Sustainable Approach for The Removal of Cu(II) from Aqueous Solutions Using Lotus Seedpod-alginate Composite Biosorbents

Abstract

Turning waste or agricultural byproducts into valuable products has recently become a concern of scientists. In this study, the facile and cost-effective synthesis of a biocomposite derived from lotus seedpod (LS) and alginate (AG) was further applied for Cu²⁺ ion uptake from aqueous solutions. SEM images revealed the layered structures of the composites, which were thin and irregularly stacked sheets of a complex 3D network. The abundant functional groups on the surface of the LS-based material and its negative zeta potential value of -37.50 mV also facilitated efficient Cu²⁺ removal. Adsorption results revealed a Cu²⁺ adsorption efficiency (AE) and experimental capacity of 68.99% and 17.38 mg g^-1, respectively, after 30 min. The coefficient values of the Sips isotherm (R² = 0.952) and pseudo-second-order kinetic models (R² = 0.995) suggest that the monolayer adsorption mechanism on a heterogeneous surface is governed primarily by physicochemical interactions. Although the AEs decreased from 68.99% to 44.81% after four cycles, LSA showed strong adsorption potential, highlighting LS as a sustainable and inexpensive material for the development of low-cost and high-efficiency biocomposites for wastewater treatment. This approach supported environmental treatment and agricultural waste valorization, while the chemical and mechanical stability of the composite further confirmed its practical applicability.