Rationally tailored synergy between adsorption efficiency of cotton shell activated carbon and PMS activation via biogenic Fe0 or Cu0 for effective mitigation of triphenylmethane dyes

Abstract

This study investigates the utilization of Ficus religiosa (Linn.) bark extract-mediated green synthesis to immobilize zerovalent copper (ZVC@CSAC) and zerovalent iron (ZVI@CSAC) onto cotton shell activated carbon (CSAC) for peroxymonosulfate (PMS) activation and degradation of triphenylmethane dyes, Rhodamine B (Rh B), and Crystal violet (CV). Key parameters such as initial pH, catalyst and PMS dosage, dye concentration, and co-existing ions were systematically examined to elucidate their effects on Rh B and CV degradation. A synergistic effect was also established between the dye adsorption efficiencies of CSAC, heterogeneous Fenton-like degradation, and PMS activation by Fe0 or Cu0 for the removal of triphenylmethane dyes. The ZVI@CSAC and ZVC@CSAC were compared for their dye removal efficiencies, with ZVI@CSAC exhibiting superior performance in terms of higher PMS utilization efficiencies and inherent stabilities. Under optimal conditions, high removal efficiencies were achieved for Rh B (87.6 %) and CV (99.8 %) within treatment times of 60 and 10 min, respectively. The degradation rates (kobs) for CV (4 × 10−1 min−1) and Rh B (3.7 × 10−2 min−1) using the heterogeneous ZVI@CSAC-PMS activation process was significantly higher than those observed for the ZVC@CSAC-PMS process for CV (2.3 × 10−1 min−1) and Rh B (3.4 × 10−2 min−1) dyes. This indicates that the ZVI@CSAC-PMS process was more efficient in removing both Rh B and CV dyes. Characterization using FESEM, EDX, and XRD analysis confirmed the catalytic reusability of the nanocomposites. Potential ROS attack sites were identified using DFT optimization studies, and the Rh B and CV degradation pathways were elucidated using intermediates detected by HRMS analysis. The establishment of water quality parameter toxicity profile’s post-reaction further highlights the innovative contributions of this research. Overall, the synergistic interaction between adsorption and activation processes enhances the overall efficiency of dye degradation, making ZVI@CSAC-PMS and ZVC@CSAC-PMS promising candidates for wastewater treatment applications.