Modeling of CO₂-Activated Adsorption on Chitosan Hydrogel for Dye Removal in Aqueous Solution

Abstract

This work focuses on adsorption kinetics and isotherm modelling in CO 2-activated chitosan. Removal e ciency and adsorption capacity were measured for three anionic dyes: Brilliant Blue FCF (BBF), Congo Red (CR), Orange II (O-II) and one cationic dye: Crystal Violet (CV). While the highest removal e ciencies of BBF, O-II and CR were 97%, 91% and 48%, it was found that very low adsorption capacity occurred in the case of CV due to the repulsion between the cationic groups of CV and that of CO 2-activated chitosan. In terms of adsorption kinetics, pseudo-rst-order and pseudo-second-order models were applied. The adsorption in the CO 2-activated system was found to follow the pseudo-rst-order model. The activation of adsorption by CO 2 was found to lead to a higher adsorption rate constant and a higher adsorption capacity due to the protonation of chitosan's amino groups. Interestingly, as the temperature of the CO 2-activated system increased, the pseudo-rst-order model predicted a decrease in adsorption rate constant, k 1. This is thought to be a result of lower CO 2 dissolution into the aqueous solution, which leads to a slower protonation process of chitosan's adsorption sites. The chemical structure of the dye species a ects the adsorption kinetics in the CO 2-activated system. There are four charged functional groups on the CR molecule and three on the BBF molecule, which allow faster alignment onto adsorption sites compared with O-II molecules with only one charged group. In terms of adsorption isotherm, BBF adsorption was found to follow the Langmuir model in the CO 2-activated system.

Chitosan- or glycidyl methacrylate-based adsorbents for the removal of dyes from aqueous solutions: a review

“…In terms of the adsorption isotherm, BBF adsorption was found to follow the Langmuir model in CO 2 -CS. 84 Mixed azo dyes present in various effluents may often impair the adsorption efficiency, thereby calling into question the…”

“…Le and Shimoyama 84 focused on the adsorption kinetics and isotherm modeling in CO 2 -activated CS (CO 2 -CS). The removal efficiency and adsorption capacity were measured for brilliant blue FCF (BBF), Congo red (CR), and orange II (O-II), and the highest removal efficiencies of BBF, O-II, and CR were 97%, 91%, and 48%, respectively.…”

“…In terms of the adsorption isotherm, BBF adsorption was found to follow the Langmuir model in CO 2 -CS. 84…”

“…In terms of the adsorption isotherm, BBF adsorption was found to follow the Langmuir model in CO 2 -CS. 84 Mixed azo dyes present in various effluents may often impair the adsorption efficiency, thereby calling into question the applicability of the adsorbent in a real-time scenario. The simultaneous adsorption of acid yellow 36 (AY36) and acid blue 74 (AB74) from their aqueous solutions onto graphene oxide (GO) nanoplatelets embedded in a CS matrix (GO-CS) under ultrasound exposure was investigated.…”