Fabrication of low-cost magnetic Kaolin/Graphene oxide nanocomposites for oil droplet removal from oil-in-water emulsions: batch adsorption experiments

Abstract

Low-cost nanocomposites composed of magnetite, and kaolin clay with two-dimensional graphene oxide (Fe₃O₄@GO@Ka) were fabricated with different ratios of graphene oxide (GO@Ka_1(2:1), GO@Ka_2(4:1), GO@Ka_3(8:1)) by cheap, and simple approach for oil droplets adsorption. FT-IR, XRD, SEM, HR-TEM, VSM, and BET were utilized to characterize Fe₃O₄@GO@Ka morphology and structure. The outcomes of characterization demonstrated that the graphene oxide had been prepared successfully on the kaolin surface. The influence of contact time, composite amount, oil droplets concentration, temperature, and pH of emulsion on the adsorption process was tested. The adsorption outcomes demonstrated that, in each experiment condition, an increase in the graphene oxide ratio on kaolin could efficaciously improve the elimination of oil droplets from the emulsion solution. Oil removal efficiency of 99.99% was achieved by Fe₃O₄@GO@Ka₃, higher than bare kaolin (25.3%). Optimum conditions were contact time 60 min, adsorbent dose 5 mg, initial oil 25 mg/L, temperature 308K and pH 7. Pseudo-second order kinetic model fitted the data best with chemisorption mechanism. Thermodynamic parameters were ΔH° = 187.5 kJ/mol, ΔS° = 0.6600 kJ/mol K, ΔG° = − 15.81 kJ/mol at 308K, confirming endothermic and spontaneous process. Maximum monolayer adsorption capacity from Langmuir model was 1428 mg/g. XRD validated structural stability after 4 cycles of reuse. An excellent regeneration performance of Fe₃O₄@GO@Ka₃ was observed via an ethanol-washing technique. These findings show the great potential of the Fe₃O₄@GO@Ka₃ nanocomposite as an adsorbent for the removal of oil droplets from oil-in-water emulsions.