Reverse Osmosis Analysis

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1.1.1.4 Reverse osmosis (RO): Reverse osmosis is another pressure driven process which uses thin-film composite membranes. RO uses higher pressure than other processes (200-1200 psi) to force the feed solution through a semi-permeable membrane with the smallest pore size (0.0005-0.002 nm). RO membranes are the tightest of all the membranes and allow only water to pass through it while rejecting almost everything. It can reject all dissolved and suspended solids and even the monovalent ions from the water hence producing water of very high purity. RO depends on ionic diffusion to effect the separation. Reverse osmosis is used in the desalination of sea water and brackish water and in industrial processes including cheese whey concentration,…show more content…
This technique is also called as pore-piercing technique wherein the membrane preparation involves a two step process. In the first step the prepared polymer film is irradiated with high energy particles which are generated by nuclear reactor or by any other radiation source. The high energy particles used in this technique includes α- particles, accelerated heavy ions, fission fragments and thermal neutrons. These high energy particles pierce through the polymer film breaking polymer chains and leaving behind sensitized or damaged tracks. The second step involves submerging of the irradiated film in an etching solution bath. This etching solution etches the polymer film along the sensitized tracks forming channel like structures or pores. The pore density and size can be controlled by controlling the irradiation time and by adjusting the concentration of the etching solution as well as etching…show more content…
Stretching technique usually involves three steps; extrusion, annealing and stretching. First step involves the extrusion of uniaxially oriented films, the morphology and orientation of the prepared film depends on the processing condition and the type of polymer used. The second step involves the annealing of the prepared films to carry on the crystalline morphology of the films. The third step involves two types of stretching; cold stretch and hot stretch. Cold stretch is carried out at lower temperature and high strain rate to form pore like structures followed by hot stretch at high temperature and slow strain rate to increase the pore

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