Regeneration of an Aqueous Cleaner Using Ultrafiltration: A Case Study

his article describes the use of an ultrafiltration process for the T regeneration of an aqueous alkaline cleaner. Techniques for regeneration of aqueous cleaners are desirable due to the large number of industrial users that have replaced vapor degreasers with aqueous cleaners. Successful regeneration of aqueous cleaners would result in large cost savings for these industrial users who are currently paying for disposal and replacement of contaminated aqueous cleaners. Lockheed Martin Tactical Aircraft Systems (LMTAS) has replaced all of its vapor degreasers and cold cleaning tanks with aqueous alkaline cleaning systems for cleaning aluminum and steel parts.'-' Prior to the adoption of aqueous cleaning technology at LMTAS, trichloroethylene (TCE) was used for vapor degreasing operations and I,l,l-trichloroethane (TCA) was used for cold cleaning operations. Both TCE and TCA are toxic chlorinated solvents and TCA is an ozone-depleting compound. The Montreal Protocol London Amendments of 1990 scheduled a. 100% reduction in TCA usage by January 2005 for all ratifying nations, including the United States. LMTAS currently uses aqueous cleaners to clean metal tubing and formed metal parts. These parts are heavily contaminated with petroleum oil-based lubricants from the manufacturing process. These lubricants tend to become fully emulsified in the aqueous cleaner used at LMTAS. One of the problems with aqueous cleaners is that they lose their ability to clean when the concentration of oils in the cleaner reaches a level of several percent. At present, when the used alkaline cleaner no longer cleans effectively, it is disposed of at a significant cost to the company. Ultrafiltration has been touted as an effective method for removing emulsified and free oils from aqueous cleaners so that the cleaners can be reused. Unfortunately, very little useful information has appeared in the scientific literature concerning the use of ultrafiltration for the regeneration of aqueous cleaners. LMTAS has recently explored the use of ultrafiltration for the regeneration of an aqueous alkaline cleaner. This article describes practical experience with the use of ultrafiltration for the regeneration of aqueous cleaners in a factory setting. The evaluation of ultrafiltration technology attempted to answer the following questions: