TECHNICAL FIELD

[001 ] Embodiments of the present invention generally relate to water treatment systems and more particularly to a membrane for brackish water reverse-osmosis for high salinity brackish water application and a process for formation of the membrane thereof.

BACKGROUND

[002] Groundwater is one of the main water resources in the QATAR. The total volume of the groundwater is slightly high at around 640 billion cubic meters, but only 3% is the freshwater while the remaining water is highly salty. The Groundwater in the QATAR is fast depleting because of prolonged drought conditions. About 10,000 farms in the QATAR are at the risk because of the high depletion of groundwater which ends up producing high saline water. Almost half of the wells located at DUKHAN and other Eastern Region are also affected by the high-water abstraction. In recent years the extent of salinity in the groundwater has increased as a result of over-abstraction of the groundwater which causes a huge transfer of either seawater or older saltier groundwater into the fresh groundwater wells.

[003] A survey of many wells in QATAR found that ninety percent of the wells had a salinity of more than 2,000 parts per million, and out of these wells, 65% have a salinity over 6,000 ppm and one fifth had salinities greater than 8,000 ppm. The salinity has even increased more recently due to the large depletion of the groundwater. On many farms, brackish water RO desalination is a must to reduce the salinity of the groundwater for irrigation applications. The brackish desalination capacity has expanded over the last few years in many of the areas as a result of the increased salinity levels.

[004] Based on the classification of FAO all QATAR underground water is fall into moderate, high and very high saline water which require a highly sophisticated desalination treatment systems to be treated. The harsh conditions of QATAR seawater, brackish water, and wastewater is the motivation to come up with a local water technology to develop specific membranes to treat water. There is a need of special type of brackish water reverse-osmosis (BWRO) that can treat their brackish water ranging from 5000-15000 ppm which is not available in the market. [005] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks with a membrane for brackish water reverse-osmosis for high salinity brackish water application and a process for formation of the membrane thereof.

SUMMARY OF THE INVENTION

[006] According to a first aspect of the present invention, there is provided a process for formation of a membrane for brackish water reverse-osmosis for high salinity brackish water application. The process comprises steps of coating a first layer on a polymer, with a first solution of a predetermined weight percentage of Acacia gum added in 1,3 phenylenediamine dissolved in deionized water, for a predetermined time period; coating a second layer on the polymer, with a second solution of 1,3,5- Benzentricarboxylic acid chloride dissolved in n-hexane solvent, for a predetermined time period thereby forming a composite; dipping the composite in the water for the removal of access amounts of solvents and accelerate pore formation on the composite for a predetermined time period; and heating the composite at a predetermined temperature, for a predefined time period thereby forming a thin-film composite polyamide membrane.

[007] In accordance with an embodiment of the present invention, the heating predetermined temperature of the thin-film composite polyamide membrane is in the range of 50-70 °C for the predefined time period of 5-15 min.

[008] In accordance with an embodiment of the present invention, the weight percentage of the Acacia gum in the first solution is in range of 0.01-1.5 wt.%.

[009] In accordance with an embodiment of the present invention, gelling the composite in water for a predetermined time period of 2-6 minutes.

[010] In accordance with an embodiment of the present invention, coating the first layer over the second layer on the polymer using interfacial polymerization forming the composite.

[Oi l] In accordance with an embodiment of the present invention, the polymer is selected from a group comprising polysulfone and polyethersulfone or a combination thereof.

[012] In accordance with an embodiment of the present invention, thickness of the polymer is in range of 100-300 microns.

[013] In accordance with an embodiment of the present invention, the thin-film composite polyamide membrane formed with uniform thickness ranging from 100-200 um, smooth surface and uniform pores on surface ranging from 5-10 nm. [014] In accordance with an embodiment of the present invention, the Acacia gum at predetermined concentrations of range 0.01 to 0.05; the 1,3,5-Benzentricarboxylic acid chloride solution of 0.02-0.3 wt% ; and the 1,3 phenylenediamine in range of 1-5 wt.% in deionized water.

[015] According to a second aspect of the present invention, there is provided a membrane for brackish water reverse-osmosis for high salinity brackish water application. The membrane comprises a thin-film composite polyamide membranes blended with a predetermined weight percentage of Acacia gum.

[016] In accordance with an embodiment of the present invention, the weight percentage of the Acacia gum in the thin-film composite polyamide membranes is in range of 0.01-0.5 wt.%.

BRIEF DESCRIPTION OF THE DRAWINGS

[017] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may have been referred by embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[018] These and other features, benefits, and advantages of the present invention will become apparent by reference to the following text figure, with like reference numbers referring to like structures across the views, wherein

[019] Figure 1 illustrates a process for formation of a membrane for brackish water reverseosmosis for high salinity brackish water application; and

[020] Figure 2 illustrates steps of fabrication of the membrane, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[021] The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description.

[022] While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim.

[023] As used throughout this description, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense, (i.e., meaning must). Further, the words "a" or "an" mean "at least one” and the word “plurality” means “one or more” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes.

[024] Referring to the drawings, the invention will now be described in more detail. Figure 1 illustrates a process for formation of a membrane for brackish water reverse-osmosis for high salinity brackish water application. As shown in figure 1, at step 110, the process may start with coating a first layer on a polymer. The polymer is selected from a group comprising polysulfone and polyethersulfone or a combination thereof. The polymer may have a thickness in range of, but not limited to, 100-300 microns.

[025] In accordance with an embodiment of the present invention, the polymer may be coated with a first solution of a predetermined weight percentage of Acacia gum added in 1,3 phenylenediamine dissolved in deionized water. The Acacia gum, also called gum arabic, is a dried gummy exudate which may be sourced from, but not limited to, trunk and branches of Acacia Senegal and Acacia seyal trees. The Acacia gum is rich in soluble fibers of low viscosity. The weight percentage of the Acacia gum in the first solution may be in range of, but not limited to, 0.01-1.5 wt.%. The polymer may be dipped or applied with the first solution for a predetermined time period ranging from, but not limited to, 2-8 minutes, and preferably for 5 minutes. In a preferred embodiment, as the first step, the first solution may be coated on the polymer by uniform casting of the first solution layer on to the polymer, preferably, non-woven sheet roll by membrane casting knife.

[026] Further, as shown in figure 1, at step 120, a second layer is coated on the polymer. The polymer after being coated with the first solution, may now be coated with a second solution of 1,3,5- Benzentricarboxylic acid chloride dissolved in n-hexane solvent. The polymer may be dipped in or applied with the second solution for a predetermined time period thereby forming a composite. The polymer may be dipped or applied with the second solution for a predetermined time period ranging from, but not limited to, 2-8 minutes, however, preferably for 5 minutes. Similar to the first step, the second solution may also be coated on the polymer by uniform casting of the second solution layer on to the polymer, preferably, non-woven sheet roll by membrane casting knife. In a preferred embodiment, the first layer and the second layer are coated on the polymer using interfacial polymerization forming the composite.

[027] Next, at step 130, as shown in figurel, the composite is dipped in the water for the removal of access amounts of solvents and accelerate pore formation on the composite for a predetermined time period. In accordance with an additional or alternative embodiment of the present invention, the composite may be gelled by dipping the composite in water for a predetermined time period. In accordance with an embodiment of the present invention, the composite is gelled in water for a predetermined time period of 2-6 minutes to solidify. Furthermore, at step 140, as shown in figure 1, the composite is heated at a predetermined temperature, for a predefined time period thereby forming a thin-film composite polyamide membrane (hereinafter, also denoted as “the membrane”). In accordance with an embodiment of the present invention, the composite is heat at predetermined temperature in the range of, but not limited to, 50-70 °C for the predefined time period of, but not limited to, 5-15 min. The thin-film composite polyamide membrane formed with uniform thickness ranging from 100-200 um, smooth surface and uniform pores on surface ranging from 5-10 nm.

[028] In order to produce the thin-film composite polyamide membrane in abundance, roll-to- roll process may be used which involves continuous processing of a flexible substrate as it is conveyed along a roller-based processing line. The steps of the fabrication of the membrane are shown in figure 2. The roll-to-roll process requires dedicated tension control, environmental condition control (temperature, humidity) and roll-to-roll automatic control. Once the roll-to-roll equipment fails to adjust the right tension or control with specific non-woven mechanical properties, the substrate casting layer will not be uniform, and this subsequently affects the quality of the second step and the subsequent final product quality. [029] A motor may be used with tension control to adjust the right tension for uniform casting of the first solution and the second solution over the polymer. Meanwhile, the environmental conditions (humidity and temperature) need to be controlled within a stable range for each specific of first and second solutions. Further, as shown in figure 2, the thin-film composite polyamide membrane may be rinsed multiple times before rolling. Once the membranes are rolled, they are needed to be cut into pieces and assembled into RO elements before usage. As first step, RO feed spacer roll is auto cut into preset sizes and welded onto core tube as one on Permeate Carrier Autocutter and Welding Machine.

[030] Meanwhile, the membrane roll is also automatically cut and folded together with permeate carrier as RO leaf. Core tube (with feed spacer) and RO leaf are then brought to the rolling machine with robotic glue dispenser. An accurate amount of glue is dispensed at a fixed rate and the positions are guided by the light beam. After gluing and rolling, the element auto-trimmer may trim off excess RO membranes from the element, followed by installation of ATD end-cap. For the last two steps, fiber reinforced plastics (FRP) is wrapped on the RO external area, followed by a final curing process for all the glue and FRP to solidify and cure.

[031] The invention has various advantages. The thin-film composite polyamide membranes blended with 0.01-0.2 wt.% of Acacia gum as an additive increases the membrane’s hydrophilicity by 45%, surface charge by 16% as well as water flux by 1.2-fold compared with plain already available membrane. Besides, the membranes possess reduced surface roughness by 63% and improved antifouling behavior while maintaining NaCl rejection above 96%. The membranes against with seawater show higher salt rejection and lower flux decline during filtration compared to commercially available membranes (GE™ Osmosis and Dow™ SW30HR). The Acacia gum is an efficient additive to enhance the properties of membranes.

[032] The membranes can carry out filtration of gulf seawater without any pre-treatment. The compaction of the membrane porous structure as well as the formation of a cake/gel layer from a suspended, organic and microbiological matter in seawater on the membrane surface results in a higher salt rejection. The salt rejection can reach up to 99.1% with filtration time. It may worth mentioning that TDS of the salt water after 24 h of filtration time may be increased by more than 55% (from 45,000 ppm at the beginning to about 70,000 ppm at the end). As seen from this comparison, present membranes show much higher rejection with seawater (about 45,000 ppm) compared to the commercial, which is an indication of the enhancement in the performance of the Acacia gum containing membranes. [033] In accordance with an embodiment of the present invention the method may be understood with following example:

[034] Process of Thin-Film Composite (TFC) Membrane Fabrication:

[035] The innovation encompasses the integration of varying concentrations of alginate (AG), specifically 0.01, 0.025, and 0.05 weight percent (wt.%), into a TMC solution constituting 0.1 wt.% in an n-hexane solution. This solution undergoes overnight stirring. The procedure for constructing the TFC membranes includes the following steps:

[036] Substrate Preparation:

[037] The commercial substrate used is first immersed in water for a period of 48 hours, aiming to remove any entrapped air bubbles. Post immersion, surplus water present on the surface of the substrate is eliminated using a rubber roller.

[038] Application of MPD Solution:

[039] Subsequently, a 40-milliliter MPD solution, prepared at 2 wt.% concentration in deionized water, is evenly applied over the substrate and left in place for 2 minutes. This solution is then drained off, and any remnants are removed with a rubber roller.

[040] TMC Solution Application and Polymerization:

[041] Following the MPD application, a 0.1 wt.% TMC solution in n-hexane is applied onto the substrate's surface. This application is maintained for 1 minute to promote the polymerization process. Post-reaction, the TMC solution is similarly drained and cleared off the surface using a rubber roller.

[042] Drying and Curing:

[043] After these applications, the membrane is allowed to air dry for 1 minute and is subsequently cured in an oven maintained at 60 °C for 5 minutes.

[044] Final Preparation:

[045] Finally, the fabricated membrane is removed from the oven and subjected to an overnight immersion in deionized water in preparation for subsequent testing and evaluation.

[046] The aforementioned description details the novel approach and materials employed in the fabrication of RO membranes, highlighting the specific methods and concentrations used in the innovative process. The Poly sulfone ultrafiltration membrane (PS -20 UF) may be characterized by a molecular weight cutoff of 20 kDa.

[047] The present invention may treat the groundwater with the salinity ranging from 5000 to 15000 ppm. As mentioned before, the average salinity of the groundwater in QATAR is about 10,000 ppm where no BWRO are available in the local or international market to treat this type of water. Many Farms that are facing high salinity will benefit from this product. The advantage of the present invention is its ability to reject the saltwater up to 15,000 ppm, with much less energy consumption compared to SW-RO membranes, with higher flux. The goal od the present invention is to produce sustainable water for domestic, industrial, and agriculture applications. The development of this technology will benefit QATAR, GCC countries, and worldwide in the short and long runs. The membrane disclosed in the present invention shows high salt rejection, high chlorine resistance, high antifouling, high flux, high separation removal, high performance compared to commercial membranes.

[048] Further, the operations need not be performed in the disclosed order, although in some examples, an order may be preferred. Also, not all functions need to be performed to achieve the desired advantages of the disclosed system and method, and therefore not all functions are required.

[049] The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Examples and limitations disclosed herein are intended to be not limiting in any manner, and modifications may be made without departing from the spirit of the present disclosure. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the disclosure, and their equivalents, in which all terms are to be understood in their broadest possible sense unless otherwise indicated.

[050] Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providing broadest scope of consistent with the principles and the novel and inventive features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and appended claims.