Hollow-structured Pd/TiO2 as a dual functional photocatalyst for methyl orange oxidation and selective reduction of nitrate into nitrogen

Nitrate pollution in wastewater has posed a threat to human health and the environment. Photocatalytic reduction is a promising technology to remove nitrate due to its high adaptability, low cost, and high effi-ciency. However, there is a great challenge to design photocatalyst with high nitrate reduction and high selectivity of nitrogen (N2) yield. In this study, a novel hollow-structured Pd/TiO2 (PHT1) photocatalyst is synthesized with large specific surface area (SBET) and pore volume, strong UV adsorption, high reduction potential than nitrate to nitrite, high charge transfer rate, and low electron-hole recombination rate. PHT1 exhibits a superior photocatalytic activity on the removal of methyl orange and nitrate. In addition, PHT1 exhibits high N2 selectivity (>95 %). A lower pH can promote the reduction of nitrate and the selec-tivity of N2 by PHT1. Electrons (e-) and CO2-center dot are the main active species for nitrate reduction with center dot OH as auxiliary radicals. Three main pathways for nitrate reduction are proposed: i) the reaction with formic acid under acidic conditions; ii) the reduction by electrons and the loaded Pd of photocatalyst to capture electrons to inhibit electron-hole recombination; iii) the reduction by CO2-center dot generated from formic acid oxidation by center dot OH. CO 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

Nitrate pollution in wastewater is a threat to human health and the environment. Photocatalytic reduction using a novel hollow-structured Pd/TiO2 photocatalyst shows high efficiency in removing nitrate and high selectivity for N2 yield.