Adsorption of sulfamethoxazole and reactive blue 19 using graphene oxide modified with imidazolium based ionic liquid

The adverse effect of organic pollutant such as dyes and pharmaceuticals on aquatic life is of great concern. Thus, in this work, a highly hydrophobic composite made up of graphene oxide (GO) and ionic liquid (IL) was synthesized for the removal of reactive blue 19 (RB19) and sulfamethoxazole (SMZ). GO was first synthesized with the Tour method and the long chain C14 imidazolium IL through a green technique. ¹³C, ¹H NMR and HRMS were used to determine the structure of the synthesized ionic liquid. GO-IL was produced by co-precipitation of GO and IL. FTIR confirmed the presence of the new functional groups on GO-IL. XRD confirmed GO synthesis and the crystalline nature of GO-IL. SEM and TEM confirmed the sheet like morphology of GO and GO-IL and showed enmeshment of IL in the lateral GO sheets. The experimental conditions for the adsorption of RB19 on GO was at 25℃, with pH 2.04 and 3 g/L dose of adsorbent. For GO-IL the optimum dose of 0.5 g/L and 0.9 g/L at pH of 4.01 and 6.28 for RB19 and SMZ adsorption, respectively. Maximum adsorption (qm) of 27.25 mg/g and 416.7 mg/g were obtained for adsorption of SMZ and RB19, respectively on GO-IL. Thermodynamic studies revealed adsorption was exothermic and the data obtained supported the pseudo-second order kinetic model, and both Langmuir and Freundlich isotherm models. The adsorption mechanism was attributed to hydrophobic effects, hydrogen bonding, electrostatic and π-π interaction. Regeneration studies showed adsorbent reusability. This is the first report that shows the adsorption study of RB19 and SMZ on GO modified with a C14 long chain imidazolium IL. The hybrid adsorbent improved dispersion in aqueous medium, thus enhancing efficiency and cost effectiveness for the removal of RB19 and SMZ. This study helps to provide mechanistic insight into the adsorption process of RB19 and SMZ.