Hyperfiltration membrane, dynamic

Thomas, D.G. and Watson, J.S., "Reduction of Concentration Polarization of Dynamically Formed Hyperfiltration Membranes by Detached Turbulence Promoters", I EC Process Design and Develop., 1968, T, July, 397. 

Johnson, J.S., Jr., 1972, Polyelectrolytes in aqueous solutions filtration, hyperfiltration and dynamic membranes, inrReverse Osmosis Membrane Research (H.K. Lonsdale and H.E. Pondall, Eds.), Plenum, New York, USA, p. 379. 

Dynamic membranes originated in the research at the Oak Ridge National Laboratory in the 196O s. Development has produced commercial ultrafiltration and hyperfiltration membranes for industrial separation applications. Research continues in several laboratories to improve the selectivity and productivity of the membranes and to tailor them for specific applications. The development of dynamic membranes and current research is reviewed briefly. Research on polyelectrolyte blend membranes is described in detail as a representative method for tailoring dynamic membranes. 

CARRE, Inc. also produces a series of dynamic hyperfiltration membranes on porous metal tubes. The major product is the ZOPA hyperfilter hydrous zirconium oxide-poly(acrylic acid) on porous stainless steel tubes. The hyperfiltration properties of the ZOPA membranes are also listed in Table I. The most attractive properties of the ZOPA membrane are durability at temperatures of at least 100 C, high membrane permeability, and reformation capability. The hydrous zirconium oxide-poly(acrylic acid) membranes provide modest rejection of simple electrolytes. Although the membrane permeability is high compared to most cast reverse osmosis /hyper-... 

Additional types of hyperfiltration membranes produced by CARRE, Inc. Include polyblend membranes prepared by the deposition of pairs of polymers that form miscible blends ( 5). High rejection of molecular solute species in the molecular weight range above about 80 is obtainable with these dynamic polyblend membranes. 

Dynamic Hyperfiltration Membrane for High Temperature Spacecraft Wash Water Recycle," National Aeronautics and Space Agency, 1978. 

A need exists to fractionate the solutes in the dye filtrate into retained organic and passed inorganic salt fractions. The passage of simple electrolytes occurs through ultrafiltration membranes and ion-exclusion hyperfiltration membranes at a high salt concentration. Both types of dynamic membranes were tested. 

Table IV. Chemical Analyses of Concentrate and Permeate Module i 52. for a Dynamic Hyperfiltration Membrane 5...

Dynamically-formed hyperfiltration membranes of the ZrOg polyacrylate type on porous stainless steel were used in two high volumetric recovery applications. The first is the separation of dyes from a saline dye manufacturing process effluent and the second the renovation of wash water from a dye range for reuse. The dependence of the performance characteristics on recovery is described and discussed. Separation factors (dye from salt) in the first system are large and increase with concentration in two cases, but not in a third. Acceptable rejections and fluxes for reuse of the wash water were obtained to recoveries of O.96 in the second system. The fluxes are concentration dependent. 

Belfort G. (1980), Artificial particulate fouling of hyperfiltration membranes IV. Dynamic protection from fouling. Desalination, 34,159-169. 

There is another type of membrane that is conceptually different from the membranes prepared according to the above methods. It is called dynamic membranes. They are formed, during application, on microporous carriers or supports by deposition of the colloidal particles or solute components that are present in the feed solution. This in-situ formation characteristic makes it possible to tailor them for specific applications in ultrafiltration and reverse osmosis (hyperfiltration). 

The state-of-the-art in membrane techniques is shown in the figure ( via[8])where the advances in individual membrane operations are defined in terms of availability, service reliability, and price warranty. Research on the first group of methods primarily covers process optimization problems. From the data included in the figure, it is obvious that by far the most advanced methods are the long established membrane processes such as dialysis, microfiltration, ultrafiltration, hyperfiltration, reverse osmosis and electrodialysis. It is also evident that the dynamics of sale shows a tendency to decrease. 

Following a brief review of the development of dynamic membranes and an overview of the current state of the art, Spencer (10) discusses dynamic polyblend membranes. In particular, he looks at the Influence that polymer selection and membrane preparation procedures have on membrane performance. Dynamic membranes composed of a poly(acrylic acid)/basic polyamine blend deposited on a ZOSS (hydrous zirconium oxide on stainless steel) ultrafiltration membrane are discussed. Their hyperfiltration or reverse osmosis properties are compared to the more traditional ZOPA (zirconium oxide plus poly(acrylic acid)) membrane. 

The poineering research and subsequent development of useful dynamic membranes was accomplished by Johnson and co-workers at the Oak Ridge National Laboratory. This very extensive research has been reported in a series of reports and in numerous publications and patents. Papers of special interest are the detailed report of the initial process for forming dynamic membranes with attractive hyperfiltration properties by Marcinkowsky, et al. (1 ), an early review of the research properties by Johnson ( ), and a subsequent review of hyperfiltration models and the development of hyperflltra-tion membranes by Dresner and Johnson ( ). These reviews cite the major references related to the formation, theory, properties, and applications of dynamic membranes. 

Two useful membranes developed by the group at the Oak Ridge National Laboratory have dominated the application of dynamic membranes the hydrous zirconium oxide ultrafilter and the hydrous zirconium oxide-poly(acrylic acid) hyperfilter. The technology of formation and utilization of zirconium oxide-poly(acrylic acid) dynamic membranes has been described in detail by Thomas ( ). The effects of molecular weight of the poly(acrylic acid), pore diameter of the porous support, formation cross-flow velocity, formation pressure, and pH of poly(acrylic acid) solution during initial deposition of the polyacid on the hyperfiltration performance are described and discussed. 

Table II. Hyperfiltration Properties of a Dynamic Polyelectrolyte Membrane and its Precursors...

Shor, A.J. et al.. Hyperfiltration studies. XI. Salt-rejection properties of dynamically formed hydrous zirconium(IV) oxide membranes, J. Phys. Chem., 72, 2200, 1968. 

---