Microfiltration of sodium nitrate and Direct Red 2 dye using asymmetric titanium dioxide membranes on porous ceramic tubes

Filtration studies using titanium dioxide membranes fused on porous ceramic tubes with pore diameters of 0.2 mu m is reported for solutions containing sodium nitrate and solutions containing an anionic direct dye, Direct Red 2 (C.I. no. 23 500). Solution pH was adjusted with dilute sodium hydroxide and nitric acid to maintain maximum solubility of all ions present in the system. Electrolyte rejections and color rejections were measured at pH values of four to ten. Tubes were supplied by Rhone-Poulenc, Cranbury, NJ. Results show that the charge or ionic nature of the membrane surface was responsible for the ion rejections and decreased as the salt concentration was raised from 50 to 5000 ppm. Salt rejections ranged from 12-64% and dye rejections ranged from 82-99% over the salt concentrations and temperatures of the experiments that ranged from 30 to 60 degrees C. The results are interpreted in terms of the current and past research involving microfiltration.