1.Definition & Kind Nanofiltration Membrane
The early Nanofiltration Membrane was called Loose RO Membrane ,which was developed after typical RO composite membrane in the early 80S. So far it has no unified definite definition in academic circle. So here is temporarily expression as: (1)Nanofiltration Membrane is between RO and UF Membrane ,Whose removal rate is below 90% for Nacl. The RO Membrane has high removal rate for all solutes,but the NF Membrane only has high removal rate for specific solutes; NF Membrane mainly removed the solute particles of diameter 1 nm,that cut- off 100-1000 molecular weight.Which mainly used for removing three halogenated methance intermediates,odor,color,pesticide,synthetic detergent,composition and evaporationof soluble organic matter,calcium,and other residual material hardness .The body of NF Membrane have electric charge ,that is its main characteristic.this is why has high removal rate and can cut-off 100-2000 molecular weight under very low pressure ,and it can also remove inorganic salt.
2.Application of Nanofiltration
(2)Use for removal of harmful substance from drinking water ,the traditional drinking water treatment mainly by flocculation ,sedimentation,sand filters and chlorine disinfection to remove suspended substance and bacteria in water ,but which have low effect for the variety of solubility chemical .With increasing of polluted water source and the improvement of drinking stardards in various countries ,to can remove variety of organic substances and harmful chemicals that get more pepole’s attentions.A number of provened practices express that NF Membrane can remove three halomethane intermediates containing THM removal in groundwater and river water(chlorination side suspension products are carcinogenic substances),low molecular organic compounds,pesticides,odor substances,nitrate,sulfate,fluorine,boron,arsenic and other harmful substances
(3)Treatment of reclaimed water and wastewater. (4)Widly used for Food ,beverage ,pharmaceutical industries ,such as the concentration and refinement of various proteins ,amino acids,vitamins,milk,liquor,soy sauce,spices and so on (5)The seperation &concentration of aqueous solution in chemical engineering process .