Using three types of low-pressure reverse osmosis membranes-NF-70 supplied from Film Tech, NTR-729HF from Nitto Denko Co., and SU-600 from Toray-reverse osmosis experiments were carried out under the operating pressure of 0.14, 0.34, and 0.49 MPa to separate aqueous solution of MgSO
4 of which feed concentrations were 100,500, and 2,000 mg/
l.
The results were analyzed to obtain membrane constants based on the irreversible thermodynamics model proposed by Kedem & Katchalsky and modified by Ohya
et al.; the agreements between the experimental data and that predicted by the models are excellent.
The results of fluxes and salt passages were converted values at the standard conditions of 500 mg/
l and 0.34 MPa with correction factor for pressure (PCF), for temperature (TCF), and for salt passage (SPCF) proposed by the American Society for Testing and Materials, ASTM D4516. PCFs estimated by ASTM and the model agree quite well with PCF obtained from the experimental results; SPCF and SP xperimentally obtained also agreed well with those by the model, but not with these by ASTM.
The standardizing procedure proposed by ASTM particularly for salt passes may not be applied for the data obtained with low-pressure reverse osmosis method.
View full abstract