Ultrafiltration future

Segall, M.D., Measurement of drug-protein binding by immobilized human serum albumin-HPLC and comparison with ultrafiltration, Future Drug Discov., 81, 2004. 

Since membranes no longer had important nuclear applications in future, SPEC was sold in 1987 by the CEA to the French company Rhone-Poulenc which merged them with their polymeric membrane division to form the new subsidiary, currently known as Tech Sep. Zr02 based ultrafiltration membranes on 6 mm inner-diameter carbon tubes continues to be the main product line of Tech Sep in terms of inorganic membranes. 

The principles behind ultrafiltration are sometimes misunderstood. The nomenclature implies that separations are the result of physical trapping of the particles and molecules by the filter. With polycarbonate and fiberglass filters, separations are made primarily on the basis of physical size. Other filters (cellulose nitrate, polyvinylidene fluoride, and to a lesser extent cellulose acetate) trap particles that cannot pass through the pores, but also retain macromolecules by adsorption. In particular, these materials have protein and nucleic acid binding properties. Each type of membrane displays a different affinity for various molecules. For protein, the relative binding affinity is polyvinylidene fluoride > cellulose nitrate > cellulose acetate. We can expect to see many applications of the affinity membranes in the future as the various membrane surface chemistries are altered and made more specific. Some applications are described in the following pages. 

There remain some exciting challenges in the oil-refining industry for the future. The introduction of new technologies (e.g., use of enzymes, ultrafiltration, etc.) may require the development of specific refining and deodorization methods. 

Whether we cail the process we have talked about during this week reverse osmosis or hyperfiltration or ultrafiltration is of little importance. The important thing is that the membrane invented by Loeb and Sourirajan slightly over 20 years ago is a marketable product and has a fantastic future. Too often we allow semantics to act as a barrier to our mutual understanding of this technology. 

Focusing on the recent advances and updates, this section addresses new development in chemical and pharmaceutical industries and in the conservation of natural resources. Included in this edition are newer practices and technologies and their applications or trends for future applications with relevant references that have appeared in the literature since the first edition was published. Several new chapters on emerging areas such as membrane separation in petrochemical oil refinery, chitosan as new material for membrane preparation, new membrane material for ultrafiltration (UF) and nanofiltration (NF), and potential application of reverse osmosis (RO) in chemical industry have been added in the second edition. 

Tremendous opportunity exists for hybrid processes consisting solely of membrane processes or a combination of membrane and non-membrane processes. Of the large number of potential combinations, studies of several are reported in the literature including nanofiltration with reverse osmosis [99] nanofiltration with electrodialysis [100] ultrafiltration with nanofiltration and reverse osmosis [101] ultrafiltration with membrane distillation [102] nanofiltration with reverse osmosis and a microfiltration membrane-based sorbent [103] microfiltration with flotation [104] microfiltration and ultrafiltration with ozone and activated carbon adsorption [105] and membrane processes with photocatalysis [106-107]. Despite the activity in this area, a comprehensive approach to designing hybrid systems does not exist future work would benefit from the development of such a design framework. 

Ceramic membranes, which are tougher and longer lasting than polymeric membranes, offer many advantages in ultrafiltration applications but are more than 10 times more costly than equivalent polymer membranes. Thus their use has been limited to small-scale, high-value separations that can bear this cost. One area where ceramic membranes may find a future use is clarification of chemical or refinery process streams, where their solvent resistance is needed. However, it is difficult to see a major business developing from these applications unless costs are reduced significantly. 

A future potential use for ultrafiltration might be in combination with the fractionation techniques described earlier. Using ultrafiltration it should be possible to concentrate the proteins in each of the individual fractions. As a result, more functional ingredients might be prepared. The possibilities of ultrafiltration to remove minerals from solutions might aid in the desalting and removal of phosphate from these proteins after fractionation. 

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