Reverse osmosis

About: Reverse osmosis is a research topic. Over the lifetime, 20780 publications have been published within this topic receiving 299185 citations. The topic is also known as: RO.

Sodium Hydroxide Production from Seawater Desalination Brine: Process Design and Energy Efficiency

Abstract: The ability to increase pH is a crucial need for desalination pretreatment (especially in reverse osmosis) and for other industries, but processes used to raise pH often incur significant emissions and nonrenewable resource use. Alternatively, waste brine from desalination can be used to create sodium hydroxide, via appropriate concentration and purification pretreatment steps, for input into the chlor-alkali process. In this work, an efficient process train (with variations) is developed and modeled for sodium hydroxide production from seawater desalination brine using membrane chlor-alkali electrolysis. The integrated system includes nanofiltration, concentration via evaporation or mechanical vapor compression, chemical softening, further ion-exchange softening, dechlorination, and membrane electrolysis. System productivity, component performance, and energy consumption of the NaOH production process are highlighted, and their dependencies on electrolyzer outlet conditions and brine recirculation are investigated. The analysis of the process also includes assessment of the energy efficiency of major components, estimation of system operating expense and comparison with similar processes. The brine-to-caustic process is shown to be technically feasible while offering several advantages, that is, the reduced environmental impact of desalination through lessened brine discharge, and the increase in the overall water recovery ratio of the reverse osmosis facility. Additionally, best-use conditions are given for producing caustic not only for use within the plant, but also in excess amounts for potential revenue.

Nanofiltration and reverse osmosis membranes: theory and application in separation of electrolytes

Abstract: Membranes are widely used for separation of ions from a mixture in aqueous solution. Major applications include removal of sulfate from seawater, removal of salt from cheese whey, and separation of sodium chloride from seawater for manufacture of table salt and brine for soda industry. The conventional reverse osmosis membranes are not capable of selectively separating electrolytes from the aqueous mixture. The charged nanofiltration membranes that have been developed over the last decade are now being used for some of these applications. This review is based on the theories of transport of solute and water through these membranes and the mechanism of permselectivity. The application of these theories to estimate the membrane design parameters, i.e., pore size, porosity, charge density and thickness has been discussed. The capabilities of different nanofiltration membranes have been illustrated with examples and compared with reverse osmosis membranes. The information provided here is expected to provide an extensive information on the subject.

Pretreatment processes for seawater reverse osmosis desalination systems—A review

Abstract: An efficient pretreatment system forms the backbone of a sea water desalination unit using reverse osmosis process. The pretreatment of sea water is done to bring down the turbidity, microorganisms, colloidal contaminants, total dissolved solids and silt density index of the raw sea water to acceptable levels and make it suitable for the Reverse Osmosis membrane process. The two kinds of pretreatment processes used are the conventional system and the membrane systems. The present review paper makes an effort to understand the conventional process, microfiltration, ultrafiltration, nanofiltration and integrated membrane systems for the seawater pretreatment, their advantages and limitations and the effect of the pretreated water on the performance of reverse osmosis membranes through the studies conducted by researchers as well as by considering certain case studies.