Elucidating the mechanism and parameters influence of the gas phase (air bubbles) in the separation of oil from a complex oil-in-water emulsion

The destabilization of a hexadecane, water, and baker’s yeast (O/W/Y mixture) emulsion by aeration and formation of a clear oil layer was investigated. The role of the air bubbles to destabilize the emulsion and form a clear oil layer was observed on previous research, but not investigated further until the current research. Initial hypotheses stated that the air bubbles were assisting the mechanism by rupturing the protein film and inducing coalescence by direct contact between droplet/droplet or droplet/oil layer, and by surface aided contact, using the bubble as a mediator for coalescence. A sensitivity analysis of the 4 phase mixture (O/W/Y/A) system to yield a clear oil layer by changing operational parameters was used to determine and explain the existing interaction of the air bubbles with the oil droplets to induce their coalescence according to the results obtained and phenomena observed. Preliminary experiments were performed to identify the factors influencing the aeration process and understand the requirements to compare the parameters individually. The dynamics of the separation process were studied using a setup consisting of 4 custom made glass columns, custom made steel plate spargers and air flow mass controllers. The value to compare the different series of experiments was the percentage of oil recovered in each column. The results revealed an influence in the four parameters changed, superficial gas velocity, height, bubble size and yeast concentration. The increase of the superficial gas velocity resulted in a higher percentage recovery but without the presence of a clear oil layer (large droplets accumulated at the top instead). The increase of height in the mixture aerated resulted in a lower percentage recovery and large droplets accumulated at the top. In contrast, the reduction of the height resulted in a very positive recovery and the formation of a clear oil layer, almost immediately. The increase of the air superficial area by reducing the bubble size produced a higher recovery but with a large variation for the results obtained with the smallest bubble size. The increase of yeast concentration affected negatively the percentage of oil recovered as expected. Taking these results into account the hypothesized mechanism was adapted to consider the multilayer protein adsorption at the oil and bubbles to explain the phenomena observed.

Subject

emulsion
aeration
droplets
protein
bubbles

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Embargo date

2016-07-15

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Student theses

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master thesis

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