Visible light excited graphitic carbon nitride for efficient degradation of thiamethoxam: Removal efficiency, factors effect and reaction mechanism study

Abstract In this decade, photocatalytic degradation of organic contaminants has attracted great attentions. In this study, we used graphic carbon nitride (g-C3N4) nanosheets as the photocatalyst for the degradation of thiamethoxam (THM). The properties of g-C3N4 nanosheets have been fully characterized by the analysis techniques. The experiments results shown that under the optimum condition, 91.3% of THM degradation efficiency can be reached in the presence of g-C3N4 nanosheets within 60 min under visible light irradiation. Take the realistic application into consideration and to fully investigate the reaction process, the influence of reaction parameters, including the dosage of g-C3N4 nanosheets, initial THM concentration, and initial solution pH value, co-existence ions, humic acid (HA) and fulvic acid (FA) have been systematically studied and discussed. Results demonstrated that weak acidity and neutral condition is benefit for THM decomposition, and Ca2+ and Mg2+ present enhanced inhibition effect than Na+ for THM removal. Meanwhile, PO43- and CO32- show strong inhibition effect, but HA and FA performed weak inhibitory effect. The trapping experiments and electron spin resonance (ESR) measurement demonstrated that superoxide radical (•O2-), hydroxyl radical (•OH) and holes (h+) are all generated during the reaction process. There are all participated in the THM decomposition process and •O2- plays the major role on it. The results obtained in this study indicated that metal free g-C3N4 present great photocatalytic activity and stability for THM removal and owns great potential in the application of actual agricultural environment.