Photodegradation Of Roxarsone And The Enhancement Of The Photodegradation Process

Roxarsone(ROX)as a feed additive was widely used in poultry in past two decades.Roxarsone is barely metabolized in animal body and excreted chemically unchanged in manure.The ROX can enter surface water by rainfall causing its high water solubility.Some studies indicated that the ROX in water can degrade under light irradiation,and further leading to the arsenic contamination in the environment.Therefore,this work focused on investigating the ROX photodegradation behavior in aquatic environment,and modeling the photodegradation process.In addition,synthesize the 2',3',4',5,-tetraacetylriboflavin and carbon nitride to strengthen the photodegradation ROX.The main researching contents and results obtained are as follow:1.The degradation mechanism and influential factors of ROX were investigated,and the ROX photodegradation model was built.ROX can degrade by sunlight irradiation and further be oxidized to inorganic arsenic,the mechanism of ROX degradation was that ROX was degraded by 1O2 which generated through ROX self-sensitized under sunlight irradiation.The influential factors of ROX photodegradation were also investigated,the results indicated that strong light intensity and higher temperature could hasten the photodegradation rate of ROX,ROX initial concentration and pH also had affection on ROX photodegradation.In addition,NO3-could hasten ROX degradation obviously and photodegradation was inhabited significantly by DOM.The ROX photodegradation ANN model was built by using the results data of factors affecting ROX photodegradation.The precision of the built model was verified by ROX degradation data in natural condition,and the results indicated that ANN model can predict the ROX degradation in different conditions with high precision and less predictive error.It provides basis for controlling the pollution caused by ROX.2.The photocatalytic degradation of ROX using RTA as photosensitizer was investigated.ROX was degraded to As(?)by RTA in 90 min,and As(?)was further oxidized to As(V).ROX degradation followed pseudo-first-order kinetics.ROX degradation was inhibited under acidic or alkaline pH conditions,while was favorable under neutral pH conditions,because the stability of RTA structure was pH dependence.For the degradation of ROX,reaction with 1O2 and O2·-was the dominant mechanism of ROX photodegradation and As(?)oxidation,while the role of ·OH was negligible.In addition,there was another pathway in the ROX photodegradation.The excited RTA reacted directly with ROX and As(?).Thus,the photocatalytic degradation of ROX by RTA can reduce mobility of arsenic and the environmental risk caused by organoarsenicals.3.The photocatalytic degradation of ROX using C3N4 as photosensitizer was investigated.ROX was degraded to As(?)by C3N4 in 60 min,and As(?)was further oxidized to As(?).The degradation mechanism of ROX was that C3N4 absorb photon to generate radicals,like 1O2,O2·-and ·OH,which play main role in ROX degradation.Among of those radicals,the 1O2 was the dominant contribute radicals.In addition,the C3N4 was shown high stability,and which can be multiple reuse.Thus,the C3N4 can also photocatalytic degrade ROX,further reduce mobility of arsenic and the environmental risk caused by organoarsenicals.