Surfactants under control by Tensioline

Press release / June 01, 1998

At the Fraunhofer IGB an apparatus has been developed for the automatic on-line controlling of surfactants concentration in industrial process and cleaning baths or in surface waters.

Whether washing the car or the dishes or taking a shower - it is always the surfactants that make things getting clean. Because of their molecular structure surfactants are capable to render the otherwise unsoluble dissolvable and therefore are used for many applications in industry. A car for example meets surfactants already whilst being manufactured. As additives in electroplating baths they make chromed auto parts shiny by providing an even layer formation. And before carbody sheets are primed and painted, surfactants help to degrease them cleaning baths.

Usually the surfactants hereby are consumed. However, in order to guarantee a constant product quality, they have to be replenished. Therefore, monitoring of the surfactant concentration is required to reduce costs for manufacturing as well as for disposal and to not unnecessarily pollute the environment. Untill to date, various samples have to be taken and analyzed subsequently in the laboratory. This does not only take time and money but also endangers the staff members working at electroplating baths which often contain toxic and harmful substances. Scientists at the Fraunhofer Institute for Interfacial Engineering and Biotechnology found a solution: They developed an apparatus called "Tensioline" which facilitates the automatic determination of surfactants in water solutions.

"Tensioline" constitutes an advanced form of drop-volume tensiometry. In principle, the surface tension is evaluated from the measured volume of drops which form at the end of a capillary tube. The automatic tensiometer is easy to handle and - when furnished with relevant pilot valves - can be used for parallel control of several baths. According to Dr. Christian Oehr, head of IGB's interfacial engineering department, Tensioline's most advantageous feature is "that controlling can be carried out on-line without interfering with the manufacturing process. This enables an immediate reaction on dropping concentrations."

Furthermore, "Tensioline" is not only applicable in manufacturing processes but also opens new perspectives in controlling contamination of surface waters. Surfactants are toxic to fish, crabs and larvae, and as organic contaminations increase both COD and BOD. An automatic device for control of surfactants and their degradation products in rivers and is a task for further development.

Meanwhile, the second prototype of "Tensioline" is being constructed. The new method is ready for application.