Cellulose and chitosan derivatives for enhanced sorption of erbium(III)

Cellulose (Cell) was chemically modified by grafting thiourea (Thio-Cell) and glutaraldehyde cross-linked chitosan (GLA-Chit) was functionalized by poly(aminocarboxymethylation) (PCM-Chit); material was also prepared as a composite material that incorporates a magnetic core (Magn PCM-Chit). The sorption properties of these materials have been compared to non-modified cellulose and GLA-Chit for Er(III) uptake. Sorption increases with progressive deprotonation of reactive groups, such as R-OH, R-SH, amine and carboxylic acid groups. The chemical modification significantly increases sorption performance and more specifically the poly (aminocarboxymethylation): sorption capacities increase up to 117-145 mg Er(III) g(-1). Sorption capacities also increase with temperature: the sorption is endothermic and spontaneous. The spontaneity of the reaction significantly increases with chemical modification of chitosan-based sorbent. The entropy of the system is negative for GLA-Chit, Cell and Thio-Cell and positive for PCM-Chit materials. Acidic solutions of thiourea efficiently desorb Er(III) and allows the recycling of the sorbents for a minimum of 5 sorption/desorption cycles. FT-IR spectrometry, XRD, TGA, elemental analyses and SEM observations have been used for characterizing the materials. The magnetic properties of Magn PCM-Chit were also characterized by VSM.