CO₂-Activated Adsorption: A New Approach to Dye Removal by Chitosan Hydrogel

Abstract

This study focuses on development of a new adsorption technique by CO 2 -activated chitosan. Carbon dioxide was utilized to form the functional chemical groups of chitosan on the adsorptions of anionic dyes, Brilliant Blue FCF and Congo Red, in the aqueous solution. CO 2 -activated chitosan results in the dye adsorption significantly faster than that of chitosan in pure water. The adsorption capacities and removal efficiencies of the dye are increased by CO 2 -activated chitosan. Furthermore, the dye adsorptions on CO 2 -activated chitosan were investigated at various temperatures and initial dye concentrations in the aqueous solution. Interestingly, the high temperature adsorption provides the enhancement of adsorption capacities and removal efficiencies of the dye by the carbamate cross-linking of chitosan with CO 2 . CO 2 -activated chitosan was further characterized by Fourier transform infrared spectra, amino group ratio, zeta potential, and thermal gravimetric analysis. These characterizations can be used for understanding the unique adsorption of the dye on CO 2 -activated chitosan. Carbon dioxide-activated chitosan in this work will provide an effective operation and a clean process of dye adsorption in wastewater treatment.

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

“…In our previous work (Le et al, 2018), it was found that since carbamate cross-link formation, is exothermic, an increase in temperature would not favor cross-link formation 63.72 0.44×10 −3 g mg −1 min −1 39.4 Fig. 7 Pseudo-first-order and Pseudo-second-order fitting of BBF adsorption on CO 2 -activated chitosan; T=45°C; C 0 =20 mg L −1 ;…”

“…The removal efficiencies of BBF, O-II and CR reached 97%, 91% and 48%, respectively. In our previous work (Le et al, 2018), it was found that the electrostatic repulsion between -NH 3 + groups on CR molecules and -NH 3 + groups on CO 2 -activated chitosan leads to a lower adsorption capacity of CR compared with BBF. In this work, it can be seen that for O-II, a dye species that does not have any cationic groups, the removal efficiency is higher than CR.…”

“…In our previous work (Le et al, 2018), the high temperature in the CO 2 -activated system is required for the activation of carbamate formation, which enhances chitosan's stability and prevents dissolution. The numerical values of the fitted parameters are listed in Table 5.…”

“…The Freundlich model is an entirely empirical model, thus providing little physical meaning compared with Langmuir model. Recently, our group has introduced a CO 2 -activated system as a new dye adsorption technique (Le et al, 2018).…”

Barium/Cobalt@Polyethylene Glycol Nanocomposites for Dye Removal from Aqueous Solutions

“…Furthermore, metal–organic frameworks (MOFs) was tested for anionic and cationic dyes removal by adsorption and a zirconium-metalloporphyrin MOF [ 15 ], or a polyoxometalate (POM) composite [ 2 ], were used to enhance their adsorption capacity in aqueous solution. Dye adsorption on CO 2 -activated chitosan was studied recently, providing a simple, economical, and quick operation [ 16 ].…”