As(Ⅲ) Removal From Synthetic Wastewater By Flocculation And Oxidation Coupled With Flocculation

The arsenic is applied abroad, and is a toxic trace element, especially arsenite. With the arsenic standard of ground water been further stricted, the problem of arsenic contamination is more prominent.The removal efficiency and mechanisms of As(â…¢) were investigated, which was removed by iron flocculation and H₂O₂ oxidation coupled with iron flocculation process.For the synthetic wastewater that simply contained 5mg/L As(â…¢), the removal efficiency of arsenic by FeSO₄ flocculation was higher than Fe₂(SO₄)₃ flocculation. The results of infrared absorption and zeta potential showed that the hydrolysis products forms and surface electric potential of Fe(â…¡) and Fe(â…¢) hydrolyzing were same, while the results of surface area and particle size distribution showed that the hydrolysis products of Fe(â…¡) had bigger surface area and smaller particle size than the hydrolysis products of Fe(â…¢), therefore, Fe(â…¡) flocculation could adsorb more As(â…¢).Fe(â…¡)/H₂O₂(Fenton) and Fe(â…¢)/H₂O₂(Fenton-like) oxidation coupled with flocculation were used in removing arsenic, and the removal efficiency of arsenic by Fenton oxidation coupled with flocculation reached more than 96%, while Fenton-like oxidation coupled with flocculation was only about 70%. The results of open circuit potential - time curve and infrared absorption indicated that As(â…¢) was oxidized to As(â…¤) more effectively by Fenton oxidation coupled with flocculation, and there was a coupled process between oxidation and flocculation.The part FeSO₄ was replaced by poly ferric sulfate(PFS), and then the influences of FeSO₄/PFS, pH value of flocculation, dosage of oxidant and flocculant, and the different initial concentration of As(â…¢) were investigated. The results showed that the mole rate of FeSO₄/PFS was 6/9, and pH value of flocculation was 7, and the dosage of oxidant and flocculant were 20 and 15mg/L, respectively, then the removal efficiency of As(â…¢) with 0.5¹0mg/L was more than 90%. The FeSO₄/PFS/H₂O₂ oxidation coupled with flocculation process had a stronger capability to suit large concentration change of arsenic, and enhanced the sedimentation performance of flocs. The process could also reach excellent removal effect for arsenic in sulfuric acid plant and non-ferrous smelting plan wastewater, and the removal efficiency was more than 97%, which has a reference value to treat arsenic in the industrial wastewater.