Patent GB-627702-A (GB)
Title: Improvements relating to ion-exchange processes
IPC: B01J41/04
Filed: 1946-07-23
Abstract: A weak organic acid having an ionisation constant less than 1 x 10-2 is removed from a solution by an alkali - regenerated anion-exchange material, the material is treated with a stronger acid to displace the weak organic acid, and some at least of the weak organic acid so displaced is recovered in the free state. Preferably the process is a cyclic one using a bed of anion-exchange material through which is passed first the weak acid solution, then the stronger acid, after which the bed is regenerated with alkali, the effluent from the bed during treatment with the stronger acid being collected in fractions, one of which is recovered as a solution of free weak acid, and another used as displacing acid in a further cycle.  There is used as displacing acid preferably sulphuric acid, hydrochloric acid, or hydrobromic acid, though sulphurous, oxalic, dichloracetic, trichloracetic, phosphoric, or phosphorous acids may be used, in concentrations of from 0.5 to 20 per cent.  The fraction recovered as a solution of free weak acid may be treated further to produce a more concentrated solution, or may be freed from water to produce the acid itself.  In an example a 200 c.c. bed of an aliphatic amine anion-exchange resin was used for the absorption of tartaric acid from a grape waste extract containing 0.2 per cent tartaric acid. Sulphuric acid was used as the displacing acid.  In a second example aconitic acid was obtained from sorghum juice.  The Specification as open to inspection under Sect. 91 comprises also an example in which the sulphuric acid in the effluent is neutralised with barium hydroxide, and the barium sulphate filtered out; besides tartaric and aconitic acids citric, succinic and malic acids are obtained.  This subject-matter does not appear in the Specification as accepted.ALSO:A weak acid having an ionization constant less than 1 x 10-2 is removed from a solution by an alkali-regenerated anion-exchange material, the material is treated with a stronger acid to displace the weak acid, and some at least of the weak acid so displaced is recovered in the free state.  Preferably the process is a cyclic one using a bed of anion-exchange material through which is passed first the weak acid solution, then the stronger acid, after which the bed is regenerated with alkali, the effluent from the bed during treatment with the stronger acid being collected in fractions, one of which is recovered as a solution of free weak acid, and another used as displacing acid in a further cycle.  The process is most easily applied to the recovery of an organic acid, using as displacing acid preferably sulphuric acid, hydrochloric acid, or hydrobromic acid, though sulphurous, oxalic, dichloracetic, trichloracetic, phosphoric, or phosphorous acids may be used, in concentrations of from 0.5 to 20 per cent.  The fraction recovered as a solution of free weak acid may be treated further to produce a more concentrated solution, or may be freed from water to produce the acid itself. In an example a 200-cc bed of an aliphatic amine anion-exchange resin was used for the absorption of tartaric acid from a grape waste extract containing 0.2 per cent tartaric acid. After rinsing with water and draining to just above the top of the bed, 120-cc of 12 1/2 per cent sulphuric acid were added at 20-cc/min., the effluent being collected in 100-cc fractions.  The first 200-cc were discarded, the next 400-cc, containing considerable quantities of both acids, were reserved for recycling, and the next 300-cc containing a major proportion of sulphuric acid were set aside for making the 12 1/2 per cent sulphuric acid for the next cycle.  A second bed identical with the first was similarly treated, but after the draining step the 400-cc of effluent containing tartaric and sulphuric acids from the first cycle were passed through the bed, followed by 120-cc of 12 1/2 per cent sulphuric acid and a water rinse.  The first 200-cc were discarded, the next 100-cc, containing a little of both acids, were used to make up 12 1/2 per cent sulphuric acid, and the next 700-cc containing considerable quantities of tartaric and sulphuric acid, were reserved for re-cycling.  The first bed was then again treated with the grape waste extract and rinsed, and then with the 700-cc from the previous cycle and again rinsed.  After the first 200-cc, the next 900-cc contained up to 5 per cent tartaric acid and no sulphuric acid, and were set aside for crystallisation.  After passing 120-cc of 12 1/2 per cent sulphuric acid through the column, 100-cc of effluent containing tartaric acid and free from sulphuric acid were obtained and were added to the above 900-cc.  This was followed by a water rinse, after which 500-cc of mixed acid were obtained and re-cycled through the second bed.  The two beds had now reached a steady state, yielding 1,000-cc pure concentrated tartaric acid solution and 500-cc for recycling, at each run.  In a second example aconitic acid was obtained from sorghum juice.  The Specification as open to inspection under Sect. 91 comprises also an example in which the sulphuric acid in the effluent is neutralised with barium hydroxide, and the barium sulphate filtered out; besides tartaric and aconitic acids, citric, succinic and malic acids are obtained.  This subject-matter does not appear in the Specification as accepted.