Promoting photosensitized reductive dechlorination of chlorothalonil using epigallocatechin gallate in water.

Chlorothalonil (CTL) is a broad-spectrum fungicide. Photodegradation is a main degradation pathway of CTL in water. Because of the high aquatic toxicity of CTL and its metabolite 4-hydroxy CTL (CTL-OH), it is significant to develop an effective method to degrade CTL but without formation of CTL-OH. Epigallocatechin gallate (EGCG) is an abundant tea byproduct and has more than 100-fold reducing power than vitamin C. The present study reports photosensitization effects of EGCG on CTL photodegradation in water under sunlight and artificial lights. The results indicated that EGCG significantly photosensitizes CTL photodegradation. Under high-pressure mercury light illumination, CTL underwent primarily reductive dechlorination. CTL-OH, a main CTL photolytic product, was not detected when EGCG was added in the water. We concluded that EGCG not only significantly enhances CTL photodegradation rate but also alters the photodegradation pathways, avoiding the production of the highly toxic CTL-OH. The results indicated high potential of using EGCG to minimize CTL aquatic toxicity and pollution.