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

Abstract

Novel Cyanoguanidine-modified chitosan (CCs) adsorbent was successfully prepared via a four-step procedure; first by protection of the amino groups of chitosan, second by insertion of epoxide rings, third by opening the latter with cyanoguanidine, and fourth by restoring the amino groups through elimination of the protection. Its structure and morphology were checked using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The adsorption capacity of CCs for Congo Red (CR) dye was studied under various conditions. It decreased significantly with the increase in the solution pH value and dye concentration, while it increased with increasing temperature. The adsorption fitted to the pseudo-second order kinetic model and Elovich model. The intraparticle diffusion model showed that the adsorption involved a multi-step process. The isotherm of CR dye adsorption by CCs conforms to the Langmuir isotherm model, indicating the monolayer nature of adsorption. The maximum monolayer coverage capacity, qmax, was 666.67 mg g−1. Studying the thermodynamic showed that the adsorption was endothermic as illustrated from the positive value of enthalpy (34.49 kJ mol−1). According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The value of ΔS° showed an increase in randomness for the adsorption process. The value of activation energy was 2.47 kJ mol−1. The desorption percentage reached to 58% after 5 cycles. This proved that CCs is an efficient and a promising adsorbent for the removal of CR dye from its aqueous solution.

Fabrication of polyamide-12/cement nanocomposite and its testing for different dyes removal from aqueous solution: characterization, adsorption, and regeneration studies

“…Therefore, electrostatic attraction between the positively charged surface of PA-12/PC nanocomposite (pH < 5) and negatively charged CR results in adsorption, while from pH 5 to 10, there is electrostatic repulsion between anionic charges of both PA-12/PC nanocomposite and CR, resulting in decreased adsorption. Recent studies have also reported pH 4 as an optimum pH for CR adsorption 69 , 70 . For other cationic dyes, i.e., BG, MB, and MR, qe increases with increasing pH from 2 to 6 and then decreases slightly with increasing pH from 8 to 10.…”

Adsorptive Removal of Rhodamine B Dye Using Carbon Graphite/CNT Composites as Adsorbents: Kinetics, Isotherms and Thermodynamic Study

“…If the value of activation energy requirement is small (E a = 0–40 kJ·mol −1 ), and since the forces involved are weak, the adsorption process flows by chemical ion exchange. If the activation energy E a < 40 kJ·mol −1 , then the adsorption process is physical in nature, whereas if the E a value is within the range of 40–800 kJ·mol −1 , then the adsorption process is chemisorption in nature and involves forces much stronger (chemical bonds) than physical adsorption [ 46 , 47 , 48 , 49 , 50 ]. Therefore, the values of activation energy ( E a ) (i.e., minimum energy required for a reaction to occur), calculated using the Arrhenius equation (E a = 7.126 and 11.124 kJ·mol −1 ), are less than 40 kJ·mol −1 for KS44-0 and KS44-20, respectively ( Table 6 ).…”

Dynamic Modelling of Enzymatic Hydrolysis of Oil Using Lipase Immobilized on Zeolite

“…The Langmuir isotherm is the simplest and most common model to describe adsorption and can be effective when describing chemical adsorption. The adsorption in this model is assumed to be a monolayer, where a single layer of molecules is adsorbed on the adsorbent surface [14]. Therefore, the adsorbent surface is homogeneously structured, wherein all adsorption sites are identical, energetically equivalent, and uniform.…”