Photoelectrocatalytic Degradation Of The Polycyclic Aromatic Hydrocarbons And Anthracene In Aqueous Environment

Polycyclic aromatic hydrocarbons(PAHs)are a type of organic compounds that consisting of two or more condensed benzene rings.Due to their strong carcinogenic,mutagenic,teratogenic and photoinduced toxicity potential,PAHs are listed as one of the129 priority pollutants identified by US EPA(United States Environmental Protection Agency).PAHs are persistent organic pollutants due to their chemical stability and biodegradation resistance,so they can be enriched through the food chain,have become one of the important carcinogens to human beings,andare significantly harmful to the ecological environment and human health.Titania nanotubes were prepared by anodic oxidation,as the working electrode and a titanium plate was thecounter electrode in a photoelectrocatalytic system,and the destruction of Anthracene(Ant)was carried out through irradiation under different light sources.The mechanism of degradation of Ant and the kinds of intermediates were also studied.(1)Firstly,Titania nanotubes electrode was fabricated by anodic oxidation in the electrolyte solution which contained fluorine ion and sintering was done by high temperature.The Titania nanotubes electrode was characterized with XRD,SEM,UV-Vis diffuse and linear sweep,to evaluate the Photocatalytic activity of the Titania nanotubes electrode;(2)Secondly,16 kinds of PAHs and Ant in aqueous solution were degraded by using Titania nanotubes electrode under the irradiation of UV light.The degradation of Ant in different system and the maininfluentialfactors were investigated.The results showed that the degradation of PEC was higher than PC and EO systems.The current density presented little effect on the degradation of Ant,and the removal efficiency reached 98.5%under a current density of 0.05 mA/cm~2 in 30 min.Anthrone and Anthraquinone are the intermediates and their concentrations increased first and then decreased.The initial pH value had relatively high effect on the generation of Anthraquinone.The initial concentration and the presence of humic acid(HA)had high effect on the apparent reaction constant;(3)Finally,Ant in aqueous solution was degradedby using Titania nanotubes electrode under the irradiation of solar light.The degradation of Ant in different systems and the main operation factors were investigated.The free radicals in the system were tested by ESR technique and the quenching experiments were conductedto investigate the main active species.The results showed that when the applied bias was 1V,the degradation of Ant was best and the removal ratereached86.5%.The degradation of Ant was better when the pH value was adjusted.The degradation of Ant under acidic conditions was the best,and the removal efficiency of Ant increased with the decreasein pH.The mainly free radicals in the photoelectrocatalytic system are hydroxyl radical and superoxide free radical,and the latter plays a major role in the degradation of Ant.