Heterogeneous Fenton treatment of textile wastewater using rGO/nZVI: Batch and flow column evaluation

Abstract

Textile wastewater contains recalcitrant dyes and organics that are difficult to degrade via conventional treatments. This study evaluated the reduced graphene oxide (rGO)-supported nanoscale zero-valent iron (nZVI) composite (rGO/nZVI) for treating real textile wastewater in batch and continuous systems. The rGO/nZVI catalyst was synthesized and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) analyses, confirming uniform iron dispersion, active functional groups, and a mesoporous structure. Batch experiments under varying pH (3.0–5.5), catalyst dosages (150–1 000 mg/L), and H₂O₂ concentrations (150–1 000 mg/L) identified optimal conditions (pH of 3, 750 mg/L of rGO/nZVI, 1 000 mg/L of H₂O₂, and a reaction time of 110 min), achieving 81.5% chemical oxygen demand (COD) removal (from 450.8 mg/L to 83.5 mg/L) and approximately 90.0% color reduction (from 355–473 platinum–cobalt units (PCU) to 31.9–38.5 PCU). The packed-bed column tests achieved 77.4% COD removal (from 452.4 mg/L to 102.3 mg/L) and approximately 88.0% color reduction (from 362–488 PCU to 42.1–51.8 PCU), demonstrating stable continuous performance. Reusability tests demonstrated catalytic durability over five cycles, with COD removal decreasing from 94.6% to 51.4% and color removal from 96.2% to 65.1%. Overall, rGO enhanced nZVI dispersion, stability, and catalytic activity, supporting rGO/nZVI as a scalable advanced oxidation technology for textile wastewater treatment.