Photocatalytic remediation of organic chemicals from wastewater using MnO₂–TiO₂: Linking structural and magnetic properties to aquatic water quality improvement

The increasing discharge of industrial and domestic wastewater containing toxic organic pollutants and dissolved ionic contaminants demands efficient and sustainable remediation technologies. Herein, pristine TiO₂ nanoparticles and MnO₂/TiO₂ heterostructures were systematically evaluated for photocatalytic treatment of real wastewater under sunlight and UV irradiation (60 W). The MnO₂/TiO₂ composite exhibited superior photocatalytic performance, achieving substantial reductions in electrical conductivity (EC), total dissolved solids (TDS), nitrate, total hardness, alkalinity, biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Under UV irradiation, the composite reduced the COD and BOD of industrial wastewater to ∼70 and ∼35 mg/L, respectively, demonstrating significantly higher degradation efficiency than pristine TiO₂. XRD confirmed excellent structural stability and retention of the anatase phase after photocatalytic operation. UV–Vis spectroscopy revealed pronounced bandgap narrowing to ∼2.157 eV, indicating enhanced light harvesting and defect-mediated electronic reconstruction. FTIR and XRF analyses confirmed increased surface hydroxylation and effective reduction of residual inorganic species, respectively, supporting improved photocatalytic activity. VSM measurements showed enhanced saturation magnetization (∼0.0196 μB/f.u.), attributed to oxygen-vacancy-induced Ti³ ⁺ defect states, Mn-mediated interfacial exchange interactions, and efficient charge separation. These findings demonstrate that defect-engineered MnO₂/TiO₂ heterostructures are robust multifunctional photocatalysts with excellent structural stability, enhanced electronic and magnetic properties, and significant potential for sustainable industrial and domestic wastewater remediation.