Removal of heavy metals of cadmium and lead from aqueous solutions using graphene oxide nanosheets process optimization by response surface methodology

Abstract

Background and Objective: Water pollution due to heavy metals is a critical and increasing problem worldwide. In this study, removal of cadmium and lead heavy metals using a graphene oxide (GO) adsorbent was examined. Materials and Methods: GO nanosheets were synthesized through Hummer’s method, and its characterizations were examined using FTIR, XRD, and SEM. The effect of independent variables pH, contact time and initial concentration of the solution on removal efficiency of Cd2+and Pb2+ using response surface methodology was evaluated according to Box-Behnken experimental design. Applying quadratic model, adsorption rate of Cd2+ and Pb2+ achieved 99%. ANOVA was applied for statistical analysis of responses. Results: According to SEM images, the average size of graphene oxide sheets was 1 to 3 µm. After optimization through RSM, the adsorption capacity for Pb2+ and Cd2+ was 136 mg/g and 68 mg/g, respectively. Examination of the isotherms suggested that Cd2+ and Pb2+ adsorption follows Langmuir and Freundlich isotherm, respectively. Conclusion: the results show that the graphene oxide performed well in removing both Cd2+ and Pb2+ ions from aqueous solutions. The most influential parameters on the above-mentioned heavy metals adsorption were pH of the solution and the initial concentration.

Keywords

• oxide graphene
• heavy metals
• response surface method
• removal
• surface absorption