Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1998-06-02
1999-11-02
Therkorn, Ernest G.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210670, 210677, 210678, 210681, B01D 1504
Patent
active
059763795
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to metathetic processes. More particularly, the present invention relates to a metathetic process utilizing at least one cation exchange column, wherein both the reagents and the products are water-soluble salts.
Metathetic processes are internal ion exchange processes between two salts, a salt and an acid, and a salt and a base, according to the general equation: and X and Y are different anionic species, one of which could be hydroxyl.
Many metathetic processes are known; some of them are applied in the chemical industry. A driving force is required to drive the reaction towards completion. Such driving force might result from low solubility of one of the products compared to the reagent, e.g., in the reaction: volatility of one of the products, e.g., in the reaction:
If both products are water soluble and non-volatile, and if one of them is an acid or a base, the reaction could be driven forward by acid-base properties. That is, for example, the case when a weak acid is displaced from its salt by a strong acid, e.g., in the reaction:
Here, however, both products are obtained in a solution (comprising NH.sub.4, SO.sub.4 and HLa) and a separation means is required for receiving the products. Such separation means could be a basic binding agent that binds the displaced acid, preferably over the displacing acid.
A suitable binding agent could also provide the driving force for the reaction. One example is the displacement of a strong acid (HCl) from its salt by a weak acid (carbonic acid) in the presence of an amine-based extractant that prefers the stronger acid, as described in Israel Patents 33551 and 33552, wherein the following reaction is described: Cl.sup.-.sub.(Org) +NaHCO.sub.3
The product-binding agent interaction should be reversible in order to allow recovery of the product and for regenerating the binding agent. The needs for strong enough binding and reversibility are sometimes conflicting. Selecting or designing binding agents of suitable selectivity and binding power is relatively easy in cases where one of the products is an acid or a base, since acid-base interactions are at one's disposal. That is not the case when both products are salts.
Metathetic processes forming two water soluble salts are sometimes attainable in highly concentrated solutions, or in non-aquous media where one of the products is soluble. Processes in alcohols [such as described in German Patent 3113612] and in concentrated ammonia solutions [U.S. Pat. No. 1,835,704] have been proposed. These processes are highly complicated, require many recycles, lead to a build-up of impurities and thereby to large bleeds and low yields, and require, in many cases, distillation of large amounts of solvent or solution components.
Processes comprising extraction of one of the salts have also been proposed [U.S. Pat. No. 3,433,584]. It is very difficult, however, to find a selective extractant for a salt as such. As a result, very complex, multi-stage processes are required.
In describing a process for separating MgCl.sub.2 and MgBr.sub.2 from a brine left after carnalite crystallization [Israel Patent 41225], one of the inventors, R. Blumberg, wrote [Handbook of Solvent Extraction, Lo, Baird and Hanson, Eds., p. 832]: for separating desired components of such essentially similar types . . . one can anticipate that separations of this type will not be straightforward; in other words, it will not be possible to achieve the desired purity of any one product in a single extraction battery, irrespective of the number of contact stages . . . highly integrated flow that permits these separations, using six solvent extraction batteries."
Extractants comprising water immiscible amines and organic acids have been found to show higher selectivity in extraction of salts [Eyal, et al., Ind. Eng. Chem. Res., Vol. 33, p. 1067 (1994)]. Operating such extractions, one encounters many difficulties. Furthermore, the extraction capacity of these extractants in extracting alkali metal salts is low.
One could consider perform
REFERENCES:
patent: 1978447 (1934-10-01), Austerweil et al.
patent: 3475330 (1969-10-01), Gilles
patent: 3876537 (1975-04-01), Dulin
patent: 4564455 (1986-01-01), Flynn
patent: 5248804 (1993-09-01), Nardelli
Therkorn Ernest G.
Yissum Research Development Company of the Hebrew University of
LandOfFree
Metathetic process utilizing a cation exchanger does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metathetic process utilizing a cation exchanger, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metathetic process utilizing a cation exchanger will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2130339