Adsorption of Cu(II) and Pb(II) from aqueous solutions onto a metakaolin-based geopolymer

Metakaolin-based geopolymer was investigated as absorbent to remove Cu(II) and Pb(II) from aqueous solution. The effects of adsorbent quantity, pH, contact time, and initial concentration of Cu(II)/Pb(II) in solutions were investigated. Furthermore, kinetics and isothermal adsorption were fitted by using equations. Kinetic adsorption of Cu(II) and Pb(II) fitted well to pseudo-second-order model. The isothermal adsorption of two heavy metals by the metakaolin-based geopolymer fitted well with Langmuir isotherm adsorption model. The maximum monolayer adsorption capacities were found to be 178.6 mg/g (2.79 mmol/g) and 312.5 mg/g (1.51 mmol/g) for Cu(II) and Pb(II), respectively. Results clearly showed that the adsorption of metal ions on geopolymer was accompanied by ion exchange. Low-cost, convenient, and effective adsorption of Cu(II) and Pb(II) make metakaolin-based geopolymers potential candidates for heavy metal removal in wastewater treatment.