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排序方式: 共有526条查询结果,搜索用时 15 毫秒
31.
Sari Metsämuuronen 《Desalination》2005,175(1):37-47
The effect of solute size relative to membrane pore size on the critical flux during the ultrafiltration of protein solutions was investigated using the constant pressure method. Hydrophilic regenerated cellulose membranes with a cut-off of 10, 30 and 100 kg mol−1, model proteins and skimmed milk solutions were used. The critical flux mainly increased with the pore size of the ultrafiltration membrane. The lowest critical fluxes, 40-50 L m−2h−1, were obtained with the retentive 10 kg mol−1 cut-off membrane. This membrane had a very low permeability and, thus, the critical fluxes were achieved at high transmembrane pressures (TMP): 1.7-2.3 bar. With the 100 kg mol−1 cut-off membrane critical fluxes were obtained at 0.2 bar TMP, which were around 100 L m−2 h−1, slightly declining with increasing protein molar mass. In skimmed milk experiments the permeate flux decreased when the protein molecules were enzymatically split to peptides. A critical flux for skimmed milk solution could not be found unless the protein concentration was diluted to 0.3-w% or lower. The results with model proteins were then compared to those obtained with skimmed milk resulting in β-lactoglobulin being the worst foulant. 相似文献
32.
Nanofiltration of process liquors from viscose-type textile fibre production was investigated using a laboratoryscale crossflow test apparatus. Feed solutions contained about 200 g/l sodium hydroxide and a high concentration of hemicellulose as a contaminant originating from the raw material wood. The effects of various pretreatments and the addition of reagents on flux, retention and irreversible fouling were studied. Reagent addition affected the solution state of hemicellulose thus purposely provoking aggregate formation. Dynamic light scattering and turbidity measurements were used to track the evolution of hemicellulose aggregates. Aggregation generally coincided with distinct flux decline during nanofiltration thus indicating that this phenomenon may result in the build-up of gel layers at the membrane surface. Partial neutralisation with sulfuric acid caused extremely severe fouling, whereas methanol addition had a minor effect. The impact of heat treatment and oxidative degradation of hemicellulose on nanofiltration performance was attributed to changes in molar mass distribution. 相似文献
33.
Color and COD retention by nanofiltration membranes 总被引:3,自引:0,他引:3
In the present study the application of the nanofiltration process was investigated mainly in the retention ofcolor and chemical oxygen demand (COD) present in textile industry wastewater. Nanofiltration experiments were carried out in a pilot unit, operating in crossflow. Three different types of spiral wound membranes, DK 1073, NF 45 and MPS 31 were used simultaneously in the same unit. The results of the tests showed that for color retention, the values were around 99% for the DK 1073 and NF 45 membranes and the 87% for COD retention for the DK 1073. The permeate flux for the different wastewaters varied from 30.5 to 70 L/h.m2. Fouling was observed in all membranes due to the accumulation of molecular species close to the filtering surface. The process was efficient and promising for the reuse of wastewater from this type of industry. 相似文献
34.
Dattatray S. Wavhal 《Desalination》2005,172(2):189-205
Carbon dioxide plasmas were used to modify hydrophobic polysulfone ultrafiltration membranes to create hydrophilic surfaces throughout the membrane structure. The water contact angle of the upstream side of the membrane (facing the plasma) decreased to zero after treatment and did not change even after several months of aging. The water contact angle of the downstream side decreased with increasing CO2 plasma treatment time and became zero for treatment times ≥ 1 min (P = 10 W). Functional groups introduced by CO2 plasma treatment were examined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). For the treated membranes, the atomic concentration of oxygen increased dramatically and small amounts of nitrogen incorporation were also observed. Membrane performance was tested with water flux measurements as well as protein fouling studies. For treated membranes, the water flux recovery measured after protein fouling was significantly higher than that for control membranes, with nearly 100% recovery after gentle cleaning in water. Moreover, the amount of protein adsorption decreased by over 75% for the treated membranes compared to control membranes. This suggests the protein fouling layer is essentially completely reversible on the CO2 plasma treated membranes. 相似文献
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Commercial 50 and 100 kD polyethersulfone (PES) and polysulfone (PS) ultrafiltration membranes were surface modified by UV photografting of poly(ethylene glycol) methacrylate (PEGMA) monomer. The modified membranes were characterized by the degree of grafting, water flux and molecular weight cutoff (MWCO) rating. The flux and fouling of the modified and unmodified membranes were examined with sugarcane juice and its polysaccharide fraction. Under the conditions of this study, the modified membranes displayed a low degree of grafting (26-36 μg/cm2), which was independent of the UV exposure duration; however, both membrane water flux and MWCO rating were affected by the irradiation time. In the best case, the modified membranes exhibited lower fouling with sugarcane juice; furthermore, the propensity to foul also decreased. More significantly, juice flux recovery was almost complete for successive UF-cleaning cycles. 相似文献
38.
Iris Sutzkover-Gutman 《Desalination》2010,264(3):289-5
Effective membrane pretreatment is a crucial requirement for trouble free and cost effective RO desalination. Pretreatment construction costs are significant and may reach as much as 10%-20% of the total desalination plant capital costs. This paper presents a general review of the central factors involved in assessing raw water quality. The main foulant categories are described and the various unit operations commonly applied are reviewed. Pretreatment aspects of desalination offer fertile grounds for advancing desalination technologies. Promising research directions are highlighted. 相似文献
39.
In bench-scale tests of seawater reverse osmosis desalination it is important to carefully consider osmotic pressure effects and determine the extent of concentration polarization so that sources of flux variation—whether from fouling, compaction, or osmotic pressure changes—can be properly assessed. Rigorous modeling of concentration polarization is difficult because of the complex geometries and flow regimes in RO modules; typically, concentration polarization must be measured. However, concentration polarization measurement usually requires knowledge of membrane permeability, which can vary from coupon to coupon. In this study a method is presented to determine both the membrane permeability and the concentration polarization regime in a single test. The key to the test is to allow the salt concentration to vary over time in a predictable way and extract parameters from a model fitted to the flux data. The usefulness of this technique is highlighted by evaluating results from several seawater experiments. It was found that specific flux decline in the experiments was caused by changes in osmotic pressure and membrane compaction. RO fouling by seawater organic-matter was not significant for the several seawater samples tested. 相似文献
40.
Fouling characteristics of an ultrafiltration membrane used in drinking water treatment 总被引:1,自引:0,他引:1
The fouling characteristics of ultrafiltration membranes used in drinking water were investigated when used alone and when used in an integrated biofilter-membrane system to treat a humic-acid laden solution. Membrane strands from sacrificial modules operating in parallel with bench-scale modules were analysed from both systems (with and without pretreatment). Chemical and microbiological analyses were performed on these strands together with different process streams along the treatment train. Microscopic observations performed on the sacrificial membrane strands revealed that most of the fouling material was organic in nature with high numbers of viable microorganisms. When comparing their fouling characteristics, a positive effect from the biofilter was observed on the performance of the membrane with pretreatment, decreasing in general the amount of material deposited and reducing the fouling rate. Membranes were tested at two different permeate fluxes; this variable did not have an effect on the overall amount of material deposited, but it significantly impacted the membrane fouling rate. 相似文献