g-C 3 N 4 /TiO 2 nanocomposite coated with zinc oxide for selective photocatalytic degradation of nitrate in aquatic media

Healthy drinking water, free of toxic chemicals, is essential for human health. Nitrate ion in water causes poisoning. Photocatalytic removal of nitrate from water and its conversion to nitrogen gas is of great importance. Heterogeneous photocatalytic nanocomposite g-C 3 N 4 /TiO 2 /ZnO (CTZ) has been considered in this study to remove nitrate in the presence of UV light and formic acid as hole scavenger. The CTZ structure was characterized using FT-IR, SEM, EDS, TEM, BET, and XRD techniques. In this work, an aqueous solution containing NO 3 − -N anion (50 mg L −1 ) was examined using different CTZ. Nitrate removal results showed the highest rate 95.24% in the first 60 min. The use of CTZ was assosiated with improved results in nitrate reduction under visible light irradiation (91.82% nitrate conversion, 95.39% N 2 selectivity). Promising results under visible light are attributed to decrease in the CTZ bandgap, and thus the ease of electron–hole pair formation. Graphical Abstract In this research, the ternary nanocomposite g-C3N4/TiO2/ZnO was prepared in a different way that makes it cost-effective to produce at higher scales. On the other hand, this research is innovative in terms of using the ternary nanocomposite g-C3N4/TiO2/ZnO in the removal of aqueous nitrate in the presence of UV light and formic acid as hole scavenger. Nitrate removal results showed the highest rate of nitrate conversion to nitrogen gas (95.24%) in the first 60 min. The use of composite nanophotocatalyst g-C3N4/TiO2/ZnO was associated with improved results in nitrate reduction under visible light irradiation (91.82% nitrate conversion, 95.39% N2 selectivity).