Elaboration of hybrid Luffa cylindrica−CuO materials and a study of their performance in the biosorption of pollutants

Synthetic dyes pose a significant threat to aquatic ecosystems. Several methods have been developed and implemented to eliminate these important contaminants. This paper explores the development of a new, economical, and environmentally friendly bio-adsorbent, originally extracted from Luffa cylindrica fibers and copper ions Cu²⁺, at different percentages (1%, 2%, and 4%) by applying a precipitation method. The retention of Methyl Orange, as a model pollutant dye, was studied in this work. The physicochemical characterization of the pure biomass and the hybrid materials was carried out using zero charge point and Boehm methods. Moreover, infrared (IR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) were applied to the original materials. Mathematical modeling of the Brouers−Sotolongo kinetics was performed to describe the retention process. The process was optimized according to the amount of Methyl Orange (MO) anionic dye adsorbed on Luffa cylindrica and the hybrid materials. Luffa cylindrica is basic (pH_pzc 8.131). Surface characterizations showed that, at low Cu²⁺ percentage (1%), the material surface remains basic, but at higher percentages (2% and 4%), Cu²⁺ becomes acidic by reacting with other components. Infrared characterization confirmed the binding of Cu²⁺ to Luffa cylindrica through the creation of Cu–O–C and Cu–OH bonds. The results showed the effectiveness of the hybrid materials in removing MO, as they accelerate the biosorption process and improve the performance of Luffa cylindrica fibers. The amount of Methyl Orange adsorbed increased from 0.242 mg g⁻¹ for pure Luffa cylindrica to 0.392 mg g⁻¹ for Luffa cylindrica−1% Cu²⁺. The hybrid material incorporating 1% Cu²⁺ presented the highest adsorption capacity. This work showed a clear relationship between the surface function content and the retention capacity of MO by biomaterials.