Synergetic Degradation And Mechanism Of Chloroacetic Acid By TiO₂Photocatalytic Oxidation Reaction Cooperated With Fenton Reagent

Haloacetic acids (HAAs) are the main disinfection by products with high boilingpoint、high carcinogenic risk and they are hardly degraded. Trichloroactic Acid (TCAA)as the main form of HAAs, has been confirmed that it is a potential attractant of livertumor for male mouse, it also can cause DNA strand breakage and damage formammalian cells. At present, TCAA has become one of the important controlparameters of drinking water quality standards in most countries. Therefore, it is of animportant practical and scientific value to investigate the removal method on green, safe,and efficient of TCAA and its degradation mechanism. Base on these, we carried outthe research of Fenton reagent synergistic TiO2photocatalytic degradation of TCAA andits mechanism.This paper investigated the effect of different factors on the degradation of TCAAin Fenton reagent, UV/TiO2, Fenton/UV/TiO2,respectively；also examined the change ofpH during TCAA degradation; then, analyzed the degradation reaction kinetics forFenton reagent, UV/TiO2, Fenton/UV/TiO2, and alculated the rate constant and half-lifefor these reactions. Finally, discussed the synergistic effect of Fenton reagent on TiO2photocatalytic degradation of TCAAand the synergistic mechanism.Experimental results showed that:(1) the removal ratio of TCAA in Fenton reagent, UV/TiO2, Fenton/UV/TiO2,respectively at the same conditions is8.76%、83.38%、99.78%; and the pH of solutionshowed a decreasing trend during TCAA degradation;（2） The degradation kineticsrate constant of TCAA in Fenton reagent, UV/TiO2, Fe2+/UV/TiO2respectively, is0.0009min-1、0.0131min-1、0.0456min-1, meanwhile, the half-life is770.16min、52.92min、15.20min, respectively;（3）Both Fenton reagent and UV/TiO2reaction cangenerated an obvious synergetic effect, and the effect probably occurred because①much OH radicals were produced in the Fe(OH)2+and H2O2decomposition reactionsirradiated by UV light;②many photoinduced electrons voluntarily participated in thereduction from Fe3+to Fe2+, resulting in improved TCAA degradation efficiency due tosuppressed recombination of photogenereated electrons and holes;（4）TCAA was firstdegraded to DCAA, and then DCAA was degraded to MCAA or other harmlessproducts, such as: carbon dioxide, carbon monoxide, hydrochloric acid and waterthrough the oxidation of OH. Thereforce the degradation method of Fenton/UV/TiO2 for TCAAis safe, efficient and economical.