|Title of Invention||
SYNTHESIS AND USE OF REDOX RESIN
|Abstract||The present invention relates a redox having a resin matrix and at least one metal salt immobilized within said matrix, immobilization being effected by base fixation, said media having an effective pH in the range of 7 to 8.|
|Full Text||FORM-2 THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
(See section 10 and rule 13)
SYNTHESIS AND USE OF REDOX RESIN
an Indian Company
of D-13, MIDC Industrial Area, R. D. Aga Road, Chinchwad,
Pune 411019, Maharashtra, India
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.
This invention relates to synthesis and use of Redox resin.
FIELD OF THE INVENTION
The present invention envisages, generally, polymeric ion exchange materials, including resins and adsorbents, in which a metal group or redox substance is not only exchanged on the materials but is also loaded inside the pores of the resin. Also described are methods for making redox materials and it's use for removing oxidants such as free chlorine from water for example, potable water, Industrial feed water to membrane plants.
BACKGROUND OF THE INVENTION
Chlorine and such oxidants are commonly used for disinfection of water. Chlorine as gas or in the form of hypochlorite salts of sodium and calcium are commonly used for disinfection of potable and industrial water. Many similar oxidants such as ozone, Chlorine dioxide and less commonly potassium permanganate are used for disinfection. The same oxidants are used for control of microbes in industrial water treatment; more commonly in cooling towers and reverse osmosis plants.
Although, use of chlorine is permitted for potable water up to a limit, it is always preferred to have chlorine free drinking water. In recent years, the presence of chlorine and its analogues are considered as harmful and hence it is preferred that chlorine is removed along with all such other oxidants prior to use. In industries, the oxidants in water are not acceptable specially when used as feed to an ion exchange unit, reverse osmosis plants and such membrane systems. Hence, such plants always have a system to remove the chlorine or such oxidants.
Typically, the removal of chlorine or such oxidants from water is done by activated carbon, reducing agents such as sulphite and thiosulphates. Activated Carbon is commonly used for drinking water and ion exchange units. Chemical removal of the oxidants from water before feeding to membrane is done commonly by using
reducing chemicals such as sulphites. Use of carbon and reducing agents is found in all design documents.
All the traditional treatment methods for the removal of chlorine and such oxidants from water especially for membrane systems have limitations. For example, activated carbon is not easily regeneratable and many a times itself acts as a media for bacteria growth. The use of reducing chemicals requires close control and monitoring in addition to additional system for feeding chemical.
SUMMARY OF THE INVENTION
The present invention relates, generally, to the art of incorporating metal in reduced form into ion exchange or adsorbent materials to provide a reducing materials with a metal or metals inside the materials such that the modified materials effectively and efficiently remove various oxidants such as chlorine, by oxidizing the metal present in reduced state to next oxidized state, for example, from process solutions, effluents and aqueous solutions. For example, oxidants such as chlorine, chlorine dioxide and ozone are effectively removed from an aqueous solution by the redox resin of the present invention.
The redox resin of the present invention has at least one metal which has capability to go in various oxidation states. Such adsorbent materials may include, but are not limited to, cation & anion exchange resins, polymeric & porous materials, membranes and structures. The ion exchange material or adsorbents with which one starts may be any particular water-insoluble material which contains ion exchange group or the pores which can hold the reducing metal or metals. Such ion exchange or adsorbent materials are known to those of ordinary skill in the art and selection of a particular starting material or structure is considered within the skill of those knowledgeable in this field.
Specifically, the present invention is directed to compositions and modified cation exchange materials having at least one metal wherein at least a portion of the
metal is inside the material. For example, a strongly acidic cation exchange resin bead impregnated with a metal containing substance is part of the present invention.
Another aspect of the invention relates to methods for making modified cation exchange materials after adding a metal containing substance such as salt, acid or base material to form a substance comprising at least a metal. The method includes, but is not necessarily limited to loading the metal on a cation exchange material; and immobilizing or precipitating the metal containing complex inside the cation substance to form a modified redox exchange material.
In other aspects of the invention, methods of regenerating and recovering the redox resin for reuse. For example, described herein are methods of regenerating and recovering the reducing capacity of the adsorbent; comprising the steps of: reducing the oxidized sites of the adsorbent with a reducing agent.
Thus, the present invention provides low cost, very robust, modified redox exchange materials having a metal inside the materials in reducing form which are capable of functioning in a variety of apparatus as in a very wide range of operating conditions since the metal inside the exchange materials is not easily displaced from the material.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates, in part, to getting a metal to enter or go inside ion exchange or adsorbent materials in order to provide redox exchange materials. More specifically, the present invention relates to compositions and materials in which redox metal is located, precipitated or immobilized inside an ion exchange or adsorbent material retaining its ability to change the reduction or oxidation state. As used above, "redox metal " means an atom, molecule, ion or chemical group which, upon being bonded, attached, sorbed or physically located at, close to or throughout the volume of a solid surface or a porous structure or support, the resultant material has capability to reduce and oxidize depending upon the nature
of media in contact. The mechanism by which this effect is achieved may consist of the formation of a coordinate covalent complex species, an insoluble or scarcely soluble compound with high surface area.
It is well known that metal have various levels of oxidation. The oxidation state depends on the environment. When these metals are loaded on ion exchange resin , they leach out and contaminate the water. It is necessary that the metal remains inside the resin during use and regeneration and also retains its redox potential. For example, when an cationic resin loaded with iron is used for normal water, the iron is displaced or removed from resin due to exchange with calcium and sodium & the metal is not able to stay inside the materials. Accordingly, an important aspect of the present invention is to provide improved modified redox exchange materials by methods which enable a metal to, not only go inside materials as an redox material but also remain inside the materials as either a cation or as a neutral species which do not come out during operation or regeneration. Any metals having capability to exchange on either cation or anion or get adsorbed and having various oxidation state such as group VIIB and Group VIII and transition metal in the periodic table.
By the present invention, metal is loaded on the resin at sub stoichiometric to the total capacity have been achieved by a mixing resin with metal salt solution at suitable concentrations suitable for the resin. For example, a IN to 3 N solution of ferrous sulphate , sodium sulphate and sodium sulphite is combined with cation resin Tulsion T 62 H and allowed to equilibrate for two or more hours. The solution is then drained from the resin and replaced with the same amount of a fresh neutral water and again allowed to sit for 2 hours, drained and replaced as a multistage batch wash approach to remove free & soluble iron. This is to create right redox exchange capacity of the resin. Similarly, a large volume of solution can be passed slowly thru the resin in a column operation until the resin is loaded with metal ion and the right redox capacity of the resin is achieved. Whether batch contacts or column operation is employed it may be found to be more practical to use 10 to 60 % of the theoretical capacity.
In order to overcome the metal exchange with other ions when the oxidants from water are being removed by media , the further reaction is done with alkali or alkaline earth metals hydroxide or carbonate . For example , the strong acid cation resin loaded with 40% to of the capacity by iron by the process described above is treated in batch reactor with 120 to 140% of stoichiometric qty of the caustic at 0.1 to 1% concentration followed by wash with neutral water to remove excess caustic produces redox resin which is capable of removing oxidant and is also stable during multiple redox cycles. Thus, the present invention also relates to preparation of the redox resin which are very stable during multiple redox reaction cycles. The redox resin can be either in the same or different ionic form as the metal salt. Accordingly, an unexpected benefit of the redox resin of the present invention is that a metal is contained or trapped in the exchange material in a solid state but is still able to take part as though it were finely dispersed within the exchange material. Meanwhile, the ion exchange material continues to function in a similar or the same manner as it was capable of functioning prior to containing the metal. In other words, the cation exchange material with the metal inside the material, as described in more detail below, acts as both its original cation exchange material and as a redox resin.
The modified redox resin of the present invention can be used with a variety of apparatus and have wide point of applications including, for example, the treatment of drinking water at point of use, effluent water before discharge, RO feed water, cooling towers discharge etc., as well as point of use applications in other similar fields, including sanitization and sterilization, food and animal disinfection, bacteria control, waste treatment, and pharmaceutical plants. It will be appreciated by those from this field the other uses of the redox resin of the present invention are possible without departing from the broad invention concept thereof.
A primary purpose of the present invention is to provide a redox resin which effectively and efficiently reacts with or adsorbs chlorine & such oxidants used in water treatment such that chlorine can be removed from water used for drinking, membrane and Ion exchange resin and waste water disposal etc . In addition to
effectively and efficiently reacting with free chlorine, the improved anion exchange material of the present invention can also effectively and efficiently react with or adsorb other oxidants, including but not limited to, chlorine dioxide, ozone, peroxides etc. The redox resin of the present invention is also useful as oxidation-reduction or redox media and as catalysts for various chemical reactions.
As used herein, the term "redox resin" includes granules, beads, grains and powders. These materials can be macro porous but are preferably gel-type materials. The redox resin of the present invention is preferably cation exchange resins which are formed by the sulphonation of an organic polymer, such as polystyrene. The underlying polymer may contain ring-based materials, such as benzene rings, or non-ring based materials, such as, but not limited to, acrylic acid or methacrylic acid. Such resins have a large number of electrically charged functional groups disbursed throughout their structure which are capable of exchanging metal ions as cation and metal complexes as anion.
The ion exchange resins suitable for preparing the modified materials of the present invention are organic porous materials with or without ionic charges and metal exchange capacity. Preferably, the cation exchange resins are polymer-based and, as described above. Polymer-based ion exchange materials are commercially available or can be readily prepared from materials that are commercially available and cover a broad spectrum of different ion exchange materials with varying exchange capacity, porosity, pore size and particle size.
All ion exchange resins are ionically charged polymer. The polymer can be gel , porous on a molecular scale to allow ions to travel freely through out the particle or macro porous which have physical porosity. Materials, especially resins, with physical porosity are typically referred to as "macro porous" or "macro reticular." The terms "macro porous" and "macro reticular" are typically used interchangeably. The gel ion exchange materials are particularly preferred in the practice of the present invention which applies to both macro porous and gel type resins as well as polymeric adsorbents. Gel type resins are cheaper and offer higher capacity.
Ion exchange resins are characterized as either strong or weak exchange resins depending on the active ion exchange sites of the resin. The resins can be cationic or anionic. Both cationic and anionic as well as strong and weak resins have capability to exchange or adsorb metal ions and with present invention can be converted to redox resin.
Ion exchange resins are present in various ionic form such as Sodium, calcium in case of Cation and sulphate, chloride etc in case of Anion. These functional groups are known as active sites and are distributed through out the volume of the resin. All ion-exchange resins have the capacity to undergo ion exchange and regardless of the initial ionic form, if resin can be converted to any metal the metal containing complex form & when is followed by subsequent process , the redox resin can be prepared by the present invention.
Examples of suitable ion exchange resins are known in the experts in Ion Exchange Separations. Preferred Cation exchange resins are those resins in H form whereby the resin is in the counter ion form before the start of the process or converted to that form during the during the exchange process. Hence, preferred ion exchange resins are those resins which are strong Cation exchange resin in H form, for example, styrene-divinyl benzene copolymers having sulphonic acid as functional group.
Preferred cation exchange resins also include cross linked polystyrene. Such resins are typically sold in a variety of ionic forms. The term "ionic form" refers to the counter ion attached to the charged functional group of the resin. Virtually any positively charged ion can become a counter ion. Some examples of counter ions are Hydrogen, sodium, calcium, lithium etc. Experts in ion exchange will recognize that the counter ion is often included in the name of the resin.
The ion exchange resins which effectively exchange and adsorb metals having redox potential are also with in purview of this invention.
The process of removal or adsorption of the oxidant or reducing compounds , for example, an oxidant such as but not necessarily limited to, chlorine, chlorine dioxide , hydrogen peroxide , peracetic acid and permangnates and reducing agents such as sulphite, sculpture dioxide, thio sulphates etc. Some organic compounds such as isocyanuret are also within the purview of the present invention.
The redox resin of the present invention is capable of operating effectively in a wide pH range. For example, the modified anion exchange materials of the present invention can work effectively at a pH range of between 5.0 and 11.0., although some leaching is expected to occur below pH 5. Preferably the range of the pH is between 9.0 and 10.0, most preferably between 7. to 9, since the pH of potable water is usually in the range of approximately 5 to 9. The pH of any source coming into contact with the redox resin should be monitored and adjusted, if necessary.
The present invention is also directed to methods of making redox resin, which involve "loading" metal on the ion exchange resin and then reacting the resin metal complex in a manner that leaves the metal in complex or precipitated or immobilized inside the anion exchange material. Thus, in the present invention, the metal compound or metal complex are first loaded as ions into the ion exchange resin and then further reacted so that the metal compound inside the ion exchange resin is broken and the metal is contained or trapped within the resin . As a result, the metal is immobilized and unable to easily escape or be displaced from the material.
The methods of making the redox resin of the present invention can be conducted either in a column or batch reactor. The batch method can be varied by using multiple contacts or with a single contact under proper conditions able to make a product with acceptable performance. The column method enables the amount of metal loading to be controlled by allowing a solution to reach equilibrium as it passes through a bed by varying the flow rate, composition and/or contact time. In addition, the solution containing the complex can be recalculated which allows for
complete or partial use of the complex solution for producing a predefined amount of metal loaded product. Multistage contacts, by either the batch or column methods of either a resin or the solution, allow loading to occur as required and reuse of the spent solutions to optimize the performance of the solution and minimize waste discharge thereby improving operating efficiency during production.
Preferably, the method of using redox resin of the present invention involves passing oxidant containing water or solution through the bed of redox resin at flow rate of 2 to 40 times the volume of the resin . The flow rate can be adjusted depending upon the quality of water, the temperature and the quality expected. The experts in ion exchange resin use this as design document. Once the unacceptable leakage of oxidant is observed, the redox resin is back washed and regenerated using standard procedures used in ion exchange technology. The regenerator to be used & are covered by this invention are sodium sulphite, sodium bi sulphite , thiosulphate and any such common reducing agents. The concentration of the reducing agents is between 0.01 N to 10 N depending on type of the reducing chemical.
In its simplest form, the method of making redox resin of the present invention comprises the steps of: loading metal having redox potential onto an ion exchange resin ; and immobilizing or precipitating the metal containing complex inside the ion exchange resin using suitable alkaline or alkaline earth salt in appropriate form to form a redox resin. The redox resin can be used like normal ion exchange resin in granular, or any other form using service, backwash regeneration and rinse cycle. The regenerators used are chosen from the range of commercial reducing agents.
The present invention further relates to methods of removing reducing agent from process and aqueous streams which is reverse process of removal of oxidants. Moreover, it is within the scope of the present invention to provide an apparatus or container which contains the redox resin of the present invention which is made according to the method described above. It will be appreciated by those experts in
the ion exchange resins that steps can be added, or the steps mentioned repeated, to the methods described above without departing from the broad inventive concept thereof.
In a reactor 1000 ml of Strong acid macro porous cation product Tulsion T 62 MP was added. 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water. This solution was mixed with cation resin. The resin was rinsed with demineralised water . This resin was further added in 1500 ml of 1 N NaOH & mixed for 3 hrs .Excess NaOH was removed & Finally the resin was rinsed with demineralised water till pH was 10. The resulting product was black coloured beads.
Tap water containing 200 ppm free chlorine was passed through this resin at rate of 10BV/ hr . The outlet water was tested for residual chlorine .The capacity of resin was found to be 0.05meq/ml & outlet water was analyzed for Fe , no leakage was observed
34 In a reactor 1000 ml of Strong acid macro porous cation product T 62 MP was added for conversion. 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water. This solution was passed through cation resin in lots. The resin was Backwashed & rinsed with demineralised water between lots of FeS04,7H20 solution in water. This resin was added in 1500 ml of 1 N NaOH & mixed for 3 hrs . Excess NaOH was removed & Finally the resin was rinsed with demineralised water till pH was 10. The resulting product was black coloured beads.
Tap water containing 200 ppm free chlorine was passed through this resin at rate
of 10BV/ hr . The outlet water was tested for residual chlorine .The capacity of resin
was found to be 0.06meq/ml & outlet water was analyzed for Fe, no leakage was
In reactor 1000 ml of Strong acid macroporous cation product T 62 MP was added for conversion. 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water . This solution was passed through cation resin. The resin was rinsed with demineralised water. Then resin was added in 1500 ml of 1 N NaOH & mixed for 3 hrs . Excess NaOH was removed & finally the resin was rinsed with demineralised water till pH was 6-6.5. The resulting product was black coloured beads.
Tap water containing 200 ppm free chlorine was passed through this resin at rate of 10BV/ hr . The outlet water was tested for residual chlorine .The capacity of resin was found to be 0.4meq/ml & outlet water was analyzed for Fe , no leakage was observed.
In a reactor 1000 ml of Strong acid macro porous cation product T 62 MP was added for conversion . 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water . This solution was passed through cation resin in lots. The resin was Backwashed & rinsed with demineralised water prior to addition of next lot of Ferrous sulphate solution .. Then resin was added in 1200 ml of 1 N NaOH & mixed for 3 hrs . Excess NaOH was removed & finally the resin was rinsed with demineralised water till pH was 6-6.5. The resulting product was black coloured beads .
Tap water containing 200 ppm free chlorine was passed through this resin at rate of 10BV/ hr . The outlet water was tested for residual chlorine. The capacity of resin was found to be 0.5meq/ml & outlet water was analyzed for Fe, no leakage was observed.
In a reactor 1000 ml of Strong acid cation product T 62 MP was added for conversion . 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water . This solution was passed through cation resin . The resin was rinsed with
demineralised water . Then resin was added in 1200 ml of 1 N NaOH & mixed for 3 hrs . Excess NaOH was removed from resin &finally the resin was rinsed with demineralised water till pH was 4.5-5. The resulting product was black coloured redox resin beads .
Tap water containing 200 ppm free chlorine was passed through this resin at rate of 10BV/ hr . The outlet water was tested for residual chlorine .The capacity of resin was found to be 0.7meq/ml & outlet water was analyzed for Fe , no leakage was observed
In a reactor 1000 ml of Strong acid cation product T 62 MP was added for conversion . 300gms of FeS04, 7 H20 was dissolved in 1000 ml of demineralised water . This solution was passed through cation resin in lots. The resin was backwashed & rinsed with demineralised water prior to addition of next lot of ferrous sulphate solution. Then resin was added in 1200 ml of 1 N NaOH &mixed for 3 hrs .Excess NaOH was removed & Finally the resin was rinsed with demineralised water till pH was 4.5-5. The resulting product was black coloured redox beads .
Tap water containing 200 ppm free chlorine was passed through this resin at rate of 10BV/ hr . The outlet water was tested for residual chlorine .The capacity of resin was found to be 0.7meq/ml & outlet water was analyzed for Fe , no leakage was observed .The leakage of free chlorine was not detectable in the outlet of the redox resin.
The resin above after was backwashed and rinsed to loosen the bed. 2.5 liters of 4% solution of sodium bisulphate was passed at 2 bed volumes/hr flow for regeneration. The resin was rinsed and reused for free chlorine removal. The capacity of 0,7 meq/ml was observed.
Finally, it will be appreciated by those experts in field of Ion exchange technology that changes could be made to the embodiments described above without departing from the broad invention concept thereof. It will further be appreciated by those experts based on the description provided above that one or more of the individual steps described above could be eliminated with various degrees of success based on the on the operating conditions and requirement of the steps in order to get the performance and cost effective production. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit.
Dated this 3rd day of July, 2006.
OF R. K. DEWAN & COMPANY
APPLICANTS' PATENT ATTORNEY
|Indian Patent Application Number||1053/MUM/2006|
|PG Journal Number||24/2011|
|Date of Filing||03-Jul-2006|
|Name of Patentee||THERMAX LIMITED|
|Applicant Address||D-13, MIDC INDUSTRIAL AREA, R.D.AGA ROAD, CHINCHWAD, PUNE-411 019,|
|PCT International Classification Number||B01D39/14|
|PCT International Application Number||N/A|
|PCT International Filing date|