Evaluation of three methods for the characterisation of the membrane-solution interface: streaming potential, membrane potential and electrolyte conductivity inside pores

Filtration and separation performances of microfiltration, ultrafiltration and nanofiltration membranes can be greatly affected by the charge (or elec trical potential) on their surface. These surface properties can be charact erised in terms of potential in the Outer Helmholtz Plane (Psi(d)) A theore tical analysis of electrical and electrokinetic phenomena (electrolyte cond uctivity inside pores lambda(pore), membrane potential E-m and streaming po tential SP) occurring in charged capillaries was developed in the framework of the linear thermodynamics of irreversible processes with the aim of stu dying the variation of SP, E-m and lambda(pore) as a function of Psi(d) for various pore sizes and electrolyte concentrations. From these results, the accuracy on the determination of Psi(d) from experimental measurements of lambda(pore), E-m and SP could be estimated and a 'method limitation' diagr am was constructed using the constraints of pore size and surface charge. ( C) 2000 Elsevier Science B.V. All rights reserved.