HCO₃^-promote antimony （Ⅴ） removal. The presence of Ca²⁺, SiO₃^2- or PO₄^3- inhibit antimony （Ⅴ） removal. Ventilation with N2 could improve the removal rate of antimony （Ⅴ）.In order to increase the antimony （Ⅴ） removal, given concentration of Na₂SO₃ as reduction agents was added into the electrochemical cell. Reduction of antimony （Ⅴ） using individual iron electrocoagulation or Na₂SO₃ did not occur. By contrast, efficient reduction of antimony （Ⅴ） to antimony （Ⅲ） was observed by the electrocogulation process in the presence of Na₂SO₃ reduction agents, leading to the efficient removal of antimony （Ⅴ）. In this process, the distribution of antimony （Ⅴ） and antimony （Ⅲ） in the aqueous and solid phase with the reaction evolution was investigated at various conditions. Effect of current density, initial pH values, and Na₂SO₃ concentration on the antimony （Ⅴ） removal was investigated. Meantime, the oxidation-reduction potential （ORP） under various conditions were measured and correlated as well as the ferrous generation. The obtained results indicated that the antimony （Ⅴ） removal increased with the current density. An optimal pH value of 4.5 was obtained. Less pH value contributes to the slower generation of iron oxides and iron coagulants. Higher pH value leads to the higher ORP value. The removal of antimony （Ⅴ） and reduction of antimony （Ⅴ） to antimony （Ⅲ） increase with the initial concentration of Na₂SO₃ reduction agent. Addition of PO₄^3- ions inhibited the antimony （Ⅴ） removal and reduction of antimony （Ⅴ） to antimony （Ⅲ） by competing with the active site of iron coagulants and iron oxides. FT-IR spectra was used to characterize the coagulants sample collected at various time treated by freeze-dried. The obtained results furthermore confirmed the reduction of antimony （Ⅴ） to antimony （Ⅲ） by electrocoagulation process in the presence of Na₂SO₃ reduction agent, the removal of antimony （Ⅴ） can be greatly enhanced if it is reduced to antimony （Ⅲ）.