SYNTHESIS AND CHARACTERIZATION OF MANGANESE (MN) DOPED TUNGSTEN OXIDE (WO₃) HYDROGELS FOR ENHANCED PHOTOCATALYTIC APPLICATION IN WASTEWATER TREATMENT

Abstract

Water contamination by dyes, heavy metals, and agricultural effluents presents an urgent global challenge requiring sustainable treatment solutions. Semiconductor photocatalysis has emerged as a promising eco-friendly approach; however, limitations such as wide band gaps and rapid electron–hole recombination hinder its efficiency. This study presents the synthesis and characterization of Mn-doped WO₃ nanoparticles and Mn-WO₃/(C₁₂H₁₄CaO₁₂)ₙ hydrogel composites for efficient photocatalytic degradation of organic pollutants in wastewater. The materials were prepared via a hydrothermal route, with Mn doping narrowing the WO₃ bandgap from 2.91 to 2.80 eV, enhancing visible-light absorption. Characterization techniques, including FTIR, XRD, and UV-Vis DRS, confirmed successful doping and hydrogel incorporation. Photocatalytic activity was evaluated against methylene blue under solar irradiation, with optimized parameters of pH 3, catalyst concentration (15 mg/100 mL for composites), and oxidant dose (11 mM H₂O₂). The Mn-WO₃/hydrogel composites achieved >92% degradation within 100 minutes, outperforming pure Mn-WO₃. Radical scavenging experiments identified hydroxyl radicals as the primary reactive species. The composites exhibited good reusability, maintaining ~82% efficiency after three cycles. Kinetic modeling revealed pseudo-first-order behavior, while response surface methodology (RSM) validated the robustness of the composites under varying pollutant concentrations. The dual-function system of adsorption and photocatalytic degradation offered by Mn-doped WO₃ hydrogels provides a cost-effective, recyclable, and solar-driven strategy for wastewater remediation, with potential applications in environmental purification, antimicrobial treatments, sensing, and energy storage.