Preparation, characterization, and removal of nitrate from water using vacant polyoxometalate/TiO2 composites

• Published in: Environmental technology Vol. 44; no. 22; pp. 3393 - 3404
• Main Authors: Wang, Lingsheng, Fu, Weizhang, Sun, Shujuan, Liu, Huaihao, Wang, Jinhua, Zhong, Wanzhen, Ma, Bin
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02.10.2023; Taylor & Francis Ltd
• Subjects: Catalysts; Catalytic activity; Copper; Formic acid; Free radicals; Groundwater pollution; Industrial development; Irradiation; Nitrate N; Nitrate removal; Nitrates; Nitrogen; Photocatalysis; Polyoxometallates; Reduction; Sol-gel processes; Spectroscopy; Titanium dioxide; Ultraviolet radiation; vacant POMs
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2022.2058424

Due to the rapid development of industry and agriculture, nitrate pollution in groundwater has been continuously increasing. NO 3 -N is a chemically stable nitrogen species and is quite difficult to remove. In this study, using heteropoly silicotungstate K 8 [α-SiW 11 O 39 ] and Cu 2+ as the active components, SiW 11 and Cu 2+ were loaded onto TiO 2 by a sol-gel method to prepare a composite photocatalyst SiW 11 /TiO 2 /Cu. The photocatalytic reduction of dissolved NO 3 -N was subsequently performed using SiW 11 /TiO 2 /Cu under UV irradiation, and the influence of different experimental parameters on the photocatalytic performance was investigated. The mechanism of NO 3 -N reduction by the composite catalyst was also investigated. Free radicals existing within the system were detected by ESR spectroscopy, and the results indicated that anion free-radicals were generated by the reaction of photogenerated holes and formic acid (HCOOH). At a SiW 11 /TiO 2 /Cu dose of 1.2 g L −1 and in the presence of HCOOH as a hole scavenger, the proposed composite catalytically reduced NO 3 -N anddemonstrated significantadvantages in terms of its photocatalytic activity in comparison with pure TiO 2 . In particular, the removal efficiency of NO 3 -N and the selectivity of nitrogen achieved a maximum of 96% and 77%, respectively.