Turbidity Control – Cleavage of Stable Emulsions

Emulsions are major issues in different processes. It is for example a common task in biobased processes to recover valuable components from the fermentation broth. This is for example done by liquid-liquid extraction. Despite the advantages of this unit operation like the processing at low temperature there are a few drawbacks which have to be overcome. The ability of emulsification is a specific problem which is often encountered in biobased industry since surface active components may be side products in the broth. Both the extract and the raffinate phase can be contaminated with unwanted turbidity. However the results are very different. While a contamination in the extract phase may reduce the product quality, stable solvent fines in the raffinate phase limit the wastewater quality and the economic feasibility of the process due to solvent loss.

Turbidity control of the raffinate phase can be performed using different techniques like thermal, chemical, mechanical or electrical splitting. While the first two are quite expensive in terms of energy and material demand the latter two can be provided in an efficient way. In this context admixture of flocculants as example for chemical splitting shall be mentioned. This operation may help to control turbidity, but a second separation step is necessary to recover the flocculating agent. Additionally a negative impact on product quality has to be considered.

This project focuses on turbidity control of aqueous effluents using flotation as example for mechanical splitting and electro coalescence, which can be seen as a representative of electrical splitting technology. A dodecane spiked aqueous feed emulsified with surfactants and a high shear mixer is prepared as effluent. To compare the results with the cleavage of an industrial effluent the settling behavior is investigated in the flotation equipment as well as in the electric field coalescence equipment. For this experiments the aqueous phase consisted of different mixtures of alcohols, carboxylic acids and water and the organic phase of undecane and 4‑dodecylbenzenesulfonic acid (4DBSA). Phase separation experiments are monitored using a camera to see even slightest changes in the system. Flotation technique as well as electro coalescence as well as technology combinations are applicable for successful turbidity control.