共查询到20条相似文献,搜索用时 0 毫秒
1.
Ilyes Jedidi Sami Saïdi Sabeur Khmakem André Larbot Najwa Elloumi-Ammar Amine Fourati Aboulhassen Charfi Raja Ben Amar 《Arabian Journal of Chemistry》2009,2(1):31-39
This work aims to develop a new mineral porous tubular membrane based on mineral coal fly ash. Finely ground mineral coal powder was calcinated at 700 °C for about 3 h. The elaboration of the mesoporous layer was performed by the slip casting method using a suspension made of the mixture of fly ash powder, water and PVA. The obtained membrane was submitted to a thermal treatment which consists in drying at room temperature for 24 h then a sintering at 800 °C. SEM photographs indicated that the membrane surface was homogeneous and did not present any macro defects (cracks, etc.). The average pore diameter of the active layer was 0.25 μm and the thickness was around 20 μm. The membrane permeability was 475 l/h m2 bar.This membrane was applied to the treatment of the dying effluents generated by the washing baths in the textile industry. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 l/h m2). The quality of permeate was almost the same with the two membranes: the COD and color removal was 75% and 90%, respectively. 相似文献
2.
Microfiltration of whey protein solutions by tubular ceramic membranes, under constant cross-flow and trans-membrane pressure, with periodic backwashing, is investigated using a fully instrumented pilot unit. Relatively large nominal membrane pore size (0.8 μm) insures very high protein transmission, which is desirable in applications such as microbial load reduction. In the first of a sequence of three filtration-backwashing cycles, irreversible and reversible fouling are identified, over the tested pressure range of 5–17.5 psi. Early in the first cycle, especially at the higher pressures, a pore constriction/blocking mechanism appears to be responsible for the irreversible fouling. In the other two cycles only the reversible fouling is significant, possibly due to some kind of protein layer formation on the membrane surface. The permeate flux level tends to increase by increasing trans-membrane pressure up to a near-optimum value of 10 psi, beyond which pressure has a negative effect. This interesting trend is attributed to the interplay of cross-flow velocity, which tends to reduce fouling by promoting re-suspension and breakage of colloidal protein agglomerates, with the trans-membrane pressure (and related flux) which leads to protein layer formation on the membrane and may impose compressive stresses, thereby increasing its resistance to permeation. 相似文献
3.
Jason A. Morehouse Dana L. Taylor Douglas R. Lloyd Desmond F. Lawler Benny D. Freeman Leah S. Worrel 《Journal of membrane science》2006,280(1-2):712-719
Atomic force microscopy (AFM) was used to characterize the surface morphology of uni-axially stretched and non-stretched microporous microfiltration (MF) membranes. The effect of stretching on the pore structure and bulk properties of MF membranes has been previously reported [J.A. Morehouse, L.S. Worrel, D.L. Taylor, D.R. Lloyd, B.D. Freeman, D.F. Lawler, The effect of uni-axial orientation on macroporous membrane structure, J. Porous Mater. 13 (2006) 63–75.]; this paper focuses solely on the use of AFM to characterize the surface of stretched and non-stretched MF membranes. A new way of representing surface roughness that may prove useful in relating roughness to performance in cross-flow applications is presented. 相似文献
4.
Sherwood JD 《The journal of physical chemistry. B》2007,111(13):3370-3378
The primary electroviscous effect in a nondilute suspension of charged spherical particles is studied by means of cell models. The governing equations are derived, and then analytic results are obtained by restricting attention to the limit of thin double layers, small Hartmann and Peclet numbers, and small potentials. Previous work has assumed that the velocity at the outer boundary of the cell is identical to the imposed flow, as proposed by Simha (J. Appl. Phys. 1952, 23, 1020). Results with this boundary condition are compared against those predicted when the tangential shear stress on the outer boundary is assumed to be unperturbed, as proposed by Happel (J. Appl. Phys. 1957, 28, 1288). Both the hydrodynamic and electroviscous contributions to the effective viscosity are smaller with the Happel boundary condition, showing that such cell models offer a range of predictions and should be used with caution. 相似文献
5.
NaA zeolite microfiltration (MF) membranes were prepared on α-Al2O3 tube by in situ hydrothermal synthesis method and investigated for water separation and recovery from oily water. NaA/α-Al2O3 MF membranes with average inter-particle pore sizes of 1.2 μm, 0.4 μm and 0.2 μm were prepared. The membranes were characterized by scanning electron microscope (SEM) and the inter-particle pore size distribution (PSD) was determined by gas bubble pressure method. Membranes with pore sizes of 1.2 μm (NaA1) and 0.4 μm (NaA2) were used to treat an oil-in-water emulsion containing 100 mg/L oil. Better than 99% oil rejection was obtained and water containing less than 1 mg/L oil was produced at 85 L m−2 h−1 by NaA1 at a membrane pressure of 50 kPa. Consistent membrane performance was maintained by a regeneration regime consisting of frequent backwash with hot water and alkali solution. 相似文献
6.
《Journal of Colloid Science》1954,9(3):215-222
From the viscosities of oil-in-water emulsions of varying particle size and concentration (prepared with the same oil and emulsifier) an apparent increase in oil concentration during flow was derived. The particle sizes were calculated from light-scattering data of these emulsions. Combination of these data makes it possible to calculate an apparent increase in particle diameter during flow in cases where interaction between oil droplets is precluded. This increase seems to be independent of particle size and is ascribed to the electric charge on the surface of the particles. 相似文献
7.
T.Y. Chiu A.E. James 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):58-65
The microfiltration of commercially available amphoteric surfactant using ceramic membranes has been investigated. Various combinations operating conditions such as pH, electrolyte and surfactant concentrations were employed. Zeta potential and adsorption isotherms were obtained for the components of membrane surfactant system as functions of pH using surfactant or indifferent electrolyte (KCl). The shift in the membrane isoelectric point induced by the surfactant is linked to the carboxylic groups present on the surfactant which are believed to play a dominant role in the net surface charge of the membrane. A minimum in the permeate flux was found at the pH corresponding to the isoelectric point of the zwitterionic surfactant. This behaviour is ascribed to the interactions occurring between the surfactant–surfactant molecules and the surfactant–membrane. The higher fluxes obtained at low pH as compared to high pH arise from different fouling mechanisms and ionic strengths. Lower fluxes were found when inorganic electrolytes were used in conjunction with surfactant. However, as the valency of the salt increases, flux behaviour of the zwitterionic surfactant (close to isoelectric point) does not vary whilst the cationic and anionic state of the surfactants are much more affected. Interactions between surfactant molecules as a result of the charge screening effects by the larger valence ions are encouraged. The permeate flux declines with an increasing surfactant concentration even though some concentrations fall under the critical micelle concentration (c.m.c.). This is attributed to concentration polarisation in which the accumulated surfactant concentration at the membrane surface could form a stable viscous phase which is resistant to permeate flow in the secondary layer next to the membrane surface. This paper demonstrates the role interactions such as surfactant–surfactant and surfactant–membrane play in influencing the filterability of surfactant solutions using ceramic membranes. 相似文献
8.
Valentina S. Espina Michel Y. Jaffrin Matthieu Frappart Lu-Hui Ding 《Journal of membrane science》2008
This paper investigates the microfiltration of skim milk in order to separate caseins micelles from two whey proteins, α-lactalbumin (α-La) and β-lactoglobulin (β-Lg), using a modified dynamic filtration pilot (MSD) consisting in 6 ceramic 9-cm diameter membrane disks of 0.2 μm pores, rotating around a shaft inside cylindrical housing. A comparison was made with another dynamic filtration module consisting in a disk rotating near a fixed PVDF 15.5 cm diameter membrane with 0.15 μm pores. Maximum permeate fluxes were 120 L h−1 m−2 with the MSD module at 1930 rpm and at 40 °C, and 210 L h−1 m−2 at 2500 rpm and 45 °C, with the rotating disk module. Casein rejection was around 99% at high speed for both membranes. α-La transmission decreased with increasing transmembrane pressure (TMP) from 75% to 60% for ceramic membranes and from 25% to 10% for the PVDF one. β-Lg transmissions were lower, ranging from 23% to 15% for ceramic membranes and from 20% to 5% for the PVDF one. In a concentration test with the PVDF membrane at 2000 rpm, the flux decayed from 200 L h−1 m−2 at initial concentration to 80 L h−1 m−2 at VRR = 3.2 and 22.1% of the initial α-La mass was recovered in the permeate, against 8.1% for β-Lg. Permeate fluxes in the mass transfer limited regime (Jlim) of the MSD and rotating disk module operated at various speeds were well correlated by the equation Jlim = 17.13 Vav where Vav denoted the disk azimuthal velocity averaged over the membrane area. Measurements of Jlim, taken from Ref. [G. Samuelsson, P. Dejlmek, G. Tragardh, M. Paulsson, Minimizing whey protein retention in crossflow microfiltration of skim milk. Int. Dairy J. 7 (1997) 237–242] during MF of skim milk using tubular ceramic membranes at velocities from 1.5 to 8 m s−1 with permeate co-current recirculation were found to obey the same correlation. 相似文献
9.
F. J. Rubio-Hernndez A. I. Gmez-Merino E. Ruiz-Reina C. Carnero-Ruiz 《Colloids and surfaces. A, Physicochemical and engineering aspects》1998,140(1-3):295-298
An investigation on the primary electroviscous effect of polystyrene latexes has been made. Capillary viscometers of Ubbelohde type have been used. The comparison of the results obtained with the theories allow us to conclude that the effect is underestimated for low electrolyte concentrations. We suggest that this underestimation is due to an additional surface conductance into the electric double layer. This interpretation is consistent with previous studies on electrophoretic mobility of the same system. 相似文献
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11.
The intrinsic viscosity and the dynamic mobility of four silica sols have been measured as a function of the ionic strength. It was found that intrinsic viscosity decreased with increasing ionic strength, which we attribute to the primary electroviscous effect. The geometry and the charge of the particles were fitted using experimental viscosity, light scattering, and dynamic mobility data, where the intrinsic viscosity measured at the highest ionic strength for a given sol was used as input data in our analysis. Further, the boundary element (BE) method was used to calculate the primary electroviscous effect and electrophoretic mobility of charged prolate ellipsoids. These calculations were then compared with experimental data, and the primary electroviscous effect was subtracted from the intrinsic viscosity at a given ionic strength, which led to a slightly altered geometry of the particles. This revised geometry was used as input data using the BE method, and the procedure was repeated iteratively until agreement was obtained at high ionic strength. In general, good agreement between theory and experiment was found. 相似文献
12.
《Journal of Colloid Science》1958,13(2):148-150
The electroviscous effect has been measured in a H-sol of AgI to which 0–10 mmole/l. of KNO3 had been added. The results are interpreted with the theory of Booth, which gives satisfactory results. 相似文献
13.
Filtration of suspensions of emulsifier-free monodisperse polystyrene latexes with particle sizes of 0.25, 0.3, and 0.4 μm through acetylcellulose microfilters is studied as depending on the composition of liquid phases, the rate and time of filtration, and the particle-to-pore size ratios. The effect of particle-membrane interactions, which are governed by the electrostatic repulsion and molecular attraction forces, on particle rejection by membranes is considered. It is shown that, when analyzing the mechanism for the rejection, it is necessary to take into account the electrophoretic motion of particles in the field of the streaming potential arising in the course of suspension filtration. 相似文献
14.
Rubio-Hernández FJ Gómez-Merino AI Ruiz-Reina E García-Sánchez P 《Journal of colloid and interface science》2002,255(1):208-213
The primary electroviscous effect has been investigated in dilute suspensions of titanium oxide (anatase), the viscosities of which were measured by means of a capillary viscometer with automatic timing. The linear relation between viscosity and solids volume fraction was first determined at the isoelectric point of the particles when the particles are uncharged, and the electroviscous contribution to the intrinsic viscosity was then determined at other values of pH. Booth's theory (Proc. R. Soc. London Ser. A203, 533 (1950)) agrees well with the experimental results when the particle zeta potential is small and the double layer is thin (kappa alpha approximately 7.3), but agreement is poor when the double layer is thick (kappa alpha approximately 0.6). 相似文献
15.
A novel approach towards thin-layer molecularly imprinted polymer (MIP) composite membranes was developed based on using benzoin ethyl ether (BEE), a very efficient alpha-scission photoinitiator. The triazine herbicide desmetryn was used as the template, and a mixture of the functional monomer 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and the cross-linker N,N'-methylene-bis-acrylamide (MBAA) in methanol was copolymerised via photoinitiation followed by deposition on the surface of either hydrophobic or hydrophilically precoated polyvinylidene fluoride (PVDF) microfiltration membranes. Blanks were prepared under identical conditions, but without the template. Especially, the degree of functionalization (DF) of the PVDF membranes with poly(AMPS-co-MBAA), the membrane permeabilities and non-specific vs. MIP-specific template binding from aqueous solutions during fast filtration were studied in detail to evaluate the effects of the preparation conditions, in particular the coating of the membrane surface with the photoinitiator prior to UV irradiation and the influence of the precoated hydrophilic layer on PVDF. Significant template specificities of the MIP membranes compared with the blanks were only achieved for the preparations including coating the two types of PVDF membranes with BEE. In contrast, a homogeneous photoinitiation of the copolymerisation in the membrane pore volume yielded functional layers with similar DF but with only non-specific desmetryn binding. All data clearly indicate the significant contribution of MIP stabilization by the support material in layers of optimum thickness to the MIP specificity. Main advantages of the novel approach are the potential to synthesize MIP composite membranes by controlled deposition onto any kind of polymer support, and the very fast MIP preparations due to a very efficient photoinitiator and small MIP layer thickness. Due to the mechanical and chemical stability in combination with high permeabilities, thin-layer MIP composite membranes have a large application potential, e.g., in solid phase extraction. 相似文献
16.
A. Bismarck J. Springer A. K. Mohanty G. Hinrichsen M. A. Khan 《Colloid and polymer science》2000,278(3):229-235
ζ-potential measurements using the streaming potential method were performed on several differently modified jute fibers.
The time dependence of the ζ-potential measured in 1 × 10−3 M KCl solution offers the possibility to characterize the water-uptake behavior and the velocity constant of this process
for almost all the jute fibers investigated. All the jute fibers contain, as expected, dissociable acidic surface functional
groups as could be verified by measuring the pH dependence of the ζ-potential. Remarkably a peak (increase in the negative
ζ-potential values) was detected while measuring the ζ–pH dependency. The origin of this peak is still questionable; however,
it could be observed that this peak is a function of the degree of surface coverage of additional components, such as fats,
waxes or grafted polymers, i.e. the accessibility of ether functions in the jute fiber surface.
Received: 26 May 1999/Accepted in revised form: 28 September 1999 相似文献
17.
18.
《Journal of membrane science》1997,135(2):195-202
The effect of operating parameters on fouling of a ceramic microfiltration membrane by corn starch hydrolysate of 95 dextrose equivalence was studied. Transmembrane pressures above 100 kPa had little or no effect on flux. Cross-flow velocity had a significant beneficial effect. The rate of flux decline was reduced significantly when the feed was adjusted from its natural pH of 4.2 to 10. However, this resulted in a dark brown clarified syrup (permeate). Scanning electron microscopy showed extensive fouling layers on the alumina surface with conventionally processed dextrose solutions and the least fouling layer with corn starch hydrolysate adjusted to pH 10. Maximum steady state flux for unconcentrated hydrolysate at its natural pH was 178 LMH obtained at low transmembrane pressures (103 kPa, 15 psi) and high cross-flow velocities (5 m s−1). Adjustment of the pH to 10 can increase the flux by 40%. 相似文献
19.
《Journal of membrane science》1999,155(2):309-314
The transformation of membrane channels during the sintering process conforms to the Rhines' topological decay model of intermediate sintering stage. The pore size of the membranes enlarges with the increase of sintering temperature. The pore size increment caused by the increase of sintering temperature is more obvious for thin membranes than for thick membranes. With the increase of sintering temperature, the water permeance of membranes increases at first and then decreases after a turning point of sintering temperature. 相似文献
20.
Ohshima H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):6453-6461
A theory for the primary electroviscous effect in a dilute suspension of soft particles (i.e., particles coated with an ion-penetrable surface layer of polyelectrolytes) in an electrolyte solution is presented. The general expression for the effective viscosity eta s of the suspension and the primary electroviscous coefficient p, which is further expressed in terms of a function L, is given. On the basis of the general expressions, we derive approximate analytic expressions for eta s and p, which are applicable when the density of the fixed charges distributed within the surface layer is low. Further we obtain a simple approximate analytic expression (without involving numerical integrations) for p applicable for most practical cases. It is found that the function L exhibits a minimum when plotted as a function of kappa a (kappa is the Debye-Hückel parameter and a is the particle core radius), unlike the case of a suspension of hard particles, in which case L decreases as kappa a increases, exhibiting no minimum. The presence of a minimum for the case of a suspension of soft particles is due to the fact that L is proportional to 1/kappa 2 at small kappa a and to kappa 2 at large kappa a. Because of the presence of this minimum, the difference in L between soft and hard particles becomes very large for large kappa a. 相似文献