Effective biosorption of Cu(II) using hybrid biocomposite based on N-maleated chitosan/calcium alginate/titania: Equilibrium sorption, kinetic and thermodynamic studies

Abstract

In this research work, a hybrid biocomposite based on N-maleated chitosan, amino-thiocarbamate functionalised calcium alginate and anhydrous Titania nanoparticles (NMC-MCA-TiO₂) was fabricated. The study involves the one pot facile synthesis of N-maleated chitosan and amino-thiocarbamate functionalised alginate under moderate conditions. Sorbent was conditioned in the form of hydrogel beads and characterized through FT-IR and SEM analysis. Newly grafted functional groups could act as potential chelating sites for enhanced Cu(II) sorption. Modified biopolymers were organo-functionalised which provided excellent support for immobilization of Titania nanoparticles (TiO₂) as inorganic filler. Kinetic data illustrated the manifestation of intrinsic chemisorption instead of simple bulk/film diffusion. Equilibrium sorption data fitted well with Freundlich adsorption model (R² ≈ 0.99) which designated the heterogeneous nature of sorbent. Maximum sorption capacity of biosorbent was found 192 mg/g at 298 K and pH = 6.0. Standard Gibbs free energy change ∆G^o (-21.53, -21.97, and - 22.42 kJ/mol), standard enthalpy change ∆H^o (5.12 kJ/mol) and standard entropy change ∆S^o (0.09 kJ/mol K^-1) values suggested that the sorption process to be spontaneous and endothermic. The sorbent 3NMC-MCA-TiO₂ could be competitive candidate for economical and rapid adsorptive removal of Cu(II) from dilute contaminated liquids.

Keywords: Chemically modified calcium alginate; Cu(II) biosorption; N-maleated chitosan; Titania encapsulation.