Heterojunction-Driven Photo-Oxidation for Pathogen and Dye Synergistic Degradation in Decentralized Wastewater Systems

Abstract

Heterojunction photocatalysts permit the advancement of oxidation with sunlight energy to both eliminate recalcitrant dyes and immobilize microbial pathogens in the course of decentralized wastewater treatment. This review summarizes 2025 improvements in S-scheme, Z-scheme and photo-Fenton hybrid systems to harness internal electric fields and H2O2 autocatalytic cycles to suppress charge recombination and increase •OH fluxes, and is able to achieve high mineralization of azo dyes (e.g. reactive blue 19, methylene blue) and 46 log reduction of Escherichia coli in actual effluents. These include needle-like structures of ZrOo/NiFe2O4 to remove bisphenol A and 4-nitrophenol, and ternary systems such as MoS2/Bi2O3/CdS to remove nitrophenols, ZnO-hydroxyapatite to remove ciprofloxacin and methylene blue in domestic sewage, and Ti/graphite photoelectrodes to remove scaly reactive blue 19 in textile wastewater. The applications focus on arid Middle Eastern dye effluents and tropical agro-industrial wastewaters, using fixed-bed reactors and chloride-tolerant designs as well as floating platforms to provide rural and coastal resilience. The obstacles like scattering of light caused by turbidity and humic acid poisoning are neutralized by means of pre-coagulation, filtration, and mild annealing. The review combines dual-target kinetic models with the H2O2 production consumption cycles under the AM1.5G illumination to forecast the over 95% performances. These innovations are in accordance with WHO guidelines on pathogen and in favor of additive-free and scalable solutions to decentralized sanitation in underserved areas.