Separation Processes for Water Treatment

There are various types of membrane-separation processes for water treatment, as shown in Fig. 3 the details of the four major processes, MF, NF, UF, and RO, will be 

Microfiltrahon (MF) is a membrane-filtrahon process that removes micron-sized particles from fluids. MF membrane has pore sizes ranging from 0.1 to 10.0 pm, through which microorganisms cannot pass. As a result, microfilters can be used to disinfect water solutions. For example, the smallest bacterium Pseudomonas diminuta with a diameter of 0.3 pm can be disinfected by a MF membrane with smaller pore sizes. On the other hand, both organic and inorganic substances are able to pass through MF membranes. 

List of Applied Pressure for Typical Membrane Filtration Processes 

While the mechanism for conventional depth filtration is mainly adsorption and entrapment, MF membranes use a sieving mechanism with distinct pore sizes for retaining particles larger than the pore diameter. Hence, this technology offers membranes with absolute rating, which is highly desirable for critical operations such as sterile filtration of parental fluids, sterile filtration of air, and preparation of particulate, ultra-pure water for the electronics industry. 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

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Membrane and Membrane Separation Processes for Water Treatment... 

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