Separation of water-soluble solutes

摘要

Aqueous liquid containing at least two solutes to be separated is introduced at 9, Fig. 1, to a column 3 containing a bed of ion-exchange resin. During downward flow of the liquid, one of the solutes is preferentially absorbed by the resin (by physical absorption: not by ion-exchange) and the liquid containing the remainder is withdrawn at 15. At the same time water is introduced at 11 and washes from the resin in the upper part of the column solute previously absorbed by the resin when in the lower part of the column (see below). Water containing the washed-out solute is withdrawn at 13. At regular intervals (e.g. once every three minutes) valves 10, 12, 14 and 16 are closed, a valve 5 (normally open) is closed and a valve 7 (normally closed) is opened and water (e.g. 20 c.cs.) is forced from a conduit 20 by a pump 18 into a resin reservoir 6 during a period of, e.g., 10 seconds. The whole system being permanently liquid-filled, the pressure-drop thus created across the mass of resin causes piston-like movement of it in an anticlockwise direction (e.g. of one inch in column 3), excess from column 3 passing into tube 4 where it is temporarily stopped by valve 5. The valves are then re-set to re-start normal operation. The two solutes may be (1) a highly ionized solute having an ionization constant of not less than 5 X 10-2 and (2) a less extensively ionized solute having an ionization constant not exceeding 2 X 10-1 and preferably not more than 70 per cent of that of (1). Examples are: sodium chloride and formaldehyde; sodium chloride and glycerine; sodium chloride and ethylene glycol; hydrogen chloride and methyl alcohol; sulphuric acid and ethylene glycol; sodium acetate and acetic acid; ammonium chloride and glycine; sodium hydroxide and acetone. The resin may be either a cation-exchange resin or an anion-exchange resin, and in each case it must have an ion identical with an ion of the highly-ionized solute, in consequence of which it is the lowly-ionized solute which is preferentially absorbed by the resin. Alternatively, the resin may contain both cationic and anionic groups (see, e.g., Specification 795,624, [Group IV (a)]), in which case it is the highly ionized solute which is absorbed. Examples are: sodium-salt of a sulphonated phenol-formaldehyde resin; ammonium salt of a sulphonated phenol-formaldehyde resin; hydrogen form of a sulphonated styrene-divinylbenzene copolymer; sodium salt of a sulphonated styrene-divinylbenzene copolymer; an insoluble resinous quaternary ammonium hydroxide; an insoluble resinous quaternary ammonium chloride. Alternatively the two solutes may be organic compounds each having an ionization constant not exceeding 1.75 X 10-5 at 25 DEG C. and differentially absorbed by the resin. Examples are: glycerine and triethylene glycol; pentaerythritol and ethylene glycol; acetone and ethylene glycol; acetone and formaldehyde; acetone and methyl alcohol; acetone and diethylene-triamine; formaldehyde and glycerine; methylamine and methyl alcohol; sucrose and ethylene glycol; sucrose and acetic acid. The resins are as before, together with, as an additional example, the sodium form of a carboxylic acid type resin. One resin is a nuclear sulphonated copolymer of approximately 88 per cent styrene, 4 per cent ethyl-vinylbenzene and 8 per cent divinylbenzene. In Fig. 2 (not shown), the directions of resin and liquid flow are reversed and the absorption and washing zones are transposed. The apparatus of Fig. 1 is substantially identical with that described in a publication referred to in the Specification. Specifications 577,707, [Group IV], 654,706, 679,850, [both in Group IV (a)], 709,550, [Group I], 731,335 and U.S.A. Specifications 2,341,907 and 2,642,417 are also referred to. Reference has been directed by the Comptroller to Specification 778,859, [Group I].ALSO: Aqueous liquid containing at least two solutes to be separated is introduced at 9, Fig. 1, to a column 3 containing a bed of ion-exchange resin. During downward flow of the liquid, one of the solutes is preferentially absorbed by the resin (by physical absorptions not by ion-exchange) and the liquid containing the remainder is withdrawn at 15. At the same time water is introduced at 11 and washes from the resin in the upper part of the column solute previously absorbed by the resin when in the lower part of the column (see below). Water containing the washed-out solute is withdrawn at 13. At regular intervals, e.g. once every three minutes, valves 10, 12, 14 and 16 are closed, a valve 5 (normally open) is closed and a valve 7 (normally closed) is opened and water, e.g. 20 c.cs., is forced from a conduit 20 by a pump 18 into a resin reservoir 6 during a period of, e.g. 10 seconds. The whole system being permanently liquid-filled, the pressure-drop thus created across the mass of resin causes piston-like movement of it in an anticlockwise direction, e.g. of one inch in column 3, excess from column 3 passing into tube 4, where it is temporarily stopped by valve 5. The valves are then re-set to re-start normal operation. The two solutes may be (1) a highly ionized solute having an ionization constant of not less than 5 X 10-2, and (2) a less extensively ionized solute having an ionization constant not exceeding 2 X 10-1 and preferably not more than 70 per cent of that of (1). Examples are: sodium chloride and formaldehyde; sodium chloride and glycerine; sodium chloride and ethylene glycol; hydrogen chloride and methyl alcohol; sulphuric acid and ethylene glycol; sodium acetate and acetic acid; ammonium chloride and glycine; sodium hydroxide and acetone. The resin may be either a cation-exchange resin or an anion-exchange resin, and in each case it must have an ion identical with an ion of the highly-ionized solute, in consequence of which it is the lowly-ionized solute which is preferentially absorbed by the resin. Alternatively, the resin may contain both cationic and anionic groups (see, e.g. Specification 795,624, [Group IV (a)]), in which case it is the highly ionized solute which is absorbed. Examples are: sodiumsalt of a sulphonated phenol-formaldehyde resin; ammonium salt of a sulphonated phenolformaldehyde resin; hydrogen form of a sulphonated styrene-divinylbenzene copolymer; sodium salt of a sulphonated styrene-divinylbenzene copolymer; an insoluble resinous quaternary ammonium hydroxide; an insolube resinous quaternary ammonium chloride. Alternatively, the two solutes may be organic compounds, each having an ionization constant not exceeding 1.75 X 10-5 at 25 DEG C. and differentially absorbed by the resin. Examples are: glycerine and triethylene glycol; penta-erythritol and ethylene glycol; acetone and ethylene glycol; acetone and formaldehyde; acetone and methyl alcohol; acetone and diethylene-triamine; formaldehyde and glycerine; methylamine and methyl alcohol; sucrose and ethylene glycol; sucrose and acetic acid. The resins are as before, together with, as an additional example, the sodium form of a carboxylic acid type resin. One resin is a nuclear sulphonated copolymer of approximately 88 per cent styrene, 4 per cent ethyl-vinylbenzene and 8 per cent divinylbenzene. In Fig. 2 (not shown), the directions of resin and liquid flow are reversed and the absorption and washing zones are transposed. The apparatus of Fig. 1 is substantially identical with that described in a publication referred to in the Specification. Specifications 577,707, [Group IV], 654,706, 679,850, [both in Group IV (a)], 709,550, [Group I], 731,335 and U.S.A. Specifications 2,341,907 and 2,642,417 are referred to. Reference has been directed by the Comptroller to Specification 778,859, [Group I].