A chitosan-based composite for adsorption of uranyl ions; mechanism, isothems, kinetics and thermodynamics

Abstract

The present paper describes a green and cost-effective approach to investigate chitosan-sepiolite (Ch-Sep) composite as an adsorbent for removal of UO22+ ions in aqueous solution. The Ch-Sep composite was prepared as a beads using with two cross-linking agents: tripolyphosphate (TPP) and epichlorohydrin (ECH). Their adsorption properties for the removal of UO22+ ions in aqueous solution by batch experimental conditions were studied. The adsorptive removal processes of UO22+ ions from aqueous solution were evaluated by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models, and was found to be perfectly fit to the Langmuir model (R2 = 0.971). The maximum adsorption capacity was 0.220 mol kg−1 at 25 °C from Langmuir isotherm model. Adsorption energy was 12.1 kJ mol−1 indicating that the adsorption process was chemical. The adsorption kinetics followed the pseudo second order and intra particle diffusion models. The thermodynamics parameters of UO22+ ions removal from aqueous solution was confirmed spontaneous, endothermic and possible at higher temperatures behavior of adsorption process. The adsorption mechanism of UO22+ ions onto Ch-Sep composite beads was investigated by FT-IR and SEM analysis. These findings revealed the effectiveness and potential of the newly synthesized Ch-Sep composite beads for the removal of UO22+ ions.