Centrum pre Nanodiagnostiku Materiálov

Shalu Atri, Hamidreza Behtooei, Frantisek Zazimal, Arshitha Madhusudhan, Mário Kotlár, Jana Makukova, Andrea Sevcovicova, Tomas Roch, Marcello Brigante, Michael Naguib, Olivier Monfort 

In: Chemical Engineering Journal, 2026, 534, 174993

https://doi.org/10.1016/j.cej.2026.174993

Abstract

The increasing occurrence of pharmaceutical residues in treated wastewaters, together with the emergence of MXene-based composites as novel and promising catalysts for advanced oxidation processes (AOP), motivates the development of more efficient and selective treatment technologies. In this study, a novel Nb₄C₃T_x-Co₃O₄ nanohybrid AOP catalyst was synthesized for peroxymonosulfate (PMS) activation under dark conditions to degrade four pharmaceutical pollutants including caffeine (CAF), ibuprofen (IBU), paracetamol (PAR), and sulfamethoxazole (SMX). Structural and morphological characterization confirmed successful integration of Co₃O₄ nanoparticles onto the Nb₄C₃T_x MXene surface. Under optimized conditions, complete degradation of the pharmaceuticals was obtained within 60 min, except for IBU, which required >100 min due to steric hindrance in its molecular structure, resulting in fewer sites available for attack by reactive species. The contribution of reactive species differs among the pharmaceutical where degradation of IBU and PAR was predominantly governed by sulfate radicals (), contributing over 50% while CAF and SMX followed a degradation mechanism involving singlet oxygen (¹O₂, up to 30%),  (20–40%) and  (20–40%). The AOP involved a redox-mediated PMS activation mechanism predominantly on Co and Nb surface sites. The Nb₄C₃T_x-Co₃O₄ catalyst exhibited robust performance in cocktail of pollutants and maintained satisfactory degradation efficiency, especially for SMX and PAR in tertiary effluents from wastewaters treatment plant (WWTP) collected in Bratislava. In addition, the chemical structure of degradation by-products was characterized by LC-MS analysis and a degradation mechanism was proposed. Colorimetric MTT assays of the treated waters showed no acute cytotoxicity from either the PhACs or their degradation products on short-term exposure. This study provides new insights into pollutant-specific oxidation mechanisms and reactive species profiles in PMS-based AOPs, establishing Nb₄C₃T_x-Co₃O₄ as a promising non-conventional catalyst for potential quaternary treatment in WWTP technology.