Characterization of hollow fiber membranes by impedance spectroscopy

Evaluation of liquid transport properties of hydrophobic polymers of intrinsic microporosity by electrical resistance measurement

“…For example, the electrical properties of the different membrane sub-layers can be inferred from impedance measurements over a range of frequencies (impedance spectroscopy) [20][21][22][23][24][25][26][27][28]. The most used technique is the difference method in which the membrane resistance is obtained from the difference between the cell resistance measured in AC mode with and without the membrane [22][23][24][25][26][27][28][29][30]. For most experimental devices the current lines are normally oriented to the membrane surface and the system made up of the membrane surrounded by two identical solutions is then equivalent to an electrical circuit with serially-connected elements.…”

“…Electrical conductivity is one of the most important characteristics of ion-exchange membranes [31][32][33][34] but also measuring of electrical properties make it is possible to estimate the thickness of active layer in reverse osmosis or nanofiltration membranes [20][21][22]35], porosity of 4 porous sublayers [25,26,36], monitoring of deposition (fouling) on top of the membrane [25,26,36], to get insight in the transport behavior of different charged species within the membrane [21,23] or evaluate the wetting of microporous hydrophobic membranes used in membrane contactors [27]. It should be noticed that electrical impedance spectroscopy is widely used for characterization of resistance and capacitance of active and porous sub-layers of reverse osmosis membranes [20], nanofiltration membranes [20][21][22]35], evaluation of (bio)fouling [25,26,36], water presence and ionic liquid loss in supported liquid membranes [37], monitoring of membrane modification with the charged species [38], wetting of porous membranes used in membrane contactors [27] and study of piezoelectric properties of porous membranes [39].…”

In-situ monitoring techniques for membrane fouling and local filtration characteristics in hollow fiber membrane processes: A critical review

“…Electrical impedance spectroscopy (EIS) is a technique that has proved to be a powerful tool for in-situ and invasive monitoring membrane fouling processes [50]. Recently, Bannwarth et al [52] firstly extended the EIS technique from the flat-sheet membrane to the hollow fiber membrane using a 2-terminal method. To perform EIS on a hollow fiber membrane, a special module was designed and constructed.…”

“…(a) Schematic diagram of the EIS measurement principle and (b) the bode plots of the impedance measurements[52].…”

Development of monitoring tools based on electrical impedance spectroscopy for water treatment and integrated process for wastewater recovery

“…EIS has been successfully employed to characterize various types of membranes, including synthetic (Antony et al, 2013;Chilcott et al, 1995;Chilcott et al, 2002;Coster et al, 1992;Fortunato et al, 2006;Gaedt et al, 2002;Gao et al, 2013;Xu et al, 2011) biological membranes (Chilcott et al, 1983;Ogata et al, 1983;Smith et al, 1985) and recently, hollow fiber membranes (Bannwarth et al, 2015;Bannwarth et al, 2016). The porosity of the membrane can be estimated from the capacitance determined from EIS when the dielectric constant and the thickness of the membrane polymer are known (Coster et al, 1996;Coster et al, 1992).…”