Synthesis of pomegranate peel-activated carbon encapsulated onto carboxymethylcellulose and polyethylenimine for cadmium (II) adsorption: Optimization, kinetics and isotherm modeling

This research explores pomegranate peel as a precursor for activated carbon to eliminate cadmium (II) ions from aqueous solutions. The produced activated carbon was encapsulated with carboxymethylcellulose and polyethylenimine, then crosslinked with epichlorohydrin to form activated carbon carboxymethylcellulose and polyethyleneimine (ACCP) hydrogel beads. Numerous analytical methods were working to characterize the adsorbent, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and nitrogen adsorption/desorption isotherms. The BET analysis revealed a surface area of 110.02 m²/g, indicating a highly porous material with numerous active adsorption sites. A pore volume of 0.13 cc/g shows significant capacity for retaining adsorbed ions. The average pore radius of 1.88 nm classifies as mesopores, typically found near the transition between micropores and mesopores. Examine the influence of various factors, including pH, concentration of Cd(II), amount of adsorbent, duration of contact, and temperature, on the adsorption process. The adsorption isotherm monitored the Langmuir equation, suggesting a specific adsorption procedure. Kinetics were defined by the pseudo-second-order model, linking the adsorption rate to the square of unoccupied sites. Thermodynamic parameters yielded ΔH^o of 97.94 kJ/mol and ΔS^o of 334.8 J/mol.K, indicating an endothermic and spontaneous adsorption process. Various mechanisms for Cd(II) interaction with ACCP may include ion exchange, electrostatic forces, or complexation. Data indicate that optimal parameters for efficient Cd(II) removal in water are a pH of 6, 0.02 g of ACCP per 25 mL solution, and an adsorption capacity of 301.6 mg/g. To enhance the adsorbent's efficacy, various influential parameters must be thoroughly examined. A Box-Behnken design (BBD) and response surface methodology (RSM) are used to help identify the ideal conditions for Cd(II) adsorption. An investigation of the adsorbent's reusability over five cycles shows a substantial reliability for removal applications.