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21.
《分离科学与技术》2012,47(16):2623-2640
Abstract The resistance analyses for ultrafiltration of macromolecular solutions by the resistances-in-series model and the modified gel-polarization model, respectively, have been extended to the turbulent ultrafiltration system in this study. The experiments are carried out by ultrafiltrating dextran T500 solutions in a tubular membrane module with membrane material of ZrO2-TiO2/carbon. It is found that the permeate fluxes are predicted very well by these models for both laminar and turbulent systems, and the resistance caused by the concentration polarization/gel layer (R p) can be reduced by increasing the crossflow velocity on the membrane surface. Analysis by the resistances-in-series model showed that, R p decreases with flow velocity with exponents of 0.49 and 0.99 for the laminar system and the turbulent system, respectively. 相似文献
22.
The objectives of this research are to identify the membrane fouling potential due to different fractions of NOM and correlate
the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane and investigate the
mechanism of coagulation affecting UF, and find the optimum conditions of the combined of coagulation with UF membrane filtration
for NOM removal. For Nakdong river water, the humic acid fraction was the most reactive precursor fraction for the formation
of the ratio of THMFP/DOC (STHMFP) and TOXFP/DOC (STOXFP). The result of adsorption kinetics tests showed that hydrophobic
organics adsorbed much more quickly than hydrophilic organics on both membranes. Thus, hydrophobic compounds exhibited a preferential
adsorption onto membrane. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption
ratio (C1/Ce) was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions.
For combined coagulation with membrane process, flux reduction rate showed lower than the UF process alone. Also, the rate
of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying the coagulation
process before membrane filtration showed not only reduced membrane fouling, but also improved removal of dissolved organic
materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle
size distribution occurred under rapid and slow mixing conditions due to the simultaneous formation of microflocs and NOM
precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved not only dissolved
organic removal efficiency but also DBP (Disinfection By-Product) precursor's removal efficiency. 相似文献
23.
Kraft black liquor lignin is a biofuel that is separated from the cellulose during kraft pulping. Improved technology and energy integration in paper mills have led to an energy surplus at many mills. It is therefore of great interest to extract the lignin from the pulp mill and sell it as fuel to replace fossil fuel in other furnaces. The fractionation of kraft black liquor with a total dry matter content of about 15 wt% has been studied using ultrafiltration. The flux for three polymeric membranes with different cut-offs was investigated as well as their retention of lignin and other process specific substances. The retention of lignin for the three membranes with cut-offs of 4,8 and 20 kDa was 80%, 67% and 45%, respectively. The retention of sulphur and sodium was zero for all three membranes. The purity of the final lignin fuel is of importances as the ash content preferably should be as low as possible. The flux and retention during concentration and diafiltration of the black liquor were therefore studied. The dialfiltration operation was conducted in batch and semicontinuous mode. The lignin purity was 36% in the original kraft black liquor and 78% after semi-continuous dialfiltration. 相似文献
24.
Olive oil production results in important quantities of wastewater containing large amounts of total solids and organic carbon as well as low oil concentrations. This paper describes the treatment of olive mill wastewater (OMW) by combining an ultrafiltration (UF) technique and an advanced oxidation process (AOP) using UV/H2O2. It further demonstrates the technical feasibility of this compact and stable process to remove a large part of total solids and organic carbon. Indeed, OF reduces the pollutants contained in the OMW with an apparent rejection coefficient RCOD in the range of 94%. The UV/H2O2 oxidation process may be easily used, in combination with UF, to finish the treatment of the permeate. The results obtained in batch and continuous mode showed that this technique offered a treated solution which complies with legal requirements. A final concentration of 17 mgTOC dm−3 was obtained, which corresponds to a final COD of 52 mg dm−3, while the legal requirement is 125. Furthermore, the final effluent is fully decolorized. 相似文献
25.
Summary
Hydrophobic polymer surfaces show higher tendency to protein adsorption and bacteria attachment, thus hydrophobic polymeric
membranes foul rapidly in water purification operations. A change in membrane surface properties can reduce fouling; this
may be accomplished by increasing the hydrophilicity of the membrane surface, and by using a membrane with smaller pore size.
The ultrafiltration membranes were prepared via phase inversion process in our laboratory. Negatively charged hydrophilic
ultrafiltration membranes were prepared from acrylonitrile-vinyl acetate (CP16)/Acrylonitrile-vinyl acetate-sodium p-sulfophenyl
methallyl ether (CP24). Scanning electron microscopy (SEM) revealed the asymmetric structure of these membranes. The roughness
of the surface was measured by atomic force microscopy (AFM). The basic characteristics of these membranes like water permeability,
water content and membrane selectivity were also measured.
Received: 29 April 2001/Revised version: 14 September 2001/Accepted: 14 September 2001 相似文献
26.
In membrane filtration, solution environment factors such as pH and solvent density are important in controlling the filtration
rate and the rejection of the particles and/or the macromolecules. The filtration rate and the rejection in membrane filtration
have been investigated from physicochemical aspects. It was shown that the properties of the filter cake formed on the membrane
surface play a vital role in determining the filtration rate in mem-brane filtration. It was clearly demonstrated that such
filtration behaviors as the filtration rate and the rejection are highly dependent on the electrical nature of the particles
and/or the macromolecules. Furthermore, it was shown that the solvent density ρ has a large effect on the steady filtration
rate in upward ultrafiltration. 相似文献
27.
Claudia Muro Urista Jesús Escobar Jiménez María Del Carmen Díaz Nava Rosa Elvira Zavala Arce Beatriz García Gaitán Francisco Riera Rodríguez 《Chemical Engineering Communications》2013,200(2):163-177
Two ultrafiltration membranes with different geometries (spiral polymeric and tubular ceramic) but similar cutoffs were used to treat wastewater from a food industry. Hydrodynamic conditions were optimized by statistical methods as a strategy to get more accurate values of the critical parameters and then to produce higher water flux and minimization of membrane fouling. The validation of the optimization method was obtained by experimental critical flux determination at critical parameters. Membrane fluxes revealed significant differences during filtration. The polymeric membrane showed an optimal flux of 45.60 Lh?1 m?2 at 3.21 bar while operating at a stable time of 11.61 h, whereas optimal flux of the ceramic membrane was 32.43 Lh?1 m?2 at 3.98 bar for 16.03 h. Experimental critical flux values were only slightly lower than optimal fluxes for both membranes, showing the validity of the statistics models applied. Negligible osmotic pressure was found on the two membranes at critical flux parameters, indicating irreversible fouling for both cases. The polymeric membrane revealed strong fouling behavior and the ceramic membrane showed a weak form; the flux decline occurred first in the polymeric membrane, whereas the ceramic membrane exhibited high stability during the filtration operations. A high degree of purification of wastewater was obtained by this membrane at critical flux conditions. 相似文献
28.
29.
Extensive laboratory investigations and mill scale trials confirmed the applicability of ultrafiltrated high molecular weight Ca-ligno-sulfonates in adhesive composition with phenolic resin for insulation board manufacture based on mineral wool. Insulation materials produced with adhesive components with a formulation of lignosulfonate/PF resin between 10/90 and 30/70 have appropriate technical and commercial properties. 相似文献
30.
The mass transfer for the systems of dialysis with ultrafiltration in cocurrently parallel-flow rectangular membrane modules was investigated, based on mass balances with the assumption of uniform ultrafiltration flux. Considerable improvement in separation efficiency is achievable if the effect of ultrafiltration is applied, especially for the system with low mass transfer coefficient. The enhancement in separation efficiency is significantly increased with increasing ultrafiltration flux, as well as with increasing the volumetric flow rates. Furthermore, increasing the volumetric flow rate in retentate phase is more beneficial to mass transfer than increasing in dialysate phase. 相似文献