Effect of spunbond nonwoven microplastics on dye wastewater treatment via hydrogen peroxide–based catalyst–assisted advanced oxidation processes

Abstract

The increasing prevalence of microplastics (MPs) in textile wastewater poses significant challenges for treatment processes. This study evaluates the impact of MPs on the decolorization of Reactive Red 239 (RR239) dye using hydrogen peroxide–based advanced oxidation processes, specifically UV/H₂O₂, H₂O₂/Fe²⁺ (Fenton) and H₂O₂/Fe²⁺/UV (photo–Fenton). UV/H₂O₂ oxidation exhibited superior decolorization efficiency compared to both Fenton and photo–Fenton processes. The optimal decolorization efficiency for RR239 was achieved at 94.1% at pH 3 in the Fenton process with H₂O₂ and Fe²⁺ concentrations of 2.5 mg/L and 12.5 mg/L, respectively. For UV/H₂O₂ oxidation, complete decolorization was achieved in 60 min at an optimal UV light intensity of 11 W and H₂O₂ of 75 mg/L at neutral pH. The presence of spunbond nonwoven MPs in RR239 wastewater significantly inhibited decolorization efficiency and kinetic rate constants. The pseudo–second–order rate constant (K_app) for the Fenton process without MPs was 0.0101 M^–1 min^–1, whereas the presence of MPs reduced the K_app to a range of 0.0026 to 0.0034 M^–1 min^–1. The UV/H₂O₂ process maintained a K_app of 0.1301 min^–1 as pseudo–first–order regardless of MP content but was affected by MP size. MPs in the size range of 200–500 µm improved decolorization efficiency, while larger MPs (500–1000 µm) reduced it. The results highlight the necessity of separating MPs to maintain high decolorization efficiency in dye wastewater treatment processes. The findings suggest that optimizing these parameters can enhance the efficacy of advanced oxidation processes in treating dye wastewater containing MPs.