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

Abstract

SynopsisThe reverse osmosis separations of some ethers, ketones, aldehydes, monocarboxylic acids, and inorganic salts in singlosolute (55454 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 pK, value of -4.8. The values for the free-energy parameter for Li+, Na+, K+, Rb+, Cs+, and F-, C1; Br-, I-, and IOs-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.

Effect of salt type on mass transfer in reverse osmosis thin film composite membranes

“…This indicates that the anion is attracted and the cation is repelled by the membrane surface which means that the membrane surface is positively charged and hence it acts as an acid (proton donor). This result confirms the observation made earlier for polyamide material [5,6]. In contrast, an opposite sign of (AAG/RT)~ was observed for cellulose acetate membranes used in RO [4].…”

“…The utility of the free energy of ions for predicting solute separations in RO was illustrated with particular reference to cellulose acetate membranes [4]. The object of this part of the work was to obtain data on free energy for different monovalent and divalent ions in aqueous solutions with respect to polyamide thin film composite membrane used in spiral wound configuration and to compare such data with the corresponding ones applicable for cellulose acetate and polyamide membranes reported earlier [4][5][6]. The theoretical approach developed by Matsuura et al [1,4], based on free energy parameter, is applied in this study to predict the RO solute separation of polyamide thin film composite membrane arranged in spiral wound module for inorganic salts in aqueous solutions.…”

Reverse Osmosis Concentration of Flavor Components in Apple Juice-and Grape Juice-Waters

“…The aroma-laden fruit juice-waters which permeated through the membranes used in the first stage operations, were used as feed solutions for the second stage operations. The latter experiments were carried out in a cold box maintained at 5± 1°C using laboratory made aromatic polyamide membranes of the type reported earlier (14)(15)(16). Fruit juice-waters which constituted the feed of second stage separation were clear solutions without any turbidity.…”

Parameters for prediction of reverse osmosis performance of cellulose acetate propionate membranes

“…(3), (4), and (5) for calculating the pertinent D A M I K~ values with respect to CAP membranes of different surface porosities and aqueous feed solutions involving alkali metal halides or nonionized polar organic solutes of the type studied in this work.…”