MODIFIED HYDROXYETHYLCELLULOSE: A REGENERABLE SUPER-SORBENT FOR Cd2+ UPTAKE FROM SPIKED HIGH-HARDNESS GROUNDWATER

摘要

A benign super-sorbent, i.e., the sodic form of succinylated hydroxyethylcellulose (HEC-Suc-Na), was investigated for the sorption efficiency to remove cadmium (Cd) from spiked high-hardness groundwater (HGW). Hydroxyethylcellulose succinate (HEC-Suc) was synthesized and converted into its sodic form by treating with saturated NaHCO3 solution. Batch-wise methodologies were used to sorb Cd2+ from HGW solution by HEC-Suc-Na. The results show that more than 90% Cd2+ removal was achieved within the first 30 min at pH 6 from HGW at 298 K. The Langmuir isotherm model and the pseudo-second order kinetic model provided the best fit for the sorption data of Cd2+ uptake. The estimation of the thermodynamics parameter indicated the spontaneous and exothermic nature of the sorption. As compared with other polysaccharidal sorbents, HEC-Suc-Na suggested its highest efficiency for Cd2+ uptake from HGW (666.66 mg g(-1)). The sorbent showed high selectivity for Cd removal over background ion naturally present in HGW. The sorbent was easily regenerated using mild conditions and used for Cd2+ uptake over three cycles with no significant decrease in its sorption capacity. It suggests the possibility for manifold use of the sorbent before it needs to be replaced.