Catalytic ozonation of an organophosphorus pesticide using microporous silicate and its effect on total toxicity reduction

Catalytic ozonation is promising as one of the advanced oxidation processes because of its effective use of ozone and its improved treatability of organic compounds through radical reactions. In this article, we investigated the feasibility of microporous silicates as a potential catalyst for a catalytic ozonation process. Organophosphorus insecticide, dichlorvos (DDVP), was employed as a model chemical for assessing conventional ozonation and catalytic ozonation, because its oxidative intermediate is toxic and is not degraded by direct ozonation. It was found that ozone was well adsorbed and simultaneously decomposed in microporous silicates, resulting in the production of possible radical species. In the presence of microporous silicates, radical reactions by decomposed ozone were evidenced by phosphate ion release that shows a degradation of a toxic intermediate of DDVP. Accordingly, cytotoxicity was successfully decreased. In a continuous treatment process combining a conventional ozonation vessel and a microporous silicate column for an effective use of residual ozone, enhanced degradation of DDVP was demonstrated by a decrease of DOC, an increase of the PO43- concentration and reduction in the cytotoxicity. This new treatment mechanism is likely to be promising as an advanced water treatment process particularly when we think about better toxicity reduction of wastewaters.