Sustainable removal of Cd(II) using β-Cyclodextrin/Polyethylenimine hydrogel beads embedded with silver-MOFs: Synthesis, characterization, mechanism, and process optimization.

This research focuses on the development of a biopolymeric hydrogel adsorbent that is both environmentally friendly and highly effective. It is specifically designed to remove cadmium (II) ions from various water sources and industrial wastewater. The innovative adsorbent, designated as Ag-MOF/CD-PEI hydrogel beads, was formulated by embedding a silver based metal-organic framework (Ag-MOF) within a β-cyclodextrin (CD) and polyethylenimine (PEI) structure, which was chemically crosslinked with epichlorohydrin. A thorough investigation into the structural characteristics and surface properties of the hydrogel composite was carried out, employing a variety of analytical methods, such as XRD, FT-IR, XPS, SEM-EDX, and nitrogen adsorption-desorption isotherms. Additionally, batch adsorption tests were systematically approved to assess how variables such as interaction time, initial metal concentration, adsorbent amount, pH, and temperature impact the adsorption procedure. The optimum condition on the removal of Cd(II) was at pH 6, adsorbent dose 0.02 g, contact time 100 min. The adsorption equilibrium data demonstrated a strong position with the Langmuir isotherm model, revealing a maximum adsorption capacity of 370.7 mg/g. Kinetic analysis indicated that the adsorption procedure adhered to a pseudo-second-order model, suggesting that chemisorption is the principal mechanism at play. Statistical optimization, facilitated by the Box-Behnken design, pinpointed critical operational parameters and their combined effects on the efficiency of adsorption. Importantly, the Ag-MOF/CD-PEI hydrogel beads displayed remarkable reusability, retaining over 85 % of their initial adsorption capacity after five successive cycles.