Adsorption of cadmium onto modified nanosized magnetite: kinetic modeling, isotherm studies, and process optimization

Abstract

In this study, adsorptive removal of cadmium(II) from aqueous solutions using sodium dodecyl sulfate-modified magnetite nanoparticles was modeled. To this aim, central composite design as one of the most favorable designs in response surface methodology (RSM) was employed to optimize the removal of Cd(II) from solution under different variables such as adsorbent dosage (0.1–0.55 g), initial ion concentration (6–90 mg/L), and reaction time (5–30 min). Furthermore, the experimental data of Cd(II) adsorption were tested with various kinetic and isotherm models at various initial ion concentrations of 10–50 mg/L and adsorbent dosages of 0.1–0.25 g. The adsorption process followed the intra-particle diffusion model (R² > 0.94) very well. The equilibrium adsorption data were analyzed using various isotherm models. The results showed that Freundlich isotherm, with a relatively high coefficient of determination (R² > 0.96), fits well with the experimental results of Cd(II) adsorption. Ultimately, the optimum Cd(II) ions removal of 91.07% was obtained at the reaction time of 30 min, the adsorbent dosage of 0.35 g, and the initial ion concentration of 30 mg/L.

Keywords:

• Cadmium
• Central composite design
• Isotherm
• Kinetic
• Magnetite
• Response surface methodology

Acknowledgments

The financial support of the Environmental Technologies Research Center (ETRC) and the Research and Technology Deputy of Ahvaz Jundishapur University of Medical Sciences [grant number: ETRC9008] for the study are thankfully acknowledged.