Study on factors affecting, isotherms, kinetics, thermodynamics, and optimi- zation of chromium ion adsorption process in aqueous solution by modified mussel shells

In this study, the adsorption of chromium(VI) ions using mussel shell samples modified with organic substances, including sodium dodecyl sulfate and ethylenediaminetetraacetic acid, was investigated. The optimal conditions for the Cr(VI) ion adsorption process using modified mussel shell powder, such as pH, temperature, and time, were determined using response sur-face methodology and the Box-Behnken model, combined with Design-Expert 11.1.0.1 software. The results indicated that the adsorption capacity of Cr(VI) ions in the initial solution tended to decrease sharply, from 67% to about 24%, as the initial content of Cr(VI) ions increased from 0.1 to 10 mg/L. A similar trend was also observed in the Cr(VI) ion adsorption process as the tem-perature of the solution increased. Moreover, the ability to remove Cr(VI) ions in different pH environments was also evaluated, and clear results showed that the removal ability was best at a neutral pH. The adsorption isotherms of Cr(VI) ions by powdered modified mussel shells were investigated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm mod-els, and the equations were fitted statistically. Additionally, the kinetics of the Cr(VI) ion adsorp-tion were assessed. Optimal adsorption conditions for the removal of Cr(VI) ions by modified mussel shells were found at a solution pH of 6.61, the temperature of 46.2 degrees C, and the contact time of 2 h. The obtained results demonstrated the effective removal of Cr(VI) ions from mus-sel shell material after modification. These findings suggest that modified mussel shell powder is very promising and highly efficient for removing heavy metal ions from wastewater.