[Copper (II)/Cellulose-Chitosan] microspheres complex for dye immobilization: Isotherm, kinetic and thermodynamic analysis

Abstract

Considered as ligands due to the presence of donor atoms in their chemical structures, and being also among the major pollutants of water, Eriochrome Black B (Erio), Calmagite (Calma) and Acid Blue 25 (AB25) were successfully immobilized on cellulosechitosan microspheres loaded with copper ions. Prepared supports were characterized by Fourier Transform Infra-Red (FTIR) spectral study and Thermogravimetic analysis (TGA). The effect of experimental factors during dye immobilization such as pH, contact time, temperature, and initial dye concentration were studied. The experiments demonstrate that the adsorption capacities of dyes on [Cu(II)/cellulose-chitosan] are much higher than the unloaded microspheres. This indicates that these dyes can act as efficient ligands for coordinating metals already involved in [cellulose-chitosan]. At least, in the case of AB25, a 60% of difference in target removal was achieved at equilibrium. The kinetic adsorption fitted well to the intra-particle diffusion model and the corresponding rate constants were obtained. In addition, the interpretation of the equilibrium sorption data complies well with the Freundlich model. The thermodynamic parameters were also determined and the enthalpy change (ΔH°) was found to be low, between -5.93 and -20.68 Kj.mol-1, indicating that the adsorption phenomenon is exothermic and physical. A probable mechanism of the Dye/Copper(II)/cellulose-chitosan complex is also proposed.