BIODEGRADABLE MEMBRANES AND DEPTH FILTERS

In contrast to membranes, which reject material at the interface between the feed solution and the membrane, depth filters are designed to trap material within the filter structure.  Depth filters are widely used in biological separations, including the food, beverage, and pharmaceutical industries, as well as a variety of water treatment applications.  Because the trapped material builds up within the depth filter it necessarily has a short useful service period, after which it must be disposed of.  Unfortunately, current depth filters are manufactured from polymers that do not readily break down in the environment.  Consequently, disposal of depth filters poses an environmental problem.  The objective of this project is to develop depth filters from ecologically friendly biodegradable polymers.  Poly(lactic acid) is a promising candidate for the production of biodegradable depth filters for the following reasons:

·               Poly(lactic acid) is biodegradable.  Because it is biodegradable, the cost and area required for disposal is much lower than for the plastics currently used for depth filters.

·               The monomers required to make poly(lactic acid) can be made from agricultural products/by-products and food wastes.  Therefore, unlike the polymers currently used for depth filters, the cost of poly(lactic acid) is not dependent on the production and price of oil. 

·               The production of lactic acid and poly(lactic acid) has been improved recently to reduce the cost.

We are developing porous depth filters from poly(lactic acid) using the TIPS method.  The pore size, permeability, and rejection capabilities of the filter are being controlled by manipulating the kinetics of phase separation (see Membrane Formation.)

Publications from this project:

• T. Tanaka, T. Tsuchiya, H. Takahashi, M. Taniguchi, D.R. Lloyd, “Microfiltration Membrane of Polymer Blend of Poly(L-lactic acid) and Poly(å-caprolactone).”  Desalination, 193, 367–374 (2006).
• T. Tanaka, T. Tsuchiya, H. Takahashi, M. Taniguchi, H. Ohara, and D.R. Lloyd, “Formation of Biodegradable Polyesters Membranes via Thermally Induced Phase Separation.”  Journal of Chemical Engineering of Japan, 39(2), 144–163 (2006).
• T. Tanaka, S. Eguchi, T. Aoki, T. Tamura, M. Taniguchi, H. Ohara, K. Nakanishi, and D.R. Lloyd. "Production of laccase by membrane-surface liquid culture of Trametes versicolor using a poly(L-lactic acid) membrane."  Biochemical Engineering J., 33, 188–191 (2007).
• T. Tanaka, S. Eguchi, H. Saitoh, M. Taniguchi, and D.R. Lloyd, “Microporous foams of polymer blends of poly(L-lactic acid) and poly(epsilon-caprolactone).”  Desalination, 234, 175–183 (2008).