Patent ES-371174-A1 (ES)
Title: Permselective,aromatic,nitrogen-containing polymeric membranes
IPC: B01J47/12
Filed: 1969-09-03
Abstract: A process for the permselective separation of components in a solution, especially an aqueous salt solution, comprises:- (a) contacting one surface of a membrane according to the invention with the solution, and (b) recovering from the other side of the membrane liquid which has passed through the membrane and which contains a reduced amount of one component of the solution. Where the membrane is in the form of a hollow fibre, the liquid referred to in (b) is recovered from the inside of the membrane. The membrane of the invention is a permselective, polymeric membrane comprising at least one synthetic, organic, nitrogen-linked, arcuate, linear condensation polymer represented by the formula -(LR) n - wherein (a) each L independently is a divalent linking group of the formula or vice versa each X independently is O or S each Z independently is H, lower alkyl, or phenyl (2) i and j are each 1 or 2 and k, 1, and m are each 0, 1, or 2 provided that i+j+k+ 1+m#8 (b) each R independently is a divalent organic radical, both of whose terminal atoms are carbon atoms (see Division B5). The L groups may be amides, hydrazides, acyl hydrazides, ureas, semi-carbazides, or oxamides or N-alkyl substituted analogues of any one thereof, or mixtures of two or more of the aforementioned groups. All the terminal atoms of R that are bonded to L may be carbon atoms and may be members of aromatic nucleii. A number of preferred structures of both L groups and R groups are listed. The membrane, which may 'be in the form of a hollow fibre, may be made by extracting an unextracted membrane composed of:- (a) 25-80%, based on the weight of solvent and polymer, of the condensation polymer of formula -(LR) n -, referred to above. (b) 20-75% of organic polar solvent for the polymer, based on the weight of solvent and polymer, (c) 0-30% by volume of dissolved salt, based on the polymer, and (d) 0-25% of water, based on the weight of polymer, with a rinse medium which (a) is miscible with the organic solvent (b) dissolves the salt, (c) is essentially chemically inert toward the polymer, and (d) is essentially a non-solvent for the polymer at a temperature of from -20 to 50 C, for a time sufficient to extract 75-100% of the salt. After extraction with the rinse medium, the membrane is suitably stored in contact with water. The unextracted membrane is suitably made by forming a dope containing the polymer and solvent, and partially drying the formed dope. Preferably, the desalination membrane is asymmetric, comprising a skin layer having a Crystal Violet surface-dyeability of less than 0.5 overlying a substrate having a p-nitro aniline dyeability of at least 0.7. As shown, (Fig. 5) a permeator 100 comprises a liquid light tubular casing assembly 101, suitably of steel, through which the feed passes as shown, the permeate product leaving at 108. The membranes comprise a plurality of very small fibres packed in groups 110, each group being enclosed in a porous sleeve member 112, and the assembly of groups being enclosed in a further porous sleeve member 113. A conduit 109 may be provided for the passage of a sweep liquid. An alternative form of permeater is shown in Fig. 9. The shell 60 is packed with U-shaped bundles of hollow fibres 64, the open ends 65 of which exit through a single pressure tight epoxy cast end member 16. Feed is pumped in at 61 permeate passing through the fibre walls exits from ends 65 of the fibres and outlet 72, while liquid rejected by the hollow fibre walls leaves at 62.