Cu(ii)-modified Mg–Al hydrotalcite/bentonite composites for adsorption and visible-light-driven photocatalytic degradation of Rhodamine B in textile wastewater

Abstract

Dye pollution from textile effluents poses significant environmental challenges, necessitating efficient and sustainable treatment technologies. In this study, Cu(II)-modified Mg–Al layered double hydroxide (5CuH) and its bentonite-supported composites were synthesized via a facile co-precipitation strategy and systematically characterized by XRD, SEM, BET, EDX, and UV-Vis DRS. Structural analysis confirmed successful Cu incorporation and uniform LDH dispersion on bentonite, resulting in narrowed band gaps (1.42–2.12 eV) and enhanced visible-light responsiveness. Under visible-light irradiation, 5CuH and 5CuH/Bent-2 achieved over 90% RhB degradation within 60 min at 50 ppm, accompanied by substantial mineralization. The 5CuH catalyst maintained high stability over four cycles with only 4.7% efficiency loss, while the composite showed moderate decline due to partial Cu²⁺ leaching but preserved structural integrity. Both materials effectively treated real textile wastewater, reducing COD to meet QCVN 40:2025/BTNMT discharge standards. This work demonstrates a synergistic clay-LDH design strategy that enhances charge separation and reactive oxygen species generation under visible light. Unlike adsorption-dominated systems, pollutant removal is primarily governed by photocatalytic oxidation, enabling efficient degradation and mineralization in complex wastewater matrices. The combination of low-cost raw materials, simple synthesis, and strong practical performance highlights the scalability and industrial potential of clay-supported LDH photocatalysts for sustainable textile wastewater remediation.