Green-synthesized Cu-WO₃ for efficient persulfate activation under UV–Vis irradiation: A novel sustainable approach for wastewater treatment

The development of cost-effective and eco-friendly photocatalysts for wastewater treatment remains a challenge. This study presents a Cu-doped WO₃ photocatalyst synthesized using Eichhornia crassipes extract via a green method for persulfate activation under UV–Vis light to degrade methylene blue (MB) as a model pollutant. Characterization analyses revealed that Cu incorporation into WO₃ reduced the band gap energy from 2.71 eV to 2.48 eV, improving charge carrier transfer. The photocatalyst exhibited an irregular nanosheet morphology with an average particle size of 24.53 ± 10.30 nm. The Cu-WO₃/PS/UV–Vis process achieved a 93.82 % MB degradation efficiency under optimized conditions. Additionally, a predictive model showed strong agreement with experimental data (R² = 0.9862). Scavenging tests revealed that SO₄^•– and ^•OH were the dominant radicals in MB degradation, while O₂^•– and h⁺ showed lower contributions. Moreover, chemical oxygen demand (COD) analysis indicated 82 % mineralization efficiency. An economic assessment estimated a treatment cost of US$9.47/m³, a profitability index of 1.3, and a 5.7-year payback period. The study supports the achievement of several UN Sustainable Development Goals (SDGs), including SDGs 3, 6, 8, 12, 13, and 14, demonstrating that the Cu-WO₃/PS/UV–Vis process is an effective, sustainable, and economically viable approach for treating textile wastewater.