Sugar – starch – and carbohydrates – Apparatus – Treating sacchariferous material
Patent
1983-10-12
1988-01-05
Fisher, Richard V.
Sugar, starch, and carbohydrates
Apparatus
Treating sacchariferous material
127 461, 127 54, 127 55, 210263, 210295, 21050023, 210644, 210651, 210660, 21032179, C13D 316, B01D 1301
Patent
active
047174250
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION(S)
This United States application stems from PCT International Application No. PCT/AU/83/00023 filed Feb. 2, 1983.
TECHNICAL FIELD
The present invention relates to the modification of diffusion barriers by the immobilization of inorganic species therein to increase the selectivity of the barrier, and to the use of such barriers in the separation of small molecularspecies from a solution.
BACKGROUND ART
Various types of membrane diffusion barriers are known according to the published prior art. Molecular and ionic species diffuse through such membranes according to the value of their diffusion coefficient, and for that reason their selectivity is generally poor. Also known according to the prior art are liquid membranes, immobilized liquid membranes or interfacial polymerization membranes which, whilst useful in certain specific applications, suffer the same defects as other previously known membranes.
Small molecular weight separations are not easily achieved by economical industrial stage processes. Classical hyperfiltration requires high pressure and high-equipment cost for the low selectivity, low fluxes and the always present risk of membrane fouling. Chromatography, including high pressure liquid chromatography, gives excellent selectivity but is limited to laboratory scale separations, and is a too costly operation for most industrial applications. Ion exchange, ionic exclusion, transport depletion and reverse electrodialysis are processes applicable only when macro-molecules, with isoelectric points different to the overall pH, are not present in large quantities, otherwise poisoning occurs. Furthermore, high investment cost and high operating cost prohibits their use for the treatment of cheap feedstocks for the fermentation industry.
DISCLOSURE OF THE INVENTION
It is an object of this invention to provide a diffusion barrier for a fluid medium (gas or liquid) with a porosity greater than about 10-20% for channel dimensions of the order of only several Angstrom.
It is also an object of this invention to provide a selective diffusion barrier wherein a predetermined inorganic species is immobilized within the matrix thereof, to produce a diffusion barrier having a substantially uniform molecular grid structure which functions as an effective molecular screen for the selective separation of small molecules (e.g. molecular weight less than about 1,000 daltons) and provides means for the more effective separation of ionic species. The matrix used can be any known diffusion barrier e.g., sintered glass, dialysis membranes, porous metals, or any other suitable porous structure.
It is another object of the present invention to utilize existing diffusion barriers as a support to undergo chemical reaction to manufacture a substantially uniform grid of precise molecular size, with regard to the molecular size of the species to be separated.
It is an object of the present invention to provide a substitute for ion exchange; to provide a method of separating ionic species and non-charged species from an organic media wherein said method has the same effect as direct ion exchange treatment but which avoids the disadvantage of poisoning of the ion exchange resin.
It is a further object of this invention to provide a method of, and means for, the separation of small ionic or molecular species from a liquid and for fractionation of said liquid by the use of a diffusion barrier having a uniform pore or molecular grid structure or uniform permeability, wherein the diffusion of small ionic or molecular species is obtained against the osmotic current through said molecular grid structure to achieve a selectivity greater than the ratio of the relative diffusion coefficient of the separated species. As used herein, the phrase "against the osmotic current" is meant to signify the fact that in the presently claimed processes small molecular species (solutes) diffuse through the counter diffusion barrier from the side higher in solute concentration to the side lower in solute
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Fisher Richard V.
Jones W. Gary
Limitinstant Limited
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