Photoredox Dechlorination of the Fungicide Chlorothalonil with Sodium Lignosulfonate in Water

Chlorothalonil (CTL) is a well-known water contaminant and has high toxicity to aquatic species and amphibians. Sodium lignosulfonate (SL) as an inexpensive surfactant is renewable, biodegradable, and environmentally benign. Effects of SL on photodegradation of CTL were studied under different light. SL enhanced the photodegradation rate of CTL by 14, 18, 7.4, and 18.5 fold under a high-pressure mercury lamp (HPML), an UV lamp, a xenon lamp, and sunlight, respectively, compared to the SL-free control. The mechanism of SL-enhanced CTL degradation was revealed as a reductive dechlorination reaction by radical scavenging activity and electron donation of SL. Further experiments evidenced that the photoreductive capacity of SL generated electrons to reduce generation of hydroxyl radicals (•OH) and singlet oxygen (¹O₂) under irradiation and promoted dechlorination of CTL̇. The results are helpful to understand the effects of SL on phototransformation and the high potential of using SL as a catalyst to abate chloroarenes pollution.