(479b) Turbidity Control

In biobased processes it is a common task to recover valuable components from the fermentation broth by liquid-liquid extraction. Despite the advantages of this process like processing of effluents at low temperature etc., a few drawbacks may cause severe problems. A problem often encountered in biobased processes is the formation of emulsions. This behavior is caused by surface active constituents which may be byproducts from metabolizing the substrate or may be added intentionally for other purposes. Examples for these components are proteins or surfactants.

Splitting of these emulsions can be performed with several splitting methods like thermal, chemical, mechanical or electrical splitting. Due to the limited performance of thermal, chemical and mechanical splitting technologies electrical splitting was investigated. This project focused on the investigation and modelling of turbidity control in the electrical field.

The emulsions were prepared by mixing ShellSol^® K (SSK), deionized water and 4-dodecylbenzenesulfonic acid (4DBSA). Prior to the experimental investigation of splitting stable oil in water emulsions had to be prepared. The stirring intensity and the amount of dispersed phase were therefore varied in a mixing cell. Afterwards the emulsion was analyzed in a Rhosonics SUSS 2008 ultrasonic scanner. After phase separation the aqueous phase still contained residual turbidity. The turbidity (oil in water emulsion) contained 0.5 wt% of solvent phase consisting of SSK and 0.1 wt% of 4DBSA. For investigating turbidity control solvent mixtures according to this composition were prepared by homogenizing the “turbidity-mixture” with a rotor stator device IKA T18 with the dispersing element S18 N – 19 G. The separation progress for different electric field intensity and different electrode geometries was then monitored by time lapse photography. The cell was illuminated from the backside of the test cell to detect the brightness (intensity I) of the sample. A Matlab routine was used to compare the brightness I₀ before, during and after complete separation (complete separation I/I₀ = 1) and the brightness at the beginning (separation I/I₀ = 0).

The resulting separation (splitting) trends were then correlated with the field intensity.