Claims:We Claim:
1. A method (300) for producing Sericin coated filtration membrane, said method comprising:
Preconditioning (304) a primary liquid filtration membrane to obtain a hydroxylated membrane (306);
coating (308) said hydroxylated membrane with Sericin toobtain a coated membrane;
treating (312) said coated membrane with a crosslinkingagent; and
curing (314) said treated membrane.
2. The method as claimed in claim 1, wherein said preconditioning (304) comprises of treating said primary membrane with a solution comprising Sulphuric acid and Hydrogen peroxide.
3. The method as claimed in claim 2, wherein said solution comprising Sulphuric acid and Hydrogen peroxide is in a ratio of 3:1.
4. The method as claimed in claim 1, wherein said preconditioning (304) is performed at a temperature in the range of 45-65 degrees Celsius for a duration in the range of 1 to 2 hours.
5. The method as claimed in claim 4, wherein said temperature is 65 degrees Celsius and said duration is 1 hour.
6. The method as claimed in claim 1, wherein said hydroxylated membrane (306) obtained from preconditioning (304) is further washed with de-ionized water.
7. The method as claimed in claim 1, wherein said coating (308) comprises of exposing said hydroxylated membrane (306) to a solution comprising Sericin.
8. The method as claimed in claim 7, wherein said solution comprises Sericin a range of 10 to 30 g/L.
9. The method as claimed in claim 7, wherein said coating (308) is performed at a pressure in the range of 4 to 7 kPa.
10. The method as claimed in claim 1, wherein said coating (308) is performed at a temperature in the range of 20 to 40 degree Celsius for a duration in the range of 3 to 6 hours.
11. The method as claimed in claim 10, wherein said temperature is 40 degree Celsius and said duration is 3 hours.
12. The method as claimed in claim 1, wherein said coated membrane is dried (310) at room temperature.
13. The method as claimed in claim 1, wherein said treating (312) with crosslinking agent comprises of treating said coated membrane with a crosslinking agent for a duration of 1 to 3 hours.
14. The method as claimed in claim 13, wherein said crosslinking agent is a solution comprising Glutaraldehyde and Sulphuric acid.
15. The method as claimed in claim 14, wherein concentration of said Glutaraldehyde is 0.25 to 0.75 wt % and concentration of said Sulphuric acid is 0.1 %.
16. The method as claimed in claim 1, wherein said curing (314) comprises of exposing said treated membrane to a temperature in the range of 40 to 50 degrees Celsius for a duration of 6 to 10 hours.
17. The method as claimed in claim 1, wherein said method comprises washing of said sericin coated membrane with deionized water.
18. The method as claimed in claim 1, wherein said method comprises regenerating said sericin coated membrane by treating said membrane with a solution comprising Sodium hydroxide.
19. The method as claimed in claim 18, wherein said regenerating is performed after 500 liters of filtration cycles.
20. The method as claimed in claim 1, wherein said primary membrane is at least one membrane selected from a group consisting of polyvinylidene fluoride membranes, polypropylene membranes, polysulfone membranes, cellulose acetate membranes, polyacetonitrile membranes, Polyether sulfone membranes, Polyacrilonitrile membranes, Polyethylene membranes and Polyvinyl chloride membranes.
21. The method as claimed in claim 1, wherein said primary membrane is at least one ultrafiltration membrane module selected from a list consisting of hollow fibre ultrafiltration module, tubular ultrafiltration module, spiral wound ultrafiltration module, and plate and frame ultrafiltration module.
22. A sericin coated polypropylene ultrafiltration (PP UF) membrane produced by a method as claimed in claim 1.
23. A system (500) for producing sericin coated filtration membrane, said system comprising:
a preconditioning unit (502) for hydroxylation of primary
membrane;
a sericin coating unit (504) for coating hydroxylated primary membrane, further comprising a sericin feed tank and a primary membrane module;
a crosslinking unit (506); and
a curing unit (508) comprising a temperature control unit;
24. The system as claimed in claim 23, wherein said preconditioning unit (502) is adapted to house at least one primary membrane and a solution comprising Sulphuric acid and Hydrogen peroxide.
25. The system as claimed in claim 23, wherein said sericin feed tank (602) includes an outlet which is adapted to provide sericin solution to said primary membrane module (606), and an inlet which is adapted to receive permeate from said primary membrane module (606).
26. The system as claimed in claim 23, wherein said primary membrane module (606) includes an outlet which is adapted to provide permeate to sericin feed tank (602), and an inlet which is adapted to receive sericin solution from sericin feed tank (602).
27. The system as claimed in claim 23, wherein said sericin coating unit (504) further comprises of a flow regulator for regulating the flow of sericin solution from sericin feed tank to primary membrane module.
28. The system as claimed in claim 23, wherein said crosslinking unit is adapted to house at least one coated membrane and at least one crosslinking agent.
, Description:TECHNICAL FIELD
[001] Theembodiments herein generally relate toSericin coated filtration membranes,and more particularly to a system and method of producing Sericin coated filtration membranes.

BACKGROUND
[002] Environmental pollution has become a cause of concern in urban civilization.The various forms of contaminants polluting the environment around us have severe implications on human health. Pollution of air and water may be caused by pollutants such as particulate matter, heavy metals, drugs, volatile organic compounds, chemicals from personal care products, pathogens etc. These pollutants infiltrate air and water sources through various means such as vehicle emission, agricultural runoffs, wastewater drains, industrial discharge etc. Therefore, filtration/purification systems that can render air and water devoid of harmful pollutants is crucial in today’s urban life.
[003] Filtration systems are of many types and vary depending on the nature of the permeate. Membrane filtration is a commonly used technique in filtration of air and water to remove particulate matter and microorganisms. The controlled pore size of membrane filtersallows targeted separation of contaminants. Membrane separation techniques such as microfiltration, ultrafiltration, nanofiltration and reverse osmosis are commonly employed in fluid filtration systems.
[004] Micro-pollutants, such as heavy metals, drugs, personal care products, chemicals etc., are persistent and bioactive in nature. They are not completely biodegradable,and it is a challenge to remove them with conventional wastewater treatment technologies. Moreover, unregulated and continuous release of micro-pollutants in water sources is believed to cause long-term hazards in both target and non-target organisms including humans. Membrane filtration processes like ultrafiltration(UF), Nanofiltration (NF) and Reverse osmosis (RO) are widely used for drinking water treatment application and are highly efficient for removal of micro-pollutants.
[005] The ultrafiltration (UF) process which uses polymeric semi-permeable membranes for filtration has evolved as a prominent technology for production of ultra-pure drinking water. UF membranes facilitating high water flux has key application for pre-treatment of grey water, surface water, seawater and municipal effluent prior to reverse osmosis (RO) treatment. However, membrane fouling has been an inexorable problem with UF membrane, especially with hydrophobic membranes, which eventually lead toreduced efficiency and performance. In order tomaintain desired throughput in such low performing UF membrane,high pressure and frequent chemical cleaning become inevitablewhich in turn not only escalate total operational cost but also drastically reduces the overall lifetime of the membrane. The incidence of membrane fouling is mainly influenced by parameters such as operating conditions, feed characteristic and membrane properties. Among which, -membrane properties can be tailored to suit requirementsand provide a targeted approach at separation of contaminants.Therefore, the modification of membrane surface properties with antifouling elements to effectively improve resistance or even prevent fouling becomes an irrefutable demand for maintaining the filtration performance.
[006] The air filtration systems employ mechanical filtrationtechnologies, which include micro-glass based media for high efficiency filtration, membrane filtration, etc. The use of membranes has been observed to increase over the past few years.Polytetrafluoroethylene (PTFE) filtration membranes and ultra-high molecular weight polyethylene (UPE) filtration membrane find extensive use in air filtration systems. However, such membranes are inherently hydrophobic and therefore, require modifications to render hydrophilicity. Improved hydrophilicity is a desirable trait in filtration membranes.
[007] Various attempts have been made in order to improve overall performance and membrane life. Numerous membrane modification technologies that alter the membrane structure (for example roughness, pore size, etc.) and/or surface properties (for examplehydrophilicity, active functional groups, charge etc.) have been employed to improve overall performance. Typical membrane modification includes physical modification such as heat treatment, blending and coating, or chemical modification such as chemical grafting, plasma and high-energy irradiation, Ultra violate and ozone-induced grafting etc. Most of these methods allows hydrophilic functionality to the surface, which leads to formation of hydration layer thus preventing foulant deposition and hence render antifouling properties to the membrane.Recent technologies have also employed nanoparticles in coating of membrane surface, such as Silver nanoparticles, Titanium dioxides, Silicon dioxides, etc. to improve fouling resistance properties of a membrane. However, there exists a need for improved filtration systems that are long lasting and are able to provide targeted separation of pollutants.
OBJECT
[008] The principal object of the embodiments disclosed herein is to provide a Sericin-coated liquid filtration membrane.
[009] A second object of the embodiments disclosed herein is to provide a Sericin-coated air filtration membrane.
[0010] Another object of the embodiments disclosed herein is to provide a systemfor coating Sericin on filtration membranes.
[0011] Further, another objectof the embodiments disclosed herein is toprovide a methodfor coating Sericin on filtration membranes.
[0012] Further, an objectof the embodiments disclosed herein is to provide a system and method for producing Sericin-coated polymeric Ultrafiltration membrane.
[0013] Yet another objectof the embodiments disclosed herein is to provide a system and method for producing Sericin-coated Polyester membranes.
[0014] Further, an object of the embodiments disclosed herein is to provide a method of improvingfiltration membrane performance and membrane life.
[0015] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS
[0016] The embodiments disclosed herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0017] FIG 1. is a schematic representation illustrating the binding of Sericin on the surface of Polypropylene-Ultrafiltration membrane, according to embodiments as disclosed herein;
[0018] FIG.2A, 2B and 2C are schematic representations illustrating Sericin crosslinking via Glutaraldehyde at amino and hydroxyl ends, according to embodiments as disclosed herein;
[0019] FIG.3 is a flow chart illustrating a method (300) for producing Sericin coated Ultrafiltration membrane, according to embodiments as disclosed herein;
[0020] FIG. 4 is a flow chart illustrating a method (400) for producing Sericin coated bicomponent polyester sheet, according to embodiments as disclosed herein;
[0021] FIG. 5 is a schematic representation ofa system (500) for producing Sericin coated filtration membranes, according to embodiments as disclosed herein;
[0022] FIG. 6 is a schematic representation of a flow through system (600) for coating Sericin on filtration membrane, according to embodiments as disclosed herein;
[0023] FIG.7 is a pictorial representation of anultrafiltration membrane moduleimmersed in Glutaraldehyde solution for crosslinking;according to embodiments as disclosed herein;
[0024] FIG. 8 is a pictoral representation of the Sericin coated HF-UF membrane module,according to embodiments as disclosed herein;
[0025] FIG. 9A, 9B and 9C are Fourier transform infrared spectroscopy (ATR-FTIR) spectra of Sericin coated UF membrane, Sericin, and PP UF membrane,according to embodiments as disclosed herein;
[0026] FIG. 10A, 10B and 10C are representations of the contact angle depicting the hydrophilicity of PP HF-UF membrane, acid hydrolysed PP HF-UF membrane, and Sericin coated PP HF-UF membrane,according to embodiments as disclosed herein;
[0027] FIG. 11A, 11B, 11C, 11D, 11E, 11F, 11G, 11H, 11I, 11J, 11K and 11L are representations illustrating the results of Field-emission scanning electron microscope (FE-SEM) analysis,according to embodiments as disclosed herein;
[0028] FIG. 12A, 12B, 12C and 12D depict the results of Energy dispersive X-ray spectroscopy (EDX) analysis,according to embodiments as disclosed herein;
[0029] FIG.13 is a graph depicting the time dependent permeate flux and turbidity inSericin coatedUF-membranes and uncoated UF-membranes,according to embodiments as disclosed herein;
[0030] FIG.14 is a graph depicting the profile of reversible and irreversible fouling in Sericin coated UF-membranes and uncoated UF-membranes with pure water backwash and chemical cleaning,according to embodiments as disclosed herein;
[0031] FIG. 15 is a graph depicting the Sericin coated HFUF membrane performance for drug removal from an aqueous solution,according to embodiments as disclosed herein;
[0032] FIG. 16A, 16B and 16C are graphs depicting the influence of different salt (100ppm) on the removal of drugs by Sericin-coated HFUF membrane,according to embodiments as disclosed herein;
[0033] FIG. 17A and 17B are graphs depicting the removal efficiencies of the drug from aqueous mixed drug solution using Sericin-coated HFUF membrane,according to embodiments as disclosed herein;
[0034] FIG. 18 is a graph depicting the effect of striping solution on drug desorption efficiency from an embodiment of the Sericin coated membrane surface,according to embodiments as disclosed herein;
[0035] FIG. 19A and 19B are graphs depicting the Particulate matter (PM) removal,according to embodiments as disclosed herein; and
[0036] FIG. 20 shows percentage (%) removal of Volatile Organic compounds (VOC) over a period of time,according to embodiments as disclosed herein.
[0037] FIG. 21 shows performance of sericin-coated air filter for 2160 cycles over a period, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0038] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0039] The embodiments herein achieve a Sericin coated filtration membrane. The embodiments of the Sericin coated filtration membrane are such that they exhibit improved performance and membrane life.The embodiments herein provide a system and method for producing Sericin coated filtration membrane. The Sericin coated filtration membrane produced by the method as disclosed in the various embodiments herein exhibits enhanced anti-fouling properties and separation of micro pollutants such as Particulate matter (PM), Volatile organic compounds (VOC), drug compounds, heavy metals, etc. The embodiments herein disclose a system and method of coating Sericin on filtration membranes such as liquid filtration membranes and air filtration membranes.Embodiments also include a method of improving filtration membrane performance and membrane life. Further embodiments disclose a system for producing Sericin coated filtration membranes such as liquid filtration membranes and air filtration membranes.

[0040] Method:The embodiments herein provide a method for producing Sericin coated filtration membranes. The disclosed method may be used to provide Sericin coating on any filtration membrane that is generally used in liquid and/or air filtration systems. The term ‘filtration systems’ and ‘filtration membranes’ used in the various embodiments herein include systems and membranes intended for achieving the separation of retentate and filtrate (or permeate). It may include systems intended for purification, separation and/or filtration of liquid or air.
[0041] According to the embodiments disclosed herein, the method for producing Sericin coated filtration membranes includes preconditioning of a primary membrane to obtain a hydroxylated membrane; coating of the hydroxylated membrane with Sericin; treating the coated membrane with a crosslinking agent; and curing of the treated membrane. The filtration membrane may further be subjected to washing with de-ionized water. In one embodiment, prior to pre-conditioning, the primary membrane is soaked in deionized waterfor a period of about 4 hours, by replacing water every hour. It is then rinsed thoroughly.
[0042] Preconditioning:The step of preconditioning of primary membrane, according to the various embodiments herein is performed to generate functional groups on the membrane surface which would facilitate the binding of Sericin on to the membrane. In an embodiment, preconditioning of the filtration membrane is performed by soaking the membrane in chemical solutions in order to generate hydroxyl groups on the membrane surface. The chemical solutions that may be used in preconditioning include any chemical solution that is capable of generatinghydroxyl groups on polymeric membrane surfaces.In an embodiment, the filtration membrane is soaked in at least one solution selected from a group consisting of Sulphuric acid, Sodium hydroxide and/or Hydrogen peroxide, at a temperature of about 60 to 90 degrees Celsius for a period of about 1 to 2 hours. Further, the preconditioned membrane (also referred to as the hydroxylated membrane) is washed with deionized water and subjected to coating.
[0043] Coating:Coating of the preconditionedmembrane is performed by treatment with Sericin solution.In an embodiment, the preconditioned membrane is treated with Sericin solution at a temperature of about 20 to 40 degree Celsius for a time period of about 3 to 6 hours. In one embodiment, coating is performed by passing the Sericin solution through the preconditioned membrane in a flow through system at low pressure (of about 4 to 7 kPa) for a period until Sericin in deposited on the membrane.In another embodiment,coating is performed by dipping the preconditioned membrane in Sericin solution for a period until Sericin in deposited on the membrane. FIG 1. is a schematic representation illustrating the binding of Sericin on the surface of Polypropylene-Ultrafiltration membrane, wherein (a) depicts the linkage between the membrane and side-chain hydroxyl group and (b) illustrates the linkage between the membrane and hydroxyl group at the carboxyl end.
[0044] Crosslinking: Cross linking is performed by treating the coated membrane with at least one crosslinking agent selected from a group consisting of Glutaraldehyde and Sulphuric acid. Alternatively, other crosslinking agents generally known in the art such asN,N’-Bis(hydroxymethyl)urea, and Sulfosuccinic acid may also be used. In an embodiment, the coated membrane is treated with a crosslinking agent for a period of about 1 to 3 hours. FIG.2A, 2B and 2C is a schematic representation illustrating Sericin crosslinking via Glutaraldehyde at amino and hydroxyl ends. FIG.2A illustrates the crosslinking at amino ends, wherein Sericin is bound to the membrane by the side chain hydroxyl groups. FIG.2B illustrates the crosslinking at carboxyl ends, wherein Sericin is bound to the membrane by the side chain hydroxyl groups.FIG.2C illustrates the crosslinking at amino ends, wherein the hydroxyl groups at the carboxyl end bind Sericin to the membrane.
[0045] Curing: Curing of the membrane is performed by exposure to a temperature in the range of 35 to 60 degrees Celsius. In an embodiment, the coated and cross-linked membrane obtained from the earlier step is subjected to curing by exposure to a temperature of about 40degrees Celsius for a period until fixation of the cross linked Sericin on to the membrane occurs.In an embodiment, curing is performed for a period of about 6 to 10 hours, or overnight.The filtration membrane, after curing may further be washed and stored in de-ionized water until further use.
[0046] The Sericin coated membranes, produced by embodiments of the method disclosed herein, once used may be cleaned and/or regenerated to improve membrane performance and membrane life. Cleaning or Regeneration may be performed after about 500 liters of filtration cycle. Cleaning may be performed by any physical and/or chemical methods generally known in the field. Cleaning may be performed by cleaning chemicals that are generally known to clean filtration membranes. The cleaning chemical may be at least one chemical selected from a group consisting of Sodium hydroxide, Hydrogen chloride, Hydrogen peroxide and Nitric acid. In one embodiment, cleaning of the Sericin coated membrane includes cleaning with an alkaline solution. In another embodiment, regeneration of the disclosed Sericin coated membrane includes washing with a solution of sodium hydroxide. In an embodiment, cleaning of the Sericin coated membrane includes chemical cleaning with 0.01M Sodium hydroxide (NaOH) solution. Sodium hydroxide was found to be very effective in cleaning fouled UF-membrane. Both, physical and chemical cleaning method provided better flux recovery with Sericin coated membrane than the uncoated membrane. After chemical cleaning the flux recovery for Sericin modified and unmodified membrane was observed to be 99.74% and 97.6%, respectively.
[0047] A person skilled in the art will appreciate that any existing filtration membrane can be used as the primary membrane for the purpose of coating Sericin. One embodiment of the invention uses an ultrafiltration membrane as the primary membrane.In another embodiment, the ultrafiltration membrane is a hollow fiber ultrafiltration membrane module. Another embodiment includes membrane in high-pressure systems like NF and RO systems which are highly efficient in removing smaller particles. The embodiments disclosed herein provide an adsorptive filtration membrane with antifouling properties, which can provide high water flux and efficient micro-pollutant removal. The method disclosed herein may be used to modify any polymeric filtration membranes that is commercially available. In an embodiment, the primary membrane that is used for coating sericin is any polymeric membranes with inherent hydroxyl, nitrile groups or membranes in which such groups can be developed through pre-treatment (i.e., polypropylene, poly-acrylonitrile etc.). The selection may be based on physical and chemical stability of polypropylene material.
Method for coating polymeric ultrafiltration membranes suitable for liquid filtrationsystems
[0048] In one embodiments, the disclosed method is instrumental in coating of polymeric ultrafiltration membrane that are suitable for liquid filtration or separation systems, the polymeric membranes include, but are not limited to, polyvinylidene fluoride (PVdF), polypropylene (PP), polysulfone (PS) cellulose acetate (CA), polyacetonitrile, Polyether sulfone, Polyacrilonitrile, Polyvinylidieneflouride, Polypropylene, Polyethylene, Polyvinyl chloride, etc.The ultrafiltration membrane modules disclosed in the embodiments herein include, but are not limited to, hollow fibre module, tubular module, spiral wound module and plate and frame module. In an embodiment, the disclosed method is used to coat polypropylene hollow fiber ultrafiltration(PP HF-UF) membrane having surface area of 1.27m2, outer diameter of 0.5mm and average fiber length of 0.38m, wherein the total number of fibers is about 2100.Referring now to the drawings, and more particularly to FIGS. 3 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0049] FIG.3 illustrates a method (300) for producing Sericin coated Ultrafiltration membrane. The ultrafiltration membrane is soaked (302) in deionized waterfor a period of about 4 hours, by replacing water every hour. The membrane is prepared for preconditioning by rinsing thoroughly. The membrane is preconditioned (304) by treatment with a solution of Sulphuric acid (H2SO4) and Hydrogen peroxide (H2O2). In an embodiment, the solution of H2SO4and H2O2is usedat a volume ratio of 3:1. In another embodiment, preconditioning (304) is performed at a temperature of about 65 degrees Celsius to obtain hydroxylated UF membrane (306).The hydroxylated UF membrane is washed with de-ionized water (not shown in the flow chart) to remove any residual solution. The hydroxylated UF membrane(306) is coated (308) with Sericin by passing the Sericin solution through a flow through system in full circulation mode. In anembodiment, the Sericin solution is passed at low pressure in the range of4 to 7 kPa, at a controlled temperature. In one embodiment, the Sericin solution is passedfor a period of about 3 to 6 hours. In another embodiment, the Sericin solution is passed at a temperature in the range of 20 degrees Celsius to 40 degrees Celsius.In a specific embodiment, the temperature of serine solution used for coating (308) is 40 degree Celsius. In an embodiment, theSericin solution is passed at low pressure of 4 kPa for a period of 3 hours. In an embodiment, the concentration of serine solution used for coating (308) is in the range of to 10 to 30 g/L.In a specific embodiment, the concentration of serine solution used for coating (308) is 20 g/L. The pH of Sericin solution may be in the range of 4 to 8. In an embodiment, the pH of Sericin solution is 4. A person skilled in the art will appreciate that the coating process parameters such as temperature, Sericin concentration, pressure, pH, etc may be appropriately optimized to enable maximum Sericin deposition.The UF membrane is air dried (310) at room temperature until there are no liquid remains on the membrane. Crosslinking (312) is performed by dipping the UF membrane in a solution of Glutaraldehyde and Sulphuric acid for a period of 1 to 3 hours. In an embodiment, the solution of Glutaraldehyde and Sulphuric acidis an aqueous solution wherein the concentration of Glutaraldehydeis in the range of 0.25 to 0.75 % (wt/wt) and Sulphuric acid is in an amount of about 0.1%. The extra solution after crosslinking is drained (not shown in the flow chart). The membrane is cured (314) by exposure to a temperature of about 40 degrees Celsius,and washed with deionized water to obtain Sericin coated UF membrane. The Sericin coated UF membrane may be stored in deionized water until further use.The various steps in method 300 may be performed in the order presented, in a different order or simultaneously. Further, in an embodiment, some steps listed in FIG. 3 may be omitted. For example: In polymeric membranes which readily include hydroxyl or carboxyl groups, the preconditioning step disclosed in the various embodiments herein may be omitted.
Method for coating Sericin on Polyester sheets suitable for air filtration systems
[0050] In an embodiments, the disclosed method is instrumental in coating of Polyester sheets for air filter. In an embodiment, the disclosed method is used to coat bicomponent polyester sheet having a dimension of 2 meters x 0.5 meters. Referring now to the drawings, and more particularly to FIGS. 4 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
[0051] FIG.4 illustrates a method (400) for producing Sericin coated bicomponent polyester sheet. The polyester sheet is soaked (402) in deionized waterfor a period of approximately 4 hours, while replacing water every hour. It may then be rinsed (not shown in the flow chart) thoroughly with water. The polyester sheet is preconditioned (404) by treatment with a solution ofSodium hydroxide to obtain a hydroxylated polyester sheet (406). In an embodiment, polyester sheet is preconditioned (404) by treatment with 2M Sodium hydroxide solution, at a temperature of 90 degrees Celsius for a period of about 1 hour with 1:100 material to liquor ratio.In an embodiment, the total weight loss in polyester sheet after preconditioning(404) was found to be about 7%. The hydroxylated polyester sheet(406) is optionally washed with de-ionized water (not shown in the flow chart) to remove any residual solution. The hydroxylated polyester sheet(406) is coated (408) with Sericin by dipping inSericinsolution. In an embodiment, the hydroxylated polyester sheet (406) is dipped in Sericin solution at a temperature of about 40 degrees Celsius for a period of about 6 hours. In one embodiment, the concentration of serine solution used for coating (408) is in the range of 10 to 30 g/L. In an embodiment, the concentration of serine solution used for coating (408) is 20 g/L. The pH of Sericin solution may be in the range of 4 to 8. In an embodiment, the pH of Sericin solution is 4. A person skilled in the art will appreciate that the coating process parameters such as temperature, pressure, concentration, etc. may be appropriately optimized to enable maximum Sericin deposition. The polyester sheet is dried (410) at room temperature under aseptic conditions. Crosslinking (412) is performed by dipping the polyester sheet in a solution of Glutaraldehyde for a period of 1 to 3 hours. In an embodiment, crosslinking (412) is performed by dipping the polyester sheet in an aqueous solution of 0.75% (wt/wt) Glutaraldehyde for a period of about 1 to 3 hours. The extra solution after crosslinking is drained (not shown in the flow chart). The polyester sheet is cured (414) by exposure to a temperature of about 40 degrees Celsiusand washed with deionized water to obtain Sericin coated polyester sheet. The Sericin coated UF membrane may be stored in deionized water until further use.The various actions in method (400) may be performed in the order presented, in a different order or simultaneously. Further, in an embodiment, some steps listed in FIG. 4 may be omitted.For example: In polymeric membranes which readily include hydroxyl or carboxyl groups, the preconditioning step disclosed in the various embodiments herein may be omitted.
System
[0052] The embodiments disclosed herein provide a system for producing Sericin coated filtration membranes. The system disclosed herein may be used to coat Sericin on filtration membranes instrumental in air and liquid filtration systems.According to the embodiments disclosed herein, the system includes a preconditioning unit for hydroxylation of primary membrane; a Sericin coating unitfor coating hydroxylated primary membrane,a crosslinking unit, and a curing unit.
[0053] Referring now to the drawings, and more particularly to FIGS. 5 where similar reference characters denote corresponding features consistently throughout the figures, in which there are shown preferred embodiments.
[0054] FIG. 5 illustrates systems (500) for producing Sericin coated filtration membranes. The system (500) disclosed in the embodiments hereinincludes preconditioning unit (502); Sericin coating unit (504); crosslinking unit (506) and curing unit (508). Each unit of the system (500) may be operational as a continuous system or as a system wherein each unit is independent of each other. The preconditioning unit (502)is adapted to house at least one primary membrane and a solution comprising atleast one of Sodium hydroxide, Sulphuric acid and Hydrogen peroxide. In an embodiment, the preconditioning unit (502) includes at least one ultrafiltration membrane and a solution of Sulphuric acid and Hydrogen peroxide in a ratio of about 3:1. In another embodiment, the preconditioning unit (502) includes at least one bicomponent polyester membrane primary membrane and a solution comprising Sodium hydroxide.In an embodiment, the preconditioning unit (502) performs preconditioning (304) of UF membrane suitable for liquid filtration systems. In another embodiment, the preconditioning unit (502) performs preconditioning (404) of polyester membranes suitable for air filtration system.
[0055] The Sericin coating unit (504) for coating hydroxylated primary membrane. The Sericin coating unit (504) may include at least one of: a flow through coating systems or a dip coating system.
Sericin coating unit-flow through system suitable for water filtration systems
[0056] FIG. 6 is a schematic representation of a flow through system (600) for Sericin coating of filtration membrane. Accordingly, in an embodiment, the Sericin coating unit further includes a sericin feed tank (602) and a primary membrane module (606). The sericin feed tank (602) includes an outlet which is adapted to provide sericin solution to said primary membrane module (606), and an inlet which is adapted to receive permeate from said primary membrane module (606). The permeate according to the various embodiments herein is the filtrate that passes through the primary membrane module. The sericin feed tank (602) includes sericin solution which is used for coating (308) filtration membranes. The module (606) includes an outlet which is adapted to provide permeate to sericin feed tank (602), and an inlet which is adapted to receive sericin solution from sericin feed tank (602).
[0057] The system (600) is such that it allows entry of Sericin solution from theSericin feed tank (602) into the module (606) and exit of the permeate from the module (606) into the Sericin feed tank (602) in a circulation mode. The system may further optionally comprise of a Dampner (604) connected between the Sericin feed (602) and module (606). The Dampner (604) may be included in the system (600) such that any possible turbulence and fluctuation in flow rate and pressure may be avoided. The Sericin feed(602) is further connected to a pump (602p) which pumps Sericin solution into the module (606). In an embodiment, the pump (602p) is a submersible centrifugal pump. The flow of Sericin solution into the membrane module is regulated by a flow regulator (602m), and the pressure is maintainedwith the help of a pressure guage (606p). The system may further include a pH meter (not shown in the figure) to monitor pH of the Sericin solution (pH maintained in the range of 4-8). The preferable pH of the Sericin solution is 4. The Sericin coating unit (602) may also include a water bath (not shown in the figure) that is instrumental in maintaining the temperature of the system. The module (606) is also connected to a reject outlet (606r) for removal of the rejected solution. The rejected solution may include the excess sericin solution that may be present in the module.
Sericin coating unit-Dip coating system for air filtration membranes
[0058] In another embodiment, the Sericin coating unit is adapted to house at least one hydroxylated membrane and a sericin solution. The Sericin coating system is maintained at a temperature of about 40 degrees Celsius. The hydroxylated membrane (406) is dipped (408) in a solution comprising sericin for a period of about 6 hours.
[0059] The crosslinking unit (606) is adapted to house a coated membrane and a crosslinking agent. In an embodiment, the crosslinking unit (606) includes a coated ultrafiltration membrane and a solution of Glutaraldehyde and Sulphuric acid. In another embodiments, the crosslinking unit (606) includes a coated bicomponent polyester membrane and Glutaraldehyde solution.The curing unit (508) comprises of a temperature control unit capable of regulating the temperature of the curing unit (508). In an embodiment, thecuring unit (508) is maintained at a temperature of 40 degrees Celsius. FIG. 7 is a pictorial representation of the module (606) having coated ultrafiltration membrane immersed in Glutaraldehyde solution for crosslinking (312). FIG. 8 is a pictoral representation of the Sericin coated HF-UF membrane module.
Sericin coated filtration membrane
[0060] The embodiments herein provide a Sericin coated filtration membrane. According to the embodiments disclosed herein, the Sericin coated filtration membrane is one produced by the method disclosed in the various embodiments herein. In one embodiment, the Sericin coated filtration membrane is sercine coated PP HF-UF membrane produced by an embodiment of the disclosed method (300). The Sericin coated Ultrafiltration membrane produced by the disclosed method (300) is capable of being used in liquid separation systems such as water filtration systems. In another embodiment, the Sericin coated filtration membrane is serine coated bicomponent polyester sheet filter produced by an embodiment of the disclosed method (400). The serine coated bicomponent polyester sheet filter produced by the disclosed method (400) is capable of being used in air filtration systems.

Characterization of the Sericin coated membrane
[0061] The Sericin coated membrane produced according to the various embodiments herein was characterized via Field-emission scanning electron microscope(FE-SEM), Energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) to ascertain deposition of Sericin on to the membrane surface. Change in contact angle brought about by Sericin coating wasanalysed via water-contact angle measurement technique (using sessile drop method) to verify increased hydrophilicity.
[0062] FIG. 9A, 9B and 9C are ATR-FTIR spectra of Sericin coated HF-UF membrane, Sericin, and PP HF-UF membrane, respectively. The FTIR results show the presence of amide groups in the Sericin coated membrane and changes related to hydrogen bonding of Sericin with PP. Also, the appearance of peak for secondary amine group shows Sericin crosslinking via glutaraldehyde.
[0063] FIG. 10A, 10B and 10C are representations of the contact angle depicting the hydrophilicity of PP HF-UF membrane, acid hydrolysedPP HF-UF membrane, and Sericin coated PP HF-UF membrane. From the FIG. 10A, 10B and 10C, it is evident that the membrane hydrophilicity significantly improved after coating of Sericin layer and exhibited low water contact angle of about 38 degrees.PP HF-UF membrane displayed a water contact angle of 81.5 degrees while acid hydrolysedPP HF-UF membrane exhibited a water contact angle of 73 degrees.
[0064] FIG. 11A, 11B, 11C, 11D, 11E, 11F, 11G, 11H, 11I, 11J, 11K and 11L are representations illustrating the results of FE-SEM analysis. FIG. 11A, 11B, 11C and 11D are images illustrating the surface morphology of the membrane before and after Sericin coating. FIG. 11A depicts the surface view of the membrane before coating at 100 KX magnification. FIG. 11B depicts the surface view of the membrane after Sericin coating at 100 KX magnification.FIG. 11C depicts the surface view of the membrane before coating at 150 KX magnification. FIG. 11D depicts the surface view of the membrane after Sericin coating at 150 KX magnification. FIG. 11E depicts the cross-sectional view of the membrane before coating at 3.5 KX magnification. FIG. 11F depicts the cross-sectional view of the membrane after Sericin coating at 3.5 KX magnification. FIG. 11G depicts the cross-sectional view of the membrane before coating at 20 KX magnification. FIG. 11H depicts the cross-sectional view of the membrane after Sericin coating at 20 KX magnification. FIG. 11I depicts the cross-sectional view of the membrane before coating at 50 KX magnification. FIG. 11J depicts the cross-sectional view of the membrane after Sericin coating at 50 KX magnification. FIG. 11K depicts the cross-sectional view of the membrane before coating at 100 KX magnification. FIG. 11L depicts the cross-sectional view of the membrane after Sericin coating at 100 KX magnification. Changes in surface texture and reduction in pore diameter with deposition of Sericin on to the membrane was observed in microscopic analysis. The cross-sectional view of modified membrane shows deposition of Sericin on to the inner surface as well as pores of the membrane.
[0065] FIG. 12A, 12B, 12C and 12D depict the results of the EDX analysis.FIG. 12A illustrates the EDX pattern on the surface of unmodified PP-UF fiber. FIG. 12B illustrates the EDX pattern on the surface of Sericin coated PP-UF fiber. FIG. 12C illustrates the EDX pattern on cross section and inner surface of unmodified PP-UF fiber and color mapping for carbon and oxygen distribution.FIG. 12D illustrates the EDX pattern on cross section and inner surface of Sericin coated PP-UF fiber and color mapping for carbon, oxygen and nitrogen distribution.EDX analysis showing the presence of nitrogenon membrane surface depictsSericin deposition on the membrane surface as well as pores.
Antifouling properties
[0066] The antifouling properties conferred by the embodiments herein may be verified by processes known in the art. In one preferred example,the Sericin coatedand uncoated UF-membrane was tested and compared for enhanced performance in terms of permeation and antifouling properties.It was observed that the sericin coated membrane, disclosed in the various embodiments herein, exhibited decreased fouling as compared to uncoated membranes.
[0067] Permeation:The volumetric flux of the membrane was determined by measuring the permeate water volume collected over a certain period (in terms of Lm-2S-1) and calculated using the following equation:
??=??/(?? ×? ??)
where J is the volumetric permeate water flux (m3/m2.s), A is the UF-membrane area (m2) for permeation, and V is the volume of permeate water (m3) over a time interval ?t (sec). The pure water flux obtained (Jw) under transmembrane pressure (?Ptm) was then used to evaluate the pure water permeability (Pm) of the membrane.
[0068] Fouling resistance:Fouling resistance of the modified membrane was evaluated using synthetic grey water solution.
[0069] Grey water solution was formulated using 15 g of commercially available detergentwhich was dissolved in 50 L of fresh water along with CaCl2. An increasing volume (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mL) of CaCl2 solution (at 10,000 ppm) was dissolved in the detergent solution (200mL). The point where active precipitation was observed (i.e. 6 mL in 200mL detergent solution), CaCl2 concentration just before that point (˜250 ppm)was used to formulate synthetic grey water solution for further fouling studies.
[0070] Material and Methods:Diaphragm booster pump (Hi-Tech Pvt. Ltd., India, Model number E-B300) for pumping the grey water solution, flow meter (MICRO-FLO from OMEGA Engineering, USA) to regulate flow control, turbidity meter (Eutech Instruments, model number TN100), water bath (model: WB 2000V, Rated Supply: 230V, 50Hz, Sr. No.: WB 201508002 from ANM Industries www.anmalliance.com) to maintain temperature, pH meter (Cyberscan pH 510, Eutech Instrument Pvt. Ltd., Thermo Fisher Scientific) to monitor pH of coating solution.
[0071] A feed flow rate of 45 L/Hr at 18 kPa transmembrane pressure was maintained during grey water filtration cycle of, both, Uncoated membrane and Sericin coated membranes. After every 50L, filtration cycle of both membraneswas backwashed for 2 minutes.
[0072] Observation:The uncoated/unmodified membrane had a relatively slightly lower pure-water permeability of about 1.9135 x 10-9 m3/m2.s.Pa.Sericin coated/Modified membrane exhibited an improved high pure-water permeability (pH 4 = 2.3746 x 10-9m3/m2.s.Pa).
[0073] Fouling behaviour was assessed in term of flux decline and permeate turbidity. FIG.13 is a graph depicting the time dependent permeate flux and turbidity of Sericin coated/modified and uncoated/unmodified UF-membranes (error on normalized flux is ±1.04%).FIG.14 is a graph depicting the profile of reversible and irreversible fouling with pure water backwash and chemical cleaning.During grey water filtration cycle the Sericin coated membrane exhibited lesser fouling than uncoated/unmodified UF-membrane. Partial recovery of membrane flux with pure water backwash was more efficient in modified UF membrane than unmodified. Sericin coated membrane had comparatively 18% less fouling than the unmodified membrane, showing Sericin layer can mitigate foulant deposition and thereby improving the fouling resistance. The presence of hydration layer obstructs interaction and deposition of foulants on to the membrane surface. Moreover, presence of negative (OH-) and positive charges (NH2+) on the modified-membrane surface must have reduced deposition of both anionic and cationic foulants. The higher rate of flux decline indicates that comparatively severe fouling has happened with the uncoated membrane thereby delivering around 15% less volume of treated grey water as compared to the Sericin-coated membrane at same interval. The mitigation of membrane fouling is mainly attributed to improved surface hydrophilicity and smoothed surface morphology. Permeate turbidity was decreased by more than 80% and hence better removal capacity was observed for modified UF membrane, though there was not very noticeable change in TDS after filtration. Coating of Sericin on to the membrane might have brought about reduced pore size. The mean pores size of uncoated membrane was about 0.41 microns while the mean pore size reduced to about 0.20 microns post Sericin coating.Further detailed anti-fouling analysis is based on reversible and irreversible fouling percentage.The following formulas were used in arriving at the Irreversible fouling percentage (%) and Reversible fouling percentage (%).


where J0 is pure water flux of new membrane, J1 is pure water flux after each backwash and J2 is pure water flux of fouled membrane at end of each cycle. As shown in FIG.14, the Sericin coated membrane is able to reduce reversible and irreversible fouling percentage compared to unmodified/uncoated membrane.
[0074] The recovery rate of the modified membrane flux varied from about 99.02% to 100% with an average of 99.79% while for uncoated membrane it varied from 94.38% to 100% with average of 97.79%. The results revealed that the Sericin coated membrane flux recovery was significantly higher than the uncoated membrane with backwashing. The cleaning results shows that the membrane fouling was reversible, and can be cleaned by physical method. It was observed that both reversible and irreversible fouling for Sericin coatedmembrane was significantly less when compared to uncoated membrane after each cycle of backwashing.
Removal of drug-based micro-pollutants
[0075] The disclosed embodiments of the Sericin coated membrane may be used for removal or separation of drug-based pollutants from air or water. The efficiency of the same may be measured by means generally known in the field.
[0076] In one example, an embodiment of the disclosedsercine coated membrane was tested for removal of six drugs from different class of application which were selected based on their use and existence in water. Ibuprofen, Diclofenac sodium (NSAID), Ciprofloxacin, Amoxicillin (antibiotics), Estrone and ß-Estradiol (steroid-hormones) were used as model drug for evaluation.
[0077] Material and Method: Diaphragm booster pump (Hi-Tech Pvt. Ltd., India, Model number E-B300) for pumping feed solution, flow meter (MICRO-FLO, OMEGA Engineering, USA) to regulate flow control, water bath (model: WB 2000V, Rated Supply: 230V, 50Hz, Sr. No.: WB 201508002, ANM Industries, www.anmalliance.com) to maintain temperature. A pH meter (Cyberscan pH 510, Eutech Instrument Pvt. Ltd., Thermo Fisher Scientific) to monitor pH, clicklock micro centrifuge tubes for collecting permeate samples, high performance liquid chromatography (Shimadzu) for determining feed and permeate concentration.
[0078] A total of 3 liters volume was passed through the Sericin coated UF-membrane and the permeate discharge was analyzed for removal of selected drugs. The analysis was performed at a fixed initial feed concentration of 500 µg/L at pH 7 and room temperature (27°C) to evaluate removal of selected drugs (Ibuprofen, Diclofenac, Amoxicillin, ciprofloxacin, Estrone and ß-estradiol) using Sericin coated UF-membrane.
[0079] Observation: The drug removal efficiency of the uncoated UF membrane was found to be zero. FIG. 15 is a graph depicting the Sericin coated HFUF membrane performance for drug removal from aqueous solution at a feed concentration of 500µg/ L, pH 7, and about 25°C. Ibuprofen and Diclofenac exhibited higher removal (91.83 and 83.47%), whereas, Amoxicillin and Ciprofloxacin showed moderate removal (82.74 % and 62.89%) while Estrone (47.48%) and ß-estradiol (11.30%) showed lower removal efficiency with the Sericin-coated UF membrane. Though steroid drugs had positive log P and log D value the Sericincoated UF membrane provided comparatively low removal for steroid drugs than in case of other drugs. The contact angle analysis of different drug solution on Sericincoated membrane reveals that the steroid drug solution (Estrone= 46.90°-56.20°; ß-estradiol=40.64°-38.17°) had low contact angle than NSAID drug solution (Ibuprofen=70.83°-62.92°; Diclofenac= 68.41°-64.29°) and antibiotics solution (Amoxicillin=65.49°-61.54°; Ciprofloxacin=53.97°-56.20°).
[0080] Inference:Theobservations indicate that the charged drug particles interact directly with membrane surface via hydrogen bonding and hence water contact angle increased, while in case of uncharged drug particles the water and membrane surface interaction was dominant and hence contact angle was found close to pure water. The Ibuprofen and Diclofenac particles exhibited a zeta potential of (-5.74mV) and (-5.65mV), respectively and exist predominantly in anionic phase (˜ 99.2 and 99.8%, respectively) above dissociation constant at pH 7. Thus, they may have high potential to bind withthe protonated amine group of the Sericin-coated layer (surface charge +5.72mV). Hence, Ibuprofen and diclofenac were easily captured on the membrane surface and show high removal efficiency. Amoxicillin (-2.06mV) and Ciprofloxacin (0.34mV) exists in zwitterionic phase at neutral pH (˜7). However, they have deprotonated carboxyl end (whether anionic or zwitterion) at pH 7 and hence would interact with amine group present on the membrane surface. All of these charged drugs have a carboxylic functional group to form hydrogen bonding with protonated amine group present on the membrane surface and hence exhibited high removal efficiency. In case of Steroid hormones, which exists predominantly in uncharged state at neutral pH the removal efficiency decreased, particularly with ß-estradiol showing very low removal. Though the chemical structure of estrone and ß-estradiol are almost similar, the presence of ketone group at the C-17 position in estrone which is an active hydrogen acceptor than hydroxyl group present in ß-estradiol may result in better interaction via hydrogen bonding. Presence of carboxyl functional group (a strong hydrogen acceptor) in ibuprofen, diclofenac, amoxicillin and ciprofloxacin facilitate better adsorption via hydrogen bonding with amide groups on the membrane surface, otherwise lacking in estrone and ß-estradiol.
Effect of background salt on drug removal
[0081] The embodiment of Sericin coated membrane disclosed herein were also tested for salt interaction with selected drugs. The study on effects of background salt on drug removal may be performed by methods generally known in the field. In one example, monovalent (NaCl) and di-valent (CaCl2, MgSO4) salts at 100 ppm strength were used to assess the interaction effect. FIG. 16A, 16B and 16C are graphs depicting the influence of different salt (such as NaCl, CaCl2, MgSO4, and salt mix) (100ppm) on the removal of drugs by Sericin-coated HFUF membrane. FIG 16A depicts the influence of different salt (100ppm) on the removal of Ibuprofen (500µg/L).FIG 16B depicts the influence of different salt (100ppm) on the removal of Amoxicillin (500µg/L). FIG 16C depicts the influence of different salt (100ppm) on the removal of Estrone (500µg/L).Presence of salt resulted in an earlier breakthrough for Ibuprofen i.e., after 1250ml of volume filtered, which was 1750ml without salt, except NaCl (FIG. 16A). The reduction in removal efficiency may have happened because of the screening effect of salt on the membrane surface, where charged ions may have accumulated around opposite charge sites on the membrane surface and thereby obstructing binding sites for drug particles.
[0082] Similar results were observed for amoxicillin also where divalent salts exhibited an inhibitory effect on removal efficiency, which eventually resulted in the early appearance of Amoxicillin in permeate. Amoxicillin can form complex with divalent ions (i.e., Ca2+, Mg2+) and hence its removal may have been affected by the presence of background divalent salt (FIG.16 B). Pre-binding of salt to deprotonated carboxylic end of amoxicillin must have inhibited interaction with amide group of the coated membrane surface.
[0083] However, the presence of divalent cations exhibited poor removal efficiency for estrone and almost no removal was noticed (FIG 16C). Estrone at neutral pH is un-dissociated, and only polar moieties contribute to its charge distribution within the molecule. It mostly exists as a hydrophobic but ionizable group. Hydroxyl and carbonyl functional groups present in estrone facilitate the formation of weak hydrogen bonding between the molecule and the membrane surface which was further disturbed in the presence of salt. Therefore, the presence of counter-ions in the solution must have partially screened the bonding of these functional groups with the membrane surface. Sodium chloride did not show any inhibitory effect on adsorption of drugs in all three cases.
Effect of interaction among drugs
[0084] The behaviour of multi-drug mixture is expected to be entirely different and complicated than in standalone condition, and its study becomes crucial for further application. The embodiment of Sericin coated membrane disclosed herein were tested for interaction among drugs (for example: Ibuoprofen, Diclofenac, Amoxicillin, Ciprofloxacin, Estrone and ß-estradiol). This study may be performed by any method known to a person skilled in the art. In an example, the removal efficiency of the Sericin coated UF membrane for individual drug in presence of other drugs was studied at a concentration of about 20 µg/L and 100 µg/L for each drug. FIG. 17A and 17B are graphs depicting the removal efficiencies of the drug from aqueous mixed drug solution using Sericin-coated HFUF membrane. FIG. 17A depicts the removal efficiencies of the drug at an initial feed concentration of about 100 µg/L for each drug.FIG. 17B depicts the removal efficiencies of the drug at an initial feed concentration of about 20 µg/L for each drug. The adsorption of drugs on membrane surface involves molecular interaction which includes ionic interaction, dipolar interaction, ion-dipole interaction and hydrogen bonding. In multi-drug mixture, all the drugs have a bipolar functional group such as hydroxyl, carboxylic and/or amine groups, which may interact with each other via hydrogen bonding. The interaction among the drugs and between drug and membrane will play a major role in multi dug mixture removal. Except for ß-estradiol, removal of all selected five drugs is found to be very high and efficient(FIG. 17B). At higher concentration as expected, when multi drugs particles compete for sorption at the same site on the membrane surface, the sorption of each drug was less than that in the single-solute system (FIG. 17A). In low concentration experiment, all selected drugs were removed entirely in a 3-litre filtration cycle except ß-estradiol. While at high concentration (100µgL-1/solute), the interaction was observed to be high and hence the relative adsorption between drugs to membrane inhibited the overall drug removal efficiency. The removal capacity follows the sequence; Ibuoprofen> Diclofenac > Amoxicillin > Ciprofloxacin > Estrone > ß-estradiol, showing the role of charge-based interaction and hydrogen bonding as the main mechanism behind removal as infered earlier.
Regeneration of Sericin coated membrane
[0085] In one example, in order to check the possibility of membrane regeneration, the used Sericin coated membrane was washed with different cleaning solution to test for desorption of drugs. As aforementioned, the adsorption of drugs on the membrane surface is highly influenced by charge-based interaction and is endothermic. Hence, altering pH and temperature of stripping solution can enable the desorption of drugs from membrane surface. The used Sericin-coated membrane was washed using acidic solution (0.1N HCl; pH 3), an alkaline solution (0.1 M NaOH, pH 11), hot water (40 °C) and cold water (10 °C) to remove adsorbed drugs. FIG. 18 is a graph depicting the effect of striping solution on drug desorption efficiency from an embodiment of the Sericin coated membrane surface. Maximum drug desorption was observed when used membrane is cleaned with an alkaline solution (94.38%). Cold water (36.71%), Hot water (23.84%) and acidic solution (7.24%) were not very efficient in dissociation of adsorbed drugs. The membrane was re-tested for adsorptionefficiency, and more than 90% efficiency was observed. A cold (10°C) solution of sodium hydroxide is recommended for regeneration of Sericin-coated membrane.

Air purification by Sericin-modified bicomponent Polyester filter
[0086] FIG. 21 is a graph depicting the performance of sericin-coated air filter for 2160 cycles over a period.The Sericin coated bicomponent Polyester filter according to the disclosures made in the various embodiments herein may be used in any air purification system that are generally known to use polyester sheet filters.
[0087] FIG. 21 is a graph depicting the performance of sericin-coated air filter for 2160 cycles over a period.
[0088] In one example,the air purification systems may include a closed chamberhavingan air filter system, hot-plate, fan, PM sensor and Volatile Organic compounds (VOC) analyzer. The Air filter system is pre-fitted with an embodiment of the Sericincoated membrane according to the embodiments herein. Incense stick was burned inside the chamber to generate particulate matter (˜1000µg/m3), while the hot-plate was used to generate the VOC fumes from gasoline. In a small beaker, gasoline was heated up, and the resultant gases were distributed to the whole chamber using a fan. The air filter system was controlled from outside the chamber using a remote. The fan was used to circulate the generated PM and VOCs throughout the whole chamberto avoid from being concentrated at one fixed location. PM and VOC removal were then analyzed.
[0089] Removal of Particulate matter:Particulate matter generated using incenses stick in the closed chamber was filtered using Sericin-coated air–filter. Filtration was performed at different flow rate, and comparative analysis was performed to evaluate its performance with uncoated and HEPA filter. FIG. 19A and 19B are graphs depicting the PM removal. FIG. 19Adepicts the PM removal by Sericincoated air filterat different flow rate. 19Bdepicts the comparative performance analysis of PM removal by Sericin-coated air-filter,Uncoated filter and HEPA filter.At a low flow rate (145 m3/h), the filter was observed to be more efficient than at a higher flow rate (445 m3/h). Thiscould be due to high-pressure drop at an increased flow rate, which leads to a decreased time of contact between PM and air-filter. Also high flow rate results in turbulent condition that may cause decreases in removal efficiency. For complete removal, the Sericin-coated air-filter took 26.80, 45.91, 50.88, and 61.8 minutes at 145, 300, 375, and 445 m3/h of flow rate, respectively (FIG.19A). HEPA filter was able to remove the PM in 8.5 minutes, while Sericin coated and uncoated air filter took 26.80 minutes and 37.23 minutes respectively (FIG.19A). Although the HEPA filter is highly efficient in comparison to the disclosed Sericin coated filter, the fabricated filters according to the embodiments herein are capable of being regenerated for repeated use and are applicable in removal of VOCs.
[0090] Removal of VOC removal:The Sericincoated air-filter was also analyzed for removal of VOCs (such as Benzene, ethylbenzene, Toluene and Xylene, also known as BTEX) from the closed chamber. FIG. 20 shows percentage (%) removal of BTEX gases over a period. BTEX removal bySericincoated air-filter at a low initial concentration (100, 500, 750 and 1000 ppb). The filter was found to be more effective at a lower concentration of VOCs (100ppb-1000ppb), and almost complete removal of about >95% was observed up to 1000 ppb.All BTEX compounds were completely removed within 6 hours of operation. The filter was washed with pure water and reused with no apparent decrease in efficiency.
[0091] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation and that those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.