Ionic liquid assisted mesoporous silica-graphene oxide nanocomposite synthesis and its application for removal of heavy metal ions from water

Abstract

Ionic liquids (ILs) have attracted huge interest as templates for the fabrication of porous materials, as the possibility exists for the IL to act as both the solvent and porogen in such systems. Towards this objective, in this work, porous silica–graphene oxide nanocomposite(GO-SiO2) was synthesized using IL assisted solvothermal method. The N2 adsorption-desorption isotherm data showed that by using IL as a template highly mesoporous composite with higher surface area of 858 m2/g and average pore diameter of 5.3 nm can be obtained. Various other physiochemical properties of the nanocomposite were investigated by several sophisticated characterization techniques such as UV–Vis, FTIR, XRD, TGA, FESEM, HRTEM, XPS, and Raman spectroscopy. Later on, the synthesized GO-SiO2 nanocomposite was used as a versatile nanoadsorbent for Pb(II) and oxidized As(III) removal from water. Detailed adsorption mechanism was thoroughly studied via XPS. The effect of various parameters on adsorption such as pH, contact time, initial metal concentration and the nanoadsorbent amount was also investigated. The maximum adsorption capacities of our mesoporous nanocomposite towards Pb(II) and As(III) were found to be 527 mg/g and 30 mg/g, respectively. Kinetic studies indicated that the experimental details fit well with the pseudo-second-order kinetic model for both the adsorption process. It was also found that the Langmuir model was more suitable for Pb(II) adsorption whereas the Freundlich model was for oxidized As(III) adsorption. The thermodynamic parameters(ΔG < 0, ΔH > 0, and ΔS > 0) indicate the adsorption process was endothermic in nature and spontaneous. The synthesized GO-SiO2 nanocomposite was reusable without any significant loss for 4 cycles.