Showing papers on "Reverse osmosis published in 1969"

Ultrathin semipermeable membrane

Abstract: AN ULTRATHIN SEMIPERMEABLE REVERSE OSMOSIS MEMBRANE WHICH MAY BE MADE BY CASTING A CONCENTRATED POLYMER SOLUTION ON A LIQUID SURFACE AND THEN EVAPORATING, AND WHICH MAY BE LAMINATED WITH A SEPARATE POROUS SUPPORT MEMBRANE TO FORM A COMPOSITE REVERSE OSMOSIS MEMBRANE. A PROCESS OF SEPARATING SOLVENT FROM SOLUTION BY REVERSE OSMOSIS COMPRISING BRINGING THAT SOLUTION INTO CONTACT WITH A MEMBRANE COMPRISING A SEMIPERMEABLE ULTRATHIN MEMBRANE AT A PRESSURE ABOVE THE OSMOTIC PRESSURE.

Fluid separation apparatus and method

Abstract: A separation process of the reverse osmosis type useful for generating fresh water by forcing salt water against a semipermeable membrance that allows only pure water to pass, which uses centrifugal forces created by rotating basket to build up a pressure head of water supplied to the basket to force water through the membrance. The pure water can be expelled by a nozzle in a direction to help rotate the basket. The membrance can be in the form of a spiral or layers extending perpendicular to the axis, to increase the membrane area within a basket of given size. The membranes can extend radially with respect to the axis of rotation, and supply and removal conduits can be positioned to continually flow water in an outward radial direction to prevent the build-up of polarization layers on the membrane surfaces.

Preservation of polyamidic membranes

Abstract: Selectively permeable, polymeric membranes for use in the reverse osmosis separation of components of aqueous mixtures and solutions, particularly saline and brackish water, are chemically treated to preserve their permeability characteristics and to protect against loss thereof during the obtention of a watertight seal with the potting compounds generally employed in permeation separation devices. The desired results are achieved by effecting a substantial replacement of membrane-associated water with an inert organic medium exhibiting a lower volatility than water. Depending on the degree of hydrophilicity and water solubility of the organic medium, replacement of the membrane-associated water is accomplished by direct contact including successive contacts of the water-wet membrane with aqueous solutions of increasing organic medium concentration and/or indirect contact including successive contacts of the membrane with organic media of decreasing hydrophilicity. Reversal of the replacement process to reintroduce water to the membrane structure restores the operability of the members and renders them effective for their intended desalination and purification functions.

Supporting structures and containing vessels for reverse osmosis and filtration

Abstract: A reverse osmosis separator unit having many small composite membrane tubes 0.5 mm. to 5 mm. O.D. placed together in a membrane tube assembly. Several membrane tube assemblies are installed in a honeycomb pressure vessel to form a separator unit. A small membrane supporting tube is made by forming either a strip of solid sheet material which may or may not be perforated or a strip of porous sheet material. The seam of the formed tube, the perforations and the pores serve as intermediate passages for collecting product water into the supporting tube.

Steady‐state distribution of water in cellulose acetate membrane

Abstract: The effect of hydrostatic pressure applied to a solution on one side of a membrane on the steady-state concentration distribution of permeating solvent inside the membrane has been examined with a view to distinguishing between different mechanisms of permeation in reverse osmosis. The concentration gradients found experimentally in stacks of cellulose acetate films support the view that permeation takes place by diffusion in a nonporous membrane.

Reverse osmosis apparatus

Abstract: A reverse osmosis unit in which the membrane has a supported side and an unsupported side, with a liquid product reservoir in communication with the supported side, and a feed liquid chamber in contact with the unsupported side. The unit includes means to maintain the pressure of the feed liquid at a sufficiently high level to prevent the flow of liquid through the membrane from the supported side to the unsupported side when the inlet to the feel liquid chamber is closed. A reverse osmosis unit in which the membrane is supported by a porous layer material containing activated charcoal.

Reverse osmosis system

Abstract: Reverse osmosis system provided with means for promoting turbulence and for scouring the membrane surface whereby to prevent concentration polarization and skinning (false membrane formation). These valuable results are attained by periodic movement of a plurality of free spheres in the interface zone, at or near the membrane surface.

Evaporation-reverse osmosis water desalination system

Abstract: DESALINATION OF SALINE WATER BY EVAPORATION OF A PORTION OF THE WATER AND PASSAGE OF THE REMAINDER THROUGH A REVERSE OSMOSIS UNIT AFTER PREHEATING IN THE EVAPORATOR''S HEAT REJECT SECTION, THE PRODUCT STREAMS FROM THE EVAPORATOR AND REVERSE OSMOSIS UNIT BEING COMBINED. THE PRESSURE OF THE FEED STREAM OT THE REVERSE OSMOSIS UNIT IS CONTROLLED BY THE PRESSURE OF THE WASTE BRINE STREAM REMOVED FROM THE UNIT, AND THE VOLUME OF THE FEED STREAM TO THE UNIT IS CONTROLLED BY THE VOLUME OF PRODUCT STREAM FROM THE UNIT TO PROVIDE A COMBINED PRODUCT STREAM OF CONSTANT SALINITY.

Cellulose acetate butyrate semipermeable membranes and their production

Abstract: Semipermeable membranes are produced by casting a solution consisting essentially of cellulose acetate butyrate, triethyl phosphate, a flux promoter and an organic solvent into a film, and subsequently gelling the film by immersion in water. The membranes of the invention find particular utility in separation of solutes from solutions by osmosis or reverse osmosis.

Reverse osmosis membranes from hydroxyalkyl derivatives of cellulose

Abstract: The invention provides reverse osmosis membranes characterized by a salt-rejecting layer of a hydroxyalkyl derivative of cellulose. The membranes are useful for desalination and other processes involving reverse osmosis.

Some general equations for reverse osmosis process design

Abstract: : A generalized approach to reverse osmosis process design is presented for solution-membrane-operating systems characterized by the dimensionless parameters gamma, delta, and lamba defined in terms of the pure water permeability constant A, solute transport parameter, mass transfer coefficient k on the high pressure side of the membrane, and the properties of the solution. Analytical expressions are derived, in terms of dimensionless quantities, for the change of volume of solution, concentration of the bulk solution and that of the concentrated boundary solution on the high pressure side of the membrane, the change in the permeating velocity of solvent water through the membrane, solute separation, and the other related quantities, at any instance, as a function of concentration of the product solution on the atmospheric pressure side of the membrane, or time from the start of the operation for reverse osmosis systems specified by gamma, delta, and lamda. The equations are developed first for the case of batch-by-batch operation, and their applicability to the flow case is then indicated. (Author)

Performance of porous cellulose acetate membranes for the reverse osmosis treatment of hard and waste waters

Abstract: : The performance of a few typical Loeb-Sourirajan type porous cellulose acetate membranes is reported for the treatment of hard, polluted, and sewage waters. The membranes used are specified in terms of pure water permeability constant and solute transport parameter for sodium chloride. Using feed waters containing 300- to 800-p.p.m. hardness (expressed as CaCO3), product waters containing 2 p.p.m. or less could be obtained with 90% product recovery and an average initial flux of 38 gallons per day per sq. foot at 1000 p.s.i.g. The possibility of producing 'ultrapure' waters by repeated reverse osmosis processing is indicated. The separation of common pollutants such as nitrates, borates, fluoride, alkyl benzene sulfonate (ABS), ammonia, and phosphates, and a few others usually present in plating wastes, and the applicability of the reverse osmosis process for the treatment of sewage waters and water renovation are illustrated. (Author)

Water reclamation by reverse osmosis

Abstract: : A laboratory reverse osmosis system capable of purifying 4 liters of a mixture of 2.4 liters of urine and 1.6 liters of either wash or dehumidification water in a 24-hour period was fabricated. The quantitative rejection of urea by the membranes was found to be the major problem. Urea rejection by complexing urea with various chemicals was investigated but no significant increase was realized. The effect of storage conditions on membrane performance was investigated. A study was made of the annealing of cellulose acetate membranes and attempts were made to develop satisfactory benzyl derivatives of cellulose acetate. A method was developed which permitted a rapid evaluation of membrane performance. A satisfactory membrane was found to result from the precise control of the annealing process.

Membrane-water structural interactions in reverse osmosis transport

Abstract: Reverse-osmotic water permeabilities, equilibrium water sorption levels, and rates of approach to sorption equilibrium were measured for a series of polymers, including hydroxyethyl methacrylate (HEMA), copolymers of HEMA and ethyl methacrylate (EMA), cellulose acetate, cellulose nitrate, and poly(urethans). Pronounced equilibrium solvent clustering behavior was observed for these systems as vapor saturation was approached in sorption experiments. However, clustering tendency was not found to be a function of total membrane water content at saturation but rather appears to be a function of the chemical nature of the polymer in question. Moreover, clustering of water molecules in (relatively) hydrophobic membranes resulted in low effective diffusivities (reverse osmotic permeability divided by equilibrium water content) whereas clustering in hydrophilic membranes led to higher effective water diffusivities. Clustering tendency was not as strong in the case of the weakly interacting membranes (i.e....

Stagewise Reverse Osmosis Process Design

Abstract: : Reverse osmosis is treated as a general separation process which can be operated in stages, if necessary. Equations developed for stagewise reverse osmosis process design are based on the Kimura-Sourirajan analysis of the reverse osmosis data for water and solute transport through the Loeb-Sourirajan type porous cellulose acetate membranes. The analysis involves the specification of the membrane in terms of the pure water permeability constant, A, and the solute transport parameter. Following the formalism of the multistage distillation process, the cascade theory is applied to the multistage reverse osmosis process, and expressions for the minimum number of stages and minimum reflux ratio are derived. The ideal cascade theory is then used to establish a practical criterion for multistage reverse osmosis process design. Application of the design equations is illustrated by a set of calculations with particular reference to saline water conversion. (Author)

Reverse osmosis liquid purification

Abstract: An expendable tubular membrane structure for use in reverse osmosis liquid purification equipment including a rigid supporting tube for supporting the membrane structure, the expendable membrane comprising a porous, semirigid, thin-walled tube adapted to be received within the supporting tube, and which may have an outer, grooved surface. A liquid impervious plastic material is provided at both ends of the porous tube, and a film of semipermeable membrane material is bonded to the interior wall of the porous tube; a method of making the expendable membrane; and an apparatus utilizing the same.

Structure of porous cellulose acetate membranes and a method for improving their performance in reverse osmosis

Abstract: : Experimental data support the hypothesis that the surface layer of the asymmetric Loeb-Sourirajan type porous cellulose acetate membranes has a heterogeneous microporous structure. A general method is proposed for improving the performance of the above membranes in reverse osmosis, by which product rates are increased without decreasing solute separation. The method consists in pumping pure water past the back side of the membrane under just enough pressure for a sufficiently prolonged period of time; after such pretreatment, the membrane is used in the reverse osmosis experiments in the normal manner with the surface layer facing the feed solution. The compaction effect of a normal membrane and that of a back pressure treated membrane are the same during continuous reverse osmosis operation under 600 psig; the effects of back-pressure treatment on a normal membrane and a compacted membrane are also the same. The pure water permeability data obtained in cyclic experiments show that the smaller pores on the surface layer are opened more than the bigger ones during the back side operation. The probable structural changes taking place in the film during back-pressure treatment are discussed. (Author)

Water purification and storage apparatus

Abstract: A water purification system employs a reverse osmosis water purification unit whose purified water output is temporarily stored by introduction into one end of an elongated conduit, for example a long pipe. The other end of the elongated conduit is connected to a line supplying impure feed water under pressure to a pump which raises the feed water pressure for introduction into the reverse osmosis unit. The purified water stored in the elongated conduit is maintained under pressure by reason of its connection to the pressurized feed water supply line, and is available for use from a connection made to that end connected to the purification unit output. Mixing or intermingling of the feed water and purified water is restricted essentially to that resulting from diffusion, and is therefore small. Alternative conduits which can serve for product water storage container include a series of interconnected elongated tanks or pipes, a tank containing a separator to divide its interior into a number of flow channels and a tank containing packing, for example, raschig rings, broken tile, or inert powder or granules.

Performance of solution‐cast membranes of poly(hydroxythyl methacrylate) in osmosis and reverse osmosis

Abstract: Noncrosslinked copolymers of hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) were prepared and investigated as candidate materials for reverse osmosis membranes. Water and salt flux were calculated from the results of osmosis experiments, compared with cellulose acetate and found to be somewhat smaller. The mobility of water varies by several orders of magnitude between a high flux cellulose acetate membrane and a low flux HEMA-EMA membrane.