Comparison of centrifugation and filtration techniques for the size fractionation of colloidal material in soil suspensions using sedimentation field-flow fractionation

Sedimentation field-flow fractionation (SdFFF) with UV detection is used to systematically investigate the effect of traditional membrane filtration and centrifugation procedures on the isolation of specific size fractions from soil suspensions. Both procedures were used to isolate the nominal <0.45 and <0.2 microm fractions from a clay soil suspension. Results showed that the membrane filtration approach seriously underestimated the total mass of particulate matter present as compared to the centrifugation approach. This has serious implications forthe interpretation of results for "colloidal" and "soluble" fractions from soil suspensions and other environmental matrices obtained using the standard membrane approach. The results also show that sedimentation FFF has great potential as a robust and relatively mild technology for studying size distributions in the "colloidal" range for soil suspensions and other aquatic matrices.     

金属膜过滤食品煎炸用油效果的研究

以金属膜为过滤介质对食品煎炸用油进行过滤，并对过滤效果进行了研究。以大豆色拉油为原料，分别对过滤后的油和未过滤的油进行加热处理，每隔半小时取样一次，测定其过氧化值、酸价、黏度、颜色等理化指标。结果表明过滤后的油脂理化指标明显好于未过滤的油脂。     

产业用新型机织除尘过滤材料的关键技术

介绍新型机织除尘过滤材料研制过程中的工艺参数设计、优化以及去污漂洗、柔软处理和热定型处理等关键技术.新型机织除尘过滤材料作为环保除尘产品,可用于钢铁、水泥、金属冶炼等行业的消烟除尘.该材料的成功研制在国内属首创,项目列入上海市科委重点新产品计划,并作为上海高新技术成果转化项目,2009年获上海市科技进步三等奖.     

Gel filtration fractionation of winged bean (Psophocarpus tetragonolobus) proteins

Winged bean proteins were extracted by a pH 9.5, 0.3M borate extraction medium. The extracted proteins were fractionated by Sepharose CL-6B gel filtration chromatography into four fractions. Fraction 2 (F2, mol. wt 200 000) and Fraction 3 (F3, mol. wt 35 000) are the two major protein fractions. F3 was further resolved into Fraction 3A (F3A, mol. wt 44 160) and Fraction 3B (F3B, mol. wt 23 700) by Sephadex G-75 gel filtration chromatography. Both F2 and F3 fractions were heterogeneous when examined by polyacrylamide gel electrophoresis method. There are some varietal variations in the distribution of winged bean protein fractions recovered by gel filtration chromatography. Trypsin inhibitor and chymotrypsin inhibitor activity were found only in F3B, whereas haemagglutinating activity was found only in F3A.     

NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration

Membrane fouling by natural organic matter (NOM) was investigated in microgranular adsorptive filtration (μGAF) systems, in which a thin layer of adsorbent is predeposited on low-pressure membranes. The adsorbents tested included heated aluminum oxide particles (HAOPs), ion exchange (IX) resin, and powdered activated carbon (PAC). Size exclusion chromatography (SEC) separated the NOM into four apparent MW fractions with significant UV???. HAOPs and the IX resin performed almost identically with respect to removal of these fractions, and differently from PAC. However, while HAOPs and PAC reduced fouling substantially, IX resin did not, indicating that fouling could not be attributed to the NOM fractions detected by SEC. Rather, the key foulants appear to comprise a very small fraction of the NOM with almost no UV??? absorbance. Alginate, a strongly fouling surrogate for natural polysaccharides, is adsorbed effectively by HAOPs, but not by IX resin or PAC, suggesting that polysaccharides sometimes play a key role in membrane fouling by NOM.     

Quantification of sequential chlorinated ethene degradation by use of a reactive transport model incorporating isotope fractionation

Compound-specific isotope analysis (CSIA) enables quantification of biodegradation by use of the Rayleigh equation. The Rayleigh equation fails, however, to describe the sequential degradation of chlorinated aliphatic hydrocarbons (CAHs) involving various intermediates that are controlled by simultaneous degradation and production. This paper shows how isotope fractionation during sequential degradation can be simulated in a 1D reactive transport code (PHREEQC-2). 12C and 13C isotopes of each CAH were simulated as separate species, and the ratio of the rate constants of the heavy to light isotope equaled the kinetic isotope fractionation factor for each degradation step. The developed multistep isotope fractionation reactive transport model (IF-RTM) adequately simulated reductive dechlorination of tetrachloroethene (PCE) to ethene in a microcosm experiment. Transport scenarios were performed to evaluate the effect of sorption and of different degradation rate constant ratios among CAH species on the downgradient isotope evolution. The power of the model to quantify degradation is illustrated for situations where mixed sources degrade and for situations where daughter products are removed by oxidative processes. Finally, the model was used to interpret the occurrence of reductive dechlorination at a field site. The developed methodology can easily be incorporated in 3D solute transport models to enable quantification of sequential CAH degradation in the field by CSIA.     

Phosphorus compounds in sequential extracts of animal manures: chemical speciation and a novel fractionation procedure

Pollution of water bodies by phosphorus in runoff from soil amended with animal manures is one of the greatest threats to water quality in developed countries. The environmental fate of manure phosphorus is determined in part by its chemical composition, yet extraction procedures to assess this are poorly developed and provide no structural information. We used solution 31P NMR spectroscopy to quantify phosphorus compounds in sequential extracts of three contrasting manures (broiler litter, beef-cattle manure, swine manure). Using a procedure originally developed for soils, but commonly applied to manures, phosphorus was extracted sequentially with deionized water, 0.5 M NaHCO3, 0.1 M NaOH, and 0.5 M HCl. Water and NaHCO3 extracted readily soluble compounds, including phosphate, phospholipids, DNA, and simple phosphate monoesters, which are mobile in soil and biologically available. In contrast, NaOH and HCl extracted poorly soluble compounds, including phytic acid (myoinositol hexakisphosphate). The latter is immobile in soil and of limited biological availability. Based on these results, we developed a simplified two-step fractionation procedure involving extraction of readily soluble phosphorus in 0.5 M NaHCO3 followed by extraction of stable phosphorus in a solution containing 0.5 M NaOH and 50 mM EDTA. This revised procedure separates manure phosphorus into structurally defined fractions with environmental relevance and will facilitate research on this important aspect of environmental science.     

Flow field-flow fractionation for particle size characterization of selenium nanoparticles incubated in gastrointestinal conditions

An on-line flow field-flow fractionation (FlFFF) with inductively coupled plasma mass spectrometry (ICP-MS) was employed for particle size characterization of selenium nanoparticles stabilized by pectin, mixed alginate/pectin, ovalbumin, and β-lactoglobulin. Under the synthesis condition used herein, the particle size increased in the following order when β-lactoglobulin, ovalbumin, mixed alginate/pectin, and pectin was used as a stabilizing agent. Upon incubation of selenium nanoparticles in gastrointestinal conditions, both in enzymatic and non-enzymatic media, particle size distributions and the surface of selenium nanoparticles changed differently. Nonetheless, more than 90% of selenium was still presented in nanometer range after gastrointestinal digestion for the nanoparticles prepared by all types of stabilizers. In addition, the results show good agreement between the particle size observed from FlFFF and TEM techniques.     

Influence of surface charge distributions and particle size distributions on particle attachment in granular media filtration

Filtration experiments were performed with a laboratory-scale filter using spherical glass beads with 0.55 mm diameter as collectors. Suspensions were made with Min-U-Sil 5 particles, and two different methods (pH control and polymer dosing) were used for destabilization. In the pH control experiments, all particles had negative surface charge, and those with lower (absolute value) charge were selectively attached to the collectors, especially during the early stage of filtration. This selective attachment of the lower charged particles caused the zeta potential distribution (ZPD) of the effluent to move to a more negative range. However, the ZPD of the effluent did not continue moving to more negative values during the later stages of filtration, and this result was attributed to two reasons: ripening effects and detachment of flocs. In the polymer experiments, substantial differences were found between experiments performed with negatively charged particles (underdosing) and those with positively charged particles (overdosing). With under-dosing, the results were similar to the pH control experiments (which also had negatively charged particles), but with overdosing, the effluent's ZPDs in the early stages did not overlap with those of the influent and more highly charged particles were removed more efficiently than lesser-charged particles. It is hypothesized that, despite a substantial period of pre-equilibration of media and coagulant, this equilibrium shifted when particles were also added. It was assumed that coagulant molecules previously adsorbed to the particles desorbed and subsequently attached to the filter media because of surface area differences in the particle and filter media.     

Investigation on filtration properties of polyester needle-punched dust filter

Abstract

In nonwoven filter fabrics, virgin polyester fibre is mostly used. Therefore, this study has been conducted with the use of virgin polyester fibre and recycled polyester fibre which is obtained after recycling of post-consumer bottle flakes to reduce the cost of filter fabric. The study is concerned to examine the effect of fabric GSM (grams/m²), needling density and depth of needle penetration on filtration efficiency and also to see the suitability of recycled polyester fibre in place of virgin polyester fibre. The study has shown that the increase in fabric weight resulted in increase in the filtration efficiency percentage. The increase in the depth of needle penetration resulted in increase in the extent of filtration efficiency initially; subsequently, it decreased. Similar trends were observed in case of both recycled polyester filter fabrics and virgin polyester filter fabrics. Though the filtration efficiency of filter fabrics prepared from virgin polyester fibre was slightly higher, the filtration efficiency of fabrics prepared from recycled polyester fibre was lower by only 2 to 3 per cent due to close difference in values of molecular weight (Mw) and polydispersity index (PDI). Therefore, looking to the filtration efficiency percentage, it may be suggested that recycled polyester fibre can be used in place of virgin polyester fibre for the manufacturing of needle-punched nonwoven filter fabrics.     

Structural characterization of barley β-glucan extracted using a novel fractionation technique

A barley β-glucan concentrate prepared according to a novel technology was further purified and subjected to detailed structural characterization by NMR spectroscopy. β-Glucan was hydrolysed with β-glucan-4-glucanohydrolase (lichenase). Fractions of hydrolysate were collected using an HPLC-fraction collector. Intact β-glucan and the major fractions collected were subjected to MALDI-TOF–MS and NMR analyses. The two major oligosaccharides produced by lichenase hydrolysis of purified barley β-glucan were identified as β-d-Glc p-(1 → 4)- β-d-Glc p-(1 → 3)-β-d-Glc p and β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 3)-β-d-Glc p based on ¹³C and ¹H NMR data. Spectrums were similar to those documented for barley β-glucan in the literature.     

Comparison of lipoprotein fractionation by sequential density gradient ultracentrifugation with precipitation or fast phase liquid chromatography

Lipoprotein fractions, i.e. very low density (VLDL, ρ=0.93−1.019), low density (LDL, ρ=1.019−1.063), and high density lipoprotein (HDL, ρ=1.063−1.21) were separated by sequential gradient density ultracentrifugation (SDGU) and their cholesterol values were determined and compared with values determined by fast phase liquid chromatography (FPLC) or HDL cholesterol by phosphotungstic acid-MgCl₂ (PTMg) precipitation in hamsters fed diets containing various levels of cholesterol. The correlation coefficient (r) for LDL between the SDGU and FPLC methods in plasma from hamsters fed 0–3% cholesterol diets was 0.21–0.51, n=45. The FPLC method over estimated (+45%) LDL and the HDL values were under estimated (−18%). The agreement between FPLC and SDGU methods was also evaluated by plotting mean values against the differences between the values obtained by the two methods. FPLC method overestimated LDL 22–49% (mean 36%) and HDL was underestimated 14–27% (mean 20%). This was significant systematic bias with the FPLC method in VLDL, LDL and HDL values with the level of cholesterol in the diet. As FPLC is a fast method, it could be used in intervention type experiments to monitor the progress, however final results may need validation for research studies with the SDGU method. HDL determined by the SDGU method and phosphotungstic acid MgCl₂ precipitation in hamsters (n=26) fed 0.25% cholesterol diets was represented by two significantly different (P⩽0.05) divergent lines when a regression fitted model and a one-to-one relationship model by the two methods were plotted. The data suggest that in hamsters fed either no added cholesterol or cholesterol-containing diets, lipoprotein fractions determined by the precipitation method or by FPLC need to be validated against a SDGU for critical samples.     

Enumeration of clostridia in goat milk using an optimized membrane filtration technique

A membrane filtration technique developed for counting butyric acid bacteria in cow milk was further developed for analysis of goat milk. Reduction of the sample volume, prolongation of incubation time after addition of proteolytic enzyme and detergent, and a novel step of ultrasonic treatment during incubation allowed filtration of goat milk even in the case of somatic cell counts (SCC) exceeding 10⁶/mL. However, filterability was impaired in milk from goats in late lactation. In total, spore counts were assessed in 329 farm bulk goat milk samples. Membrane filtration technique counts were lower than numbers revealed by the classic most probable number technique. Thus, method-specific thresholds for milk to evaluate the risk of late blowing have to be set. As expected, the spore counts of milk samples from suppliers not feeding silage were significantly lower than the spore counts of milk samples from suppliers using silage feeds. Not only were counts different, the clostridial spore population also varied significantly. By using 16S rRNA gene PCR and gene sequencing, 342 strains from 15 clostridial species were identified. The most common Clostridium species were Clostridium tyrobutyricum (40.4%), Clostridium sporogenes (38.3%), Clostridium bifermentans (7.6%), and Clostridium perfringens (5.3%). The 2 most frequently occurring species C. tyrobutyricum and C. sporogenes accounted for 84.7% of the isolates derived from samples of suppliers feeding silage (n = 288). In contrast, in samples from suppliers without silage feeding (n = 55), these species were detected in only 45.5% of the isolates.     

A denuder-filter sampling technique for the detection of gas and particle phase carbonyl compounds

A denuder-filter sampling technique for the simultaneous collection of gas and particle phase carbonyl compounds has been developed and tested. The denuder was coated with XAD-4 resin and the derivatizing agent O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) to enable on-tube conversion of gas-phase carbonyls to their oxime derivatives which were extracted and identified by GC-MS. The performance of the PFBHA-coated denuder was tested on a range of carbonyls, dicarbonyls, aromatic aldehydes, carbonyl-containing furans, and benzoquinones. The collection efficiency of the PFBHA-coated denuder was over 90% for sampling times of 10 min and significantly higher than when using only XAD-4 as the sorbent. The collection efficiency and rate of on-tube derivatization was highest for aldehydes and lowest for ketones, consistent with the expected reactivity of carbonyls with PFBHA. The method was used to separate the gas and particle phase carbonyl products formed during the photooxidation of toluene in order to assess its potential for application to simulation chamber experiments of VOC oxidation. The results indicate that when compared to a conventional filter sampling setup, the PFBHA-coated denuder-filter reduced the extent of gas phase adsorption onto the filter by at least a factor of 2 for each of the carbonyls formed. Further potential applications of the denuder-filter sampling method are discussed.     

Impact of diffusion,transmembrane pressure and the electrical field on peptide fractionation using cross-flow electro membrane filtration

Downstream processes combining ultrafiltration and an applied electrical field as driving forces have recently been developed for the fractionation of peptides to obtain maximum fractionation coefficients, and thus, higher fractionation efficiency. However, the filtration mechanism and the overlaying effects of fractionation still remain unclear. To gain a better understanding of the dominating mechanism, the objective of this work was to evaluate the impact of diffusion, transmembrane pressure and the applied electrical field during cross-flow electro membrane filtration of micellar casein hydrolysate. Special emphasis was placed on the fractionation of six model peptides, which belong to the group of antihypertensive peptides. In addition, the apparent charge of the model peptides with different charges, peptide lengths and isoelectric points were calculated from experimental data and compared with those determined via the pk_a. The experiments revealed that the applied electrical field is an effective tool to enhance the fractionation process by 45%.     

Preparation of low-fat uptake doughnut by dry particle coating technique

ABSTRACT:  Soybean hull–wheat flour composites were prepared and used a doughnut formulation in order to decrease fat uptake during deep-fat frying. Soybean hulls were microparticulated by jet milling, and wheat flour was air-classified into coarse and fine fraction by an air classifying system. The coarse fraction of wheat flour was dry-coated with the microparticulated soybean hulls by a hybridization system. To investigate the effect on fat uptake, 4 different types of composites were prepared, which contained 0%, 1%, 5%, and 10% of soybean hulls. Doughnuts containing 1%, 5%, and 10% of microparticulated hulls decreased fat contents of 11.5%, 13.6%, and 35.8%, respectively. As soybean hulls content increased, hardness and crispiness increased. However, sensory evaluations demonstrated that there were no significant differences in appearance, flavor, crispiness, taste, and general liking ( P < 0.05). Inner crust structures of doughnut showed slight reductions in cell size and improved cellular integrity with shrinkage in the cell membrane as the content of soybean hulls increased. These results show that microparticulated soybean hulls may form a protective layer during frying process, and this process could be used by the food industry for preparing doughnuts with reduced fat uptake.     

Stickiness of skim milk powder using the particle gun technique

The particle gun method for investigating the initiation of stickiness of dairy powders was examined using skim milk powder (SMP). The point at which significant stickiness occurred was at a constant temperature above the glass transition temperature (T_g) of amorphous lactose regardless of the temperature and relative humidity (RH) conditions of the air in the particle gun. This point has been called (T–T_g)_critical. The initial water activity of SMP did not significantly affect (T–T_g)_critical, confirming that stickiness is a surface phenomenon. Changing the particle feed rate did not effect (T–T_g)_critical or the rate at which the powder accumulated on the target plate. The errors in measuring the value of (T–T_g)_critical and the rate of stickiness development [slope of the deposition line versus (T–T_g)] for SMP were found to be 33.6 ± 0.8 °C and 3.1 ± 0.7% deposition °C^?1, respectively, after standardisation of the ambient air conditions around the powder feeder and the initial water activity of the SMP.     

Effect of membrane length, membrane resistance, and filtration conditions on the fractionation of milk proteins by microfiltration

We investigated the fractionation of casein micelles and the whey protein β-lactoglobulin (β-LG) of skim milk by crossflow microfiltration (0.1 μm) for the first time by a novel approach as a function of membrane length and membrane resistance. A special module was constructed with 4 sections and used to assess the effects of membrane length by measuring flux and β-LG permeation (or transmission) as a function of transmembrane pressure and membrane length. Depending on the position, the membranes were partly controlled by a deposit layer. A maximum for β-LG mass flow through the various membrane sections was found, depending on the position along the membrane. To study the effect of convective flow toward the membrane, membranes with 4 different intrinsic permeation resistances were assessed in terms of the permeation and fouling effects along the flow channel. From these findings, we derived a ratio between transmembrane pressure and membrane resistance, which was useful in reducing the effect of deposit formation and, thus, to optimize the protein permeation. In addition, the fouling effect was investigated in terms of reversible and irreversible fouling and, in addition, by differentiation between pressure-induced fouling and adsorption-induced (pressure-independent) fouling, again as a function of membrane length.     

非织造材料过滤介质

目前很多企业将非织造材料用于过滤,其中涉及食品、饮料、生物技术、药物、饮用水、液压用油、燃料、溶剂、酸碱等。不同用途所需去除的杂质也有所不同,非织造材料种类繁多,可满足这些不同应用的需求。非织造材料随着加工原料、加工方法和表面特征的不同而不同。根据成型方法可分成两大类。第一种方法是干法成网工艺,包括梳理、针刺、纺粘和熔...