Showing papers on "Reverse osmosis published in 1975"

Theory of reverse osmosis and some other membrane permeation operations

Abstract: The general permeation equations for various transport operations using membranes were correlated according to the solution-diffusion theory. It was shown that for some important conditions, the permeation properties for reverse osmosis can be generated from those of pervaporation. The use of reverse osmosis with pressure smaller than 2000 psi is calculated to be of limited use for the purification of water with small amounts of organic compounds.

Automatic flushing system for membrane separation machines such as reverse osmosis machines

Abstract: An automatic flushing and cleaning system for membrane separation machines such as reverse osmosis machines having plural modules or membranes. Cleaning may be by way of reducing the pressure to allow the membrane to relax, by the injection of air or inert gas to provide turbulence, and/or by injection of flushing liquid which may include chemical cleaning additives. Pumps, automatic valving, and pressure controls are provided, along with a complete timer operated electrical sequencing system whereby desired purging, flushing and cleaning cycles are automatically undertaken at periodic intervals or in response to one or more preferred conditions.

Factors influencing reverse osmosis rejection of inorganic solutes from aqueous solution

Abstract: Reverse osmosis (RO) rejection is strongly influenced by the distribution of solute between the membrane and solvent phases. For this reason, we examined the partition coefficients of inorganic compounds between water and cellulose acetate (CA) membranes. Cation and anion partition coefficients were determined by independent analyses. Effects of fixed (negative) membrane charges on CA are clearly apparent at low solute concentrations. The mean cation/anion partition coefficients decrease with the product of the cation and anion valence, and increase with increasing ionic size. Un-ionized inorganic compounds, HgC1 2 and HAuC1 4 , are strongly sorbed by CA membranes. All of these observations are consistent with electrostatic theory. Experimental membrane/water partition coefficients are influenced by temperature, pH, and ion-pairing. CA membranes exhibit swelling and shrinkage when exposed to certain aqueous solutions. Swelling and shrinkage influence solute partition and diffusion coefficients, the water content of the membranes, and their RO rejection. The present results provide a comprehensive experimental basis for understanding the mechanism of RO rejection by CA membranes. Moreover, these results can be used to predict RO behavior under a wide variety of experimental conditions. The potential use of reverse osmosis in a variety of wastewater applications is considered in some detail.

Chemical modification of polybenzimidazole semipermeable

Abstract: A preformed polybenzimidazole semipermeable membrane (e.g., a film or hollow filament) is chemically modified in accordance with the present invention. Imidazole groups of the polybenzimidazole membrane are cross-linked by reaction with a strong polybasic acid or its acid chloride (as defined). During the reaction the polybasic acid is dissolved in a relatively mild acid medium (e.g., glacial acetic acid) which serves to decrease the basicity of the imidazole groups and to promote the desired cross-linking reaction. The resulting cross-linked membrane is tougher than the untreated membrane and may be more readily handled without deleterious results. Also, the resulting cross-linked polybenzimidazole membrane no longer is soluble in N,N-dimethylacetamide, and exhibits improved service characteristics such as improved compaction resistance during prolonged usage at high pressure. The product of the present invention is particularly suited for use in separations from acid waste streams. Cross-linked polybenzimidazole membranes capable of reverse osmosis separations, ion exchange separations, and ultrafiltration separations may be formed in accordance with the present process.

Process for preparing membranes for separation of substances

Abstract: A semipermeable membrane is obtained by casting a cast solution comprising a mixture of a water-insoluble high polymer and a water-soluble high polymer, a mixture of a water-insoluble high polymer and a water-soluble surfactant or a mixture of a water-insoluble high polymer, a water-soluble high polymer and a water-soluble surfactant to form a shaped article, exposing the thus formed shaped article to a plasma to crosslink the surface thereof, and then washing the exposed article with water to remove uncrosslinked water-soluble high polymer or water-soluble surfactant. The membrane can be used for such substance separation methods as reverse osmosis, ultrafiltration and the like.

Poly(arylether-sulfone) semipermeable membrane comprising substituted halomethyl and/or quaternary nitrogen groups

Abstract: A semipermeable polymeric membrane which essentially consists of modified poly (arylether-sulfone) having halomethyl groups and/or quaternized nitrogen atom-bearing groups. The membrane can be prepared by casting the polymer solution in a selected solvent or a mixture of suitable solvents on a surface, evaporating a portion of the solvent, and immersing the resulting film into a suitable non-solvent. The membrane is excellent in performance, such as water flux, and permeation selectivity, so that it can be used as a reverse osmosis membrane, an ultrafiltration membrane, and the like.

Reverse osmosis apparatus

Abstract: A reverse osmosis module comprising a semipermeable membrane, a porous membrane support structure, and a porous backing member having at least a pair of opposed surfaces and including a plurality of longitudinally extending channels, said porous backing member being mounted relative to said porous membrane support structure in such a manner that fluid passing through said membrane passes through said porous support structure and is adapted to enter said channels in said porous backing member.

Reverse osmosis separations of some organic and inorganic solutes in aqueous solutions using aromatic polyamide membranes

Abstract: The reverse osmosis separations of some ethers, ketones, aldehydes, monocarboxylic acids, and inorganic salts in single-solute (55–454 ppm) aqueous solution systems using aromatic polyamide membranes have been studied at 250 psig. It was found that reverse osmosis separation was essentially a function of steric parameter for ethers, and of both polar and steric parameters for ketones, aldehydes, and alcohols. Solute separations for monocarboxylic acids passed through a minimum at a pKa value of ∼4.8. The values for the free-energy parameter for Li+, Na+, K+, Rb+, Cs+, and F−, Cl−, Br−, I−, and IO3− ions have been calculated for the polyamide membranes used. The above values for cations are negative and those for anions are positive, suggesting that the polyamide membrane surface behaves as if it is positively charged. Further, the data show that the polyamide membrane material is only about 40% as polar as that of the cellulose acetate membrane material studied earlier.

Ultrafiltration or reverse osmosis treatment of emulsified oil metal working coolants

Abstract: A portion of the oil-in-water emulsion used as a lubricant/coolant in the shaping of metal articles such as containers is subjected to a reverse osmosis or ultrafiltration process to concentrate the oil portion and separate a water permeate. The oil concentrate is reincorporated in the remaining portion of the coolant and the permeate is used as rinse water to remove oil residues retained on the article from the metal shaping operation. The coolant is then reconstituted with the oil residue rinsed from the article.

Determination of sodium form water softener breakthrough

Abstract: Detection of exhaustion of sodium form water softeners is accomplished by subjecting sample of the outflow from a water softener to reverse osmosis in order to separate monovalent (sodium) and divalent (hardness or magnesium and calcium) ions differentially from the outflow and measuring conductivity before and after the reverse osmosis. The two conductivities are compared in a ratiometer or differential device. After the softener becomes exhausted the divalent ion concentration in the outflow increases. Consequently the conductivity ratio changes to indicate that the water softener has become exhausted.

Production of solutions

Abstract: This invention relates to the production of aqueous solutions of desired concentration for medical purposes which comprises passing water through a reverse osmosis column capable of retaining 100% of pyrogenic materials; and subsequently, in either order, passing the water through a sterilizer capable of eliminating 100% of bacterial material, and admixing, in suitable ratio, the water with a desired material or with a solution of such material of higher concentration than desired to produce said desired concentration solution.

Preparation of composite reverse osmosis membranes by plasma polymerization of organic compounds. III. Plasma polymers of acetylene/CO/H2O

Abstract: Reverse osmosis characteristics of composite membranes prepared by the plasma polymerization of acetylene/CO/H2O mixtures with various ratios of components are investigated; porous film of cellulose nitrate-cellulose acetate is used as the substrate. This monomer system seems to have the following advantages: (1) A relatively short deposition time (1–2 min) is enough to produce reasonably good reverse osmosis membranes; and (2) good chemical stability of membranes can be obtained, especially in the case of chlorine resistance.

Microstructure and ordering in cellulose acetate and reverse osmosis membranes

Abstract: The performance of cellulose acetate reverse osmosis membranes for desalination or purification is greatly affected by the microstructure of the membrane. It is, therefore, highly desirable to characterize the microstructure and its dependence on preparation conditions and past history. In this study, various types of cellulose acetate powders, flakes, and solvent cast films have been characterized by differential scanning calorimetry and thermo-optical analysis. It is shown that ordered microstructures exist in many of these samples and that this ordering can be intensified or diminished by suitable treatments. It is conjectured that a similar microordering occurs in the dense layer of asymmetric cast membranes as a result of solvent evaporation, gelation and annealing and that the extent of orientation and chain packing in the ordered regions greatly affects the performance of reverse osmosis membranes.

Preparation of composite reverse osmosis membranes by plasma polymerization. II. Copolymerization of unusual comonomers

Abstract: Preparation of composite reverse osmosis membranes by plasma polymerization of 4-picoline, 3,5-lutidine, benzene, and acetylene with unusual comonomers such as H2O and N2 is investigated using the flow system of the monomers and an electrodeless glow discharge with 13.5 MHz radio frequency. These comonomers are incorporated into the plasma polymers and change their properties. Consequently, relatively hydrophilic polymers are formed from rather hydrophobic monomers such as benzene and acetylene by the copolymerization. The addition of H2O and N2 also improves the reverse osmosis characteristics of plasma polymers from hydrophilic monomers such as 4-picoline and 3,5-lutidine. The reverse osmosis characteristics of plasma polymers are influenced by the ratio of H2O and N2 to the basic monomer as well as by the total pressure of the monomers.

A semipermeable membrane

Abstract: PURPOSE:A semipermeable membrane useful for reverse osmosis operations such as desalting of salt water and treatment of waste water.

Process for operating a reverse osmosis or ultrafiltration device

Abstract: PURPOSE: To prevent a membrane from being clogged by virtually eliminating ununiformity of turbulance due to the deflecting current in a tube. COPYRIGHT: (C)1977,JPO&Japio

Reverse osmosis membranes

Abstract: The present invention relates to the production of a novel membrane having a larger number of small sized pores therein such that the product rate in a reverse osmosis separation using said membrane is substantially increased for a particular separation factor. The invention is predicated upon the concept that the performance of a membrane in reverse osmosis separation is primarily dependent upon two interrelated factors, namely the structure of the polymer solution from which the film is cast and the evaporation rate during the period of evaporation of the organic solvent from the cast film. The present invention thus provides processes in which the solvent structure of the solution and the evaporation rate of the solution from the cast film is adjusted towards an optimum for producing a large number of small pores in the surface layer of the membrane to increase substantially the product rate at a given separation factor.