Elimination of crystal violet from aqueous solution by adsorption on naturel polysaccharide: Kinetic, isotherm, thermodynamic studies and mechanism analysis

Abstract

The colored discharges from certain tanning industries into aquatic environments are too heavy with violet crystal; these discharges have recently become a significant environmental problem. The objective of this work is to find an effective method to stop the propagation of these micropollutants in water. Although various treatment techniques have been tested, they are often ineffective in treating these micropollutants. This study focuses on optimizing the parameters involved in the adsorption process of crystal violet (CV) using crude chitin (RC). It was found that a mass of 0.08 g of RC can effectively retain CV. Modeling of the experimental results indicated that the adsorption kinetics of CV onto raw chitin follows pseudo-second-order kinetics at the temperatures studied, and the intra-particle diffusion was not only the rate controlling step. After 80 min of contact, a saturation of the surface is obtained. The Freundlich model describes adsorption isotherms. The adsorbed quantities increase when the pH goes from 4 to 12. The thermodynamic study showed that the adsorption of CV on RC is spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). The value of pHpzc is located at pHpzc = 8.4. Characterization of the raw chitin surface by FTIR, XRD, DTA/TGA and SEM/EDS before and after contact with CV shed light on the nature of interactions between CV and RC.