Allen Zelman

An automated data collection system for membrane transport experiments : Part I. Test of onsager reciprocity

Abstract This work presents a direct experimental examination of the linear phenomenological flux equations from the thermodynamics of irreversible processes for membrane transport. Results are given which confirm Onsager reciprocity in a NaClH2O—anion exchange membrane system with concentration and hydrostatic pressure differences. Data for isothermal, non-steady-state experiments are collected from a computerized and automated membrane transport apparatus. For the first time, the solvent and solute flux equations are solved simultaneously, and the four phenomenological transport coefficients are obtained from a single experiment using an ellipsoid algorithm for non-linear programming. It appears that the dependence of the L coefficients on the logarithmic mean transmembrane concentration, cse, is more important than the role of the water flux as an indicator of the limit of the linear region for membrane transport processes. Only in those experiments where cse was held nearly constant was Onsager reciprocity obtained.

Preferential glycerol transport by electroosmosis through ionic membranes

Abstract This paper describes a process in which glycerol is preferentially sorbed relative to water by an ionic membrane and transported into the product solution by electroosmosis at a significantly higher concentration than that in the feed solution. Direct measurement of the membrane distribution coefficient demonstrated preferential glycerol sorbtion for Neosepta CL-25T and AV-4T membranes. Both DC and AC electric currents significantly increase glycerol transport over that of a concentration difference alone.

An Ultrafiltration Monitor for Hemodialysis Research

The ultrafitration rate of hemodialysis membranes should be carefully controlled for maximum patient benefit. A special purpose instrument is described that takes in analog pressure information and the analog output of an appropriate weighing system and produces both digital displays and analog outputs (for a strip-chart recorder) of ultrafiltration rate and ultrafiltration index as well as the averaged mean transmembrane hydrostatic pressure drop and volume of ultrafiltrate. The instrument normally uses an averaging time of about 2 min.