Determining the zeta-potential of ceramic microfiltration membranes using the electroviscous effect (original) (raw)
Related papers
Journal of Membrane Science, 1998
Electroosmotic¯ow rate and streaming potential measurements are used to characterise electrokinetic properties of plane ceramic membranes. The study is carried out at different pH, ionic strengths and electrolytes. Effects of pH and ionic strength are studied for both techniques which lead to very close values of isoelectric points. The speci®c adsorption of Ca 2 cations is observed with the two methods. For identical pH and ionic strength electroosmosis gives greater zeta-potential values than those determined from streaming potential measurements. The gap between the two methods increases as the pH move of the isoelectric point and ionic strength increases. These results suggest that the location of the shearing plane depends on the electrokinetic method used. # 1998 Elsevier Science B.V.
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2012
It has been demonstrated that the pore size and surface charge density of micro ltration (MF) membranes can be determined from the streaming potential (SP) measured over a wide range of KCl concentrations using a microscopic model for the SP. The SP was measured for the MF membranes made of various materials and with various pore sizes. The absolute value of ζ obs , which was obtained using the Helmholtz-Smoluchowski (HS) equation, reached a maximum value with increasing KCl concentration and could be assigned to a theoretical zeta potential, ζ theory , at higher KCl concentrations. The SP versus conductivity plots showed unique curves re ecting changes in both the surface charge density and the behavior of the electric double layers (EDLs) in the pore, which will overlap at lower conductivity but be compressed at higher conductivity. The pore size and surface charge density were simultaneously determined by the analysis of this change in SP using the microscopic model for SP. In polycarbonate membranes the pore size obtained by this analysis showed a good linear relationship with the nominal pore size, which is almost equal to the morphological pore size determined by SEM image analysis, although the absolute value of the pore size obtained by this analysis was lower than the nominal pore size.
Journal of Membrane Science, 2003
Streaming potential, electroviscous effect, pore conductivity and membrane potential were measured for a ceramic ultrafiltration membrane at various KCl concentrations. A space charge model was used to calculate the surface potentials from the experimental data. Surface potentials determined from the four experimental methods are in relatively good agreement although some discrepancies occur at low ionic concentrations. Pore conductivity and membrane potential methods lead to similar surface potentials on the whole range of concentrations studied but these latter are smaller than those obtained for both streaming potential and electroviscous effect measurements.
DESALINATION AND WATER TREATMENT
Nanofiltration (NF) and zeta potential are being increasingly used in water, wastewater, and pharmaceutical applications. In this study, the zeta potential behaviors of eight different 0.01 M salts (NaCl, KCl, NaHCO 3 , MgCl 2 , CaCl 2 , Na 2 CO 3 , Na 2 SO 4, and MgSO 4) for 0.9 nm tubular ceramic titanium dioxide NF membrane were measured for the first time using a filtration potential technique by conducting in-situ two electrodes made from a composite material that consisted of pure silver and 4% gauge 21 gold. The measurements were conducted under pH 3-9 at an applied transmembrane pressure (TMP) of 0.25-1.5 bar. Experimental results showed that the membranes of the salts were negatively charged at neutral pH and had an isoelectric point (IEP) of pH 3.4−3.8. Membrane zeta potential results were compared and justified using the electrophoresis method for the same membrane. The powder dispersions of the pulverized membrane in this measuring technique were a suspension at a certain salt concentration. Experimental results from the electrophoresis method agreed with those of the filtration potential method, whose IEP was at pH 3.3−3.5. The rejection experiments of the reference solutions (0.1 and 0.01 M NaCl) were conducted at a constant applied TMP of 12 bar. Rejections results showed that both NaCl concentrations were a function of pH. The low rejections were 17% and 21% at pH 3.8 for 0.01 and 0.001 M NaCl, respectively, and the high rejections were 34.2% and 38% at pH 9. This work also investigated the effects of the measured membrane zeta potential on the ion rejection of the standard solution of NaCl (0.01 and 0.001 M) using a similar pH range.
Determining the Zeta Potential of Porous Membranes Using Electrolyte Conductivity inside Pores
Journal of Colloid and Interface Science, 2001
The zeta potential is an important and reliable indicator of the surface charge of membranes, and knowledge of it is essential for the design and operation of membrane processes. The zeta potential cannot be measured directly, but must be deduced from experiments by means of a model. The possibility of determining the zeta potential of porous membranes from measurements of the electrolyte conductivity inside pores (λ pore ) is investigated in the case of a ceramic microfiltration membrane. To this end, experimental measurements of the electrical resistance in pores are performed with the membrane filled with KCl solutions of various pHs and concentrations. λ pore is deduced from these experiments. The farther the pH is from the isoelectric point and/or the lower the salt concentration is, the higher the ratio of the electrolyte conductivity inside pores to the bulk conductivity is, due to a more important contribution of the surface conduction. Zeta potentials are calculated from λ pore values by means of a space charge model and compared to those calculated from streaming potential measurements. It is found that the isoelectric points are very close and that zeta potential values for both methods are in quite good agreement. The differences observed in zeta potentials could be due to the fact that the space charge model does not consider the surface conductivity in the inner part of the double layer. Measurements of the electrolyte conductivity within the membrane pores are proved to be a well-adapted procedure for the determination of the zeta potential in situations where the contribution of the surface conduction is significant, i.e., for small and charged pores. C 2001 Academic Press
Charge effects on inorganic membrane performance in a cross-flow microfiltration process
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998
Cross-flow microfiltration experiments were performed with 0.5 mm silica particles using an inorganic membrane of 0.2 mm pore size. We analysed how several physico-chemical factors, such as solution pH, salt concentration, and valency of the salt influenced permeate flux and fouling tendencies. The electrostatic properties of silica particles (feed suspension) and a-alumina particles (active layer of the membrane) were characterised by performing zeta potential measurements. It was found that the permeate flux is dependent on the surface charge of the suspended particles and possibly dependent on the surface charge of the membrane. High permeate fluxes are obtained at high pH and low salt concentration. Under these circumstances the repulsion between the silica particles is strong. In contrast, low filtration fluxes are measured at high salt concentration, low pH, and with a CaCl 2 electrolyte, i.e. when the surface charges are weak and in the presence of specific cations. The net energy of interaction between the charged surfaces involved in the microfiltration process was calculated using the DLVO theory. This gave qualitative arguments for the explanation of the observed changes in the permeate flux.
Journal of Membrane Science, 1997
We present and test a device designed to measure the streaming potential of plane inorganic membrane during filtration. Two kinds of microporous membranes (a membrane made of a mixture of alumina-titania and this same type of membrane covered with an additional titania layer) are studied with different pH, ionic strength and electrolyte nature. The modification of the surface acid-basic equilibriums is analysed from the streaming potential measurements. The pores size of the studied membranes is large enough to avoid overlapping of the double layers. Streaming potential measurements are used to determine the zeta potential of the membranes from the Helmholtz-Smoluchowski relationship, corrected for the lowest ionic strengths studied. The shifting of the isoelectric point of the membranes studied with CaC12 and NazSO4 solutions shows specific adsorption of calcium and sulfate ions onto the surface. The additional titania layer on the alumina-titania support does not seem to modify the electrokinetic properties of the membrane.
Ceramic membrane development and characterization for microfiltration
2018
The preparation and characterization of tubular ceramic membranes aiming to do microfiltration using alumina and kaolin powders as raw materials were carried out. The membranes were obtained by doing slip casting of the suspensions. The suspensions consisted of alumina-kaolin powders, water, and 0.9 wt.% of dolapix CE64 as deflocculant. The variations made during suspension preparation includes the use of different ratios between alumina-kaolin powder and distilled water of 60 wt.% : 40 wt.% and 65 wt.% : 35 wt.%, and also the use of addition of different percentage of starch of 0.5, 1, 2, and 3 wt.% as pore former into the suspension. Upon casting, the manufacture was then followed by sintering process in a furnace, which was also varied into up to 1000 o C, 1100 o C, and 1200 o C. The procedure was then completed by doing subsequent characterizations of the sintered membranes by determining their microstructure using SEM (Scanning Electron Microscopy) and pure water permeability and E. coli bacteria rejection experiment with McFarland turbid solution that were executed in a customized microfiltration module. All of the membrane samples succeeded to have 100% E. coli rejection. However, out of all the membrane samples, membrane with powder to distilled water ratio of 65 wt.% : 35 wt.% with 0.9 wt.% dolapix sintered at 1100 o C gave results to the highest water permeate flux.
Desalination, 2002
The retention of neutral solutes and ionic solutions on a NF ceramic membrane was measured. The Donnan Steric Pore Model (DSPM) was fitted to these observations yielding effective pore radius (r_) and thickness/porosity ratio (Ax/A~.) from neutral solutes data and the effective volume charge (X) from electrolyte &ta. Effective volume charges were also directly determined using tangential streaming potential measurements. The DSPM gives X in good agreement with the values obtained by streaming potential. However, it overestimates Ax/A k compared to the value deduced from neutral solute retention.