In this study, Cu 2 O, CdS, and Cu 2 O decorated with CdS nanorods were successfully synthesized and applied for the adsorption of crystal violet (CV) dye. Cu 2 O had a cauliflower-like shape, while CdS underwent a phase transition from cubic to the hexagonal structure, forming nanorods anchored to the Cu 2 O surface. The Cu 2 O/CdS composite achieved the highest removal efficiency with 65% CV removal. Kinetic analysis revealed that the adsorption of CV onto CdS and Cu 2 O/CdS followed the pseudo-second order model, with a rate constant (k 2 ) of 0.0268 g mg⁻ 1 min⁻ 1 , indicating that chemisorption is the dominant mechanism. Equilibrium data were evaluated using the Langmuir and Freundlich isotherms, with the Freundlich model providing a superior fit (R 2 = 0.9522) and Freundlich constants of 17.969 mg g⁻ 1 and 19.5865 mg g⁻ 1 for CdS and Cu 2 O/CdS, respectively, suggesting heterogeneous multilayer adsorption as the governing mechanism. The enhanced performance of the Cu 2 O/CdS composite is attributed to the hierarchical morphological structure of Cu 2 O and the hexagonal structure of CdS. Overall, the results demonstrate that Cu 2 O/CdS is a promising adsorbent for removing dye from aqueous systems, offering high adsorption capacity, favorable kinetics, and heterogeneous adsorption behavior. Schematic illustration of CV adsorption process using Cu 2 O/CdS
Ristiana et al. (Sun,) studied this question.