Remediation of washing machine wastewater by photo-enhanced persulfate/hematite process

Hematite nanoparticles (Fe 2 O 3 , HNPs) were synthesized to be used in washing machine wastewater treatment as a complex matrix. In order to activate persulfate (PS), HNPs and Ultraviolet-C (UVC) radiation were used to generate sulfate radicals due to photocatalytic activity of HNPs and higher energy input of UVC. The effect of operational parameters such as pH, catalyst dose, PS concentration and reaction time was investigated. The results showed that PS/UV/HNPs could remove organic pollutants from washing machine wastewater. Based on the results, the PS/UV/HNPs process can effectively remove chemical oxygen demand (COD) (77.5%) and total organic carbon (TOC) (65.9%) at optimal conditions (pH = 7, PS = 8 mM, HNPs =1.0 g/L) within 150 min. The COD and TOC removals followed a pseudo-first-order kinetic model with the rate constants of 0.0109 and 0.0074 min −1 , respectively. Reusability experiments revealed that HNPs could keep its performance for three-time use. The electrical energy was also calculated: 158.7 kWh/m 3 is required to reach 77.5% COD removal. Based on the achieved results, it can be concluded that the PS/UV/HNPs process is an effective process for COD and TOC removals in washing machine wastewater.