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

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.