Competitive recovery of copper ions using ethyl acetoacetate modified chitosan/organo-functionalized alginate hydrogel beads: kinetics and isothermal sorption studies

Abstract

Surface functionalization of chitosan using some chelating ligands not only improves sorption capacity but also induces selectivity into the biopolymer. The current study is based on the facile synthesis of ethyl acetoacetate modified chitosan and surface-functionalized alginate composite beads (EAA-MCSA). Chemical modification of sodium alginate was carried out to graft amino thiocarbamate moiety (-OCSNHNH2) to entrench selectivity and specificity across the linear chains of preliminary polysaccharide. Biosorbent (EAA-MCSA) was thoroughly characterized by FT-IR and SEM analysis and employed in the form of composite hydrogel beads for competitive Cu(II) recovery. Newly grafted aminothiocarbamate (-OCSNHNH2) and 1,3-dicarbonyl moieties (-COCH2CO-) are supposed to act as potential chelating sites for enhanced Cu(II) sorption. Kinetic data could be well depicted using pseudo-second order rate law (R2 = 0.99, qexp≈qe,th = 85.25 mg/g, k2 = 0.45–1.17 ×10−2 g/mg.min−1) and sorption data was found in close agreement with Langmuir adsorption isotherm (R2 = 0.99, qm= 390.21 mg/g at 298 K and pH = 6.0, KL= 0.44–0.49 ×10−2 L/mg). The ΔG° values (−20.75, −21.10, −21.30 and −21.50 kJ/mol) and positive ΔH° (−7.63 kJ/mol) designated the sorption process as spontaneous and exothermic, respectively. Hence, EAA-MCSA could be a better sorbent for adsorptive remediation of Cu(II) from dilute effluents.