Adsorption Optimization of VNi‐Layered Double Hydroxide Encapsulated With Chitosan and Carboxymethyl Cellulose for Rhodamine B Dye Removal From Aqueous Solutions: Adsorption Isotherm, Kinetics, and Thermodynamics

Abstract

Industrial dye–contaminated wastewater needs creative techniques to effectively remove these contaminants. An easy co‐precipitation technique was used in this work to create the VNi‐layered double hydroxide (VNi‐LDH) adsorbent. VNi‐LDH was encapsulated with chitosan (CS) and carboxymethyl cellulose (CMC) that cross‐linked with itaconic acid as the cross linker via chemical crosslinking to form VNi‐LDH/CS‐CMC hydrogel beads. FT‐IR, SEM, XPS, BET, XRD, BET, and point of zero charge (pHzpc) were employed to characterize the prepared material. Examining VNi‐LDH/CS‐CMC's ability to remove rhodamine B (RB) from water waste as an adsorbent was the aim of the study. The highest adsorption capacity of RB on VNi‐LDH/CS‐CMC was found to be 653.8 mg/g. The research findings designated that the Langmuir isotherm models provided the most accurate representation of the RB adsorption procedure for VNi‐LDH/CS‐CMC. At a dosage of 0.8 g/L for the adsorbent and an equilibrium time of 100 min, it was established that the RB adsorption of VNi‐LDH/CS‐CMC hydrogel beads occurred at a pH of 8. The model of pseudo‐second order, demonstrating chemisorption with an adsorption energy of 30.34 kJ/mol along with a diffusion‐limited adsorption process, was most appropriate for the RB adsorption kinetics on VNi‐LDH/CS‐CMC hydrogel beads. The impact of temperature was also investigated, with an analysis of the thermodynamic variables (∆H°, ∆S°, and ∆G°) revealing a spontaneous increase in positive enthalpy and entropy charge, along with a decrease in ΔG°, as the temperature rose. The adsorption process outcomes were further optimized using response surface methodology (RSM) and the Box–Behnken design (BBD). It was proposed that the elimination of RB through VNi‐LDH/CS‐CMC may occur through different potential mechanisms, such as chemisorption, pore‐filling, π‐π bonding, electrostatic interactions, and hydrogen bonding. Given that the adsorbent was made of reusable materials and could be reused more than six times with high efficiency, the VNi‐LDH/CS‐CMC hydrogel beads offer a viable low‐cost option for removing RB dye from wastewater streams.