Efficient removal of tetracycline by VCo-layered double hydroxide encapsulated with chitosan: Optimization via Box-Behnken design, and thermodynamics

The VCo-LDH/CS hydrogel beads were created by combining VCo-layered double hydroxide (VCo-LDH) and chitosan (CS) using a cross-linking process with epichlorohydrin. These beads were specifically designed to remove tetracycline (TTC). To characterize the VCo-LDH/CS hydrogel beads, several analytical techniques were used, with PXRD, XPS, FESEM, EDX, and FT-IR. The thorough characterization methods provided crucial information about the phase, crystallinity, morphology, surface properties, and chemical arrangement of the synthesized VCo-LDH/CS hydrogel beads. However, significant changes occurred in these important physical properties after TTC was adsorbed. These alterations in the physical characteristics of the VCo-LDH/CS hydrogel beads indicate that the TTC molecules have been successfully absorbed into the porous assembly of the adsorbent, filling the obtainable adsorption places and causing a decrease in the material's overall surface area, pore size, and pore volume. It was determined that a pH of 7 and an applied dosage of 0.02 g/25 mL were the most favorable conditions for achieving the highest adsorption capability of 546.6 mg/g. The Langmuir equation accurately represented the adsorption isotherm, and the kinetic information were evaluated using the pseudo- second-order model. Chemisorption was utilized for the adsorption procedure, demonstrated by an adsorption energy of 29.62 kJ/mol. Analysis of thermodynamic limits D G degrees , D H degrees , and D S degrees suggested that the adsorption procedure happened spontaneously, maintained by the progressively negative D G degrees as enthalpy and entropy values increased. This demonstrates the complex and changing nature of the adsorption procedure, with various potential mechanisms suggested to affect it, including it-it interactions, electrostatic forces, pore filling, and hydrogen bonding. The utilization of a Box-Behnken design (BBD) alongside Response Surface Methodology (RSM) enhanced the outcomes of the adsorption process.