A study on the construction of nanofiltration membrane using the phase change method and the investigation of parameters affecting the performance of the membrane

Nanofiltration (NF) is a membrane liquid-separation technology sharing many characteristics with reverse osmosis (RO). Unlike RO, which has high rejection of virtually all dissolved solutes, NF provides high rejection of multivalent ions, such as calcium, and low rejection of monovalent ions, such as chloride. Nanofiltration is a filtration process using a nanoporous membrane that is used in waters with low total dissolved solids. The purpose is to remove polyvalent ions, in addition to disinfecting it by retaining organic matter. The process uses a pressure-controlled membrane, whose ability to repel ionic or molecular molecules is an intermediate filtration between ultrafiltration and reverse osmosis. Nanofiltration membranes, organic membranes or ceramic membranes can be dense or porous. Nanofiltration membranes can increase the void space, or nanovoid, available for transport. The sizes of these nano-bodies that form the transition between microporous and dense films can be in the range of ۰.۵ – ۱ nm. Nanofiltration membranes are generally believed to have a nominal limit value between ۱۰۰۰ and ۲۰۰ Da. Compared to ultrafiltration and reverse osmosis, nanofiltration is a difficult process to define and describe. The specific properties of nanofiltration membranes are mainly a combination of very high removal capacity (>۹۹ %) for multivalent ions combined with low to moderate removal capacity (۹۰ %) for monovalent ions. Organic compounds have a higher molecular mass than membranes. The mass transport mechanism is highly dependent on the membrane structure and the interactions between the membrane and the transport molecules. Separation efficiency can be controlled by screening effects (where nanopore size and solute particle size play an important role) or the dissolution and diffusion properties of the solute particles.

Keywords:

nano ether , polyvinyl-pyrrolidone , wastewater treatment/desalination , Nanofiltration , polysulfone