Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF CHELATING ION EXCHAMGE RESINS FOR USE IN HEAVY METAL RECOVERY
Abstract	This invention relates to an improved process for the preparation of chelating ion exchange resin for use in heavy metal recovery which comprises I) preparing the copolymer resin with desired pendant group by suspension polymerization of the appropriate monomer such as herein described in the concentration ranges from 60 - 90wt%, along with a stabilizer and an initiator such as herein described at a temperature in the range of 60 -85°C under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an aquous solution containing sodium acetate and hydroxylamine hydrochloride then isolating the resin beads formed by filtration and washing followed by drying at a temperature of 100-110°C for a period of 12-16 hours, after which the resin beads are soaked in benzene for 10-20 hours, iii) separated and refluxing the said resin beads in aqueous solution containing sodium acetate and hydroxylamine chloride in the ratio of Resin:Sodum acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5 wherein after treatment of copolymer resin is refluxed in a temperature range of 70-80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 110-110°C for a period 10-20 hours to get the chelated ion exchange resin.

Title of Invention

AN IMPROVED PROCESS FOR THE PREPARATION OF CHELATING ION EXCHAMGE RESINS FOR USE IN HEAVY METAL RECOVERY

Abstract

This invention relates to an improved process for the preparation of chelating ion exchange resin for use in heavy metal recovery which comprises I) preparing the copolymer resin with desired pendant group by suspension polymerization of the appropriate monomer such as herein described in the concentration ranges from 60 - 90wt%, along with a stabilizer and an initiator such as herein described at a temperature in the range of 60 -85°C under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an aquous solution containing sodium acetate and hydroxylamine hydrochloride then isolating the resin beads formed by filtration and washing followed by drying at a temperature of 100-110°C for a period of 12-16 hours, after which the resin beads are soaked in benzene for 10-20 hours, iii) separated and refluxing the said resin beads in aqueous solution containing sodium acetate and hydroxylamine chloride in the ratio of Resin:Sodum acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5 wherein after treatment of copolymer resin is refluxed in a temperature range of 70-80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 110-110°C for a period 10-20 hours to get the chelated ion exchange resin.

Full Text	This is an invention, which relates to an improved process for the preparation of chelating ion exchange resin for use in heavy metal recovery. This invention more particularly relates to an improved process for the preparation of copolymer resin having appropriate pendant group that can be adapted to introduce chelating functional groups which can be used for the recovery of metals. The invention also relates to a process for the production of chelating ion-exchange resins which involved preparing suitable copolymer with desired pendant group as a base resin adapted for the introduction of chelating functional groups and thereafter treating the resin so as to produce chelating ion exchange resins. These resins are needed for the commercial application in the efficient recovery of heavy metals from lean solutions particularly in alkaline medium. The performance and durability of the so needed chelating ion exchange resin in the above mentioned application is governed by the following characteristics: i. The resin must be stable in strong alkaline solution ii. The resin must withstand acid treatment for long duration iii. The resin must withstand particular range of temperatures namely 30°C -100°C which is normally realized from the heat generated from the reaction when highly alkaline and acid solutions are repeatedly used for adsorption and elution process respectively during heavy metal recovery. Hitherto, chelating ion exchange resins in which the ligands capable of forming complexes with heavy metal ions are produced commercially. They are chelate resins having iminodiacetic acid group, such as for example, Dowex A-1 (product of Dow chemical Co.) and Uniselec UR-10-50 (product of Unichika Co. Ltd) (imino diacetic acid derivative) and the chelate resin with amidoxime group such as Doolite ES-346 (Rohm and Haas, Canada, Inc.) (amidoxime derivative). These resins suffer from the following disadvantages: i. poor efficiency in selective capturing of the adsorbed heavy metal ions, and in particular under strongly basic solution and ii. poor reusability in acidic media. To overcome these difficulties, chelating ion-exchange resins particularly with hydroxamic acid functional group is reported to be prepared in non-aqueous medium employing carcinogenic and highly inflammable solvents which are difficult to be implemented in an environment - conscious industrial condition [ref: J. Polym. Sci. Chem. Ed. 14, 2155-2165, (1976) and Macromolecules 11, 597-603 (1978)]. Hence, the main objective of the present invention is to provide an improved process for the preparation of chelating ion exchange resins in aqueous medium based among the drawbacks highlighted above. The process proposed accordingly in the present invention is also simple and safe to produce chelating ion exchange on a commercial scale. Accordingly the present invention provides a process for the preparation of chelating ion exchange resin for use in heavy metal recovery which comprises I) preparing the. copolymer resin with desired pendant group by suspension polymerization of the appropriate monomer such as herein described in the concentration ranges from 60 -90 wt%, along with a stabilizer and an initiator such as herein described at a temperature in the range of 60 - 85°C under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an aquous solution containing sodium acetate and hydroxylamine hydrochloride then isolating the resin beads formed by filtration and washing followed by drying at a temperature of 100-110°C for a period of 12-16 hours, after which the resin beads are soaked in benzene for 10-12 hours, iii) separated and refluxing the said resin beads in aqueous solution containing sodium acetate and hydroxylamine chloride in the ratio of Resin: Sodium acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5 wherein after treatment of copolymer resin is refluxed in a temperature range of 70-80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 100-110°C for a period 10-20 hours to get the chelated ion exchange resin. According to a feature of the invention, a copolymer capable of forming a macromolecular network with the desired pendant group is prepared using suspension polymerization mode and the required chelating functional group, namely, hydroxamic acid is introduced into the resulting resin through after treatment of the copolymer resin. The formation of such a copolymer resin with the desired pendant group forms the first stage and the incorporation of chelating functional group into the preformed copolymer resin constitutes the second stage. Consequently, the basic copolymer resin can be made for introducing required chelating functional group according to the choice of heavy metal ions as per this invention and is presently illustrated for hydroxamic acid functional group as a chelating point in the ion exchange resin so produced in this invention. One characteristic feature of the present invention is the choice of monomer and co-monomer capable of forming copolymer resin with the required pendant group adaptable for the introduction of chelating functional group. The predominant monomer unit that constitutes the copolymer chain comprises form any of the monomers having pendant groups like acrylate, methacrylate, nitrite, carboxylic acid chloride, carboxylic amides, carboxylic anhydrides and the like monomers possessing any one of the above said groups. The co-monomer unit that constitutes the rest of the copolymer chain comprises form any one of the monomers like divinyl benzene, ethyl vinyl benzene and the like. The quantity of the monomer that constitutes the predominant part of the copolymer chain in the feed for copolymerisation should preferably be in the range 60-90 weight per cent and the quantity of co-monomer unit constituting the rest of the copolymer chain should preferably be in the range of 40-10 wt % thus making the total monomers feed composition in the co polymerization scheme as 100%. A further characteristic of the present invention is the use of aqueous medium in which the suspension polymerization is adopted using any one of the stabilizers among the water soluble polymers such as starch, polyvinyl-alcohol and the like. The use of such stabilizer helps in suspending the monomers in water in the form of fine droplets which are thus stabilized and prevented from coalescing. The preferred concentration of the stabilizer for this purpose should preferably be in the range of 1-10 wt % with respect to total weights of the monomers employed in the feed for copolymerization. Another characteristic of the present invention is the use of initiators which can be selected from any one of the free radical catalysts like benzoylperoxide, azo-bis iso butyronitrile, tert butyl peroxide and the like. The preferred concentration of such free radical initiators should be in the range of 0.2-0.8 wt % with respect to the total weight of the monomer mixture employed in the feed of copolymerization. Further characteristic of the present invention is the "after treatment" of the copolymer with reagent capable of introducing hydroxamic acid group under reflux condition in aqueous medium. The reagents that can be used for this purpose are sodium acetate and hydroxylamine hydrochloride and their preferred concentration should be in the ratio 1-3:1-4:1-5 with respect to the weight of preferred resin. An embodiment of the invention is now illustrated. Typically, the said chelating ion exchange resin is prepared* in two stages. The first stage consists of suspension polymerization of monomer having the desired pendant group suitable for the introduction of chelating groups along with the copolymerizable monomers such as divinyl benzene. Any one of the monomers hailing from the acrylic or vinyl family is mixed with an appropriate quantity of divinyl benzene along with the free radical initiator in the said ranges at room temperature and thus the feed for the suspension polymerization is made ready. This mixture is slowly added to the preformed solution comprising of the stabilizer like starch or polyvinyl alcohol or the like in the said composition kept in a reaction flask which is thermostated at 60-70°C, over a period of time ranging form 15 to 30 minutes. The reaction flask is necessarily provided with a reflux condenser and a mechanical stirrer capable of stirring at various speed. The speed of the stirrer during the addition of monomer mixture is maintained in the range of 1500-2000 rpm. After the addition of monomer mixtures is complete, he reaction temperature is slowly raised to 70-85°C over 15 minutes during which time the preset stiffing speed of 1500-2000 rpm is reduced to 800 rpm and the co-polymerization is allowed to proceed for 5-7 hours. The resultant polymer beads that are formed in the reaction flask are cooled, filtered and washed with hot water and then dried for 12-16 hours in a temperature range of 100-110°C. The copolymer beads of uniform particle size are soaked in benzene for 10-12 hours for "after treatment of resin", separated and added to the reaction vessel in which an aqueous solution containing sodium acetate and hydroxylamine hydrochloride constituted in the said concentration ranges. This "after treatment" is allowed to proceed under reflux in the temperature range of 70-80°C for a period of time ranging from 24-30 hours. After completion of the reaction, the polymer bead product formed is filtered, repeatedly washed with water and dried for a period of 10-20 hours in an air oven at a temperature range of 100-110°C. The chelating ion exchange resin thus obtained is further subjected to alkali and acid treatments. The invention is illustrated in detail in the examples given below which should not, however be construed to limit the scope of the invention. Preparation of Co-potymer having acrylate pendant group Example 1 Wt. of Divinyl benzene (DVB) 20 g Wt. of Methylmethacrylate (MMA) 80 g Wt. of Benzoyl peroxide 80 mg Wt. of Starch 8 g Vol. of. Water 600 ml Temperature of reaction 60°C for 30 min. 80°C thereafter Rate of stirring Appro. 2000 rpm for 30 min Appro. 800 rpm thereafter Duration of polymerization 5-7 hrs. Wt. of MMA-DVB copolymer obtained 80-85 g Example2 Wt. of Divinyl benzene (DVB) 30 g Wt. of Methylmethaerylate (MMA) 70 g Wt. of Benzoyl peroxide 80 mg Wt. of Starch 8g Vol. of Water 600 ml Temperature of reaction 60°C for 30 min 80°C thereafter Rate of stirring Appro. 2000 rpm for 30 min Appro. 800 rpm thereafter Duration of polymerization 5-7 hrs. Wt. of MMA-DVB copolymer obtained 80-90 g Preparation of chelating Ion-exchange resin based on the Co-polymser prepared with hydroxamic acid group Example 3 Wt. of copolymer (MMA-DVB) 20 g Wt. of sodium acetate 21 g Wt. of hydroxy! amine hydrochloride 26 g Volume of water 300 ml Temperature of reaction 80°C Rate of stirring 1500 rpm Duration of polymerization 24 hrs Wt. of resin obtained Approx. 22 g Acid/Alkali stability No appreciable weight loss Example 4 Wt. of copolymer (MMA-DVB) 15 g Wt. of sodium acetate 15 g Wt. of hydroxy! amine hydrochloride 15 g Volume of water 300 ml Temperature of reaction 80°C Rate of stirring 1500 rpm Duration of polymerization 24 hrs Wt. of resin obtained Approx. 13 g Acid/Alkali stability No appreciable weight loss The chelating ion exchange resin of about 5 gm, obtained based on the preparation reported in reference example 3, was soaked overnight in pure 2M NaOH solution. The swollen resin after decantation of supernatant alkali was packed in a glass column of 250 mm height with an inner diameter of 10 mm. The height of swollen resin was about 80 mm. A strongly alkaline solution containing gallium, was allowed to pass through the resin bed at the required rate of flow. The treated alkaline solution was analyzed for its gallium content to compute gallium adsorption on the resin. The adsorption of gallium on resin is illustrated by the example given below, wherein the selectivity to gallium in alkaline medium is demonstrated. Example 5 Volume of alkaline gallate = 100 ml Initial gallium concentration - 200 mg/l Alkali concentration as NaOH = 240 gm/l Rate of flow = 100ml/h Volume of the resin bed = 8 ml Final gallium concentration = 18 mg/l % of gallium recovery = 91 % The following are the advantages of this invention. 1. The process for the production of chelating ion exchange resin in aqueous medium which is cheap and more conveniently exploitable on a commercial scale. 2. The temperature of the whole reaction sequence is 80°C, which is affordable and convenient when compared to use of non-aqueous solvents wherein the solvent molecule occlusion, solvent evaporation and handling poses a problem. 3. The process is suitable to different kinds of monomers commercially available and the characteristics of resins can be tailor made so as to suit the end use in this case for the recovery of heavy metal ions from alkaline media. 4. Since water is used as medium of reaction, the process is environment friendly. 5. The resin developed can be used to recover gallium from alkaline solution. We Claim: 1. A process for the preparation of chelating ion exchange resin for use in heavy metal recovery which comprises I) preparing the copolymer resin with desired pendant group by suspension polymerization of the appropriate monomer such as herein described in the concentration ranges from 60 -90 wt%, along with a stabilizer and an initiator such as herein described at a temperature in the range of 60 - 85°C under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an aquous solution containing sodium acetate and hydroxylamine hydrochloride then isolating the resin beads formed by filtration and washing followed by drying at a temperature of 100-110°C for a period of 12-16 hours, after which the resin beads are soaked in benzene for 10-12 hours, iii) separated and refluxing the said resin beads in aqueous solution containing sodium acetate and hydroxylamine chloride in the ratio of Resin: Sodium acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5 wherein after treatment of copolymer resin is refluxed in a temperature range of 70- 80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 100-110°C for a period 10-20 hours to get the chelated ion exchange resin. 2. A process as claimed in claim 1 wherein the monomer used is selected from any one of those having pendant groups like acrylate, methacrylate, nitrile, carboxylic acid chloride, carboxylic amides, carboxylic anhydrides monomers hailing from acrylic vinyl monomers family. 3. A process as claimed in claim 1 -2 wherein the monomer is selected from divinyl benzene, ethyl vinyl benzene . 4. A process as claimed in claim 1-3 wherein the stabilizer such as starch or polyvinyl is used. 5. A process as claimed in claim 1-4 wherein wherein the of stabilizer concentration ranges from 1-10 wt% with respect to the total weight of the monomer used. 6. A process as claimed in claim 1- 5 wherein the initiator used is selected from benzyl peroxide, azo bis butyronitrile , tetra butyl peroxide. 7. A process as claimed in claim 6 wherein the in the concentration of initiator ranges from 0.2-0.8 wt% with respect to total monomer concentration. 8. A process as claimed in claim 1-7 wherein the addition of monomer to the stabilizer is effected for a period of 15-30 minutes. 9. A process as claimed in claim 1-8 wherein the the suspension polymerization is carried out at a temperature in the range, of 60-75°C at a stirring speed of 1500-2000 rpm. 10. A process as claimed in claim 1-9 wherein the reaction temperature of the suspension polymerization is raised to 70-85°C over 15 minutes while simultaneously reducing the speed of stirring to 700-800 rpm. 11. A process as claimed in claim 1-10 wherein the suspension copolymerization is carried out for a period of 5-7 hours. 12. A process as claimed in a process for the preparation of chelating ion exchange resin for use in heavy metal recovery substantially as herein described with reference to examples.

Full Text

This is an invention, which relates to an improved process for the preparation of chelating ion exchange resin for use in heavy metal recovery.
This invention more particularly relates to an improved process for the preparation of copolymer resin having appropriate pendant group that can be adapted to introduce chelating functional groups which can be used for the recovery of metals. The invention also relates to a process for the production of chelating ion-exchange resins which involved preparing suitable copolymer with desired pendant group as a base resin adapted for the introduction of chelating functional groups and thereafter treating the resin so as to produce chelating ion exchange resins. These resins are needed for the commercial application in the efficient recovery of heavy metals from lean solutions particularly in alkaline medium.
The performance and durability of the so needed chelating ion exchange resin in the above mentioned application is governed by the following characteristics:
i. The resin must be stable in strong alkaline solution
ii. The resin must withstand acid treatment for long duration
iii. The resin must withstand particular range of temperatures namely 30°C -100°C which is normally realized from the heat generated from the reaction when highly alkaline and acid solutions are repeatedly used for adsorption and elution process respectively during heavy metal recovery.
Hitherto, chelating ion exchange resins in which the ligands capable of forming complexes with heavy metal ions are produced commercially. They are chelate resins having iminodiacetic acid group, such as for example, Dowex A-1 (product of Dow chemical Co.) and Uniselec UR-10-50 (product of Unichika Co. Ltd) (imino diacetic acid derivative) and the chelate resin with amidoxime group such as Doolite ES-346 (Rohm and Haas, Canada, Inc.) (amidoxime derivative). These resins suffer from the following disadvantages:
i. poor efficiency in selective capturing of the adsorbed heavy metal ions, and
in particular under strongly basic solution and
ii. poor reusability in acidic media.
To overcome these difficulties, chelating ion-exchange resins particularly with hydroxamic acid functional group is reported to be prepared in non-aqueous medium employing carcinogenic and highly inflammable solvents which are difficult to be implemented in an environment - conscious industrial condition [ref: J. Polym. Sci. Chem.
Ed. 14, 2155-2165, (1976) and Macromolecules 11, 597-603 (1978)]. Hence, the main objective of the present invention is to provide an improved process for the preparation of chelating ion exchange resins in aqueous medium based among the drawbacks highlighted above. The process proposed accordingly in the present invention is also simple and safe to produce chelating ion exchange on a commercial scale.
Accordingly the present invention provides a process for the preparation of chelating ion exchange resin for use in heavy metal recovery which comprises I) preparing the. copolymer resin with desired pendant group by suspension polymerization of the appropriate monomer such as herein described in the concentration ranges from 60 -90 wt%, along with a stabilizer and an initiator such as herein described at a temperature in the range of 60 - 85°C under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an aquous solution containing sodium acetate and hydroxylamine hydrochloride then isolating the resin beads formed by filtration and washing followed by drying at a temperature of 100-110°C for a period of 12-16 hours, after which the resin beads are soaked in benzene for 10-12 hours, iii) separated and refluxing the said resin beads in aqueous solution containing sodium acetate and hydroxylamine chloride in the ratio of Resin: Sodium acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5 wherein after treatment of copolymer resin is refluxed in a temperature range of 70-80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 100-110°C for a period 10-20 hours to get the chelated ion exchange resin.
According to a feature of the invention, a copolymer capable of forming a macromolecular network with the desired pendant group is prepared using suspension polymerization mode and the required chelating functional group, namely, hydroxamic acid is introduced into the resulting resin through after treatment of the copolymer resin.
The formation of such a copolymer resin with the desired pendant group forms the first stage and the incorporation of chelating functional group into the preformed copolymer resin constitutes the second stage. Consequently, the basic copolymer resin can be made for introducing required chelating functional group according to the choice of heavy metal ions as per this invention and is presently illustrated for hydroxamic acid functional group as a chelating point in the ion exchange resin so produced in this invention.
One characteristic feature of the present invention is the choice of monomer and co-monomer capable of forming copolymer resin with the required pendant group adaptable for
the introduction of chelating functional group. The predominant monomer unit that constitutes the copolymer chain comprises form any of the monomers having pendant groups like acrylate, methacrylate, nitrite, carboxylic acid chloride, carboxylic amides, carboxylic anhydrides and the like monomers possessing any one of the above said groups. The co-monomer unit that constitutes the rest of the copolymer chain comprises form any one of the monomers like divinyl benzene, ethyl vinyl benzene and the like. The quantity of the monomer that constitutes the predominant part of the copolymer chain in the feed for copolymerisation should preferably be in the range 60-90 weight per cent and the quantity of co-monomer unit constituting the rest of the copolymer chain should preferably be in the range of 40-10 wt % thus making the total monomers feed composition in the co polymerization scheme as 100%.
A further characteristic of the present invention is the use of aqueous medium in which the suspension polymerization is adopted using any one of the stabilizers among the water soluble polymers such as starch, polyvinyl-alcohol and the like. The use of such stabilizer helps in suspending the monomers in water in the form of fine droplets which are thus stabilized and prevented from coalescing. The preferred concentration of the stabilizer for this purpose should preferably be in the range of 1-10 wt % with respect to total weights of the monomers employed in the feed for copolymerization.
Another characteristic of the present invention is the use of initiators which can be selected from any one of the free radical catalysts like benzoylperoxide, azo-bis iso butyronitrile, tert butyl peroxide and the like. The preferred concentration of such free radical initiators should be in the range of 0.2-0.8 wt % with respect to the total weight of the monomer mixture employed in the feed of copolymerization.
Further characteristic of the present invention is the "after treatment" of the copolymer with reagent capable of introducing hydroxamic acid group under reflux condition in aqueous medium. The reagents that can be used for this purpose are sodium acetate and hydroxylamine hydrochloride and their preferred concentration should be in the ratio 1-3:1-4:1-5 with respect to the weight of preferred resin.
An embodiment of the invention is now illustrated.
Typically, the said chelating ion exchange resin is prepared* in two stages. The first stage consists of suspension polymerization of monomer having the desired pendant group
suitable for the introduction of chelating groups along with the copolymerizable monomers such as divinyl benzene. Any one of the monomers hailing from the acrylic or vinyl family is mixed with an appropriate quantity of divinyl benzene along with the free radical initiator in the said ranges at room temperature and thus the feed for the suspension polymerization is made ready. This mixture is slowly added to the preformed solution comprising of the stabilizer like starch or polyvinyl alcohol or the like in the said composition kept in a reaction flask which is thermostated at 60-70°C, over a period of time ranging form 15 to 30 minutes. The reaction flask is necessarily provided with a reflux condenser and a mechanical stirrer capable of stirring at various speed. The speed of the stirrer during the addition of monomer mixture is maintained in the range of 1500-2000 rpm. After the addition of monomer mixtures is complete, he reaction temperature is slowly raised to 70-85°C over 15 minutes during which time the preset stiffing speed of 1500-2000 rpm is reduced to 800 rpm and the co-polymerization is allowed to proceed for 5-7 hours. The resultant polymer beads that are formed in the reaction flask are cooled, filtered and washed with hot water and then dried for 12-16 hours in a temperature range of 100-110°C.
The copolymer beads of uniform particle size are soaked in benzene for 10-12 hours for "after treatment of resin", separated and added to the reaction vessel in which an aqueous solution containing sodium acetate and hydroxylamine hydrochloride constituted in the said concentration ranges. This "after treatment" is allowed to proceed under reflux in the temperature range of 70-80°C for a period of time ranging from 24-30 hours. After completion of the reaction, the polymer bead product formed is filtered, repeatedly washed with water and dried for a period of 10-20 hours in an air oven at a temperature range of 100-110°C. The chelating ion exchange resin thus obtained is further subjected to alkali and acid treatments.
The invention is illustrated in detail in the examples given below which should not, however be construed to limit the scope of the invention.
Preparation of Co-potymer having acrylate pendant group
Example 1
Wt. of Divinyl benzene (DVB) 20 g
Wt. of Methylmethacrylate (MMA) 80 g
Wt. of Benzoyl peroxide 80 mg
Wt. of Starch 8 g
Vol. of. Water 600 ml
Temperature of reaction 60°C for 30 min.
80°C thereafter
Rate of stirring Appro. 2000 rpm for 30
min
Appro. 800 rpm thereafter
Duration of polymerization 5-7 hrs.
Wt. of MMA-DVB copolymer obtained 80-85 g
Example2
Wt. of Divinyl benzene (DVB) 30 g
Wt. of Methylmethaerylate (MMA) 70 g
Wt. of Benzoyl peroxide 80 mg
Wt. of Starch 8g
Vol. of Water 600 ml
Temperature of reaction 60°C for 30 min
80°C thereafter
Rate of stirring Appro. 2000 rpm for 30
min
Appro. 800 rpm thereafter
Duration of polymerization 5-7 hrs.
Wt. of MMA-DVB copolymer
obtained 80-90 g
Preparation of chelating Ion-exchange resin based on the Co-polymser prepared with hydroxamic acid group
Example 3
Wt. of copolymer (MMA-DVB) 20 g
Wt. of sodium acetate 21 g
Wt. of hydroxy! amine
hydrochloride 26 g
Volume of water 300 ml
Temperature of reaction 80°C
Rate of stirring 1500 rpm
Duration of polymerization 24 hrs
Wt. of resin obtained Approx. 22 g
Acid/Alkali stability No appreciable weight loss
Example 4
Wt. of copolymer (MMA-DVB) 15 g
Wt. of sodium acetate 15 g
Wt. of hydroxy! amine
hydrochloride 15 g
Volume of water 300 ml
Temperature of reaction 80°C
Rate of stirring 1500 rpm
Duration of polymerization 24 hrs
Wt. of resin obtained Approx. 13 g
Acid/Alkali stability No appreciable weight loss
The chelating ion exchange resin of about 5 gm, obtained based on the preparation reported in reference example 3, was soaked overnight in pure 2M NaOH solution. The swollen resin after decantation of supernatant alkali was packed in a glass column of 250 mm height with an inner diameter of 10 mm. The height of swollen resin was about 80 mm. A strongly alkaline solution containing gallium, was allowed to pass through the resin bed at the required rate of flow. The treated alkaline solution was analyzed for its gallium content to compute gallium adsorption on the resin. The adsorption of gallium on resin is illustrated
by the example given below, wherein the selectivity to gallium in alkaline medium is demonstrated.
Example 5
Volume of alkaline gallate = 100 ml
Initial gallium concentration - 200 mg/l
Alkali concentration as NaOH = 240 gm/l
Rate of flow = 100ml/h
Volume of the resin bed = 8 ml
Final gallium concentration = 18 mg/l
% of gallium recovery = 91 %
The following are the advantages of this invention.
1. The process for the production of chelating ion exchange resin in aqueous medium which is cheap and more conveniently exploitable on a commercial scale.
2. The temperature of the whole reaction sequence is 80°C, which is affordable and convenient when compared to use of non-aqueous solvents wherein the solvent molecule occlusion, solvent evaporation and handling poses a problem.
3. The process is suitable to different kinds of monomers commercially available and the characteristics of resins can be tailor made so as to suit the end use in this case for the recovery of heavy metal ions from alkaline media.
4. Since water is used as medium of reaction, the process is environment friendly.
5. The resin developed can be used to recover gallium from alkaline solution.

We Claim:
1. A process for the preparation of chelating ion exchange resin for use in heavy
metal recovery which comprises I) preparing the copolymer resin with desired
pendant group by suspension polymerization of the appropriate monomer such as
herein described in the concentration ranges from 60 -90 wt%, along with a stabilizer
and an initiator such as herein described at a temperature in the range of 60 - 85°C
under stirring for a period upto 7 hrs, ii) treating the resulting copolymer resin with an
aquous solution containing sodium acetate and hydroxylamine hydrochloride then
isolating the resin beads formed by filtration and washing followed by drying at a
temperature of 100-110°C for a period of 12-16 hours, after which the resin beads
are soaked in benzene for 10-12 hours, iii) separated and refluxing the said resin
beads in aqueous solution containing sodium acetate and hydroxylamine chloride in
the ratio of Resin: Sodium acetate: Hydroxylamine hydrochloride as 1-3: 1-4: 1-5
wherein after treatment of copolymer resin is refluxed in a temperature range of 70-
80°C for a period of 24-30 hrs, dried in an air oven at a temperature of 100-110°C for
a period 10-20 hours to get the chelated ion exchange resin.
2. A process as claimed in claim 1 wherein the monomer used is selected from
any one of those having pendant groups like acrylate, methacrylate, nitrile,
carboxylic acid chloride, carboxylic amides, carboxylic anhydrides monomers hailing from acrylic vinyl monomers family.
3. A process as claimed in claim 1 -2 wherein the monomer is selected from divinyl benzene, ethyl vinyl benzene .
4. A process as claimed in claim 1-3 wherein the stabilizer such as starch or polyvinyl is used.
5. A process as claimed in claim 1-4 wherein wherein the of stabilizer concentration ranges from 1-10 wt% with respect to the total weight of the monomer used.
6. A process as claimed in claim 1- 5 wherein the initiator used is selected from benzyl peroxide, azo bis butyronitrile , tetra butyl peroxide.
7. A process as claimed in claim 6 wherein the in the concentration of initiator ranges from 0.2-0.8 wt% with respect to total monomer concentration.
8. A process as claimed in claim 1-7 wherein the addition of monomer to the stabilizer is effected for a period of 15-30 minutes.
9. A process as claimed in claim 1-8 wherein the the suspension polymerization is carried out at a temperature in the range, of 60-75°C at a stirring speed of 1500-2000 rpm.
10. A process as claimed in claim 1-9 wherein the reaction temperature of the suspension polymerization is raised to 70-85°C over 15 minutes while simultaneously reducing the speed of stirring to 700-800 rpm.
11. A process as claimed in claim 1-10 wherein the suspension copolymerization is carried out for a period of 5-7 hours.
12. A process as claimed in a process for the preparation of chelating ion exchange resin for use in heavy metal recovery substantially as herein described with reference to examples.

Documents:

601-del-1995-abstract.pdf

601-del-1995-claims.pdf

601-del-1995-correspondence-others.pdf

601-del-1995-correspondence-po.pdf

601-del-1995-description (complete).pdf

601-del-1995-form-1.pdf

601-del-1995-form-2.pdf

601-del-1995-form-4.pdf

601-del-1995-form-9.pdf

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Patent Number

190375

Indian Patent Application Number

601/DEL/1995

PG Journal Number

N/A

Publication Date

26-Jul-2003

Grant Date

24-Feb-2002

Date of Filing

31-Mar-1995

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	RAMANATHAN MEYYAPPAN	C.E.C.R.I., KARAIKUDI, INDIA
2	SETHURAMAN PITCHUMANI	C.E.C.R.I., KARAIKUDI, INDIA
3	SWATI AJITKUMAR LAHIRI	C.E.C.R.I., KARAIKUDI, INDIA
4	ALAGAPPILLAI VARADMARAJ	C.E.C.R.I., KARAIKUDI, INDIA

PCT International Classification Number

B01J 45/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA