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.     

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.     

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.     

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.     

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%.     

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...     

Simultaneous estimation of thermal conductivity and volumetric heat capacity for solid foods using sequential parameter estimation technique

Nonlinear sequential parameter estimation method based on Gauss minimization technique was used for developing a computer program capable of simultaneously estimating volumetric heat capacity and thermal conductivity using transient temperature measurements for a one-dimensional conduction food subjected to constant heat flux on one side and insulated on the other side. Monte Carlo simulation technique was used to validate and investigate the performance of the algorithm by generating simulated experimental data with random errors using typical known experimental thermal property data. Despite the variability in the initial guess of the parameters required by the algorithm no convergence problems were encountered. The accuracy of the parameters prediction depends on the level of the errors of the measured temperature. Positioning the measurement sensor closer to the heating surface resulted in accurate parameter estimation in shorter heating time minimizing the risk of long heating time and elevated surface temperature which may results in physical–chemical changes influencing the accuracy of the parameter estimation.     

Investigation of 2-step technique for jute fabric reinforced polymer matrix composite

This paper focuses on the fabrication processes of jute reinforced polymer composites (FPC) made with the use of both untreated jute fabric and pultruded jute fabric. The pultruded jute fabric performs were processed and cured separately using polymer with different components blending ratio ‘α’ (resin/solvent ratio). 2-step technique where the composite specimens were prepared using a different combination of polymer blending ratio α₁ for the pultruding jute fabric and used blending ratio α₂ polymer for the matrix, which have contributed positively to fiber/matrix tensile stress, breaking strain, toughness and Young’s modulus. The best value of α₁ and α₂ to have composite with high tensile strength and Young’s modulus was 0.6 for both the pultruded matrix and final composite matrix.     

PBS静电纺非织造布结构与过滤性能的关系分析

研究了聚丁二酸丁二醇酯(PBS)静电纺非织造布结构与过滤性能的关系。采用扫描电镜和SPSS软件,测试分析了PBS静电纺非织造布的纤维直径、孔隙率等对过滤效率的影响。实验结果表明,纤维直径和孔隙率越大,非织造布透气性越好,而过滤效率越小。     

Investigation on sequential extraction of peanut allergens for subsequent analysis by ELISA and 2D gel electrophoresis

A two-step sequential extraction method of peanut proteins was proposed with the aim to investigate the protein composition and allergen content of peanut samples. The extraction procedure reported is fully compatible with subsequent analysis by enzyme-linked immunosorbent assays (ELISA) as well as 2D gel electrophoresis (2D PAGE). This sequential extraction method was used to study three different peanut varieties and three different types of food processing. Peanuts were analysed for total protein content and the extraction efficiency of raw and processed peanuts was determined. The total protein content of the three peanut varieties was found to be comparable, but their extraction efficiency varies. The peanut extracts were characterised by employing three different ELISA test kits specific to either the allergens Ara h 1 or Ara h 2, or to soluble peanut proteins. The content of both Ara h 1 and Ara h 2 differed in the raw peanut extracts of the three varieties. However, thermal processing resulted in much larger changes in detectability. Blanching significantly increases the detectability of Ara h 2, whereas Ara h 1 detection remains almost unchanged. After roasting a clear decrease of detectability was observed for both Ara h 1 and Ara h 2, although the effect is more severe for Ara h 1. 2D PAGE was employed to compare the protein profiles and abundances of peanut extracts. Statistically relevant differences were observed for the two different protein fractions obtained by using the described method, showing the relevance of this two-step sequential extraction method.