Patent GB-450358-A (GB)
Title: Improvements in or relating to the recovery of alginous material from seaweed
Filed: 1935-01-11
Abstract: An aqueous alkaline mass containing algulose and dissolved alginous material is formed from seaweed and charged with a multiplicity of gas bubbles which rise and carry to the surface the particles of algulose.  The fresh or dried seaweed is first washed with a solution of an alkaline-earth salt such as calcium or barium chloride to remove laminarine, mannitol, and salts.  A solution containing 0,8--1 per cent calcium chloride is suitable.  It is then washed with soft water, macerated in an alkaline, for example, sodium carbonate solution to disintegrate the algulose and form a paste which is mixed with water and preferably treated with air or oxidizing agents such as hydrogen peroxide or ozone to increase the viscosity.  The solution is clarified by charging with gaseous bubbles, for example, by treating in a high speed centrifuge or in a vessel having a perforated, preferably uneven false bottom, beneath which a current of gas is fed.  Alternatively, the gas treatment is effected by charging with carbon dioxide under pressure and then slowly releasing the pressure, by electrolysis in the solution itself, or by the action on the solution of metals such as aluminium or zinc, amalgams, or compounds such as calcium hydride and sodium dioxide.  The clarified solution is decolorized by addition of an absorbent such as a jelly of hydrated alumina, or alumina together with, e.g. aluminium alginate.  From 1--3 per cent by weight of gelatinous silica may be added.  The jelly may be removed by centrifuging and regenerated for re-use.  This decolorizing treatment may be effected prior to clarification. Other absorbents can be used such as oxides of metals whose salts are precipitated by alkalies, e.g. alkaline-earth or heavier metals.  Coagulation is now effected by adding a strong acid to give a pH of 2.8--3.2.  Preferably dilute, e.g. 10 per cent by volume, H2SO4 flows into a mixing tank simultaneously with the algin solution.  The two streams may be mixed by impinging on an inclined baffle.  The coagulum separates on the surface of the overflowing liquor and is drained, pressed, comminuted, and treated with ethyl alcohol, acetone or other solvent for the impurities.  Such treatment may be effected in a battery of vessels each having a filtering plate disposed near its bottom, 90--95 per cent ethyl alcohol being circulated therethrough, or a battery of revolving drums may be used, liquid being transferred by vacuum or compressed air.  The alcohol is driven off by heating at a temperature not above 60--70 DEG  C. in vacuo or at atmospheric pressure.  Alternatively, the coagulum is purified by dialysis or electro-osmosis.  Instead of coagulating with an acid, the alginous solution may be concentrated by ultra-filtration and coagulated with alcohol.  The algin obtained is water-soluble and the addition of a substance yielding OH ions, such as ammonia or other alkali, or amines, gives a clear solution.  The solution containing laminarine and salts obtained in the first stage of the process may be treated to precipitate laminarine by addition of alcohol, or of lead sub-acetate in an alkaline medium.  The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 450,210, [Group III]. This subject-matter does not appear in the Specification as accepted.ALSO:An aqueous alkaline mass containing algulose and dissolved alginous material is formed from seaweed and charged with a multiplicity of gas bubbles which rise and carry to the surface the particles of algulose.  The fresh or dried seaweed is first washed with a solution of an alkaline-earth salt such as calcium or barium chloride, to remove laminarine, mannitol, and salts.  A solution containing 0,8-1 per cent calcium chloride is suitable.  It is then washed with soft water, macerated in an alkaline, for example, sodium carbonate solution to disintegrate the algulose and form a paste which is mixed with water and preferably treated with air or oxidizing agents such as hydrogen peroxide or ozone to increase the viscosity.  The solution is clarified by charging with gaseous bubbles, for example, by treating in a high speed centrifuge or in a vessel having a perforated, preferably uneven false bottom, beneath which a current of gas is fed.  Alternatively, the gas treatment is effected by charging with carbon dioxide under pressure and then slowly releasing the pressure, by electrolysis in the solution itself, or by the action on the solution of metals such as aluminium or zinc, amalgams, or compounds such as calcium hydride and sodium dioxide.  The clarified solution is decolorized by addition of an absorbent such as a jelly of hydrated alumina, or alumina together with, e.g. aluminium alginate.  From 1-3 per cent by weight of gelatinous silica may be added.  The jelly may be removed by centrifuging and regenerated for re-use.  This decolorizing treatment may be effected prior to clarification. Other absorbents can be used such as oxides of metals whose salts are precipitated by alkalis, e.g. alkaline-earth or heavier metals.  Coagulation is now effected by adding a strong acid to give a pH of 2,8-3,2.  Preferably dilute, e.g. 10 per cent by volume, H2SO4 flows into a mixing tank simultaneously with the algin solution.  The two streams may be mixed by impinging on an inclined baffle.  The coagulum separates on the surface of the overflowing liquor and is drained, pressed, comminuted, and treated with ethyl alcohol, acetone, or other solvent for the impurities.  Such treatment may be effected in a battery of vessels each having a filtering plate disposed near its bottom, 90-95 per cent ethyl alcohol being circulated therethrough, or a battery of revolving drums may be used, liquid being transferred by vacuum or compressed air.  The alcohol is driven off by heating at a temperature not above 60-70 DEG  C. in vacuo or at atmospheric pressure.  Alternatively, the coagulum is purified by dialysis or electro-osmosis.  Instead of coagulating with an acid, the alginous solution may be concentrated by ultra-filtration and coagulated with alcohol.  The algin obtained is water-soluble and the addition of a substance yielding OH ions, such as ammonia or other alkali, or amines, gives a clear solution.  The solution containing laminarine and salts obtained in the first stage of the process may be treated to precipitate laminarine by addition of alcohol, or of lead sub-acetate in an alkaline medium.  The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 450,210, [Group III]. This subject-matter does not appear in the Specification as accepted.