Three-dimensional rGO/CNT/g-C3N4 macro discs as an efficient peroxymonosulfate activator for catalytic degradation of sulfamethoxazole
Rajan Arjan Kalyan Hirani, Abdul Hannan, Nasir Rafique, Lei Shi, Wenjie Tian, Haitao Wang, Hongqi Sun
Abstract
Over the past few years, advanced oxidation processes (AOPs) have shown promising efficiencies for wastewater remediation. Carbocatalysis, in particular, has been exploited widely thanks to its sustainable and economical properties but has an issue of recovery and reusability of the catalysts. To address this, three-dimensional (3D) binary and ternary graphene-based composites in the form of macro discs were created to activate peroxymonosulfate (PMS) for catalytic oxidation of sulfamethoxazole (SMX). Graphene oxide served as the base, while graphitic carbon nitride (g-C3N4) and/or single-walled carbon nanotubes (SWCNTs) were added. Among the various discs synthesized, rGNTCN discs (ternary composite) were proven to be the most efficient by completely degrading SMX in 60 min owing to their large surface area and nitrogen loading. The catalytic system was further optimized by varying the reaction parameters, and selective radical quenching and electron paramagnetic resonance tests were performed to identify the active radical, revealing the synergistic role of both radical and non-radical pathways. This led to the development of possible SMX degradation pathways. This research not only provides insights into ternary carbocatalysis but also gives a novel breakthrough in catalyst recovery and reusability by transforming nanocatalysts into macro catalysts. Release of antibiotics in water has become overwhelming and such continuous exposure has led to the evolution of resistant bacteria causing adverse effects on human health. There is therefore an urgent need to exploit feasible techniques to eradicate these pollutants. Advanced oxidation systems (AOPs) have shown excellent degradation of such antibiotics but have a major shortcoming, i.e., catalyst recovery and reusability. To address this challenge, nanocatalysts have been modified to macro discs for the removal of antibiotics. The study has proven that this technique is feasible and could be possibly applied in real wastewater remediation processes.