Effective elimination of industrial dye using AlCo-layered double hydroxide coated with β-Cyclodextrin and polyethyleneimine: adsorption isotherm, kinetics and optimization through Box-Behnken design

A new composite hydrogel bead, composed of AlCo-layered double hydroxide (AlCo-LDH) incorporated into a β-cyclodextrin (β-CD) and polyethyleneimine (PEI) matrix, was synthesized through the encapsulation process, followed by crosslinking with epichlorohydrin. This multifunctional material was specifically designed for the actual elimination of Basic Fuchsin (BF) dye from water. Analytical methods counting PXRD, FT-IR, XPS, FESEM, and EDX were utilized to validate the crystalline architecture, assess chemical interactions, and examine the porous morphology of the hybrid beads. UV–visible spectroscopy demonstrated a peak absorption for BF dye at 542 nm, which was utilized to track the adsorption process. The adsorption dynamics were notably influenced by aspects like the initial dye concentration, contact period, pH level, adsorbent dosage, and temperature fluctuations (between 20 and 45 °C). The maximum dye removal capacity recorded was 430.76 mg/g at pH 8, using 0.02 g of the adsorbent in a 25 mL dye solution. Post-adsorption analysis indicated a decrease in surface area, pore size, and volume, providing evidence of successful dye capture within the hydrogel structure. The adsorption mechanisms were analyzed and were determined to align with the model of Langmuir isotherm, exhibiting pseudo-second-order kinetics. This indicates a process predominantly characterized by monolayer chemisorption, with an activation energy calculated at 31.6 kJ/mol. A thorough thermodynamic evaluation produced parameters (ΔH° = + 78.57 kJ/mol, and ΔS° = + 276.4 J/mol.K) which suggest that the adsorption procedure is both spontaneous and endothermic. The fundamental mechanisms driving the adsorption involve interactions such as π–π stacking, electrostatic forces, hydrogen bonding, and effects related to pore-filling. Importantly, this synthesis marks the first instance of integrating β-CD and PEI within the AlCo-LDH framework, resulting in a stable hydrogel bead that enhances both adsorption efficacy and reusability. Moreover, the application of optimization techniques such as Box-Behnken Design (BBD) and Response Surface Methodology (RSM) has led to a notable enhancement in process efficiency. This underscores the capability of AlCo-LDH/CD-PEI beads to function as effectual adsorbents in the dealing of wastewater polluted with dyes.