Photomineralization of urban stormwater under visible light irradiation by using new tellurium-based defect pyrochlores

Abstract

This study investigates the photocatalytic activity of AgNbTeO6 (ANTO) and Sn0.5NbTeO6 (SNTO), two new tellurides synthesized by ion-exchange from the primordial compound KNbTeO6 (KNTO) prepared by the sol-gel method, for the photomineralization of urban stormwater (UWS) and identified organic pollutants from the USW sample. All the materials were well characterized by various spectroscopic and microscope techniques. Both ANTO and SNTO materials mimic pristine KNTO, such as a cubic lattice with the Fd3m space group. All of the materials' UV–vis–DRS profiles were used to calculate their bandgap energies. The lower photocurrent of ANTO than that of SNTO and KNTO materials indicates that ANTO is a superior photocatalytic material due to the low rate of recombination of electron-hole pairs, which is also supported by EIS studies. The photomineralization efficiency of the ultra-stormwater (USW) and pollutants identified from USW sample mineralization with ANTO is in the range of 95–99%. Additionally, HPLC analysis of initial and final samples of USW and two major pollutants identified from USW and TOC analysis for USW were studied. Finally, through mechanistic studies, the active species for photomineralization of stormwater sewage and organic pollutants was identified. The scavenger and insitu ESR studies indicated that superoxide radicals are more highly active than other radical species. The ANTO and SNTO have shown higher photocatalytic activity compared to the parent KNTO due to their low bandgap energy and low rate of recombination of the hole-electron pair.

Keywords

• Defect pyrochlores
• Photomineralization
• Urban stormwater
• Hydroxy radicals
• ESR studies