Treatment of oiled beach sand using a green and responsive washing fluid with nonionic surfactant-modified nanoclay

Abstract

Marine oil spills may cause huge economic loss and detrimental effects to the coastal ecosystem and communities. In this study, a green and responsive washing fluid was developed by modifying the nanoclay with a nonionic surfactant to wash the stranded oil on beach sand. The characterization results showed changes in the basal spacing, absorption peaks, thermal degradation, surface morphology, and element weights after modification, indicating the surfactant was successfully loaded onto the nanoclay. Batch tests were conducted to investigate the effect of washing time, temperature, salinity, pH, and the modified nanoclay concentration on washing performance. The two-level factorial analysis revealed that salinity was the most significant environmental factor to the oil removal efficiency. It also indicated the interactions of temperature with salinity and salinity with the modified nanoclay concentration were significant to the response. The separation tests suggested the addition of calcium chloride could dramatically reduce the turbidity and the oil concentration in the washing effluent. In addition, the thermodynamic miscibility model was applied to explore oil/water miscibility in the presence of the modified nanoclay, and the results were in good agreement with experiments. The proposed green and responsive washing fluid with nonionic surfactant-modified nanoclay in this study has great potential in shoreline cleanup.