High-efficiency treatment of oily wastewater by photocatalytic in-situ Fenton oxidation under visible light

Oily wastewater poses a significant threat to environmental safety, and complex water environments have caused numerous disturbances in oil pollution treatment. Therefore, constructing composite systems is expected to improve oil pollution treatment efficiency. This study developed an efficient photocatalytic in-situ Fenton oxidation system, HTCC@ZnFe2O4/Ag3PO4 (HZFA), loaded onto polypropylene spheres (PP) for treating oily wastewater (diesel oil) in complex environments. The built-in electric field of HZFA promotes photogenerated carrier separation, enhancing photocatalytic effect. At a diesel concentration of 3.2 g/L, performance of HZFA degraded diesel in deionized water and artificial seawater (ASW) were 60.80 % and 52.62 %, respectively, much higher than a pure photocatalytic system (13.84 %). The dual system compensated for single system defects like instability and narrow application range, achieving 8 effective cycles in ASW. Experimental and computational results showed that high oxidation and reduction potentials in the dual system promoted hydrocarbon oxidative degradation and H2O2 production/activation. The amount of (OH)-O-center dot, O-center dot(2)-, and h(+) produced in different environments is fundamental for the stabilization of catalytic degradation by HZFA. GC-MS, and DFT analysis revealed potential oxidative chain-breaking processes for diesel components like alkanes, aromatics, alcohols, acids, aldehydes, and esters. This study offers a new method for green and efficient oily wastewater treatment, overcoming inherent defects of traditional Fenton, with broad application prospects.