Characteristic parameters and operational curves of γ-Al2O3 nanofiltration membranes

The gamma-Al2O3 nanofiltration membranes were manufactured by the sol-gel technique. The result of N-2 adsorption and desorption test indicates that the characteristic parameters of the membranes: BJH desorption average pore diameter, BJH desorption cumulative volume of pores and BET surface area are about 3.9 nut, 0.33 cm(3)/g and 245 m(2)/g respectively, and the pore size distribution is very narrow. The operational curves of gamma-Al2O3 nanofiltration membranes of the Ca2+ retention rate vs the trans-membrane pressure, feed concentration of solution treated and pH of solution treated were studied for the first time. It is found that the retention rate for Ca2+ increases with the transmembrane pressure increasing and decreases with the feed concentration of CaCl2 solution increasing. The retention of Ca2+ is very much dependent on the pH of the solution. Minimal Ca2+ retention rate is found at the isoelectric point (pH = 7.5).