Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Patent
1996-08-20
1999-08-17
Phasge, Arun S.
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
204541, 204544, B01D 6144
Patent
active
059389079
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for recovering guanidine salts from diluted and contaminated aqueous solutions.
Guanidine salts represent important products in organic synthesis processes as well as in biotechnological processes. For this reason, large amounts of waste water result during the corresponding technical uses which can contain, aside from guanidine salts, numerous further contaminants of organic but also inorganic origin. In this manner, suitable guanidine salt solutions, such as they are used, for example, in chromatography, in the denaturation and/or renaturation of protein solutions or dissolution of inclusion bodies, are usually contaminated with residual proteins, reducing compounds (such as sulfides, for example), non-ionic detergents or buffer salts. Additionally, the concentration of guanidine salts is subject to very strong variations.
From an economic point of view, but also on the basis of environmental protection, great interest exists to isolate the respective guanidine salts and/or recover them again in a form which is as pure as possible. The only technical possibility offered thus far was to first concentrate diluted solutions and subsequently purify the guanidine salts by crystallization. The high energy expenditure which is necessary to evaporate, in part, large amounts of water is particularly disadvantageous in these methods. Additionally, the clean separation of the contaminants by crystallization causes considerable problems which is why multiple recrystallization is necessary for the recovery of somewhat pure products, and therefore this method seems rather technically complex.
Therefore, the object of the present invention was to develop a method for the recovery of guanidine salts from diluted and contaminated aqueous solutions which does not have the mentioned disadvantages of the prior art, but instead makes it possible to isolate guanidine salts in high purity from these solutions with little technical effort.
The object was solved according to the invention by subjecting the corresponding aqueous solution (diluate) to an electrodialysis and enriching the guanidine salts on the concentrate side in a concentrated form.
A detailed summary of the principle of electrodialysis and its use is found in J. Fritsch et al. "Electrodialysis and Diffusion Dialysis", Galvanotechnology, volume 7, 1991, Eugen G. Lenze Publisher, Saulgau.
Namely, it has been surprisingly shown that the corresponding guanidine salt can be considerably separated from all contaminants and a product can simultaneously be isolated in very high concentration (on the concentrate side).
From U.S. Pat. No. 4,678,553 a method is known for the recovery of polypeptides and proteins from solutions containing guanidine salts with the help of electrodialysis, however, in this case, the guanidine salts are present in a relatively concentrated form and are diluted in the course of the electrodialysis.
In the method commensurate with the present invention, guanidine salts solutions which partially have a concentration of <1% by weight, are electrodialysed. In this connection, practically all technically important salts can be used as guanidine salts, such as for example guanidine hydrochloride, sulfamate, phosphate, sulfate, thiocyanate or nitrate.
The electrodialysis itself can be carried out in technically customary electrodialysis cells which are equipped with known ion-selective membranes (essentially ion exchange membranes). With respect to the electrode rinse to be used, it has been proven to be particularly advantageous to rely on guanidine salts solutions such as guanidine phosphate or sulfate. In this manner, it is ensured that no undesired contaminants infiltrate into the concentrate.
The electrical parameters such as current density and voltage can vary in accordance with the technical possibilities of the electrodialysis cells. Normally, 200 to 1000 A/m.sup.2, especially 300 to 700 A/m.sup.2 electrode surface and voltages of approximately 0.5 to 3 volts per cell pair are technically appropria
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Obering et al., "Elektrodialyse und Diffusionsdialyse," Technical Report of the FIGAWA Working Group `Membrane Technology` (with English-language translation of pertinent parts).
Kiesewetter Erwin
Stengele Klaus Peter
NIGU Chemie GmbH
Phasge Arun S,.
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