Patent GB-402770-A (GB)
Title: Improvements relating to processes for the separation or purification of salts, saltsolutions and other solutions
IPC: B01J39/00
Filed: 1932-06-02
Abstract: Salt solutions containing undesired cations are purified by passage through a base-exchanger which has previously been fully saturated with the cation of the salt to be purified.  The passage is effected slowly whereby the undesired cation is fixed by the base-exchanger and a pure solution is obtained.  The base-exchanger may be present in a predetermined excess or passage of the solution be continued until the base exchanger is almost exhausted.  Regeneration of the base-exchanger is effected with a part of the purified solution. When cations of weak bases are to be removed, for instance iron or organic bases, their removal is facilitated by acidifying the solution, or by using the more acid boro-, chromo-, or zirconohydrosilicates as base-exchangers, or alumino-hydrosilicates combined with such more acid radicles.  In one example, a solution of cobalt nitrate containing nickel is filtered through greensand previously saturated with pure cobalt nitrate, a pure solution of cobalt nitrate being obtained.  In a second example, an artificial zeolite is saturated with a slightly acid solution of pure m-xylidine hydrochloride, and acidified crude xylidine hydrochloride solution then filtered through it.  A pure solution of m-xylidine hydrochloride is obtained.  The isomers fixed by the base-exchanger can be removed by a slightly acid sodium chloride solution, or be extracted with a volatile solvent such as benzole, or be distilled off.  Reference is made also to the production of pure potassium salts from the mixed alkaline salts obtained in potash mines; to the removal of iron from commercial aluminium sulphate; to the separation generally of isomeric omines; and to the separation of alkaloid mixtures obtained synthetically or by extraction processes.  The Specification, as open to inspection under Sect. 91, comprises also the following subject-matter:--The preparation of a mass of mixed base-exchangers, the mass being so graded that it contains cations solely of one kind at one end and cations solely of another kind at the other end, and the proportions of each cation in intervening portions of the mass varying gradually; the use of such mixed base-exchangers for the preparation of salt solutions from solutions of two reacting salts, equivalent quantities of the two salt solutions being passed through masses containing appropriate cations alternately and slowly in opposite directions. In this connection the production of potassium nitrate from calcium nitrate and potassium chloride, of potassium cyanide from sodium cyanide and potassium chloride, and of copper acetate, from slightly acid sodium acetate and copper sulphate is referred to; the use of the mixed base-exchangers to obtain a pure solution of a salt from solutions containing two salts, the mixed solution being first brought into contact with that part of the base-exchanger having the same proportion of cations as exists in the solution, the latter in its flow encountering progressively base-exchangers containing increasing quantities of cations of the salt that is to be produced pure. Regeneration is effected by a part of the pure solution.  In this connection the purification of crude potassium chloride containing sodium chloride is referred to; the use of the mixed base-exchangers for purifying and sterilizing liquids containing one or more salts in solution. Purification is effected by reaction between the mobile cations of the base-exchanger and the anions present in the liquid forming compounds such as insoluble or volatile salts than can be readily eliminated; and sterilization by reaction between the mobile cations and the anions producing solutions with a germ-killing action.  In these connections, the desalting of salt water by forming and precipitating lead or silver chloride, the purification of sugar juices by forming and precipitating calcium or aluminium phosphates with concomitant precipitation of certain organic acids and a part of the nitrogenous matter and of the albuminoids and colouring matters present, the sterilization of a bacterially soiled water containing calcium sulphate by forming a solution of silver, mercury, or cadmium sulphate with subsequent removal of the silver &c. ion by passage in the reverse direction through the mixed base-exchanger, and sterilization in an analogous manner of wine, milk, and organic extracts is referred to.  An example is also furnished of the production of sodium sulphate solution by passing water through a sodium glauconite which has been mixed with finely ground gypsum, the glauconite being regenerated by means of sea water.  This subject-matter does not appear in the Specification as accepted.ALSO:The separation of alkaloid mixtures obtained synthetically or by extraction processes and of isomeric amines is effected by passage of their solutions through a base-exchanger which has previously been fully saturated with the alkaloid or amine it is desired to obtain pure.  The passage is effected slowly whereby the undesired alkaloid or amine is fixed by the base-exchanger. The latter may be present in a predetermined excess, and its regeneration be effected with a part of the purified alkaloid or amine solution. To facilitate exchange of bases the solutions may be acidified, or the more acid boro-, chromo-, or zircono-hydrosilicates be used as base exchangers or alumino-hydrosilicates combined with such more acid radicles.  In an example, an artificial zeolite is saturated with a slightly acid solution of pure m-xylidine hydrochloride, and acidified crude xylidine hydrochloride solution then filtered through it. A pure solution of m-xylidine hydrochloride is obtained.  The isomers fixed by the base-exchanger can be removed by a slightly acid sodium chloride solution, or be extracted with a volatile solvent such as benzole, or be distilled off.ALSO:The Specification as open to inspection under Sect. 91, comprises the following subject-matter: Liquids containing one or more salts in solution are purified by a mass of mixed base exchangers, the mass being so graded that it contains cations solely of one kind at one end and cations solely of another kind at the other end, and the proportions of each cation in intervening portions of the mass varying gradually.  Purification is effected by reaction between the mobile cations of the base exchanger and the anions present in the liquid forming compounds such as insoluble or volatile salts that can be readily eliminated.  The desalting of salt water by a mixture of sodium and lead or silver base exchangers with formation and precipitation of lead or silver chloride is referred to.  This subject-matter does not appear in the Specification as accepted.ALSO:The Specification, as open to inspection under Sect. 91, comprises the following subject-matter:- Liquids containing one or more salts in solution are purified or sterilized by a mass of mixed base exchangers, the mass being so graded that it contains cations solely of one kind at one end and cations solely of another kind at the other end, and the proportions of each cation in intervening portions of the mass varying gradually. Purification is effected by reaction between the mobile cations of the base exchanger and the anions present in the liquid forming compounds such as insoluble or volatile salts that can be readily eliminated; and sterilization by reaction between the mobile cations and the anions producing solutions with a germ-killing action.  The desalting of salt water by a mixture of sodium and lead or silver base exchangers with formation of and precipitation lead or silver chloride, the purification of sugar juices by a mixture of potassium and calcium or aluminium base exchangers with formation and precipitation of calcium or aluminium phosphates with concomitant precipitation of certain organic acids, and a part of the nitrogenous matter and of the albuminoids and colouring matters present, the sterilization of a bacterially soiled water containing calcium sulphate by a mixture of calcium and silver, mercury, or cadmium base exchangers with formation of silver &c. sulphate and subsequent removal of the silver &c. ion by passage in the reverse direction through the mixed base exchanger, and sterilization in an analogous manner of wine, milk, and organic extracts is referred to.  This subject-matter does not appear in the Specification as accepted.