Sodium hydroxyethylcellulose succinate: an efficient ion exchanger to remove Cd(II) from single and binary metal system

This work deals with the use of a supersorbent, i.e., sodium hydroxyethylcellulose succinate (HEC-Suc-Na), for the removal of Cd(II) ions from aqueous solution. HEC-Suc was fabricated via esterification of HEC with succinic anhydride in the presence of dimethylaminopyridine (DMAP) as a catalyst. The treatment of HEC-Suc conjugate with saturated NaHCO3solution provided HEC-Suc-Na (sodic form). These acidic and sodic forms of the sorbent were characterized by Fourier transform infrared and energy-dispersive spectroscopy. The surface morphology and charge on the surface of sorbent were monitoredby SEM and pH corresponding to point of zero charge. Sorption data conceded well to the pseudo-second-order kinetic and Langmuir isotherm model. Maximum sorption capacity of HEC-Suc-Na for Cd(II) removal as calculated by Langmuir model was 714.2 mg g–1. Moreover, no significant decrease in the sorption capacity of the sorbent was found after five regeneration cycles suggesting its repeated use. Thermodynamic parameters (∆G°, ∆H° and ∆S°) showed negative values that indicate spontaneity and exothermic nature of the sorption process. Removal of Cd(II) in presence of Ni(II) was also studied.