Design, fabrication, and optimization of magnetic vanadium MOF-embedded CMC–chitosan hydrogel beads for high-efficiency adsorptive removal of methyl violet 2B from aqueous media

Industrial dye discharge is one of the primary causes of water contamination, which is extremely detrimental to the community health and setting. Carboxymethyl cellulose (CMC) and chitosan (CS) crosslinked chemically using epichlorohydrin as the crosslinker were used to encapsulate magnetic vanadium metal-organic framework (MV-MOF) encapsulated within a food-grade algae matrix (MV-MOF/CMC-CS). The resulting MV-MOF/CMC-CS hydrogel beads has potential applications in elimination of methyl violet 2B (MV2B) dye. A variety of investigative methods, including X-ray diffraction, scanning electron microscope, N₂ adsorption/desorption analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, were utilized in this study. The MV-MOF/CMC-CS demonstrated effective adsorption with a surface area of 886.24 m²/g and pore volume of 4.39 cm³/g. Post-adsorption, the surface area decreased to 642.86 m²/g, and pore volume reduced to 2.86 cm³/g, indicating MV2B dye infiltration into the pores and illustrating the interaction mechanisms involved. The examination encompassed multiple factors influencing the adsorption capacity, such as temperature, duration of contact, original concentration of MV2B dye, amount of adsorbent, and the solution pH. The optimal situations for achieving maximum adsorption capability were resolute to be a pH level of 8 and a dosage of 0.02 g. The peak adsorption capacity of MV-MOF/CMC-CS for MV2B dye was measured at 764.2 mg/g. The isotherm of adsorption was analyzed by means of the Langmuir model, whereas the pseudo-second-order model provided the finest appropriate for the kinetic data. Chemisorption was recognized as the primary mechanism underpinning the adsorption process, specified by an adsorption energy of 32.8 kJ/mol. Thermodynamic evaluations showed that the uptake of MV2B dye within the micropores of MV-MOF/CMC-CS is a spontaneous and endothermic process, as demonstrated by a favorable ΔH ^o value and an unfavorable ΔG ^o value. It is suggested that the dye can be effectively removed from the MV-MOF/CMC-CS material through various adsorption mechanisms, such as electrostatic interactions, pore filling, π–π interactions, and hydrogen bonding. The application of the Box-Behnken design played a significant role in enhancing these variables within the framework of Response surface methodology.