Question

Write a short note on Reverse Osmosis .

Answer 1

When two solution of unequal concentration are separated by semipermeable membrane ,flow of solvent takes place from dilute to concentrated section due to osmosis .If hydrostatic pressure which is slightly higher than the osmotic pressure is applied on concentrated section of solution ,the flow of solvent reverses i.e solvent moves from high concentration to low concentration across the membrane .This is known as Reverse Osmosis ( RO ) .
In RO ,pure solvent (water) is separated from its contaminants .
In reverse osmosis ,a pressure of 200-800 psi is applied to seawater/impure water so that pure water is forced through semipermeable membrane ,leaving behind dissolved solids . Membranes used in this process are thin films of cellulose acetate fixed to either side of perforated tube and polymethyl methacrylate PA fibre .

The use of this process is getting water for high pressure boilers and for many industrial applications like car wash water reclamation ,wastewater treatment ,etc .