Efficient removal of cationic dye from wastewater using novel low-cost adsorbent, cellulose-clay composite: Insights from isotherm, kinetic, thermodynamic, and molecular dynamics simulation studies

Abstract

This study was aimed to evaluate the potential of a natural clay modified with cellulose acetate polymer (CA) as a sustainable and cost-effective material for removing cationic dyes, particularly crystal violet (CV), from aqueous solutions. The cellulose acetate-clay composite (CA-Clay) was created by mixing CA with natural clay and characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM) and X-ray fluorescence (XRF) techniques. Batch adsorption studies were conducted to investigate the impact of contact time (10–360 min), initial concentration (50–500 mg/L), temperature (293–318 °K), and pH (2–12) on the removal of CV from aqueous solutions using both CA-Clay and raw clay. Molecular Dynamic simulations (MDS) were employed to explore the adsorptive properties of the surfaces of illite and kaolinite clay fractions and the adsorption behavior of CV on both modified and unmodified clay fractions with (CA). The results showed that the maximum equilibrium adsorption capacity for the CA-Clay and raw-Clay was 67.35 mg/g and 47.62 mg/g, respectively. The kinetic behavior and the isotherms were satisfactorily fitted with the pseudo second-order and Langmuir models, respectively. The thermodynamic parameters showed that the adsorption of CV onto CA-Clay and raw clay was a spontaneous process, and the Gibbs energy increased with increasing temperature. Molecular Dynamic simulations revealed that the higher negative value of the calculated interaction energy in the presence of the (CV-CA-Illite-Water) system was attributed to electrostatic interactions and hydrogen bonds formed between CV molecules and both the illite surface and CA oxygen atoms. Overall, this study suggests that CA-Clay is a promising adsorbent for the removal of cationic dyes from wastewater and provides insights into the adsorption mechanisms and thermodynamic parameters of CV adsorption onto CA-Clay and raw clay.