Optimization studies for the flotation of bunker oil from contaminated sand using microbubbles

This paper studies the optimization of microbubble-aided (Sauter diameter: 80 μm) flotation technology to separate high density bunker oil from oil-wet sand using response surface methodology (RSM). A second order response function was used to model the flotation efficiency under the influence of pH, temperature, experimental duration and input flow of microbubbles. The optimum flotation parameters were found to be at temperature of 60°C, pH 8, duration of 20 minutes, and input flow of 6L/min with a predicted maximum flotation efficiency of 40.4%. This was in good agreement with the flotation experimental results of 40.1%. In comparison with the control study, the natural flotation efficiency of bunker oil was only 2.9% which reinforces the fact that the presence of microbubbles could aid the removal of oil from sand. Nevertheless, the oil-wet conditions prove difficult for efficient removal of oil contaminant. The oil contaminant was easily removed in water-wet conditions, whereby increase in water content from 0 wt% to 8 wt% increased the removal efficiency from 40.1% to 76.2% under same optimum flotation conditions. This was attributed to the presence of thin film of water which weakens the attractive force between sand and oil layer.