Sodium hyroxyethylcellulose adipate: An efficient and reusable sorbent for cadmium uptake from spiked high-hardness ground water

Abstract

Herein, we report on the evaluation of chemically modified hyrdroxyethylcellulose for its sorption efficacy to remove Cd(II) from spiked high-hardness ground water (GW) and distilled water (DW) solutions. Hyrdroxyethylcellulose was chemically modified using adipic anhydride in the presence of DMAP as a catalyst under homogeneous reaction conditions. Hyrdroxyethylcellulose adipate (HEC-Adip) obtained was then converted to its sodium salt as HEC-Adip-Na after treating with saturated solution of NaHCO3. Structures were thoroughly characterized using FTIR, SEM, EDS and solid-state CP/MAS 13C NMR. The surface charge of the sorbent was monitored by pHZPC (pH of zero point charge). The sorption data fitted well to Langmuir isotherm and pseudo-second order kinetic model. Maximum sorption capacity of Cd(II) was calculated to be 114.94 mg g−1 and 112.35 mg g−1 from DW and GW, respectively. Thermodynamic parameters, i.e., ΔH°, ΔS° and ΔG°, were also calculated and showed negative values indicating spontaneous and exothermic nature of sorption process. In addition, the synthesized sorbent is more suitable for repeated use because it shows negligible decrease in its sorption capacity for the uptake of Cd(II) from aqueous solution after five regeneration cycles. Keywords: Hydroxyethylcellulose, Sodium hydroxyethylcellulose adipate, Metal uptake, Cadmium, Kinetics