A composition for a modified polysulfone membrane, process for the preparation and use thereof for the removal of phenolics from wastewater

Abstract

The present invention relates to the method for efficient removal of phenolic compounds from wastewater generated from petroleum industry. The method is two-step process. The first step is a pre-treatment process which operates through adsorption-based separation using granular activated carbon. The wastewater in this step is allowed to pass through a column packed with granular activated carbon. In the second step, the pretreated wastewater is subjected to membrane-based treatment. The present invention also relates to the design of a special membrane for effective removal of phenolic compounds from waste water. The membrane formulation includes polysulfone as the main polymeric matrix and carbon dots coated powdered activated carbon as the additive which acts as the active agent for the removal of phenolic compounds. The membranes are designed in two different types, viz., (i) flat sheet and (ii) hollow fiber. The membrane-based separation using the flat sheet membranes can be done with the help of a dead-end filtration set up. In case of hollow fiber membranes, a cylindrical membrane module with a large number of hollow fiber membranes is designed. The membranes are reusable with excellent separation efficiency. The membrane module has proper feed inlet, outlet for permeates and outlet for retentates. This present invention provides removal of ~99% phenolic compounds from petroleum industry wastewater.

Description

[0001] A COMPOSITION FOR A MODIFIED POLYSULFONE MEMBRANE, PROCESS FOR THE PREPARATION AND USE THEREOF FOR THE REMOVAL OF PHENOLICS FROM WASTEWATER

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a composition for modified polysulfone membrane, process for the preparation and use thereof for the removal of phenolics from wastewater. In particular, the present invention relates to a membrane-based separation process for effective removal of phenolic compounds from petroleum industry wastewater. More particularly, the present invention relates to a polymeric composite membrane for efficient removal of phenolic compounds from aqueous medium. The complete process consists of two steps that include a pre-treatment process followed by membrane-based separation. The pre-treatment process consists of coagulation and adsorption-based separation of phenolic compounds using granular activated carbon. A polymeric membrane using polysulfone, powdered activated carbon and amine containing carbon dots has been designed that shows high efficiency in phenol removal. The combined process exhibited ~99% removal of phenolic compounds from petroleum industry wastewater. The instant invention thus finds immense application in wastewater treatment and water pollution mitigation. It shall help attain the 6thsustainable development goal of clean water and sanitation.

[0004] BACKGROUND OF THE INVENTION AND DESCRIPTION OF PRIOR ART

[0005] It is known to persons in the art that removal of phenolic compounds from industrial wastewater is very important because of its hazards. In that view, a highly effective, easily scalable, low-cost, and less energy-consumed method for removing phenolic compounds is important. Substantial research has already been undertaken in the field of removal of phenolic compounds from aqueous media to arrive at a fool proof method for its application in wastewater treatment. It is known to the researchers that, such a fool proof method is yet to be deciphered, as much as one or the other problem(s) / disadvantage(s), remain associated with such methods.

[0006] Reference may be made to US2808375 which uses a solvent mixture of benzene, toluene and xylene for extraction of phenol from aqueous medium. Dehydroabietylamine was used as an enhancer in that process. However, such process is not continuous and hence unsuitable for large scale. Reference may be made to Yu et al, ACS Omega 2021 , 6, 8870-8883, (D0l:10.1021 / acsomega.0c06029), which experimentally demonstrates the efficient removal of phenol from water using activated carbon prepared from food waste. However, their method is a batch process and is not proven for industrial wastewater.

[0007] Thus, a fool proof method for removal of phenolics is required which will be effective in the presence of other contaminants in water because the industrial wastewater contains large amounts of other organic and suspended matter, which is essential for overall treatment.

[0008] Accordingly, keeping in view the drawbacks of the hitherto reported prior art, the inventors of the present invention realized that there exists a dire need to provide a different and novel approach, leading to the design of a composite modified membrane comprising finely powdered activated carbon coated with carbon dots prepared from chitosan, and polysulfone membrane to remove phenolic compounds from industrial wastewater, wherein the developed membrane enables the complete removal of phenolic compounds from industrial wastewater, while exempting the use of sophisticated instruments or machineries and provides easy scalability.

[0009] OBJECTIVES OF THE INVENTION

[0010] The main objective of the present invention is therefore to provide a modified polysulfone membrane to remove phenolic compounds from industrial wastewater which obviates the drawbacks of the hitherto reported prior art.

[0011] Another objective of the present invention is to provide a method that completely removes phenolic compounds from industrial wastewater in the presence of other contaminants.

[0012] Still another objective of the present invention is to design a membrane having high efficiency for removing phenolic compounds from an aqueous medium.

[0013] Yet another objective of the present invention is to design a method for completely removing phenolic compounds from industrial wastewater using low-cost, regenerable and durable materials and processes that can be easily scaled up and does not use sophisticated instruments and machinery.

[0014] Yet another objective of the present invention is to produce clean water from phenolic wastewater by a continuous process for reuse in industries.

[0015] SUMMARY OF THE INVENTION The present invention provides a composition for modified polysulfone polymeric membrane for effective removal of phenolic compounds from petroleum industry wastewater. The developed membrane is immensely useful for the removal of phenolic compounds and other inorganic and biological impurities from petroleum industry wastewater.

[0016] To meet the increasing needs of a process for producing clean water and its reuses to protect the environment, a cost-effective and easy method for removal of contaminants from petroleum industry wastewater, a membrane has been developed in this present invention.

[0017] The novel membrane developed in the instant invention is made up of finely powdered activated carbon coated with carbon dots prepared from chitosan, and polysulfone, which combination is hitherto unreported. The present invention also provides a combined process, including pre-treatment and membrane-based separation for highly efficient removal of phenolic compounds making the present invention different from the existing or prior art.

[0018] The invention further provides low-cost environment friendly and continuous method for removal of phenolic compounds from industrial wastewater. The developed method consists of two step process wherein the first step is a pre-treatment process that removes some portion of the phenolic compounds along with other solid contaminants. The second step is the membrane-based separation wherein the remaining phenolic compounds are removed and the method as a whole provides high efficiency of wastewater purification.

[0019] In an embodiment of the present invention, granular activated carbon which is a low-cost material is selected as an adsorbent material for the pre-treatment process. Activated carbon is an easily available material and used in a variety of applications. Granular activated carbon is packed in a column and the feed wastewater is allowed to pass through the column.

[0020] In another embodiment of the present invention, amine functionalized carbon dots are synthesized from chitosan. Chitosan is a natural polymer derived from exoskeleton of some marine creatures. Chitosan contains amine functional groups in their backbone which is inherited to the carbon dots. For synthesis of carbon dots, 1 % of chitosan solution was prepared in 0.1 M acetic acid. In this solution, 40% of glycerol was added. The whole solution was then neutralized using 5N NaOH. Upon neutralization, the chitosan solution turns into a hydrogel. The hydrogel was collected by filtration and again dissolved in 0.1 M acetic acid. The solution was then microwaved in a household microwave woven at power 720 watt for 5 minutes to obtain carbon dots coated activated carbon (CD-AC).

[0021] In another embodiment of the present invention, flat sheet and hollow fiber membranes are fabricated using carbon dots coated activated carbon (CD-AC). First 18% of polysulfone solution was prepared in N-Methyl-2-pyrrolidone (NMP) at 60 degree C by mechanical stirring at around 500rpm. Then 55.5% of Activated carbon and 75% of carbon dot with respect to polysulfone was added into the polysulfone solution to obtain a solution mixture.

[0022] To fabricate flat sheet membranes, the solution mixture prepared above was cast on a glass plate with the help of a specially arranged glass rod to maintain constant thickness. The casted solution was then immersed in a non-solvent bath containing distilled water. In the presence of water, polysulfone is converted to a thin porous sheet by the non-solvent induced phase inversion process. The flat sheet membranes were then washed with pure distilled water and air dried at room temperature.

[0023] For the fabrication of hollow fiber membranes, 23% solution mixture prepared above was used. Fabrication of fibers was achieved by using a spinneret. The CD-AC incorporated polysulfone solution mixture was allowed to squeeze through the spinneret fitted in hollow fiber membrane making machine and allowed to fall in a water bath. In the process, water acts as the non-solvent, and the polymeric mixture solution forms porous hollow fiber. The fibers were rolled on a roller, washed with distilled water and finally allowed to dry at room temperature.

[0024] In an embodiment, the present invention provides a composition for a modified polysulfone membrane comprising:

[0025] [a] polysulfone having molecular weight 60,000 g / mol;

[0026] [b] powdered activated carbon coated with amine functionalized carbon dots in the ratio of 50 to 57 : 65 to 85; wherein the ratio of [a] : [b] is in the range of 16 to 18 : 50 to 55.5.

[0027] In another embodiment, the present invention provides a composition, wherein polysulfone solution is prepared in the solvent N-Methyl-2-pyrrolidone at a concentration of 14% to 20%.

[0028] In still another embodiment, the present invention provides a composition, wherein the amine functionalized carbon dots are derived from chitosan.

[0029] In yet another embodiment, the present invention provides a composition, wherein the ratio of polysulfone, activated carbon and carbon dots is 18 : 55.5.

[0030] In another embodiment, the present invention provides a process for the preparation of a modified polysulfone membrane, wherein the steps comprising: a) preparing the polysulfone solution using the solvent N-Methyl-2-pyrrolidone at 60 degree C under mechanical stirring; b) simultaneously, preparing carbon dots from chitosan, wherein the steps comprising:

[0031] (i) preparing 1 % chitosan solution in 0.1 M acetic acid;

[0032] (ii) adding glycerol to the solution obtained in step (i) in the ratio of 2:5;

[0033] (iii) neutralizing the solution obtained in step (ii) using 5N NaOH to obtain a hydrogel system followed by washing using distilled water;

[0034] (iv) dissolving the washed hydrogel obtained in step (iii) using 0.1 M acetic acid;

[0035] (v) treating the solution obtained in step (iv) under microwave treatment for 5 minutes at 720 watt;

[0036] (vi) adding of 55.5% powdered activated charcoal with respect to polysulfone to the solution obtained in (v) under mechanical stirring for 3 to 4 hours followed by collecting the carbon dots coated activated charcoal by centrifugation and washing with N-Methyl-2-pyrrolidone; c) adding the carbon dots coated activated charcoal obtained in step (b)to the polysulfone solution obtained in step (a) followed by stirring for 4 hours to obtain a mixture; d) casting the mixture obtained in step (c) to obtain the desired modified polysulfone flat sheet and / or hollow fiber membranes.

[0037] In another embodiment, the present invention provides a modified polysulfone membrane wherein it exhibits 99% rejection of phenol from wastewaters.

[0038] In still another embodiment, the present invention provides a process for the removal of phenolics from a sample using the modified polysulfone membrane, wherein the steps comprising:

[0039] (a) pretreatment of the phenol containing wastewater using a PVC column of diameter 10 cm and length 50 cm, containing stone of size ~0.5 inch and granular activated charcoal; (b) treating the pretreated wastewater obtained from step (a) using flat sheet membranes, hollow fiber membranes or hollow fiber membranes as obtained by the process as claimed in claim 5.

[0040] In still another embodiment, the present invention provides a process wherein the stones are used both at the bottom and at top of the column to hold the granular activated charcoal for adsorption and retention of unnecessary particles and also phenolic compounds to some extent.

[0041] In yet another embodiment, the present invention provides a process wherein the PVC column having a diameter of 10 cm and length 50 cm.

[0042] In yet another embodiment, the present invention provides a process wherein the developed membrane can be reused upto 200 cycles with efficient removal of phenolics.

[0043] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0044] Figure 1 illustrates the schematic representation of the design of the hollow fiber module with feed inlet, outlet for permeates and outlet for retentates.

[0045] DETAILED DESCRIPTION OF THE INVENTION

[0046] The present invention provides a highly efficient membrane for removing phenolic compounds from aqueous medium. The modified polysulfone membrane developed in the instant invention comprises finely powdered activated carbon coated with carbon dots prepared from chitosan, and polysulfone.

[0047] The present invention further relates to treating the pretreated wastewater using the designed membranes. A membrane-based wastewater treatment process was adopted using the developed flat sheet and hollow fiber membranes. The treatment method comprises a two- step procedure for effectively removing phenolic compounds produced by petroleum refineries. The combination of a pretreatment process followed by the membrane treatment of wastewater is found to be very much efficient for the removal of phenolic compounds from wastewater. The present invention relates to an easy pretreatment process, and can be applied for a large volume of wastewater at a given time.

[0048] In an aspect, the present invention provides a three-step process for completely removing phenolic compounds from industrial wastewater using the designed and developed modified polysulfone membranes. The first step involves pretreatment of the industrial wastewater using Poly Aluminium Chloride [PAC] followed by granular activated carbon packed in a cylindrical column. This is followed by the collection of the pre-treated water by a microfiltration process using an industrial cloth. The third step relates to treating the pre-treated wastewater using the designed membranes. In the present invention, membrane-based wastewater treatment was done using the developed flat sheet and hollow fiber membranes which can remove phenol as well as other contaminants from wastewater. The separated phenols from the wastewater were collected by backwashing the membrane module with water. The membrane module is then regenerated by backwashing it and is reusable.

[0049] Thus, the present invention relates to a membrane-based separation process for phenols from wastewaters, which is a continuous process and considered to be a green, effective, low maintenance, easily scalable and cost-effective method.

[0050] In another aspect, the present invention relates to the development of a continuous, low cost, scalable and eco-friendly process for the removal of phenolic compounds from wastewater generated from petroleum industry. More specifically, the present invention relates to the development of a two-step method which can effectively remove the phenolic compounds from wastewater. The first step is a pre-treatment process that removes some portion of the phenolic compounds along with other solid contaminants from wastewater stream. The second step is a membrane-based process that can remove the remaining phenolic compounds from the pre-treated feed.

[0051] Most of the hitherto available processes are batch process, which are difficult to apply for a large quantity of wastewater treatment. The present invention hence attempts to provide a continuous process which is suitable for the treatment of a large quantity of wastewater. The developed method is easy to maintain.

[0052] The pre-treatment process uses activated carbon packed in a column which can treat a continuous flow feed of wastewater. The column provides adsorption-based separation of phenolic compounds in a continuous mode. Activated carbon is considered to be one of the most effective adsorbents for many different types of pollutants. The pre-treated wastewater is then subjected to membrane-based treatment process.

[0053] The membrane design in the present invention is another crucial factor for effectiveness of the whole process. Polysulfone, being one of the most popular polymeric materials with high membrane forming property is used as main matrix of the designed membrane. A composite filler system consisting of carbon dots and powdered activated carbon is incorporated inside the polymeric matrix system. The carbon dots being functionalized with amine group is derived from chitosan, a commonly used natural polymer derived from aquatic organisms.

[0054] For the synthesis of carbon dots, a 1% solution of chitosan in 0.1 M acetic acid is prepared. In this solution 40% of glycerol was added additionally. The whole solution is then converted into a hydrogel system by neutralization with 5 N NaOH. The hydrogel was collected by filtration and again dissolved in 0.1M acetic acid. The solution was then microwaved in a household microwave oven at power 720 watts for 5 minutes. Finally, a solution of carbon dots in aqueous medium is obtained that shows fluorescence under UV-light.

[0055] The synthesized carbon dots were then coated on the surface of the activated carbon to form a composite system. For this 5 wt% of activated carbon was added in carbon dots solution in 0.1 M acetic acid. The dispersion was mechanically stirred for 2 hours at room temperature. Finally, the carbon dots coated activated carbon was collected by centrifugation and washed with water and then by N-Methyl-2-pyrrolidone (NMP).

[0056] The composite carbon dots coated activated carbon-based additive was incorporated into the polysulfone matrix which is then converted to porous membranes by the non-solvent induced phase separation method. Two types of membranes were designed by using the same ingredients.

[0057] The flat sheet membranes were synthesized form 18% polysulfone solution prepared in N- Methyl-2-pyrrolidone (NMP). Required amount of CD-AC is added into the polymeric solution and the solution is then casted on a glass plate using a specially designed glass rod. The casted solution is then soaked into water bath where the phase inversion occurs with the formation of a solid porous membrane.

[0058] In case of hollow fiber membranes, 23% polysulfone solution is used. Desired amount of CD- AC is added into the polysulfone solution and thoroughly mixed using a mechanical stirrer. The solution mixture was then used in a hollow fiber spinning machine with a specially designed nozzle. The solution mixture after passing through the nozzle is allowed to soak in a water bath where the liquid solution gets solidifies and takes the shape of porous hollow fiber membranes.

[0059] The pre-treated wastewater can be treated using the flat sheet membrane using cross flow or dead-end filtration set up with proper membrane module. For hollow fiber membranes, cylindrical modules containing a large number of hollow fiber membranes is designed. The hollow fiber membrane module consists of one feed inlet, one feed outlet and two outlets for permeates. EXAMPLES

[0060] The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention in any manner Example 1 : Polysulfone flat sheet membrane used for phenol removal

[0061] Polysulfone with molecular weight 60,000 g / mol was dissolved in solvent N-Methyl-2- pyrrolidone (NMP) at 60 degree C under mechanical stirring and maintained the percentage at 18%. The Optimization of Polysulfone percentage in NMP for formation of membrane is shown in Table 1. The polysolfone solution was then cast on a glass plate using a specially designed glass rod. The casted solution and the glass plate were then immersed in water and taken in a water bath where water acts as a non-solvent for the polysulfone.

[0062] Table 1 : Optimization of %Polysulfone in NMP for formation of membrane

[0063] Phenol removal efficiency of the membrane from an aqueous phenolic solution was tested using a dead-end filtration set up at pressure 1 bar using synthetic solution of concentration 100 ppm. The removal efficiency of this bare polysulfone membrane was found to be 5-10%. The permeability of the membrane was found to be 83-90 Lm2h-1. T able 2 illustrates the results for phenol removal using the prepared membrane.

[0064] Table 2: Rejection and permeability (flux) of Polysulfone flat sheet membrane (MOFS) used for phenol removal

[0065] Example 2: Polysulfone + activated carbon membrane for phenol removal

[0066] To improve the phenol removal efficiency through MOFS membrane, powdered activated carbon was incorporated in MOFS to work as an active adsorbent. The maximum loading of activated carbon in the polysulfone matrix could be achieved upto 55.5%. Above this percent, the composite membrane could not be formed because of the compatibility issue and the results are shown in Table 3.

[0067] Table 3: Optimization of % Activated carbon in membrane for phenol removal

[0068] The phenol removal efficiency of this activated carbon-polysulfone (AC-PS) composite membrane was obtained as 57-65 %. The permeability of the AC-PS membrane was found to be 120-125Lm2h'1. Table 4 illustrates the results for phenol removal using the AC-PS membrane.

[0069] Table 4: Rejection and permeability (flux) of Polysulfone+ activated carbon flat sheet membrane (M5FS) in 6 hours experimental time used for phenol removal Example 3: Polysulfone + carbon dots coated activated carbon membrane for phenol removal

[0070] For further improvement of the removal efficiency of the membrane prepared in Example 2, an additional active agent for effective adsorption of phenol on the membrane surface was used. Chitosan having -NH2functional group was chosen for this purpose. However, to increase the surface area and to get an effective coating, chitosan was converted to carbon dots. The maximum amount of carbon dots coated activated charcoal (AC-CD) that could be incorporated into the polysulfone matrix was 75% and the results are shown in Table 5. The phenol removal efficiency of AC-CD-PS membrane is in the range of 85-97 % in 1 hour, and maximum phenol removal is obtained as 97% in case of the AC-CD-PS membrane (M8FS) where Activated carbon is coated with 75% carbon dot.

[0071] Table 5: Optimization of % carbon dots for coating on activated charcoal in membrane preparation for phenol removal (data for 1 hour experiment time)

[0072] The phenol removal efficiency of the AC-CD-PS membrane was also tested for 6 hours and the removal efficiency of the AC-CD-PS membrane was found to be 95-97%. The permeability of AC-CD-PS membrane was found to be 170-175Lm2lr1. Table 6 illustrates the results for phenol removal using AC-CD-PS membrane for 6 hours experiment.

[0073] Table 6: Rejection and permeability (flux) of Polysulfone+ carbon dots coated activated carbon flat sheet membrane (M8FS) in 6 hours experimental time used for phenol removal

[0074] Example 4: Polysulfone + carbon dots coated activated carbon membrane for phenol containing industrial wastewater treatment

[0075] AC-CD-PS membrane (M8FS) was used for the treatment of phenol contaminated industrial wastewater directly collected from an oil refinery premises. Phenol contained in the wastewater was determined to be 350-400 ppm. When this wastewater was directly used in the treatment process as a feed using the AC-CD-PS membrane (M8FS), the rejection efficiency of the membrane was found to be < 40%. This is due to the blockage of membrane pores by other particles / impurities present in wastewater. The permeability of the membrane decreased significantly up to 105-120Lm-2h-1.Table 7 illustrates the results for phenol removal using this membrane (M8FS).

[0076] Table 7: Rejection and permeability (flux) of Polysulfone+ carbon dots coated activated charcoal flat sheet membrane (M8FS) used for phenol removal from industrial wastewater.

[0077] Example 5: Pre-treatment of the industrial wastewater using granular activated charcoal

[0078] A pre-treatment process was designed for initial wastewater treatment before going for membrane treatment. In the pre-treatment process, the wastewater was passed through a PVC column containing stone (average size ~0.5 inch) and granular activated charcoal. Stones were used both at the bottom and at top of the column to hold the granular activated charcoal used for adsorption and retention of unnecessary particles and also phenolic compounds to some extent. The diameter of the column was 10 cm and length 50 cm. The column was made of PVC. The stone used was 2 Kg at the bottom and 1 Kg at the top of the granular activated charcoal. For the treatment of 10 L of wastewater, granular activated charcoal used was 200 gm. In this pre-treatment process, removal of contaminants was 74- 83%, including some phenolics.

[0079] Example 6: Membrane based separation of phenol from pre-treated wastewater using AC-CD-PS flat sheet membrane (M8FS).

[0080] The pre-treated wastewater obtained in example 5 above was subjected to the membranebased separation process using the M8 flat sheet membrane of area 12.6 cm2fitted in a deadend filtration module. The rejection efficiency of the membrane was found to be 98-99%. The permeability of the membrane was obtained as142-149Lm-2h-1.Table 8 illustrates the results for phenol removal using this membrane.

[0081] Table 8: Rejection and permeability (flux) of Polysulfone+ carbon dots coated activated charcoal flat sheet membrane (M8FS) for phenol removal after pre-treatment step.

[0082] Example 7: Removal of phenol from pre-treated wastewater using AC-CD-PS hollow fiber membrane (M8HF) module.

[0083] A cylindrical module consisting of 300 numbers of AC-CD-PS hollow fiber membranes (M8HF) was fabricated for the treatment of pre-treated phenol-containing wastewater in a continuous process. The module contains one feed inlet, one feed outlet and two outlets for permeates. Length of the designed module was 43.5 cm whereas the inner and outer diameter of the module was 7.6 and 7.9 cm respectively. Each of the hollow fiber has inner diameter ~1 .22 mm and outer diameter ~1 .7 mm. The permeate flux obtained in this process was 77-85 L / hr while using a pressure of 0.5 bar. Rejection of phenol obtained in this process (pre-treatment + membrane based separation) was 99%. Table 9 illustrates the results for phenol removal using the M8HFmembrane.

[0084] Table 9: Rejection and permeability (flux) of Polysulfone+ carbon dots coated activated charcoal hollow fiber membrane used for phenol removal.

[0085] Example 8: The membrane was examined for recyclability considering 6 hours as one cycle and it was observed that the final membrane (M8HF) can be reused upto300 cycle as illustrated in Table 7.

[0086] Table 7: Recyclability study of membrane M8 (1 cycle = 6 hours)

[0087] Example 9: Thermal and mechanical stability of membranes The prepared membranes (M8FS and M8HF) were analysed to know their thermal and mechanical stability and it was found that the membranes M8FS and M8HF are more stable thermally and mechanically than that of other membranes. Table 8 illustrates the temperature upto which the membranes are stable and also the mechanical strength of both the membranes.

[0088] Table 8: Thermal and mechanical stability of the developed membranes

[0089] ADVANTAGES OF THE INVENTION

[0090] • The developed membranes (M8FS and M8HF) are thermally and mechanically stable.

[0091] • Can be used in tubular form for large scale work and can be regenerated by washing it and can reuse.

[0092] The membrane M8HFis efficient for long time separation i.e. more than 300 cycles of operation.

[0093] • The developed membranes (M8FS and M8HF) are effective for the removal of phenolic compounds from industrial wastewater in the presence of other impurities, while ensuring complete removal of phenolic compounds. • The process using this membrane is economically viable and environment friendly, obviating the use of sophisticated or very costly machinery or equipment.

[0094] The activated carbon used in the pre-treatment step can be regenerated and reused.

Claims

WE CLAIM:1 . A composition for a modified polysulfone membrane comprising:[a] polysulfone having molecular weight 60,000 g / mol;[b] powdered activated carbon coated with amine functionalized carbon dots in the ratio of 50 to 57 : 65 to 85; wherein the ratio of [a] : [b] is in the range of 16 to 18 : 50 to 55.5.

2. The composition as claimed in claim 1 , wherein polysulfone solution is prepared in the solvent N-Methyl-2-pyrrolidone at a concentration of 14% to 20%.

3. The composition as claimed in claim 1 , wherein the amine functionalized carbon dots are derived from chitosan.

4. The composition as claimed in claim 1 , wherein the ratio of polysulfone to powdered activated carbon coated with amine functionalized carbon dots is 18 : 55.5.

5. A process for the preparation of a modified polysulfone membrane with the composition as claimed in claim 1 , wherein the steps comprising: a) preparing the polysulfone solution using the solvent N-Methyl-2-pyrrolidone at 60 degree C under mechanical stirring; b) simultaneously, preparing carbon dots from chitosan, wherein the steps comprising:(i) preparing 1% chitosan solution in 0.1 M acetic acid;(ii) adding glycerol to the solution obtained in step (i) in the ratio of 2:5;(iii) neutralizing the solution obtained in step (ii) using NaOH to obtain a hydrogel system followed by washing using distilled water;(iv) dissolving the washed hydrogel obtained in step (iii) using 0.1 M acetic acid;(v) treating the solution obtained in step (iv) under microwave treatment for 5 to 10 minutes at 720 watt;(vi) adding of 50.0 to 55.5% powdered activated charcoal with respect to polysulfone to the solution obtained in (v) under mechanical stirring for 3 to 4hours followed by collecting the carbon dots coated activated charcoal by centrifugation and washing with N-Methyl-2-pyrrolidone; c) adding the carbon dots coated activated charcoal obtained in step (b) to the polysulfone solution obtained in step (a) followed by stirring for 4 hours to obtain a mixture; d) casting the mixture obtained in step (c) to obtain the desired modified polysulfone flat sheet and / or hollow fiber membranes.

6. A modified polysulfone membrane obtained by the process as claimed in claim 5, wherein it exhibits 99% rejection of phenol from wastewaters.

7. The modified polysulfone membrane as claimed in claim 6, wherein it can be reused for upto 200 cycles with efficient removal of phenolics.

8. A process for the removal of phenolics from a sample using the modified polysulfone membrane as claimed in claim 1 , wherein the steps comprising:(a) pretreatment of the phenol containing wastewater using a PVC column of diameter 10 cm and length 50 cm, containing stones of size ~0.5 inch and granular activated charcoal;(b) treating the pretreated wastewater obtained from step (a) using flat sheet membranes, hollow fiber membranes or hollow fiber membranes as obtained by the process as claimed in claim 5.

9. The process as claimed in claim 8, wherein the stones are used both at the bottom and at top of the column to hold the granular activated charcoal for adsorption and retention of unnecessary particles and also phenolic compounds to some extent.

10. The process as claimed in claim 8, wherein the PVC column having a diameter of 10 cm and length 50 cm.

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