Study On The Influencing Factors And Mechanism Of Arsenic Removal By Electrocoagulation

The article focused on the arsenic removal by electrocoagulation during the laboratoryconditions and actual conditions. The effects of main influencing factors on arsenic removalby electrocoagulation were studied and the operational conditions were optimized by responsesurface methodology. Under the optimal operational conditions which was get in thelaboratory， Ion exchange method, X-ray photoelectron spectroscopy (XPS), Fouriertransformed infrared spectroscopy (FT-IR) and X-ray diffraction were used to study thesurface morphology and crystal structure of the precipitation formed during the reaction ofsimulation wastewater treated by electrocoagulation. The research results explored thereaction mechanism of arsenic removal by electrocoagulation. The following conclusions canbe drawn from the research：（1） Plackett-Burman(P-B) design were applied to optimize7factors for the arsenicremove by electrocoagulation. The result indicated that, reaction time, current, initial arsenicconcentration, and initial pH were the key factors.（2） Central Composite Design(CCD) were applied to optimize the operationalconditions of arsenic remove by electrocoagulation. The result demonstrated that The optimaloperational conditions were reaction time10min, current0.3A, initial pH7and initialconcentration20mg/L, and under these conditions, the arsenic removal rate was98.8%, thearsenic concentration was0.24mg/L which achieves the integrated wastewater dischargestandard (GB8978-1996).（3） The simulation wastewater which contained arsenic was treat byelectrocoagulation under the optimum operational conditions given by CCD experiment andthe precipitation was studied by XPS，XRD and FT-IR.（4） Fe was released to solution as Fe2+and was then oxidized to lepidocrocite(FeOOH). The research results indicate that some amount of As(III) is absorbed bylepidocrocite, and some amount of As(III) is oxidized to As(V) and adsorbed as bidentatesurface complex forms onto lepidocrocite.（5）When the current density is small, arsenic is mainly adsorbed as ferric arsenateforms onto lepidocrocite; when the current density is large, arsenic is mainly adsorbed asbidentate surface complex forms.（6） The electrocoagulation was used to treat actual wastewater which was sampledat a copper smelting factory located in Chenzhou city Hunan province (China). The removalrate can reach99.91%with73min of reaction time,3A of current and pH5on the optimum condition which was given by the response surface methodology. On this condition, the powerconsumption of1m3wastewater was11.66Kwh.