What is the structure of membrane materials
Chemically homogeneous, physically isotropic
Physically isotropic, chemically heterogeneous
Physically anisotropic, chemically heterogeneous
Physically and chemically heterogeneous/an isotropic
What materials form membranes?
Ceramic polymeric ion-exchange symmetric micro porous
What example materials are used?
Alumina, silicate, graphite, metals extruded silicone rubber
PTFE, polyethylene, polypropylene, polycarbonate
Functionalised polymeric materials cellulose derivatives, polyamide, polysulphone
Hydrophobic liquid in silicone rubber
Cellulose derivatives, polyamide, polysulphone
Ultra thin layer on micro porous polysulphone support
Polymeric micro porous membranes are usually manufactured using a technique called phase inversion. A process called gelation is used. This is where a solution of the polymer is put into water to produce the micro porous membranes. This technique then goes on to produce a skin layer; this then creates an integral anisotropic micro porous membrane. This is the type of membrane that is often used in the technique of reverse osmosis.
Supported liquid membranes have proven to be affective for procedures such as gas separation. Gas separation is where the improved mass of transport of gasses through liquids over that attainable in solids becomes important. Although this method has proven to be affective, it has not yet been manufactured on a large scale and is not the most common method for commercial use. The technology is being modified and improved by trying to accomplish liquid separations. Liquid separations are achieved by a combination of a high-velocity, hydrophobic immobilised in a polymer matrix, and the supported liquid is liable to contain a carrier. This is a component that has a chemical reaction and a reversible reaction with the desired component in the liquid mixture and therefore assists its transportation process through the membrane.
Another membrane that can be produced is an ion exchange membrane. This is by fictionalisation of a homogeneous polymer film or more simply by immobilising powered ion-exchange resins in an inert resin matrix. This last method is often favoured by manufacturers from china this is because the materials that are produced are less selective and has inferior mass support properties compared with the more expensive homogenous materials.What is the future for membrane technology?
The application of membrane technology is undoubtedly expanding and progressing at an incredible rate. The reasoning behind this is because the product is becoming increasingly cheaper and cheaper. Also legislation towards the environment are becoming tighter and tighter. Because of these environmental stipulations, water filtration systems in general are now in a high demand. Because of this membrane technology is so economic, it is usually the favoured approach.
The range of available membrane materials is huge. There are a large amount of membranes that are of chemical composition or of physical structure, but the most important property is the mechanism by which separation is actually achieved.
On this basis, membranes may be referred to as either porous or dense. Porous membranes let more particles through, also particle that are of a lager size. Dense membranes on the other hand are less permeable and let fewer particles through and only particles of a smaller size. This process can be altered depending on how pure the water needs to be.