A novel loofah-like chitosan/alginate composite aerogels prepared for efficient removal of perchlorate: Experimental and DFT study

Abstract

Perchlorate, an emerging contaminant in drinking water, has attracted global attention. In this study, a novel loofah-like porous chitosan/alginate composite aerogel (CTS/SA-m) was fabricated using ionotropic pregelation and freeze-dried technology to effectively adsorb perchlorate. The performance, isotherms, thermodynamics, and kinetics of perchlorate adsorption by CTS/SA-m were systematically discussed. The results showed that the loofah-like CTS/SA-m with high hydrophilicity exhibited excellent adsorption properties. Over 95 % of the removal rate in 10 min can be achieved, with initial concentration of perchlorate and CTS/SA-m dosage of 10 mg/L and 2 g/L, respectively. And 70.15 mg/g of equilibrium adsorption capacity of perchlorate could be reached at pH 5 and 298 K. pH had little effect on the removal rate of perchlorate, the removal rate surpassed 85 % over a wide pH range of 3.0–11.0. Multilayer adsorption (MLA), intraparticle diffusion (IPD), and adsorption on the active site (AOAS) models were employed to discuss the adsorption mechanism of perchlorate. It was confirmed that double-layer chemisorption played a dominant role. Density functional theory (DFT) analysis of binding energy revealed the effect of functional groups on the ClO4− adsorption strength in the order of –NH3+ > –COOH > –NH2 > –OH. Furthermore, electrostatic potential and the independent gradient model confirmed that electrostatic interactions, hydrogen bonding, and van der Waals forces contributed to the highly efficient adsorption of perchlorate. These findings have a vital promoting effect on perchlorate removal technology in water treatment. Moreover, the loofah-like CTS/SA-m aerogel material, exhibiting outstanding performance, shows great potential in effectively in trapping perchlorate anions from aquatic systems.