Oxidation Of Herbicides 2,4-D By Ozone And Ozone Combined With Mn～(2+)

The pollution of endocrine disruptors has already been classed another globalgreat environmental problem following the ozone layer destroying and greenhouseeffect. The treatment of endocrine pollutants is one of the hotspots in waterenvironmental protection. In recent years, a widely used herbicide 2,4-D has beenproved to be endocrine disruptor compound. The degradation intermediates of 2,4-Dis harm to the human health. 2,4-D is very difficult to be oxidized by commonoxidants. While some satisfactory results of degrading 2,4-D by ozone and ozonecombined with Mn²⁺ were show in this paper.Two degradation processes of 2,4-D by direct oxidation with ozone molecule andtotal oxidation were compared. The influence factors such as temperature, pH levels,2,4-D initial concentration, gas flow rate were investigated in order to find out felicityconditions. The result show that temperature and pH level strongly affects thedegradation processes, and gas flow has very little influence on the efficiency ofprocesses. The degradation rate of 2,4-D increase with the increment of temperature,pH level, and decrement of 2,4-D initial concentration. The reaction kinetics of thetwo treatments were studied. It is confirmed through experiment that degradation of2,4-D follows the pseudo-first-order reaction. And the indirect oxidation of hydroxylradical is dominant in 2,4-D degradation.The degradation mechanism of 2,4-D is studied. And degradation intermediatedsuch as 2,4-dichlorophenol, quinine, malice acid and oxalic acid detected by GC-MS,HPLC and IC, through reasonable supposition possible degradation mechanism isproposed.Though the experiment show the good result of 2,4-D degradation, the CODremoval is not well. The addition of Mn²⁺ could enhance removal of COD. Threefamiliar transition metal ions (Mn²⁺, Fe²⁺, Cu²⁺) were introduced as catalyst in theexperiment. Mn²⁺ behaved the best catalyst, Fe²⁺ took second place, Cu²⁺ did notenhance the oxidation of 2,4-D. We choose Mn²⁺ as catalyst to study on catalyticozonation. The influence factors of catalytic were investigated. Catalytic mechanismis proposed. Mn²⁺ enhance the generation of hydroxyl radical to indirectly improvedegradation of organic compounds. In order to generalize the treatment technology,the further study was required.