WATERREVERSE OSMOSISTHEORY 1 REVERSE OSMOSIS Where the solvent flow form low conc solution to higher conc solution,throughthesemipermeablemembrane,unitdifference inwaterlevelscreatesasufficientpressuretocounteract(act against&makeoflesseffect)theoriginalflowiscalledas osmosis. Thedifferenceinwaterlevelsrepresentsosmoticpressure of the solution. Thereversalofsolventflow,fromhigherconcsolutionto lowerconcsolutionthroughasemipermeablemembrane,by applyinganexternalpressureslightlyhigherthantheosmotic pressure of higher conc solution is known as reverse osmosis. Thusinreverseosmosisweseparatewaterfromits contaminants rather than contaminants from water and which can be remove particles in the size range of 0.0001-0.001micron. Diagram WATERREVERSE OSMOSISTHEORY 2 Advantages 1) It has the most efficient means of removing ionic as well asnonionic,colloidalandhighmolecularweight organic matter.2)Forwaterswithtotaldissolvesolidsof200ormore, reverse osmosis is less expensive than ion exchange. 3) It is simple to operate and maintain. 4) Themaintenancecostdependsonthereplacementof thesemi-permeablemembrane.Thelifetimeofthe membrane is two years.Industrial Application 1) Drinking water. 2) Humidification. 3) Ice-making. 4) Boiler water. 5) Biomedical applications. 6) Laboratory applications. 7) Photography. 8) Pharmaceutical production. 9) Kidney Dialysis. 10) Cosmetics. 11) Animal feed. 12) Battery water. 14) Waste water treatment. 15) Haemodialysis. WATERREVERSE OSMOSISTHEORY 3 ULTRAFILTRATION Itisacross-flowseparationprocess.Hereliquidflow tangentiallyalongthemembranesurface,therebyproducingtwo streams 1) The stream of liquid that comesthrough the membrane is called permeate (pass into every part). 2) The other liquid stream is called concentrate. Itisaseparationprocessusingmembranewithporesizeinthe range of 0.01-0.1micron & it is normally operated in the pressure range of 15-50 psig (Pound per square inch gage). Pollutedwater(proteins,fats,water,sugar&salt solution) Concentrate stream (proteins, fats) ---------------------------------------------------UF = 0.01- 0.1 & Press. 15-50 kg/cm2 --------------------------------------------------- Permeate stream (water, sugar & salt) In cross-flow separation, therefore, the membrane itself does not act as a collector of ions, molecules or colloids but it act as a barrier to these species.It will remove high molecular weight substances like colloidal materials,organic&inorganicpolymericmolecules.Itwillnot removelowmolecularweightorganic&ionslikeNa,Ca,Mg,& SO4.Becausetheosmoticpressuredifferentialacrossthe membrane surface is negligible. Lowappliedpressuresaresufficienttoachievehighflux ratesfromultra-filtrationmembrane.(Fluxisdefinedasthe amount of permeate produced per unit area of membrane surface perunittime.)ItisexpressedasGFD(Gallonspersquarefoot perday).Ultra-filtrationmembranecanhaveextremelyhigh WATERREVERSE OSMOSISTHEORY 4 fluxes,butinmostpracticalapplicationsthefluxvariesbetween 50-200 GFD at an operating pressure of about 50 psig. Reverseosmosisonlyproduces between10-30GFDat200-400 psig. Industrial applications 1. It is used to separate suspended solid from solution. 2. Paint recovery in the automotive industry. 3. Itiswidelyusedinthefractionationofmilk,whey&in protein fractionation & protein isolation. 4. Removal of colloids. 5. Alsousedinpower,food,pharmaceutical, biotechnology & semiconductor industries.