Effect of temperature and use of regenerated surfactants on the removal of oil from water using colloidal gas aphrons

Discharge of industrial wastewater polluted with oil into surrounding water bodies significantly affects groundwater resources, aquatic life, and crop production. To minimize the harmful effects, it is essential to develop efficient methods to remove oil from wastewater before it has been discharged to the environment. This work aims at utilizing colloidal gas aphrons (CGAs) generated from anionic surfactant sodium dodecyl benzenesulfonate (SDBS) for the removal of oil from water. The effect of operating parameters such as initial oil concentration (25–150 mg/L), pH of SDBS solution (3–11), pH of oil solution (3–11), the volume of solution (300–500 mL), ion concentration as sodium sulfate (50–500 mg/L), and CGAs temperature (23–50 °C) were investigated. About 91% oil removal was achieved at a CGAs temperature of 50 °C, initial oil concentration of 100 mg/L, solution volume of 500 mL, pH of SDBS 5.6, and at pH of oily water 3.0. With the application of sonic energy, oil removal increased from 66% to 81%. After the first batch of flotation experiment, graphene was used to adsorb oil from foamate, thereby allowing the reuse of the treated surfactant solution for the further generation of CGAs. The total oil carrying capacity of CGAs was predicted using a simple mathematical model in which the oil packing factor followed power-law correlations as used in minerals flotation with non-dimensional parameters such as concentration, volume, pH, and temperature of the solutions.