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

Abstract

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 ROH, RSH, amine and carboxylic acid groups. The chemical modification significantly increases sorption performance and more specifically the poly(aminocarboxymethylation): sorption capacities increase up to 117–145mgEr(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.