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The separation of Sr2+ from dilute and trace solutions of low activity by means of hollow fiber Amicon ultrafiltration membranes is studied. The cation is absorbed on colloidal particles of titanium oxide formed directly in solution, and the colloidal dispersion is filtrated. The method has been studied under several different operative conditions (pH, Ti/Sr ratio, the presence of interfering ions, colloid formation time) with the aim of determining the optimum conditions to develop a separation process.

An automated computer-controlled apparatus for gas permeability measurements through polymeric membranes is described in detail. The apparatus was specifically designed to operate with hydrocarbon streams and acid gases (CO2, H2S) and therefore special care was devoted to the control devices. The maximum capacity of the apparatus in 100 L/h at temperatures up to 70°C and pressures in the 0-15 atm range. Permeability measurements of biogas components (CH4, CO2, H2S) and their separation factors through experimental hollow fiber membranes are presented as typical data of the equipment described.

A laboratory membrane separation unit was assembled by using composite hollow fibers. It was tested in an automated apparatus for gas separation measurements. The performances of the system were measured for CH4/CO2 mixtures as functions of temperature, pressure, stage cut, feed gas composition, and flow regime. The results were analyzed on the basis of a predictive mathematical model of the process. A good fitting of the data was obtained in most cases except at high pressure, probably as a consequence of structural changes of the active layer of the fibers under pressurization.