Green synthesis of a ZnO/ZnS-decorated magnetic porous carbon hybrid for enhanced rhodamine B adsorption and photodegradation: A combined DFT and experimental study

Abstract

An important and sought-after goal in wastewater treatment is to develop photocatalysts that can effectively eliminate emerging contaminants while remaining environmentally sustainable. Semiconductor-based photocatalysis presents a promising solution for wastewater purification, offering advantages such as safety, efficiency, and cost-effectiveness. This study employs a green self-activation method to synthesize a hybrid magnetic porous carbon composite, decorated with Fe₃O₄, ZnO, and ZnS (PZZF), aimed at the degradation of Rhodamine B. A variety of characterization techniques were employed in this study, including XRD, nitrogen adsorption-desorption analysis, FESEM, FTIR, HRTEM, Zeta potential, Raman spectroscopy, contact angle measurements, DRS, Mott-Schottky analysis, and VSM. HRTEM confirmed the successful formation of heterojunction structures with the desired chemical compositions. The specific surface area of the synthesized material was measured to be 313 m².g⁻¹, and the saturation magnetization was found to be 13.51 emu.g⁻¹. The investigation of PZZF's photocatalytic activity against Rhodamine B highlights its enhanced efficiency, particularly under UV/H₂O₂ treatment, leading to complete degradation of the dye within 60 min. Several factors affecting the degradation process were explored, including pH, catalyst dosage, H₂O₂ concentration, and scavenger studies, providing comprehensive insight into the optimal conditions for maximum photocatalytic performance. The results from the radical trapping experiments demonstrated that hydroxyl radicals played a critical role in the degradation of Rhodamine B. Additionally, the total organic carbon (TOC) analysis showed that more than 96 % of the carbon in the RhB solution was effectively mineralized into CO₂ after 90 min of UV irradiation. DFT calculation results were aligned with experimental findings to validate theoretical predictions and enhance the overall understanding of the adsorption process. Ultimately, the UMAP technique was employed to visualize RhB adsorption and degradation by clustering and screening various configurations of the photocatalyst. These findings confirm the strong potential of the PZZF photocatalyst for effective dye degradation, highlighting its promising application in environmental remediation.