DESC:FIELD OF THE INVENTION
The present invention in general relates to an electrolytic process for the preparation of metal carboxylate complexes. More specifically, the present invention relates to use of a semi-permeable membrane between the electrodes, which prevents the migration of precious metal ions to cathode thus increasing the metal ion concentration in the anolyte.

BACKGROUND AND PRIOR ART
The prior art has demonstrated that the presence of copper and silver ions in an aqueous solution is useful as a disinfectant. Many in the prior art have used copper and silver ions in an aqueous solution as a disinfectant in water systems such as cooling towers, swimming pools, hot water systems in hospitals, potable water systems, spa pools and the like.

Typically, the copper and the silver electrodes were connected to a direct current power supply. When the direct current was applied to the electrodes, copper and silver ions were generated by an electrolysis process from the copper and silver anodes respectively within the water. In one example of the prior art, water was passed continuously through an ion chamber having copper and silver electrodes. The water emanating from the ion chamber contained the copper and silver ions generated by the copper and silver electrodes within the ion chamber. The water emanating from the ion chamber containing the copper and silver ions are used as a disinfectant in water systems such as cooling towers, swimming pools, hot water systems in hospitals, potable water systems, spa pools and the like. The copper and silver ions within the water systems acted as a disinfectant for controlling algae, viruses, bacteria and the like.

US6197814 discloses a disinfectant formulated by electrolytically generated silver ions in the presence of citric acid referred to as electrolytically generated silver citrate. Silver ions are generated in a water based citric acid medium by using silver metal as the anode, under a required potential, whereby the silver ions are generated near the anode. As the potential is applied across the electrodes, silver ion tends to migrate towards the cathode & gets deposited thereon thus leaving less number of silver ions in the electrolyte to form complex with the acid. Due to this, the concentration of silver citrate complex formation is less thus requiring much more time to reach the desired concentration.

US7732486 discloses anhydrous silver dihydrogen citrate compositions comprising silver dihydrogen citrate and citric acid. The anhydrous compositions can be prepared by freeze-drying. The preparation method of liquid SDC (Silver dihydrogen citrate) involves applying a D.C potential across the electrodes. The patent further discloses application of reversible current to reduce silver deposition on the cathode

There is a need for a process for preparation of metal carboxylate complexes which provides a stable ionic formulation which may be electrolytically generated in a high concentration within a short period.

SUMMARY OF THE INVENTION
The present invention relates to an electrolytic process for preparation of metal carboxylate complexes comprising the steps of:
i) Immersing at least one anode and at least one cathode at a predefined distance in an electrolyte comprising carboxylic acid and/or alkali metal salts thereof;
ii) Isolating the anode and the cathode from each other by placing a semi-permeable membrane in between; and
iii) Applying an electric potential across the anode and the cathode to generate metal ions.

BRIEF DESCRIPTION OF THE DRAWINGS
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

Figure 1 shows a perspective view of the electrolysis tank with the electrodes immersed in the electrolyte.

Figure 2 shows a top view of the electrolysis tank.

Figure 3 shows a typical anode used in the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

This invention relates to improved methods to generate transition/precious metal carboxylate complexes.

An embodiment of the invention relates to an electrolytic process for preparation of metal carboxylate complexes comprising the steps of:
i) Immersing at least one anode and at least one cathode at a predefined distance in an electrolyte comprising carboxylic acid and/or alkali metal salts thereof;
ii) Isolating the anode and the cathode from each other by placing a semi-permeable membrane in between; and
iii) Applying an electric potential across the anode and the cathode to generate metal ions.

A typical electrolysis process of the present invention entails using an organic acid as an electrolyte and using precious/transition metal electrodes. The electrodes (anode (3) and cathode (4)) are preferably formed from 99.99% pure metals. Use of high purity metal electrodes produces high quality products having impurities = 100ppm. The metal anode (3) is preferably rotated by a geared motor arrangement (15). The anolyte is continuously circulated using an anolyte circulation pump (21) and this circulation of the anolyte by magnetically coupled pump ensures that a uniform concentration of metal ion is maintained in the anolyte. In a specific example, the anode (3) is a circular disc mounted on a hollow shaft continuously rotating at 5-30 rotations per minute (rpm) and maximum area of the anode is immersed within the anolyte.

The electrolyte comprises carboxylic acids or their alkali metal salt. The carboxylic acid is selected from lactic acid, citric acid, tartaric acid etc. Similarly, the metal electrodes are selected from the transition metals or precious metals such as Copper, Silver, Gold, Palladium, Platinum etc.

The anode (3) is spaced apart from the cathode (5) at a distance of around 10-30mm under applied potential of 2-20V.

A semi-permeable membrane (18), preferably fixed onto a semi-permeable membrane locking base (20), is placed in between the electrodes i.e. the anode (3) and the cathode (5). This membrane (18) prevents the migration of the metal ions from the anode to the cathode, thus increasing the metal ion concentration in the anolyte, leading to highly increased and faster formation of metal carboxylate complex.

A suitable D.C. power supply is utilized to supply a potential having a voltage of about 2 to 20 volts to the electrodes through the bus bars (Cathode bus bar (1) and Anode bus bar (2)). The metal ions generated at the anode (3) react with carboxylic acid or its salts in the anolyte to form metal carboxylate complexes. The semi-permeable membrane (18) prevents the migration of the metal ions generated at the anode from passing through to the cathode and hence these metal ions react with the anolyte forming metal carboxylate complexes in high concentrations. This solution may be further processed, to produce solid carboxylic complex by filtration & freeze drying. Desired concentration of ions can be achieved in the electrolyte by longer application of specific voltage and time.

For a quick production of metal carboxylate complexes, a series of anodes & cathodes can be simultaneously used.

The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention.

EXAMPLES
Having described the basic aspects of the invention, the following example illustrates the specific embodiments thereof.

Example 1:
This example illustrates the production of silver citrate complex.
The electrolysis tank (22) was filled with citric acid (AR grade) having a concentration of 5-40gms/liter made with high purity distilled water. The circular anodes (3) were made of high purity silver (99.99%) and mounted on an insulating shaft (4). The shaft was connected to a DC power source through a carbon brush (12) & an electrical contact disc (13). Each anode is connected to the electrical contact disc (13) through a conductor. The current to the carbon brush is supplied through an anode bus bar (2). The insulating shaft is mounted in a ball bearing housing (9) having ball bearings (10) which was locked by a nut (11). The anode mounting shaft is coupled through a coupler (14) to a geared motor(15). The geared motor is mounted on a base plate (16) with a motor stand (17). The electrolyte was filled in the tank in such a way that maximum anode surface is submerged inside the anolyte. Semi-permeable membranes (18) were placed between anodes & cathodes. These membranes (18) were locked to a bottom plate (20). The distance between the anode & the cathode was maintained at 27 mm. Cathodes (5) made out of high purity silver plates were hung from the hanger bar (6) in such a way that a constant gap is maintained between the anode & the cathode. Current was supplied to the cathode hanger bars through a cathode bus bar (1). An anolyte circulating pump (21) was connected to the drain plug (8) at the bottom of the tank for circulating the anolyte back to the tank through the plug situated at the upper side of the tank. This circulation ensured a uniform concentration in the anolyte chamber. The shaft containing anodes were rotated at a constant speed varying from 5-50rpm. A potential of 2-20V was applied between the anode & the cathode with the help of a rectifier. The time of electrolysis was set with the help ofa timer fixed in the rectifier. Silver ion concentration in anolyte was checked from time to time and when the desired concentration was achieved the electrolysis was stopped, the anolyte filtered through a suitable filter mechanism to remove any suspended particles & stored in a tank protected from light. Fresh electrolyte was charged into the electrolysis tank for fresh batch of operation.

Other metal carboxylate complexes were also prepared according to the process in example 1.

The metal carboxylate complexes prepared by the present method have various applications. The applications include use as a disinfectant, an antimicrobial etc.

Table 1 shows various metal carboxylate complex concentrations which were prepared by the method described in example 1 and provides a comparative data with a metal carboxylate complex prepared by the prior art method.

Table 1
Example Metal Carboxylic Acid Voltage applied
(V) Time taken
(hrs) Metal carboxylate Concentration
(ppm) Prior Art method
1 Silver Citric Acid 2-20 8 5790 2400ppm in 144hrs
2 Silver Tartaric Acid 2-20V 2-6hrs 9600 No data available
3 Gold Citric Acid 2-20V 2-6hrs 5-30 ----“-----
4 Gold Lactic Acid 2-20V 2-6hrs 1-10 ----“-----
5 Palladium Citric Acid 2-20V 2-12 1-5 ----“-----
6 Palladium Lactic Acid 2-20V 2-12 1-10 ----“-----
7 Platinum Citric Acid 2-20V 2-12 1-5 ----“-----
8 Platinum Tartaric Acid 2-20V 1-4 1-5 ----“-----
9 Copper Citric Acid 2-20V 2-6 5000-15000 ----“-----
10 Copper Lactic Acid 2-20V 2-12 1000-5000 ----“-----
11 Copper Tartaric Acid 2-20V 2-6 1000-4000 ----“-----
,CLAIMS:We Claim:
1. A process for the preparation of metal carboxylate complex comprising the steps of:
iv) Immersing at least one anode and at least one cathode at a predefined distance in an electrolyte comprising carboxylic acid and/or alkali metal salts thereof;
v) Isolating the anode and the cathode from each other by placing a semi-permeable membrane in between; and
vi) Applying an electric potential across the anode and the cathode to generate metal ions.
2. The process as claimed in claim 1, where the anode is a rotating anode.
3. The process as claimed in claim 1, where at least 40% of the anode is immersed in anolyte.
4. The process as claimed in claim 1, where anolyte is continuously circulated.
5. The process as claimed in claim 1, where the at least one anode and the at least one cathode is placed at a distance of 10 -30 mm.
6. The process as claimed in claim 1, where the anode and cathode is preferably made of same metal.
7. The process as claimed in claim 1, where the anode and the cathode is made up of transition metals or precious metals selected from Copper, Silver, Gold, Palladium and Platinum.
8. The process as claimed in claim 5, where the carboxylic acid is selected from citric acid, lactic acid, and/or tartaric acid.