Modeling and Optimizing the Crystal Violet Dye Adsorption on Kaolinite Mixed with Cellulose Waste Red Bean Peels: Insights into the Kinetic, Isothermal, Thermodynamic, and Mechanistic Study

In this study, a new eco-friendly kaolinite-cellulose (Kaol/Cel) composite was prepared from waste red bean peels (Phaseolus vulgaris) as a source of cellulose to serve as a promising and effective adsorbent for the removal of crystal violet (CV) dye from aqueous solutions. Its characteristics were investigated through the use of X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and zero-point of charge (pH(pzc)). The Box-Behnken design was used to improve CV adsorption on the composite by testing its primary affecting factors: loading Cel into the composite matrix of Kaol (A: 0-50%), adsorbent dosage (B: 0.02-0.05 g), pH (C: 4-10), temperature (D: 30-60 degrees C), and duration (E: 5-60 min). The significant interactions with the greatest CV elimination efficiency (99.86%) are as follows: BC (adsorbent dose vs. pH) and BD (adsorbent dose vs. temperature) at optimum parameters (A: 25%, B: 0.05 g, C: 10, D: 45 degrees C, and E: 17.5 min) for which the CV's best adsorption capacity (294.12 mg/g) was recorded. The Freundlich and pseudo-second-order kinetic models were the best isotherm and kinetic models fitting our results. Furthermore, the study investigated the mechanisms responsible for eliminating CV by utilizing Kaol/Cel-25. It detected multiple types of associations, including electrostatic, n-p, dipole-dipole, hydrogen bonding interactions, and Yoshida hydrogen bonding. These findings suggest that Kaol/Cel could be a promising starting material for developing a highly efficient adsorbent that can remove cationic dyes from aqueous environments.

Automated summary

In this study, a new Kaol/Cel composite was prepared from waste red bean peels as a source of cellulose and demonstrated high adsorption capacity for crystal violet dye. The Box-Behnken design was used to optimize the adsorption process, with the best conditions resulting in 99.86% CV removal and an adsorption capacity of 294.12 mg/g. The Freundlich and pseudo-second-order kinetic models were found to best describe the adsorption behavior. The study also investigated the mechanisms behind CV removal, identifying various types of interactions involved. These findings highlight the potential of Kaol/Cel as a highly efficient adsorbent for cationic dyes in water.