Heterojunction-driven photocatalytic oxidation for synergistic pathogen and dye degradation in decentralized wastewater systems

Abstract

Heterojunction photocatalysts enable oxidation under exposure to sunlight and eliminate recalcitrant dyes and immobilize microbial pathogens during decentralized wastewater treatment. Harnessing internal electric fields and H₂O₂ autocatalytic cycles within S-scheme, Z-scheme, and photo-Fenton hybrid systems suppresses charge recombination and enhances ·OH flux, representing key technical advancements reported in 2025. Such systems include the needle-like structures of ZrO/NiFe₂O₄ used to remove bisphenol A and 4-nitrophenol, ternary systems such as MoS₂/Bi₂O₃/CdS used to remove nitrophenols, ZnO-hydroxyapatite used to remove ciprofloxacin and methylene blue in domestic sewage, and Ti/graphite photoelectrodes used to remove reactive blue 19 in textile wastewater. Targeted applications include chloride-tolerant fixed-bed reactors for arid Middle Eastern dye effluents and floating platforms for tropical agro-industrial wastewaters to enhance rural and coastal resilience. The obstacles like scattering of light caused by turbidity and humic acid poisoning are neutralized via pre-coagulation, filtration, and mild annealing. This review highlights the dual-target kinetic models that combine H₂O₂ production and consumption cycles under AM 1.5G illumination to achieve performances over 95%. Such innovations align with WHO guidelines for pathogen removal, providing additive-free and scalable decentralized sanitation solutions for underserved areas.