Adsorption Behavior of Methylene Blue Dye by Novel CrossLinked O-CM-Chitosan Hydrogel in Aqueous Solution: Kinetics, Isotherm and Thermodynamics

Abstract

The chemical cross-linking of carboxymethyl chitosan (O-CM-chitosan), as a method for its modification, was performed using trimellitic anhydride isothiocyanate to obtain novel cross-linked O-CM-chitosan hydrogel. Its structure was proven using FTIR, XRD and SEM. Its adsorption capacity for the removal of Methylene Blue (MB) dye from aqueous solution was studied. The effects of different factors on the adsorption process, such as the pH, temperature and concentration of the dye, in addition to applications of the kinetic studies of the adsorption process, adsorption isotherm and thermodynamic parameters, were studied. It was found that the amount of adsorbed MB dye increases with increasing temperature. A significant increase was obtained in the adsorption capacities and removal percentage of MB dye with increasing pH values. An increase in the initial dye concentration increases the adsorption capacities, and decreases the removal percentage. It was found that the pseudo-second-order mechanism is predominant, and the overall rate of the dye adsorption process appears to be controlled by more than one step. The Langmuir model showed high applicability for the adsorption of MB dye onto O-CM-chitosan hydrogel. The value of the activation energy (Ea) is 27.15 kJ mol−1 and the thermodynamic parameters were evaluated. The regeneration and reuse of the investigated adsorbent was investigated.

Kinetics, Isotherm and Thermodynamic Studies for Efficient Adsorption of Congo Red Dye from Aqueous Solution onto Novel Cyanoguanidine-Modified Chitosan Adsorbent

“…The type of adsorption process, whether it is physisorption or chemisorption, can be determined by the magnitude of activation energy. When the activation energy is found in the range 0-40 kJ mol −1 , this indicates that the reaction is physisorption, while if it is in the range 40-800 kJ mol −1 , the reaction is chemisorption [24]. The value of E a for the adsorption of CR dye onto CCs was 2.47 kJ mol −1 , as illustrated in Figure 16.…”

“…q t = (k int t 1/2 ) + C (10) where k int is the intraparticle diffusion constant (mg g −1 min −1/2 ), C is a constant (mg g −1 ) that is directly proportional to the boundary layer thickness. Both values of k int and C can be obtained by calculations from slope and intercept resulted from the linear curve of q t versus t 1/2 , respectively [24].…”

“…% Dye desorption = q d /q a × 100 (22) where q d is the amount of desorbed dye from the adsorbent surface (mg g −1 ) and q a is the amount of the dye adsorbed onto the adsorbent (mg g −1 ) [24].…”

Synthesis and Characterization of Novel Uracil-Modified Chitosan as a Promising Adsorbent for Efficient Removal of Congo Red Dye

“…where k int (mg g −1 min −1/2 ) is the intraparticle diffusion constant, C (mg g −1 ) is a constant that is directly proportional to the boundary layer thickness [18].…”

“…Studying thermodynamic parameters will give a better understanding of the adsorptive behavior for the dye towards adsorbents. Changes in Gibbs free energy, ∆G • (kJ mol −1 ), enthalpy change, ∆H • (kJ mol −1 ), and entropy change, ∆S • (J mol −1 K −1 ), were calculated for the adsorption of CR dye using four different temperatures (298, 308, 318 and 328 K) according to Equations ( 17) and (18).…”