Highly efficient removal of Cu2+ from aqueous solution using chocolate clay as adsorbent in corn starch hydrogel: isothermal and optimization study

Concerns over toxic elements in water have led to a focus on effective removal methods, aligning sustainable and effective solutions. This study introduces polysaccharide-based hydrogels (PSH) without and with Chocolate clay (PSH-C) for the removal of copper (Cu2+) from simulated effluent. Characterization using Zeta potential, FTIR, TG/DTG and SEM–EDX revealed improved properties in PSH-C. Cu2+ removal experiments investigated the impact of contact time and initial contaminant concentration. Results showed that PSH-C exhibited an enhanced porous morphology and thermal stability compared to PSH. The incorporation of clay provided more functional groups, thereby improving Cu2+ removal through electrostatic interactions. From the kinetic study, the insertion of Chocolate clay reduced the removal time for 20 min. The pseudo-first-order and pseudo-second-order models effectively represented the kinetics data.The isothermal equilibrium revealed that the Langmuir model analysis is a better fit with a maximum adsorption capacity of 221 mg g−1. Key adsorption mechanisms were identified as electrostatic interaction, active site availability, and complexation. EDS analysis confirmed successful Cu2+ ion adsorption on both materials, suggesting a potential application in water treatment for heavy metals. This study introduces a modified hydrogel adsorbent that combines starch and Chocolate clay, offering a promising and sustainable solution for water treatment.