DESC:Field of the invention:
The present invention generally relates to filter media for efficiently separating metal particles from a spent pickling liquor, more particularly the present invention relates to the method of preparation of catechol based porous filter media that can be used for trapping of metal particles in industrial waste. Invention targets preparing a media either by coating or impregnation of porous material scaffold that contains specifically benzoxazine polymer,
Background of the invention:
Metal surface pre-treatment is a process of cleaning metal surfaces using strong acids. Metal processing industry uses pickling process (metal pre-treatment) widely in primary & high-end metal processing industry segment such as electroplating, sheet, structural steel, pipe-tube as well as construction, automotive and home appliances. Disposal of spent acid waste is the major problem being faced by metal processing viz. electroplating, galvanizing industry. In case of printed circuit boards (PCB) manufacturer milder organic acids such as citric acids, ethylene diamine tetra acetic acid (EDTA) are used towards removal of residual metal particles remained after each electroplating steps. Hydrochloric, sulfuric acids &/or mixture of sulfuric & nitric acids are the most extensively used metal pre-treatment acids in this metal pre-treatment segment. Acid life cycle for virgin acids starts by rapid building-up of metal content exponentially over a period due to surface leached metal or its surface fallouts such as metal oxides. These used acid tanks tend to die &/or become obsolete in matter of 10-20 or utmost 35-45 days depending upon its usage. Spent acid (SPL) should be dumped because the efficiency of pickling decreases with increasing content of dissolved metal in the bath. Spent pickling liquors are classified as hazardous materials due to their high concentration of metals and presence of different acids. Several technologies have been developed to treat this kind of wastes. Disposal and processing of spent pickling liquor becomes complex & chaotic because of the low pH of the solution; gel-like or compressible nature of sludge developed during pickling process even after neutralization of SPA; and the dissolved metal content of the solution. The existing processes dealing with the problem need bigger facilities, investments and higher operating cost making it unaffordable to metal processing industries or metal processing industrial set ups. Commercially there are materials available in the market which cater to the needs of low moderate dissolved metal loads to a limited pH levels such as 3-5. However, when pH streams are in the range of 1-3 it becomes challenging for filtration media to sustain such aggressive conditions. It more challenging for removing metals salts in such chaotic low pH solution matrix of acid waste effluents.
To deal with the problem of such spent liquor processing is divided in two parts. In first step, the low pH spent liquor is treated to precipitate metal salts and oxides and the precipitate is treated with an additive that converts the precipitate into friendly to -process, non-compressible and environmentally benign solid material. Filtration is carried out in the second step that separates heterogeneous solid from pickling acid to extend life of acid under use. Metal chelation can be carried out for effective separation of metal particles from the spent liquor. Presently commercially available materials in market for metal chelation are chemical building blocks derived from fossil fuel. These materials are restricted to limited loads of metal chelation. These materials are high value imported items and makes unfeasible for the subject applications thereby making the precipitation and filtration method unaffordable.
Urushiol is a mixture of several catechol derivatives that are the main constituents of the irritant oil of plants of the Toxicodendron species. Urushiol is a natural product, and chemically its molecule has reportedly shown extraordinary coordination capacity towards metal ions or free metals from the transition metal category. Urushiol based Poly benzoxazine (PUBz) materials are identified as promising metal chelators from highly acidic aqueous systems. Use of such PUBz polymer is advantageous as binder in composite systems inorganic matrix. e.g. use of PUBz in metal organic frameworks (MOF) and to bind Silica materials in composite applications is also a topic of detailed investigations. Urushiol molecules bear a natural capacity to sequester or chelate and retain metal ions using its catecholate-functionality. Further polymer materials derived using Urushiol show extraordinary sustenance in very low pH conditions. This property is highly beneficial for metal sequestration or removal from very acidic effluent streams.
Polybenzoxazine (PUBz) is normally synthesized using phenol, catechol or urushiol with an established two step reaction wherein a benzoxazine monomer (UBz) is prepared in a first step followed by thermal curing of monomer to produce the polymer, in second step. The benzoxazine monomer (UBz) is synthesized by a known three component system comprising a primary amine (R-NH2), aldehyde and a phenol such as urushiol.

In the above reaction, R1 is an alkyl group, R is an alkyl or aryl group, M+ is a metal ion, and the aldehyde is a formaldehyde (HCHO) solution or paraformaldehyde powder having molecular formula HO(CH2O)8-100H
In the above reaction, the temperature required for thermal curing ranges from 120°C to 150°C. Use of metal catalysts are reported to require less energy for polymerization step which is about 75-95°C. These metal salts may be referred as accelerators than catalysts. Salts of Iron, Copper and Aluminum, such as FeCl3, CuCl2, Al2O3/ AlCl3 are preferred for polymerizing benzoxazine monomer.
One constraint for PUBz as material for applying these applications is its material morphology. Raw PUBz-material synthesized in lab is observed buoyant on liquids of interests for filtration. It is highly glossy, stiff with observed lower bulk density that offers limited surface area to allow and pass such acidic effluent containing large, dissolved metal contents.
Accordingly, there exists a need to provide a cost effective filter media that will effectively work in low pH conditions; that will offer sufficient surface area to allow and pass acidic effluent containing large, dissolved metal contents and efficiently capture larger quantities of dissolved metal part from the pickling acid solution so that reoccurring filtration processes can remove dissolved metal salts thereby keeping pickling acid solution reusable for extended or indefinite period.
Objects of the invention:
An object of present invention is to provide a novel filter media for efficiently trapping and separating metal particles from an industrial waste/ spent pickling liquor.
Another object of the present invention is to provide a filter media that will sustain the very low pH chemical streams and chelate or sequester heavy loads of dissolved metals from acidic media
Yet another object of present invention is to provide a cost effective and commercially beneficial catechol or its analogues based filter media for separating metal particles from a spent pickling liquor.
Still another object of the present invention is to provide a benzoxazine polymer based porous filter media that will retain with itself the dissolved metal ions in the industrial waste/ spent pickling liquor making the industrial waste streams reusable for long term.
Still another object of the present invention is to provide a benzoxazine polymer based porous filter media that will make the pickling acid operations a zero-spent-acid discharge process.
Yet another object of present invention is to provide a method of preparation of a benzoxazine polymer based porous filter media for separating metal particles from a spent pickling liquor.
Yet another object of present invention is to provide a method of preparation of a filter media for trapping metal particles in industrial waste that will suit to the chemical & physical conditions of Acid life Extender (ALEX) process. (ALEX is a trademark company proprietary process of filtration wherein company uses a formulation of flocculants for sedimentation & removal of colloidal and partly dissolved metals &/or metal salts from effluent.)
Yet another object of present invention is to utilize method of synthesis of benzoxazine polymer to modify hollow spherical substrate particle and use these polymer (PUBz) deposited over spherical porous particles as filter media for separating metal particles from a spent pickling liquor.
Yet another object of the present invention is to make the poly benzoxazine material afford more possible surface area to trap dissolved metal carry forwards in a spent pickling liquor.
Yet another object of the present invention is to prepare PUBz material which is engineered to perform on metal selectivity and metal removal from the waste acidic effluent.
Summary of the invention
The present invention in one aspect provides a benzoxazine polymer (PUBz) composite filter media that can be used for trapping of metal particles in industrial waste. The filter media is a polymeric benzoxazine coated on porous hollow microsphere particles, specifically mesoporous silica particles and hollow ceramic microspheres derived of fly ash, having diameters ranging from 5 micron to 1000 micron.
The present invention in another aspect provides a method preparation of benzoxazine polymer (PUBz) composite filter media. For preparing the filter media, a metal catalyst selected from chlorides of copper, iron, aluminum, and mixtures thereof, is deposited onto a surface of a hollow microsphere particles in a first step. In next step, the metal catalyst deposited microsphere particles are added to a solution of benzoxazine monomer (UBz) in an organic solvent, with weight ratio of the benzoxazine monomer (UBz) to the metal catalyst deposited microsphere particles ranging from 30: 1 to 35:1, to form benzoxazine monomer (UBz) coated microsphere particles. The benzoxazine monomer deposited on the microsphere particles is then polymerized. In an embodiment, polymerization is carried out by heating the mixture of the benzoxazine monomer (UBz) coated microsphere particles and the organic solvent wherein the benzoxazine monomer gets polymerized onto the surface of the microsphere particles and simultaneously in the solution, forming a benzoxazine polymer (PUBz) matrix thereby creating a porous passage. In another embodiment, polymerization is carried out by first solvent drying the benzoxazine monomer (UBz) coated microsphere particles under reduced pressure and subjecting the solvent dried benzoxazine monomer (UBz) coated microsphere particles to curing.
The cured filter media with dried and free flowing particle property can be used as a polymeric resin bid for filtration applications, providing a material for chelating numerous metals from strongly acidic system.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a schematic representation of method of preparation of benzoxazine polymer matrix (PUBz) through metal catalyzed polymerization, in accordance with an embodiment of the present invention;
Figure 2 shows schematic representation of removal of microspheres from polymer matrix, in accordance with an embodiment of the present invention;
Figure 3 and 4 respectively show a schematic representation of method of deposition benzoxazine monomer (UBz) on microspheres and polymerization through curing, of benzoxazine monomer (UBz) deposited on microspheres, in accordance with another embodiment of the present invention;
Figures 5A, 5B, 5C. 5D respectively show scanning electron microscopic (SEM) images of an uncoated hollow microsphere, a hollow microsphere coated with 1% Urushiol Benzoxazine (UBz) solution, a hollow microsphere coated with 3% Urushiol Benzoxazine (UBz) solution, and a hollow microsphere coated with 5% Urushiol Benzoxazine (UBz) solution, in accordance with exemplary embodiments of the present invention; and
Figures 5E and 5F show scanning electron microscopic (SEM) images of the urushiol based Poly benzoxazine (PUBz) deposited on a hollow microsphere, in accordance with the present invention. It represents metal catalyzed polymerization around metal chloride salt deposited hollow microsphere.
Detailed description of the embodiments:
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.
In one aspect, the present invention provides benzoxazine polymer composite filter media.
Throughout the description, the words ‘filter media’, ‘poly benzoxazine composite’, ‘benzoxazine polymer composite’, ‘benzoxazine polymer matrix’ are used interchangeably and mean the benzoxazine polymer composite filter media of the present invention. Throughout the description, the words benzoxazine monomer and UBz are used interchangeably and mean the urushiol based benzoxazine monomer. Throughout the description, the words benzoxazine polymer, poly benzoxazine and PUBz are used interchangeably and mean the urushiol based benzoxazine polymer.
The filter media of the present invention comprises benzoxazine polymer coated on porous hollow microspheres. The filter media is a benzoxazine polymer composite resin material in the form of semi micron sized beads, derived from locally available raw materials that will suit to the chemical & physical conditions of Acid life Extender (ALEX) process. The filter media is designed to add value, engineered with intention to chelate, and capture larger quantities of dissolved metal part from the pickling acid solution so that reoccurring filtration processes can remove dissolved metal salts thereby keeping pickling acid solution reusable for extended or indefinite period.
The porous hollow microspheres are hollow spherical particles having porous circumferential wall, with diameter ranging from 5 micron to 1000 micron. The present invention effectively uses hollow as well as porous microsphere surface for preparing the filter media. Microspheres are sometimes referred to as spherical microparticles. In general, microspheres that are solid or hollow or porous spherical particles and do not have a fluid inside. In an embodiment, the porous hollow microsphere particles are selected from Cenospheres, Bentonites, Gamma Alumina, mesoporous silica particles, cellulose particles, chitosan particles, and like. the porous hollow microsphere particles behold PUBz coating on its porous surface and provide metal scavenging bed for filtration of low pH or acidic waste effluent streams. In a preferred embodiment, the hollow microsphere particles are Cenospheres. These are hollow ceramic microspheres derived of fly ash, a natural by-product of coal combustion during the generation of electric power.
In another aspect, the present invention provides a method of preparation of the benzoxazine polymer composite filter media.
The method of preparation of the benzoxazine polymer composite filter media comprises in first step, adsorption/ pre-planting/ deposition of a metal catalyst onto the surface of porous hollow microsphere particles. In an embodiment, the metal catalyst is selected from chlorides of copper, iron, aluminum, and mixtures thereof. In a preferred embodiment, the metal catalyst is selected from anhydrous chloride salt of copper, iron, aluminum and mixtures thereof. The metal catalysts used in present invention are commercially available salts at their stable water-of-hydration level. In another embodiment, the porous hollow microsphere particles are selected from Cenospheres, Bentonites, Gamma Alumina, mesoporous silica particles, cellulose particles, chitosan particles, and like. the porous hollow microsphere particles behold behold PUBz coating on its porous surface and provide metal scavenging bed for filtration of low pH or acidic waste effluent streams. In a preferred embodiment, the hollow microsphere particles are Cenospheres. These are hollow ceramic microspheres derived of fly ash, a natural by-product of coal combustion during the generation of electric power. The metal catalyst is first dissolved in anhydrous / dry alcohol solvent selected from Methanol, Ethanol and 1-Propanol and the microsphere particles in powder form are added to the alcoholic solution of metal salts. The mixture of microspheres and the alcoholic solution of metal catalyst is sonicated for 10 to 15 min. After sonication, the alcohol solvent is evaporated at reduced pressure (380-410 mbar to 1-mbar) and with mild heating in a range from 40?C to 60?C, depending upon type of amine & phenol mole ratio in a rotary evaporator. The resulting material is heated in an oven at 80-85°C for 2-5 hours to get metal catalyst deposited microsphere particles.
In the next step the method comprises of depositing benzoxazine monomer onto the metal catalyst deposited microsphere particles, wherein the benzoxazine monomer (UBz) is taken in a three necked round bottom flask and a suitable organic solvent is added thereto. In an embodiment, the organic solvent is selected from 1,4 Dioxane, Ethanol, Chloroform, Dichloromethane, and mixtures thereof. The mixture is stirred well and the metal catalyst deposited microsphere particles are added to the solution, wherein the microsphere particles get coated with the benzoxazine monomer (UBz) particles. The weight ratio of UBz to metal catalyst deposited spherical microspheres ranges from 30: 1 to 35:1. The hollow microsphere particles coated with benzoxazine monomer (UBz) – are now ready to be polymerized.
In the next step, the method comprises polymerizing the benzoxazine monomer (UBz) which has been coated on the microsphere particles.
In an embodiment, the benzoxazine monomer (UBz) coated on the microsphere particles is polymerized by a metal catalyzed thermal polymerization process. Referring to figure 1, in the metal catalyzed thermal polymerization process, the mixture of the benzoxazine monomer (UBz) coated microsphere particles and the organic solvent selected from 1,4 Dioxane, Ethanol, Chloroform, Dichloromethane, and mixtures thereof, is heated to a temperature ranging from 80°C to 85°C with constant stirring for 2 to 5 hrs. The resulting solution is then taken in a petri dish and heated in an oven for three to four hr at 150°C for removal of solvent. The metal catalyzed thermal polymerization of the monomer UBz gets accelerated due to metal catalyst pre-planted on the surface of the hollow microsphere particles. The monomer UBz gets polymerized onto the surface of the hollow microsphere and simultaneously in the solution, forming a benzoxazine polymer (PUBz) matrix (filter media) thereby creating a porous passage. The benzoxazine polymer matrix can be utilized as a filtration media as it provides sufficient porous passage for the spent pickling liquor to flow therethrough while the catecholate-functionality helps in trapping the metal particles in the liquor. Referring to figures 5E and 5F, a porous passage created in the filtration media is seen. The filtration media is the new polymer matrix containing the micro particles bearing the adsorbed metal salts
In another embodiment, the benzoxazine monomer (UBz) coated on the microsphere particles is polymerized by curing the benzoxazine monomer (UBz) coated microsphere particles at a suitable temperature. The curing temperature ranges from 120ºC to 360C, depending upon type of amine & phenol mole ratio used. Curing can also be carried out using metal salt solution in UBz material solution from temperature ranging from 90?C to 240?C depending upon type of amine & phenol mole ratio used.
Referring to figure 3 and 4, benzoxazine monomer (UBz) coated microsphere particles are subjected to solvent drying under vacuum. The vacuum dried UBz deposited microparticles are then subjected to curing. The nature of the UBz material in presence of metal accelerator and under favorable thermal conditions are expected to polymerize UBz to PUBz. In the curing process, the deposited Ubz gets polymerized to form the polymer PUBz material with desired and warranted Catecholate functional groups that helps these materials to be used as the filtration media. Curing potentially modifies singular microparticle with warranted polymer surface there by creating a resinous polymer particle that can be used as filtration media in a cartridge for filtration application.
Referring to figure 2, the hollow microsphere particles are removed from the from the benzoxazine polymer matrix by treating the benzoxazine polymer matrix with a low pH acidic system. In an embodiment, the low pH acidic system is selected from a mineral acidic system having pH ranging from 1 to 3, and organic acid system having pH ranging from 3 to 5.
The porogen removal from polymer matrix with help of mineral acids creates newer and even higher surface area than earlier for utilizing the catecholate-functionality to make use of this material as filtration media.
Figures 5A, 5B, 5C, 5D respectively show scanning electron microscopic (SEM) images of an uncoated hollow microsphere, a hollow microsphere coated with 1% Urushiol Benzoxazine (UBz) solution, a hollow microsphere coated with 3% Urushiol Benzoxazine (UBz) solution, and a hollow microsphere coated with 5% Urushiol Benzoxazine (UBz) solution, in accordance with exemplary embodiments of the present invention.
The polymerization process of the present invention creates a polymer bulk/ composite with modified surface properties with respect to its available surface area. The cured polymer particle covered on microsphere/ Cenosphere shell with dried and free flowing particle property can be used as a polymeric resin bid for filtration applications. Such modified spheres have potential application to be used as its use in filtration media as described in the present invention document. Such materials not only can sustain very low pH chemical streams but also chelates or sequesters heavy loads of dissolved metals from the same acidic streams. Referring to the graph in figure 6, the PUBz filtration media of the present invention comprising hollow microparticles doped with metal salts from the initial batches shows reducing dissolved metal (iron) concentration by 24-25%.
The method of preparation of the benzoxazine polymer composite filter media of the present invention is further illustrated by the following example. The example is given by way of illustration and should not be construed to limit the scope of present invention:
Experimental example
In first step, the Cenosphere D500 hollow microspheres were deposited with metal salt catalyst FeCl3:
3 gm FeCl3 was taken in 20 ml ethanol dry solution in a 1-neck round bottom flask. 5 gm Cenosphere D500 powder was added to the solution. The mixture was stirred for 15-20 min while adding 10-12 ml more Ethanol to facilitate adsorption of FeCl3. The mixture was sonicated for 10-15 min. Ethanol solvent was then removed in a rotary evaporator at reduced pressure ranging from 380-410 mbar to 1-mbar and at a temperature ranging from 40?C to 60?C. The solid material was taken on petri-dish and kept it in oven at 80-85°C for 2-3 hours. Thus, prepared metal chloride deposited Cenosphere was used in experiments onwards.
In next step, Polybenzoxazine was synthesized using metal salt deposited Cenosphere D 500:
17.14 gm of prior synthesized benzoxazine (UBz) was taken in a 3-neck round bottom flask and about 25-30 ml xylene was added as solvent. The mixture was allowed to mix well and heated to 80-85°C till it turns dark. 0.51-0.54 gm of FeCl3 loaded Cenosphere 500D was added to the solution and kept under stirring for 3-4 hours. The resulting mixture was then transferred in a petri-dish and heated in a oven for 3-5 ours at 150°C. With removal of xylene a semi-cured Poly benzoxazine polymer composite is obtained.
The above step was repeated using commercially available porous cellulose beads MC-200, MC-500 & MC-700 with diameter of 200µm, 500µm & 700 µm respectively.
Table 1 shows data depiction of PUBz material resin in contact with industrial effluent from PCB-manufacturer’s metal pre-treatment line. Figure shows the selective removal of Ni salts from a mix of metal salts from PCB-industry waste effluent. Preferential selectivity of material is shown by the selective pickup of less available metal such as Nickel metal ion over the more Iron (Fe) metal ion available in its dissolved form inside the industrial effluent.

Elements Stock Solution Assay
[ppm] Post-Resin contact metal assay [ppm]
Metal reduction to stock [%]
Iron (Fe) 2173 1639 25
Nickel (Ni) 0.1 0.007 96
Tin (Sn) 0.055 0.034 38
Silver (Ag) 0.022 0.018 18
The benzoxazine polymer composite filter media obtained in the process not only sustains the very low pH chemical streams but also chelates or sequesters heavy loads of dissolved metals from acidic media. Referring to figure 6, the industrial acid waste with metal rich acidic stream (spent Pickling Acid) was treated with Poly benzoxazine polymer composite comprising hollow microparticles doped with some metal salts. The Poly benzoxazine polymer composite shows to reduce the concentration of the dissolved metal (iron) by 24-25%.
Advantages of the invention:
? The benzoxazine polymer composite filter media of the present invention is highly suitable for dynamic flow filtration system where metals are to be removed under continuous liquid flow streams.
? The benzoxazine polymer composite filter media of the present invention is a cost effective and commercially beneficial solution for an efficient trapping and separating of metal particles from an industrial waste/spent pickling liquor.
? The benzoxazine polymer composite filter media of the present invention sustains very low pH chemical streams and chelate or sequester heavy loads of dissolved metals from acidic media.
? Metals such as Iron, Copper, Aluminium, Zinc Magnesium Chromium, and other metals in the similar category may show chelating effect in presence of PUBz polymers.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.
,CLAIMS:I claim:
1. A benzoxazine polymer composite filter media for chelating and capturing dissolved metal part from acidic waste effluent of metal pre-treatment processes, the filter media comprising: benzoxazine polymer coated on porous hollow microsphere particles.
2. The benzoxazine polymer composite filter media as claimed in claim 1, wherein the porous hollow microsphere particles are selected from Cenospheres, Bentonites, Gamma Alumina, mesoporous silica particles, polymeric cellulose particles, chitosan particles, and hollow ceramic microspheres derived of fly ash.
3. The benzoxazine polymer composite filter media as claimed in claim 1, wherein diameter of the porous hollow microsphere particles ranges from 5 micron to 1000 micron.
4. A method of preparation of benzoxazine polymer composite filter media, the method comprising the steps of:
depositing a metal catalyst onto a surface of porous hollow microsphere particles;
adding the metal catalyst deposited microsphere particles to a solution of benzoxazine monomer in an organic solvent to form benzoxazine monomer coated microsphere particles; wherein the weight ratio of the benzoxazine monomer to the metal catalyst deposited microsphere particles ranges from 30: 1 to 35:1; and
polymerizing the benzoxazine monomer coated on the microsphere particles to form the benzoxazine polymer composite filter media; and
optionally removing the microsphere particles from the benzoxazine polymer composite by treating the benzoxazine polymer composite filter media with acidic system.
5. The method of preparation of benzoxazine polymer composite filter media, as claimed in claim 4, wherein the metal catalyst is deposited onto the surface of the microsphere particles by sonicating a mixture of microsphere particles and a solution of the metal catalyst in dry alcohol, evaporating the alcohol at reduced pressure ranging from 380mbar to 1mbar and with mild heating in a range from 40?C to 60?C, in a rotary evaporator, and further heating the resulting material at 80-85°C for 2-3 hours.
6. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 5, wherein the alcohol is selected from methanol, ethanol and 1-propanol.
7. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the metal catalyst is selected from chlorides of copper, iron, aluminum, and mixtures thereof.
8. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the porous hollow microsphere particles are selected from Cenospheres, Bentonites, Gamma Alumina, mesoporous silica particles, polymeric cellulose particles, chitosan particles, and hollow ceramic microspheres derived of fly ash.
9. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the organic solvent is selected from 1, 4-dioxane, Ethanol, Chloroform, Dichloromethane, and mixtures thereof.
10. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the polymerization is carried out by heating the mixture of the benzoxazine monomer coated microsphere particles and the organic solvent to a temperature ranging from 80°C to 85°C with constant stirring for 3 to 4 hrs and removing the solvent by heating the resulting solution to a temperature ranging from 140°C to 150°C for a time period ranging from 3 hr to 4 hr, wherein the benzoxazine monomer gets polymerized onto the surface of the microsphere particles and simultaneously in the solution, forming a benzoxazine polymer matrix thereby creating a porous passage.
11. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the polymerization is carried out by solvent drying the benzoxazine monomer coated microsphere particles under reduced pressure ranging from 380 to 1 mbar and subjecting the solvent dried benzoxazine monomer coated microsphere particles to curing.
12. The method of preparation of benzoxazine polymer composite filter media as claimed in claim 4, wherein the acidic system is selected from a mineral acidic system having pH ranging from 1 to 3, and organic acid system having pH ranging from 3 to 6.
Dated this on 9th day of June, 2023

Ashwini Jagdish Kelkar
(Agent for the applicant)
(IN/PA-2461)