A new adsorbent of Pb(ii) ions from aqueous solution synthesized by mechanochemical preparation of sulfonated expanded graphite

Abstract

In this study, sulfonated expanded graphite (SEG) was prepared through a mechanochemical method between EG, N,N-dimethylformamide, and a sulphur trioxide pyridine complex. XRD, XPS, FT-IR, BET, SEM-EDS, and zeta potentials were used to assess the characterizations of SEG. Thereafter, the effects of pH, adsorbent dosage, initial concentration, temperature, and contact time on adsorption performances were investigated. Results demonstrated that SEG shows superior adsorption properties to remove Pb(II) with high efficiency, and the removal capacity reached 325.12 mg g⁻¹. The Langmuir model fit the equilibrium data better than either the Freundlich model or the Temkin model. Based on kinetic experiments, the adsorption of Pb(II) with SEG was perfectly described by a pseudo-second order kinetics model. According to thermodynamic parameters, the adsorption process was endothermic and spontaneous. Adsorption–desorption results showed a superior regeneration and cyclic performance of SEG as well. In addition, results of the adsorption mechanism indicated that the sulfonated functional groups played a significant role during the adsorption process.