Multifunctional polysaccharide structure as green adsorbent for chlorophenols removal from aqueous solutions: experimental and modeling approaches

Abstract

A trifunctional polysaccharide structure based on a biodegradable matrix, Chitosan/Alginate-PolyEthylene-Imine-Phenyl-Phosphonamidic Acid (CHIT/ALG-PEIPPAA) was synthesis via a condensation reaction, using glutaraldehyde as cross linking agent. The aim of this research work is to investigate the chlorophenols adsorption in the batch process from an aqueous medium. The influence of several parameters like pH, time reaction, initial concentration, and ionic strength was followed carefully in this study. Scanning electron microscopy (SEM) micrographs show a heterogeneous morphology with different particle sizes of agglomerates around a few micrometers, and irregular particles shape. The FTIR spectrum and Zeta potential characterization confirms the presence of several hydrophilic groups and a high positive charge around 31.4 mV for CHIT/ALG-PEIPPAA surface adsorbent. The optimum pH solution for chlorophenols removal was reached at an initial pH of around 4.4. The maximal adsorption capacity was found to be 118 mg.g− 1, and 249 mg.g− 1 under optimum conditions for 4-chlorophenols and 2–4 chlorophenols respectively. The kinetic modeling followed the pseudo-second-order rate expression for both chlorophenols molecules. Thermodynamics data leads to an exothermic and spontaneous adsorption process (∆H = − 6.98KJ.mol− 1; ∆H = − 2.74KJ.mol− 1), respectively for 4-chlorophenols and 2–4 chlorophenols. The regeneration process of CHIT/ALG-PEIPPAA is more favorable in the presence of hydrochloride acid (2.0 mol.L− 1), up to 78%, and 91% of desorption yield for 4-chlorophenols and 2–4 chlorophenols, respectively.