Nitrate Removal by Sorbent Derived from Waste Lignocellulosic Biomass of Lagenaria vulgaris: Kinetics, Equilibrium and Thermodynamics

Abstract

The equilibrium, sorption kinetics and thermodynamic parameters of nitrate ions sorption using a cationic modified Lagenaria vulgaris shell as a sorbent were studied. The sorption of nitrate ions was carried out from synthetic aqueous solutions in a batch mode. For this purpose, a sorbent based on waste lignocellulosic biomass was utilized. The cationic quaternary ammonium sorbent was obtained by chemical modification of raw Lagenaria vulgaris shell using (3-chloro-2-hydroxypropyl) trimethylammonium chloride reagent. The obtained results of nitrate sorption from synthetic solutions of different concentrations (2–100 mg/L) were examined by non-linear regression analysis of different reaction kinetic and multi-linear diffusion models. To describe the sorption equilibrium in the liquid–solid system, the experimentally obtained data were fitted with typical non-linear models of sorption isotherms (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Sips isotherms). To determine the thermodynamic parameters (ΔG, ΔH and ΔS), nitrate sorption experiments on CMLVS sorbent were performed at different temperatures (20, 40, 60 °C), under previously determined optimal conditions. Nitrates desorption and CMLVS sorbent regeneration was also studied.