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Pollution Prevention and Control Technologies for Plating Operations


Section 4 - Chemical Solution Maintenance

4.3 MICROFILTRATON

4.3.2 Development and Commercialization

Although the historical roots of membrane filtration extend back to the eighteenth century, commercial and industrial applications did not emerge until the 1900ís. Early investigators experimented with animal bladders serving as membrane filters. In latter work colloidal (nitrocellulose) membranes were used, and by 1906 a technique was devised to prepare nitrocellulose membranes of graded pore size. By the 1930ís, mircroporous colloidal membranes were commercially available. During the next 20 years, other polymers were used, particularly cellulose acetate. These were used by the end of World War II for testing questionable drinking water supplies in Germany and other parts of Europe where water supplies had been damaged by the war. Research to develop these filters, sponsored by the U.S. Army, was later exploited by Millipore Corporation, the first and largest microfiltration membrane manufacturer. New developments in this area were limited until the U.S. Department of Interior sponsored research in reverse osmosis for desalination. These efforts also assisted the development of microfiltration, ultrafiltration and electrodialysis. A tremendous change occurred in this industry during the time period from 1960 to 1980. Advanced technologies were produced employing high performance membranes that were more chemically stable and mechanically sturdy than their predecessors. Also, membrane module design was advanced, with the development of the spiral-wound, hollow-fine-fiber, capillary and plate-and-frame modules. Application of the technology to degreasing and cleaning baths did not successfully occur until the development and commercialization of the ceramic membrane. These membranes, which were originally used in the food and beverage industry, could easily resist the temperatures and chemicals associated with the degreasing and cleaning baths. Also, they can be cleaned without shutting down the filtration process by back-pulsing the filter with air.

Although this application of microfiltration is fully commercialized, by no means is its development stagnant. Some respondents to the Vendors Survey indicated that equipment modifications are constantly being made to improve the process, expand its applicability, and to make it more cost effective.


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