Advanced Oxidation Removal Of Arsanilic Acid And Flocculation Mechanism

The organoarsenical are widely used as animal feed additives.P-arsanilic acid（ASA）and roxarsone（ROX）are common applied.while animal wastes bearingthese compounds are often used to fertilize agricultural land,which can cause arsenic pollution of soil,surface water,and groundwater We investigated the flocculation behavior of p-arsanilic acid and phenylarsonic acid in drinking water.We focused on the influence of Benzene substitution on the mechanism of flocculation removal,Futhermore,we studied the removal efficiency of Fenton oxidation and photocatalytic oxidation for p-arsanilic acid.We investigated the flocculation efficiency and behavior of ASA and PA in drinking water from the viewpoint of Amino substitution.The removal of As（V）,ASA and PA was examined under various conditions including flocculant dose,and water pH.The removal rates of As（V）was reach to 99% that the initial concentraion of Arsenic was 20mg/L and dosage of FeCl₃ was 40mg/L.However,when the dosage of FeCl₃ rises to 80mg/L,the removal rates of ASA and PA are just 87% and 83%.The characterization results of the flocs by FTIR and XPS showed that-OH group of Fe hydroxide played an important role on the removal of organoarsenical.During the coagulation process,the As-O group of As（V）,ASA and PA substituted the-OH group of Fe hydroxide to form a Fe-O-As complex.We analyzed the reasons why amino group and benzene ring had such a great influence on arsenic removal.With a superseding of benzene-ring,the molecular dimension of organoarsenical is increased.And it will hinder the surface complexation behavior of organoarsenical and Fe hydroxide.Otherwise,the exist of amino group in ASA,a new complex is built by amino group and Fe hydroxide.Compared with PA,ASA has more bonding sites build complex with Fe hydroxide.The result indicated that Fenton could effectively oxidize ASA and PA to As（V）.Then iron hydroxide could adsorb As（V）completely from water because of the strong adsorption capacity.The concentration of arsenic in the treatment water could meet the standard of wastewater.The best oxidation effect of ASA under the condition of pH=3 and Fe²⁺/H₂O₂=1/1.5.The study of organoarsenical removal by coagulation indicated that As（V）could be effectively removed by iron coagulation.Therefore,we can treat the real water contained ASA by Fenton.This method is entirely technically feasible and economic.The results showed that in the P25 catalysis process,similated natural light could degregate ASA into As（V）in oxidation.The total As was about 0.34 mg/L in 0.5h under the condition that the initial concentraion of ASA was 2 mg/L and dosage of TiO₂ was 1g/L.The result exhibited that the P25 could reach higher removal rate in acidic conditions than in alkalic conditions.The optimal strength of light was 68.5 mW/cm2.Hydroxide radical played an important role in P25 photo analysis oxidation of ASA.The study in this paper will provide a technical support for the engineering applications of the removal of organoarsenical in wastewater.Simultaneously,these results will offer a theoretical basis for exploring low cost and high efficiency technique for organoarsenical removal.