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International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Volume-6, Issue-4, Oct.-2018, http://iraj.in PREPARATION METHODS OF SYNTHETIC

ABDULRAHMAN ALHARBI

Faculty of Engineering, King Abdulaziz University-Rabigh E-mail: [email protected]

Abstract - Water security is a major objective of the Saudi Arabia’s Vision 2030. Due to the water shortage in the Kingdom, desalination is the primary approach for drinkable water. The current desalination methods are costly and have impact on the environment. The use of technologies increase the efficiency of desalination processes. Membranes are either Biological membranes or Synthetic membranes .In this paper, we will discuss the synthetic membrane and it's preparation methods.

Keywords - Water, Desalination, Membranes, Synthetic, Preparation.

I. INTRODUCTION selective hindrance, controlling the transport of substances between the two chambers”[1-2]. The As part of Vision 2030, an ambitious economic transport rate of a component through a membrane is reform blueprint that outlines Saudi Arabia’s future determined by driving forces such as concentration, objectives, the Kingdom will fundamentally , temperature and electrical potential restructure its resources mainly energy sector and gradients, the concentration and mobility of the water security. Vision 2030 takes into consideration component in the membrane. Membranes are either the impending threat of water shortage in the Biological membranes or Synthetic membranes . Kingdom and outlines commitments to ensure “the Biological membrane (bio membranes) is a selective optimal use of our water resources by reducing barrier within or around a cell in a living organism. consumption and utilizing treated and renewable The biomembrane is capable of recognising what is water.” Historically, one of the primary approaches necessary for the cell to receive or block for its by which water scarcity has been addressed is using survival. Biological membranes included dense films desalination processes that transform seawater into of nitrocellulose, natural rubber, and palladium. In potable sources. However, the desalination methods this paper, we will discuss the synthetic membrane that are currently in use are unsustainable because and it's preparation methods. they are energy intensive, rely on a significant amount of oil, and have a significantly detrimental II. STNTHETIC MEMBRANE METHODES impact on the environment. According to Global Clean Water Desalination Alliance, desalination There are two fundamentally different categories of plants emit around 76 million tons of carbon dioxide synthetic membrane materials: Organic (Polymeric), on an annual basis, and it is anticipated that these inorganic ( , Metallic) materials. Organic emissions will increase threefold in the next 23 years. materials are either —based or composed of To this end, there is a requirement to identify new modified organic . By contrast, inorganic novel technologies coupled with renewable energy materials such as and metals are used in sources that can adequately support desalination niche industrial applications but are usually cost- processes and, thereby, address the ongoing water prohibitive in wastewater treatment. A large majority supply and security challenges. The more recent of membranes in research and commercial use are technologies have gone a long way toward increasing polymeric-based (organic membrane) as a result of the efficiency of desalination processes, these their facile processing into viable membrane innovations are still very much in their infancy. The structures and the diverse polymers available, as well use of membranes technologies could provide a as the capability to synthesise novel medium-term solution until alternative desalination structures [3]. Recently, composite membranes and processes reach maturity.Membrane technologies are inorganic membranes have gained tremendous the alternative processes for “molecular separations” attention owing to their potentially high performance, due to its optimized energy solutions, efficiency, long lifetime and even their availability that outweigh sustainability and less footprints. Suitably designed the benefits/advantages of using polymeric membranes and its operability can lead towards membranes.Inorganic membranes posses excellent simultaneously an efficient removal of particulates thermal and chemical stability in comparison to and vapours from gaseous streams. This will result in polymeric membranes and hive higher antifouling highly pure water without the use of added heat property due to the hydrophilic nature of in organic treatment processes. A membrane is a thin layer of material [4]. But, there are some limitation in their semi-permeable material that can be defined as an use despite their wide use and application. Inorganic “interphase between two close by phases acting as a membranes are generally divided into four groups:

Preparation Methods of Synthetic Membrane

32 International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Volume-6, Issue-4, Oct.-2018, http://iraj.in glass membranes, ceramic membranes, metallic IV. PREPARATION METHODES OF membranes, carbon membranes, and zeolitic POLYMERIC MEMBRANE membranes. Although Organic membranes are less resistance to high temperature and aggressive The most dominating membranes in the market are chemicals than inorganic or metallic membranes, they the polymeric membranes. Polymeric materials that are still the most widely used materials in wastewater are used to prepare separation membranes are mostly treatment applications. This is mainly owing to easy organic compounds. A number of different preparation, low cost, high efficiency for removing techniques are available to prepare synthetic dispersed oil, particles, and emulsified, small size, membranes. In the following, we discuss some of lower energy requirement, flexibility in membrane these methods.Sintering is a Simple technique configuration, and relatively low operating allowing porous membrane to be obtained from temperature which is also associated with less organic as well as from inorganic materials. The stringent demands for the materials need in the method involves compressing a powder consisting of construction of module [5]. particles of a given size and sintering at elevated temperatures.The required temperature depends on III. ORGANIC SYNTHETIC MEMBRANE the material used.A wide range of different materials METHODS can be used such as powders of polymers (, , There Most membranes used in industries have an ), metals (stainless steel, tungsten), asymmetric structure. Figure 1 shows schematically a ceramics (aluminum oxide, zirconium oxide), typical cross-sectional view of an asymmetric graphite (carbon) and glass (silicates).The pore size membrane . It consists of two layers: the top one is a of resulting membrane (0.1-10m) is determined by very thin dense layer (also called the top skin layer), the particle size and particle distribution. The porosity and the bottomone is a porous sublayer.The top dense of porous polymeric membrane is generally low (10- layer governs the performance (permeation 20 %). Only membrane can be properties) of the membrane; the porous sublayer prepared by this technique. only provides mechanical strength to the membrane. The membranes of symmetric structures do not possess a top dense layer. In the asymmetric membrane, when the material of the top layer and porous sub-layer are the same, the membrane is Figure 3. Sintering Technique called an integrally skinned asymmetric membrane. On the other hand, if the polymer of the top skin layer Track etching A sheet of polymeric film moves is different from the polymer of the porous underneath a radiation source and isirradiated by sublayer,the membrane is called a composite high-energy particles.The spots that are subjected to membrane. The advantage of the composite bombardment of the particles are degraded or membrane over the integrally skinned asymmetric chemically altered during this process. Then, the film membrane is that the material for the top skin layer undergoes an etching process in an alkaline or and the porous sublayer can be chosen separately to hydrogen peroxide bath (depending on thematerial), optimize the overall performance. There arevarious where the polymer is etched along the path of high- methods for the preparation of asymmetric membrane energy particles. The porosity is determined by (Figure 2 ). radiation intensity and the pore size is determined by etching time. The advantage of this technique is that uniform and cylindrical pores with very narrow pore size distribution can be achieved. In order to avoid the formation of double or multiple pores, produced when two nuclear tracks are too close together, the

membrane porosity is usually kept relatively low. Figure 1. cross-sectional view of an asymmetric membrane Radiation Source

Membrane with capillary pores

Etching bath

Figure 2. Methods for the preparation of asymmetric t0 t1 t2 t3 membrane Figure 4. Track Etching

Preparation Methods of Synthetic Membrane

33 International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Volume-6, Issue-4, Oct.-2018, http://iraj.in Stretching method in this method, an extruded film made from a partially crystalline polymeric material Figures 6 shows the experement of polymeric dope (polytetrafluoroethylene, polypropylene, preparation. Polymeric dope was prepared by mixing polyethylene) is stretched perpendicular to the (PVDF)with the .The direction of the extrusion.When a mechanical stress is solution was stirred at room temperature until applied, small ruptures occur and a porous structure is complete dissolution of the components was obtained with pore size of about 0.1 – 3 m.Only achieved. (semi) crystalline polymeric materials can be used for this technique.The porosity of these membranes is much higher than that of membranes obtained by sintering, and values up to 90 % can be obtained.Phase inversion the phase inversion process was first introduced in by Loeb and Sourirajan 47 in the 1960’s and is the base for the synthesis of most commercially available membranes. During the phase inversion process, a thermodynamically stable polymer solution is transformed from a liquid into a solid state in a controlled manner. This solidification is preceded by a liquid–liquid demixing. Acertain time after initiation of the demixing into a polymer-rich and a Figure 6. Casting solution preparation 18g solvent, 2g PVDF polymer-lean phase, the phase with the highest Figures 7 shows the experement of Membrane polymer concentration will start solidifying through Casting. Membrane was casted using Evaporation processes like gelation, vitrification, or induced phase separation (EIPS) technique filming crystallisation. The polymer-lean phase will lead to the polymeric solution over a suitable smooth glass the pores in the solidified material, while the support by means of a hand casting knife. The polymer-rich phase will lead to the solid membrane membrane itself is formed during the next step which matrix. This demixing may be induced by: Evaporation induced phase separation (EIPS) where leads to the precipitation of the polymer and the polymer solution is made in a solvent or in a evaporation of solvent. mixture of a volatile solvent and a less volatile nonsolvent, and solvent is allowed to evaporate, leading to precipitation or demixing / precipitation ,Vapor induced phase separation (VIPS) where the polymer solution is exposed to an atmosphere containing a nonsolvent (typically water); absorption of nonsolvent causes demixing /precipitation ,Temperature induced phase separation (TIPS) where a system of polymer and solvent is used which has an upper critical solution temperature; the solution is cast or spun at high temperature, and cooling leads to demixing / precipitation ,Non-Solvent induced (NIPS) where the polymer solution is immersed in a nonsolvent coagulation bath (typically water); demixing and precipitation occur due to the exchange of solvent (from polymer solution) and nonsolvent (from coagulation bath), i.e., the solvent and nonsolvent must be miscible.

Figure 7. Casting with EIPS technique

CONCLUSION

Desalination is the primary approach for drinkable water in Saudi Arabia. The current desalination methods are costly and have impact on the Figure 5. Phase Inversion environment. The use of membranes technologies

Preparation Methods of Synthetic Membrane

34 International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Volume-6, Issue-4, Oct.-2018, http://iraj.in increase the efficiency of desalination processes. [3] Peyravi M, Rahimpour A, Jahanshahi M "Thin film Membranes are either Biological membranes or composite membranes withmodified supports for organic solvent nanofiltration". J MembrSci 423–424:225– Synthetic membranes .In this paper, we discuss the 237, 2012 synthetic membrane and it's preparation methods. [4] Gallucci F, Basile A, Hai F Membranes for membrane reactors: preparation, optimization and selection, 1st edn. REFERENCES Wiley, UK, 2011 [5] Buonomenna M, Choi S, Galiano F, Drioli E Membranes prepared via phase inversion. In: Basile A, Gallucci F [1] M. Ulbricht, Advanced functional polymer membranes, (eds)Membranes for membrane reactors, preparation, Polymer 47 (2006) 2217–2262. optimization and selection, 1st edn. Wiley, UK, pp 475–490, [2] Figoli A., Simone S., Drioli E., Polymeric Membranes, 2011 Chapter 1, in Membrane Fabrication, Eds. Hidal N, Ismail F. A., Wright C., CRC, 2015, ISBN-978148221045-3.

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Preparation Methods of Synthetic Membrane

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