IL22614A - Ion-specific membranes - Google Patents

Description

3 TS AND ORDINANCE SPECIFICATION I ION SPECIFIC Bloeh a Swiss citizen of 13 Hanoi Aharon an Israeli citizen of 18 Ora of 19 an Israel citizen and David Israel citizen of do hereby declare the nature of our invention and in what manner the same is to be to be particularly described and ascertained in and by the following The present invention relates to further improvements and modifications of membranes for the separation of certain predetermined components out of In our copending patent applications 18686 and 21709 there have been described novel electrically uncharged membranes adapted or the separation of certain components out of AB distinguished from conventional the permeability of which is based on electrostatic and as contrasted with conventional dialysis which are terized by their the novel membranes according to the foregoing and according to the present invention are designated by us as Solubility Amongst the main economic considerations which determine the feasibility of the use of solubility membranes are initial rate of permeation and durability of the The rate of permeation is determined by both the concentration as as its fractional While the concentration gradient within the membrane depends on the concentration of the permeating species in the phase outside the on the partition coefficient of this species between aqueous phase and the membrane phase and membrane the fractional resistance is a function of the physical structure of the depending on parameters such as plasticity or One way to increase the concentration gradient within membrane and to decrease frictional resistance is to decrease the thickness of the The minimum thickness is determined by the required mechanical and according to the present invention it becomes possible to produce solubility membranes characterized by advantageous properties in this According the present invention there are provided selective solubility membranes of high mechanical strength and a high rate of The novel solubility membranes according to the present invention comprise a support of diffusion resistance respective the permeating It has been found that such novel membranes be advantageously prepared by using paper of adequate wet strength as and especially parchment paper as this is porous and has adequate mechanical The paper support is treated as will be set out in detail and membranes thus produced can be advantageously for the separation of various According to the present invention the novel membranes are prepared by applying to paper of adequate wet strength a thin coating of an inert carrier polymer and of a plasticizer which also as selective Theoretically the coating Could be reduced to a few molecules In practice the minimum thickness is determined by techniques adapted to result in and satisfactory results can be obtained with conventional coating techniques with coatings of about 10 microns According to a preferred embodiment of the invention the coating is applied to parchment paper and comprises a plastisol polyvinyl chloride containing as plasticizer a compound which acts as selective The ratio of plastic to plasticizer and the conditions of curing of the membrane are rather Critical and the lifetime of the membrane as well as its The principle of operation believed to be similar to that In solvent where a separation between different species a solution effected by virtue of the extrao able species being by the solvent has the property of selectively dissolving that species out of the mixture with the other The material comprising the membrane according to the present invention has the property of dissolving one or several species out of a mixture with other thus transmitting said species from one compartment of the cell to the hile at the same time providing a transmitting barrier against other species contained the It well known that specific solvents are being used for metal ion separations hydrometallurgical extraction Particularly well known is the case of extraction of uranyl while in aqueous solution admixture with such as aluminum and by means of extracting solvent is highly for uranium It has been shown that the group essential for extraction of the uranyl nitrate species is the group present in the e provided the remaining valencies of the central phosphorus atom are properly substituted by other a number of aliphatic esters of phosphoric such as and other alkyl phosphates are t suitable as Other compounds containing the such as are suitable for the dame Hydrometallurgical separations by means of these or similar compounds are not restricted to the separation The membranes according to the present invention are baeed on the use of compounds of the kind described These are both for particular species or and are also capable of polyvinyl chloride or copolymers containing nant amount of By using such phosphorus compounds in combination with polyvinyl it is possible to prepare thin and durable supported by means of an and mechanically strong The ratio of plastizlser to resin oan be varied within quite wide I has been found that a ratio of from to parts by weight of plastizlser per part of gives satisfactory the ferable ratio being The proper incorporation the compound into the said enabling the production of free for the above purpose may be achieved by several ventional for a well known technique widely used in the coating trade is to this a fine powder of suitable admixed specified proportion of the phosphorus forming a fine viscous called The mixture is then applied by mean of a knife onto the backing it paper or so that a layer of plastisol of predetermined thickness is The coated is then placed an oven at a temperature which is usually the range and for a short during gellatlon sets With most of the membranes according to the presen with coatingsof from about 10 to and preferably to 60 the gellatlon time usually about minute at about In the following the invention will be described by way o example only with reference to paper membranes coated vith a plastisol containing a plasticizer which serves as selective ought to be clearly understood that this is by way of exmple only and that paper membranes can be prepared also by other methods adapted to introduce selective as set out in the aforementioned copending patent In the following there will be illustrated the preparation of a number of examples of the novel solubility membranes and the use of same for the separation of certain predetermined EXAMPLE 1 A solubility membrane was prepared by applying by a uniform layer of about 30 microns of a mixture of parts of tributyl phosphate and 1 part polyvinyl chloride to Kraft paper of high vet strength of 60 curing of the applied coating was effected at a temperature of during 30 resulting in the solidification of the The thus produced membrane clamped between two made of defining two compartments of 5 cm diameter and cm One of the compartments was filled with an aqueous solution molar respective uranyl molar respective iron nitrate and molar respective aluminum The second compartment was filled with distilled Dialysis during 1 hour resulted in the selective of of the while ater hours the entire quantity of uranium had passed into the second iron or aluminum passed through the 2 A cell was prepared as in Example the first compartment was charged wi an aqueous solution respective and molar respective potassium The second charged with 15 ml of After 12 hours of the copper had passed into the second Neither hydrochloric acid nor potassium rhodanide passed through the A cell prepared as in Example and the first was charged an aqueous solution molar respective aluminum 5 molar respective hydrochloric acid and molar respective ferric The seeond filled After 3 hours of the iron had passed into the second while no aluminum passed through the EXAMPLE 4 A solubility membrane prepared by coating parchmentissed Kraft paper a composition as set out in Example but the thickness of the coatin a 260 The curing vas carried out under identical cell used aa in the ras charged with aqueous solution molar respective phosphoric molar respective hydrochloric acid molar respective calcium second half cell charged ml of After 12 hours of the phosphoric acid had passed through The membrane impermeable towards A solubility membrane prepared by applying a coating of 30 microns of a mixture of parts phosphate 1 part of polyvinyl chloride curing under identical conditions as in used in the some cell the solution as in After 1 hour of the uranium passed into the after 4 hours the first hal free of Ho iron or aluminum passed into the second A solubility ma prepared by applying a coating of 30 microns of 1 part polyvinyl 1 and parts dioctyl curing effected as in cell described in 1 its first being aqueous solution molar respective sulfate end molar respective the second being charged with 1 16 hours of u a passed through hours all uranium had passed into the second iron passed through 7 By curing a 00 at lag of microns thickness consisting of phosphonate and 1 part chloride 60 seconds at on top of a paper a was obtained when tested as in 1 resulted after one hour in the passage of of the uranium initially while no iron through into the other half EXAMPLE 8 membrane was prepared by ooating Kraft er a of parte phosphinate and 1 part polyvinyl chlorid and curing at during 60 The coating had a thickness of Dialysis was effected in a as set out in During 1 hour the uranium passed iron or aluminum passed 9 A membrane prepared by applying on Kraft paper a coating of parts tributyl phosphine oxide and 1 part curing at during 60 membrane tested as set out in Example During 1 hour of the uranium passed into the second after 2 all the uranium through while no iron or aluminum insufficientOCRQuality

Claims (1)

1. particularly described the of our si and in manner the same is be claim membrane for the separation such as hereinbefore exemplified of a predetermined of an aqueous solution containing this compound together other in that tho membrane a polymer supported a mechanically polymer of polyvinyl or a copolymer containing predominantly polyvinyl tho being at least compound containing the at one of the other 3 valencies being substituted by or by an tho other 2 valencies being substituted by hydrogen or a hydrocarbon the total number of oarbon atoms of the suhstituents not exceeding per the pervious support being preferably paper of high wet A membrane as claimed in the ratio of plastioising o phosphorus to polymer being to parts by per part membrane as claimed in claim 1 or the thickness of the plastieised polymeric film is between 10 to microns and preferably to 60 membrane as claimed in any of claims to the support is paper or or of inert synthetic A membrane as claimed in any of claims 1 to therein tho phosphorus compound is a the substituents having from 5 to 12 carbon atoms membrane as claimed in any of claims 1 to n tho phosphorus compound is a An uncharged for the separation of a predetermined out of an aqueous solution of this compound together other substantially as hereinbefore described and reference to any of the A membrane as claimed in an of claim 1 to the se aration A membrane as claimed in any of claims 1 to 4 for the separation of uranium as containing as icizer an A membrane the separation of iron from aluminum in ohloric acid as claimed in any of claims 1 to wherein the plesticiaer is a A membrane as claimed in any of claims 1 to for the separation of calcium chloride from phosphoric containing as plastioiee phosphate0 dated this For insufficientOCRQuality