Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Organic
Reexamination Certificate
1999-08-12
2001-08-28
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Organic
C204S536000, C204S632000
Reexamination Certificate
active
06280599
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to water treatment with ion exchange materials and particularly to methods and apparatus for the electrochemical treatment of anion and cation exchange resins.
BACKGROUND ART
Ion exchange is the reversible interchange of ions between a solid (often termed resin) and a liquid in which there is no permanent change in the structure of the solid that is the ion exchange material. The utility of ion exchange rests with the ability to use and reuse the ion exchange materials, employing an appropriate regeneration step.
There is an enormous market for high purity water. It is used extensively in industrial applications, with notable major users including the pharmaceutical, electronics and power generation industries.
In the final treatment (polishing step) for most applications, dissolved salts are commonly removed from the water by passage through ion exchange materials or resins. A combination of a cation exchange resin (in the H
+
form) and an anion exchange resin (in the OH
−
form) are used to remove the cations and anions, respectively. Two beds, one containing each resin type, may be used in tandem for the removal of many salts. If the aqueous solution is first passed through a bed of cation exchange resin (in the H
+
form), the cations in the solution are taken up by the cation exchanger, and an equivalent amount of H
+
ions art released into the solution (thus preserving electroneutrality). This (now acidic) solution is then passed through a second bed of anion exchange resin (in the OH
−
form), and the anions in the solution are taken up by the anion exchanger. The OH
−
that is released neutralises the H
+
in the solution thereby forming water. After passage through the two beds, the dissolved salts have effectively been removed from the solution. (If the sequence of the desalting is reversed, a corresponding scenario, with an intermediate alkaline solution, will apply).
For a number of water purification applications, a mixed bed of ion exchange resin is preferable, either in the place of the tandem bed configuration, or in addition to it, as a final polishing step. In this case, the cation and anion resins are intimately mixed, and the cations and anions are removed from the solution at the same time, with immediate neutralisation of the H
+
and OH
−
released by the resins forming water. It is possible to achieve a greater level of salt removal from aqueous solutions with this configuration, as the chemical equilibrium process is “driven” by the loss of H
+
and OH
−
by mutual neutralisation.
In either configuration, once the resins are exhausted (i.e. once there is no more resin in the H
+
and OH
−
forms), the cation and anion beds must be regenerated. For the conventional chemical regeneration processes, the cation and anion resins in the mixed resin bed must be physically separated before chemical regeneration can be carried out. This regeneration is usually by treatment with acid (typically H
2
SO
4
) and alkali (typically NaOH), respectively. This chemical process involves the storage and handing of concentrated acid and caustic solutions, as well as the disposal of the effluent regeneration and wash solutions after use. This is undesirable in the point of view of cost, safety and environmental considerations.
Other methods not requiring harsh chemical treatment alone have been developed for the regeneration of ion exchange resins. Some of these methods include electrodeionisation systems utilising specific ion-permeable membranes and chemical treatment solutions. Often the membranes are expensive and can to leak or rupture during use. Furthermore, the apparatus needed to house the resins with the membranes can be expensive to produce and maintain. Other methods available are adapted only to regenerate cation or anion form of resin, thus requiring two systems to regenerate both forms of ion exchange material.
The present inventors have developed a method of treating ion exchange resins using mild, inexpensive and ecologically acceptable electrochemical techniques. This method does not require regenerating chemicals, and has the added advantage that the water purification process and ion exchange regeneration can be carried out in the same vessel, with no need to disturb the resin bed. In the case of the mixed bed systems, this process also has the advantage that the regeneration can be carried out on resin beds without needing to separate the cation exchange resin from the anion exchange resin.
DISCLOSURE OF INVENTION
In a first aspect, the present invention consists in a method of treating an ion exchange material, the method including:
(a) positioning at least two regions of ion exchange material between an anode and cathode electrode, wherein at least a portion of the two regions being separated by a non-ion specific permeable interface;
(b) supplying water to the at least two regions;
(c) applying an electric potential between the electrodes thereby causing generation of hydrogen ions at the anode and hydroxide ions at the cathode, which ions are caused to move through each region towards the oppositely-charged electrode and thereby displacing at least a portion of any anions or cations associated with the ion exchange material in each region such that the displaced anions and cations are also caused to move through the regions towards the oppositely charged electrode; and
(d) removing at least some of the cations and/or anions formed during step
(c) which reach the interface.
It will be appreciated that at least a portion of the two regions will be in electrical contact so that an electrical potential can be applied between the electrodes.
The two regions can include single or mixed forms of ion exchange material. It will be appreciated that when single forms of ion exchange material are placed in each region, it is necessary for efficient operation of the method that the anion exchange material is positioned in the region associated with the cathode and the cation exchange material is positioned in the region association with the anode.
In a preferred embodiment of the first aspect of the present invention, simultaneous electrochemical regeneration of the ion exchange material in the regions occurs.
The anions and cations associated with the ion exchange material and removed by the method are preferably salts. In one form, the salts have accumulated on the ion exchange material during treatment of water prior to carrying out the method according to the present invention to regenerate the ion exchange material.
The interface can be in any form which allows the removal or flushing of ions and water which reach thereto during the movement of ions under the influence of the electric potential. Suitable forms include, but not limited to, non-ion selective membrane, frit, porous spacer, cavity formed by physical separation of the two regions of ion exchange material, inert material, valve arrangement and physical boundary between the two regions. The physical boundary between the two regions may also form a suitable interface. Preferably, the interface is polypropylene frit associated with a valve to allow the removal of the ions and water.
Preferably, the cations and/or anions formed during step (c) are removed prior to crossing the interface and entering the other region of ion exchange material.
In one preferred form, the step (b) is used as a means to remove salts dissolved in water to be treated. The one or more regions are flushed with water to be treated such that any dissolved salts therein are bound to the ion exchange material. When the water-treatment process is completed and the ion exchange material is to be regenerated, steps (c) and (d) are then carried out. The distinct advantage of this form of water treatment process is that the ion exchange material can be regenerated in situ.
The anode is preferably formed of platinum coated titanium, whereas the cathode can be formed of platinum coated titanium or stainless s
Hodges Alastair
Osvath Peter
CRC for Waste Management and Pollution Control Limited
Morgan & Lewis & Bockius, LLP
Phasge Arun S,.
LandOfFree
Electrochemical treatment of ion exchange material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrochemical treatment of ion exchange material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrochemical treatment of ion exchange material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2532489