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1.
Orthokinetic flocculation of caseinate-stabilized emulsions: influence of calcium concentration, shear rate, and protein content 总被引：2，自引：0，他引：2
Calcium-induced flocculation of caseinate-stabilized soybean oil-in-water emulsions in conditions of Couette flow was studied. A concentrated emulsion (20% oil, 0.5-2.0% sodium caseinate in 20 mM imidazole, pH 7) was diluted 20 times in buffer containing concentrations of CaCl(2) between 9 and 17 mM and sheared at rates between 335 and 1340 s(-)(1). The average particle size (d(43)), measured by integrated light scattering, increased in a sigmoidal manner with shearing time. An increased shear rate resulted in an increased flocculation rate, because of the increased number of collisions between particles, but a decreased value of the maximum d(43), because higher shear rates increasingly disrupted the flocs. The flocculation rate was increased by increasing the calcium concentration, indicating an increased collision efficiency. The orthokinetic stability of the emulsions was increased with increased protein content, and it is postulated that the increased surface coverage and hydrodynamic thickness of the adsorbed protein layer increased steric repulsion between droplets, so that higher calcium concentrations were necessary to induce sufficient conformational change of the proteins to allow flocculation. At high caseinate concentrations, calcium may also induce precipitation of unadsorbed caseins from the serum to the oil-water interface, thereby increasing steric repulsion and hence increasing orthokinetic stability. 相似文献
2.
Grain size is the most basic of classification criteria for sediments. The size distribution of a given sediment records the physical transport processes involved in its formation. By using precise grain size analysis and the model of Kranck et al. (1996a,b), it is possible to break down a sediment into the three major components from which it was formed: material deposited as flocs, material deposited as single grains from suspension, and material carried under higher energy conditions. With this method, both the amount of material deposited in a flocculated state and the maximum size, or floc limit, of the particles composing the floc can be determined. Changes in floc limit indicate changes in the aggregation dynamics of the system. As most trace metals and many other contaminants associate closely with the fine particle fraction of sediments, it is important to determine both the areal distribution and reworking history of the floc settled portion of a sediment. This paper discusses the application of the method to coastal inlets in Atlantic Canada and examines the relationship between proportion of floc-settled material and trace metal concentrations. Disaggregated inorganic grain size distributions are also used to illustrate changes in the aggregation dynamics in areas of intense aquaculture. 相似文献
3.
为了系统性研究灌木植物根系的固土力学效应,探讨土体对根系的摩阻特性,以4种不同土壤粒径（原级配,1.0~2.0,0.5~1.0,<0.5 mm）和3年生的典型护坡植物种火棘及紫穗槐为研究对象,采用室内直剪的方式对根系进行根—土界面直剪摩擦试验。结果表明：（1）根—土及土—土界面的摩阻强度与垂直荷载呈明显的正线性关系;随土体粒径的增加,根—土及土—土界面的摩阻强度、摩擦系数、黏聚力和摩擦角均呈现下降趋势,且在相同粒径范围内,火棘根—土界面摩阻特性显著优于紫穗槐和素土;（2）根—土界面与素土界面的剪应力随位移的增长速率呈现先增大后减小的趋势;根—土界面剪应力与位移关系曲线呈现曲折蜿蜒式上升,而素土曲线表现为平缓式上升;（3）土体粒径越小,根土间接触面的比表面积越大,细小的土壤颗粒与根表面发生镶嵌,加大接触面的咬合力,使摩阻能力加大。研究结果对进一步探讨灌木植物根—土相互作用力学机制,以及利用灌木植物提高试验区边坡土体稳定性、防治坡面浅层滑落具有一定的理论指导意义。 相似文献
4.
P uptake by rye grass and alfalfa from smaller particle size of DCPD (≦ .18 mm) was larger than that from larger granules (0.4–0.5, 1.0–1.25, and 1.5–1.75 mm). Differences, however, became smaller with increasing time of contact. However powdered MCP was superior to all DCPD particles size fraction in an alluvial clay and a calcareous sandy clay loam indicating that under such alkaline reaction, the rate of dissolution is more limiting than the rate of immobilization. Results also indicate that the phosphate mobility in the highly calcareous was much lower than in the clay soil due to high pH and carbonate content. 相似文献
5.
Guannan Liu Juan Wang Wei Xue Jinbo Zhao Jing Wang Xinhui Liu 《Journal of Soils and Sediments》2017,17(12):2810-2821
Purpose
The size of soil particles strongly affects the accumulation and adsorption of heavy metals which partly controls the co-transport of heavy metals by soil colloids. However, the effect of the size of soil particles on the accumulation and adsorption of heavy metals in the colloidal dimension has seldom been studied. In this study, variable charge soils were selected and separated into five size fractions to elucidate the effect of the size of soil particles on Cd accumulation and adsorption.Materials and methods
Five soil particle size fractions (>10, 10–1, 1–0.45, 0.45–0.2 and <0.2 μm) were obtained from Cd-contaminated soil by natural sedimentation and fractional centrifugation. The concentrations and species of Cd were measured in various sized soil particles. Batch adsorption experiments of Cd on the obtained soil particles were conducted under different pH values and concentrations of NaCl.Results and discussion
Generally, the concentration of Cd increased with decreasing soil particle sizes, and the Cd proportion of exchangeable and carbonate fraction decreased from 43.84 to 17.75% with decreasing particle size. The soil particles with a size of 10–1 and <0.2 μm possessed a stronger adsorption ability than the other fractions in most cases. Moreover, the Cd adsorption capacities of the soil particles increased with increasing pH values and decreasing concentrations of NaCl, especially for soil particles containing more organic matter (OM) and variable charge minerals.Conclusions
Smaller soil particles are more capable of accumulating Cd and make Cd more stable. The adsorption capability of Cd is negatively related to the particle size and NaCl concentration and is positively related to the pH. The effects of the size of variable charge soil particles on Cd accumulation and adsorption are attributed to the differences in the physicochemical properties among various soil particle size fractions. This study contributes to the understanding of the co-transport of heavy metals in soil by soil colloids.6.
为研究燕麦蛋白的理化性质,本研究采用碱提酸沉法提取燕麦蛋白,并分析不同pH值与温度对燕麦蛋白溶解性、ζ-电位和粒径分布的影响。结果表明,在等电点附近(pH值5.0),燕麦蛋白的表面电荷数最低,蛋白粒度较大,溶解性和乳化性较低。当pH值远离等电点时,燕麦蛋白的表面电荷增加,蛋白粒度逐渐减小,溶解度升高,乳化性也随之升高;随着温度升高(55~95℃),燕麦蛋白聚集体解离,粒度变小,溶解度增加,稳定性变好;温度进一步升高(121、130℃),燕麦蛋白重新聚集形成粒径较大的聚集体,溶解度降低,稳定性变差。本研究结果为燕麦蛋白资源的利用提供了重要的理论指导。 相似文献
7.
Magdalena Kuśnierz 《Water, air, and soil pollution》2018,229(10):327
The light scattering method is a valuable tool for accessing particle size and structure mainly due to fast and the nonintrusive nature of the measurement. The method is based on a scattered intensity pattern and depends on particle volume, particle morphology, the light wavelength and the scattering angle. The light scattering model, for particles characterised by a fractal structure, is enabled with the use of the Rayleigh-Gans-Debye theory under constrained assumptions. The range of validity of the Rayleigh-Gans-Debye is limited when primary particles constituting aggregate have a size close to the wavelength. In this work, a range of particle sizes was characterised in order to achieve a better understanding of the relationship between flocs size and its fractal dimension. Hence, the width of the power law regime is discussed. What is more, a specific fractal dimension value of activated sludge flocs was found for each of the analysed wastewater treatment plant, which suggests that the spatial structure of suspensions constituting the activated sludge is an individual characteristic of each treatment facility. It has been shown that activated sludge consists of microflocs from the range of 1–10 μm, which constitute approximately 90% of all the population. 相似文献
8.
A model was developed for the influence of particle size on the extrusion of a fish feed and the physical characteristics of the extrudates evaluated. The study was conducted using factorial experiments in a fractional replication design for four variables with three levels, and one‐third of the replicates (34 factorial in 27 units) were examined in a laboratory extruder. The torque‐screw speed measurement was used to develop a viscosity model equation that considered different shear rates, product temperature, initial moisture content, and particle size. When particle size decreased, the apparent viscosity became smaller. The barrel pressure was important in producing extrudate with a uniform volume over the range of processing conditions tested because it had a strong correlation with the volumetric expansion. The material with lower moisture and larger particles caused the specific mechanical energy to increase. The viscosity model developed in this study can be applied to the development of large‐scale extrusion models that determine the effect of particle size on the feed material extrudates. 相似文献
9.
Chu BS Ichikawa S Kanafusa S Nakajima M 《Journal of agricultural and food chemistry》2007,55(16):6754-6760
This work demonstrated the preparation of protein-stabilized beta-carotene nanodispersions using the solvent displacement technique. The emulsifying performance of sodium caseinate (SC), whey protein concentrate (WPC), whey protein isolate (WPI), and a whey protein hydrolysate (WPH, 18% degree of hydrolysis) was compared in terms of particle size and zeta-potential of the nanodispersions. SC-stabilized nanodispersions exhibited a bimodal particle size distribution: large particles (stabilized by casein micelles) with a mean particle size of 171 nm and small particles (stabilized by casein submicelles) of 13 nm. This was confirmed with transmission electron microscopy analysis. Most of the beta-carotene precipitated (87.6%) was stabilized in the small particles. On the other hand, the nanodispersions stabilized by the whey proteins were polydispersed with larger mean particle sizes. The mean particle size of WPC and WPI was 1730 and 201 nm, respectively. The SC-stabilized nanodispersion was expected to be more stable as indicated by its higher absolute zeta-potential value (-31 mV) compared to that of WPC (-15 mV) and WPI (-16 mV). Partially hydrolyzed whey protein possessed improved emulsifying properties as shown by WPH-stabilized samples. It was interesting to note that increasing the SC concentration from 0.05 to 0.5 wt % increased the particle size of beta-carotene stabilized by casein micelles, while the reverse was true for those stabilized by SC submicelles. Microfluidization at 100 MPa of SC solution dissociated the casein micelles, resulting in a decrease in mean particle size of the casein micelle-stabilized particles when the SC solution was used to prepare nanodispersions. The results from this work showed that protein-stabilized beta-carotene nanodispersions could be prepared using the solvent displacement technique. 相似文献
10.
研究了5种模拟糙度和6种不同冲刷距离组合下3种粒径的红壤团聚体在集中水流内的剥蚀破坏规律,分析了糙度、运移距离以及相关水力学参数对团聚体剥蚀破坏的影响。结果表明,在相同运移距离条件下,随粒径和糙度的增加团聚体剥蚀破坏程度呈增加趋势,与粒径相比,糙度对剥蚀破坏程度的影响更大。相同模拟糙度下,随着运移距离的增加,剥蚀率均呈抛物线形先增大后减小的趋势;各运移距离下,7~5 mm粒径团聚体的剥蚀率随糙度的增加而增加;5~3 mm和3~1 mm粒径团聚体在各运移距离内随糙度的增加变化规律不一致。在不同糙度情况下,以运移距离等于36 m为例,团聚体与原始团聚体质量比(Wr/Wi)随径流水深、阻力系数、水流剪切力的增加均呈幂函数减小之后趋于平缓的趋势。该结果为研究红壤团聚体破碎理论机制提供了参考,对于完善土壤侵蚀过程模型,具有重要的理论意义。 相似文献
11.
Aleksandra Bawiec Katarzyna Pawęska Krzysztof Pulikowski 《Water, air, and soil pollution》2017,228(9):366
The aim of the study was to determine the changes in suspension particle size identified in biologically treated wastewater, which was then treated in hydroponic system with use of engineering lighting by the light-emitting diodes (LED). The study was subjected to wastewater purified under laboratory conditions, in a hydroponic system using the effect of macrophytes Pistia stratiotes and growing algae. Measurement of particle size was made using a laser granulometer. Analysis of the results showed that the additional lighting of the hydroponic system with LED can significantly influence the ability of the suspension particles to agglomerate and, consequently, determine their sedimentation properties. In hydroponic system supported by additional lighting, more particles were observed with equivalent diameter D(3.2) smaller than 10 μm than those in the tank without additional lighting, indicating a higher reactivity of the particles. Determining the size of equivalent diameters D(4.3) allowed us to observe that in hydroponic system, particles of relatively small size predominate, which negatively affects the sedimentation process of the suspensions. Determination of particle size of suspensions consisting mainly of algae and the dynamics of their changes are the basis for specification of an effective method of removing particles from the system to protect the receiver from excessive suspension concentrations. 相似文献
12.
The effect of the particle size of halloysite on the deflocculation of mutual floes of allophane and halloysite in the presence of anionic xanthan polysaccharide was investigated spectrophotometrically. Although allophane which flocculated at the i.e.p. (pH 6.5) exhibited polymeric (i) weak-stabilization (PWST), (li) flocculation (PFL), and (iii) stabilization (PST) with increasing addition of xanthan, allophane and halloysite which flocculated mutually at pH 6.5 inhibited the deflocculation, viz., PWST and PST. Halloysite with a smaller average particle size (i.e., 0.08,um in average diameter) than the suspended microaggregates (SMAs) of allophane inhibited significantly the deflocculation, suggesting that the halloysite particles flocculated around the allophane particles. Halloysite with a larger average particle size (i.e., 0.2 μn in average diameter) than the SMAs of allophane slightly inhibited the deflocculation, suggesting that the halloysite particles were attached to the center of the flocculated SMAs of allophane. The inhibitory effects of particle arrangements on the deflocculation of the mutual floes of allophane-montmorillonite and allophanekaolinite were also investigated comparatively. 相似文献
13.
The use of tile drains for subsurface drainage in agricultural watersheds It as created concern for the delivery of sediment to receiving waters and potential undesirable effects on surface and subsurface water quality. In this study, transport characteristics of sediment from the drains in an agricultural watershed of the Thames River, near Kintore, Ontario, Canada were tested in a 5 m diameter. rotating circular flume located at the National Water Research Institute in Burlington. Ontario. Tile drain sediments were collected and mixed with river water at different speeds in the flume to study transport processes such as deposition, erosion and flocculation as a function of bed shear stress. During deposition and erosion experiments. water samples were collected to detennine changes in the concentrations of rations, anions and dissolved organic carbon. The results show that tile drain sediments have a tendency to flocculate when subjected to a range of shear stresses. The median diameter (D50) of the floc size distribution reached a maximum value at a shear stress of 0.169 Nn2 which can be considered an optimum shear stress for flocculation for this sediment. The critical shear stress at which all of the initially suspended sediment deposited to the flume bed was measured as 0.056 Nm2. The pH and cation concentrations remained relatively constant during erosion and deposition experiments. Anion concentrations were more variable, most likely due to the presence of bacteria which could have also played a role in the flocculation mechanism oftile drain sediment. 相似文献
14.
生物炭颗粒在饱和多孔介质中的迁移与滞留 总被引：2，自引：0，他引：2
生物炭在实际生产实践中具有许多潜在的农业和环境效益,因此受到了越来越多的关注。生物炭在多孔介质中的迁移不仅会影响它在土壤中的归趋,还可能会影响微生物群体及土壤有机质的动态变化以及被吸附的污染物对环境的影响。实验通过柱实验研究了微米级生物炭颗粒在饱和多孔介质中的迁移和滞留特性,主要选取了四种影响生物炭迁移的潜在因素:原材料、裂解温度、背景溶液pH值和离子强度。实验结果显示微米级生物炭在饱和多孔介质中具有一定的迁移能力,但是大部分的微米级生物炭会滞留在饱和多孔介质的表面和孔隙间。生物炭的制备原材料对于生物炭的表面电势特性有较大影响,从而影响了微米级生物炭在饱和多孔介质中的迁移能力。热解温度越高,生物炭的表面电势越大,迁移能力越弱。随着背景溶液离子强度增加和pH值减小,微米级生物炭颗粒在多孔介质中滞留增加,迁移能力减弱。 相似文献
15.
煤矸石自然风化及人工模拟风化过程中盐分及pH值的动态变化——以平朔露天矿区为例 总被引：2，自引：0，他引：2
为揭示煤矸石初期物理崩解风化过程中盐分和pH值的动态变化规律,选择了山西平朔露天矿区17处暴露地表自然风化5年和14年粒径为0.1～10.0mm的风化煤矸石,以及经过人工破碎粒径也为0.1～10.0mm的新鲜煤矸石为对比材料。研究结果表明:自然风化14年左右的煤矸石全盐量高于风化5年左右的煤矸石。自然风化煤矸石pH值的变化幅度为6.55～9.20,人工破碎新鲜煤矸石的pH值为7.26～7.95。人工破碎新鲜煤矸石30min、48h、96h浸水试验结果表明,同一浸泡时间含盐量随着粒径缩小而升高,同一粒径随着浸泡时间的延长而变大;同一浸泡时间pH值随着粒径缩小而降低,同一粒径随着浸泡时间的延长也变大;风化煤矸石的pH值和全盐含量>新鲜煤矸石。 相似文献
16.
Direct Quantitative Analysis of Particulate Aluminum Suspended in Water Using Laser-Induced Breakdown Spectroscopy 总被引：1，自引：0，他引：1
Noriko Yamaguchi Hiroyasu Hotokezaka Shinya Nagasaki Satoru Tanaka 《Soil Science and Plant Nutrition》2005,51(6):911-916
Laser-induced breakdown spectroscopy (LIBS) has been developed as a rapid and easy in situ technique for the analysis of inorganic elements. Qualitative and quantitative determinations of an inorganic element can be achieved by analyzing the wavelength and intensity of the light emitted from the excited atoms arising from breakdown phenomena. Because the energy threshold of breakdown phenomena increases in the order of solid相似文献
17.
揭示降雨作用下坡面红土起动的影响因素,建立降雨作用下坡面红土起动条件,为深入研究云南红土坡面侵蚀提供参考。根据红土特性,结合降雨作用下坡面红土的侵蚀过程和现象,采用模型试验及力学模型相结合的研究方法。结果表明:(1)降雨作用下坡面红土侵蚀主要呈现溅蚀和结皮2种现象。(2)红土黏聚力对坡面红土颗粒起动有阻碍作用,且抗剪强度越大,坡面红土颗粒起动的临界切应力也越大。降雨及孔隙水压力对坡面红土颗粒起动有促进作用,且雨滴密度与雨滴终速越大,降雨的影响也越大;红土颗粒粒径越大、雨滴直径与水深之比越小,降雨的影响也越小。(3)建立了坡面红土颗粒在联结和松散状态下起动的临界切应力计算公式。降雨作用下坡面红土颗粒起动的临界切应力与红土颗粒粒径大小、抗剪强度以及降雨雨滴特性、坡面径流特性密切相关。松散状态的坡面红土颗粒在降雨作用下只需很小的径流切应力即可起动。 相似文献
18.
The polymeric effect of gum xanthan (GX) on the stability of allophane at pH 4.5 and 6.5 was compared with the effect of several of its hydrolytic intermediates (hGX). The polymeric effect of GX was manifested by (i) the effective flocculation at low GX concentrations, (ii) the higher stabilizing ability above the flocculation concentration (FC), and (iii) the appreciable ability of deflocculation of (a) flocculated allophane and (b) allophane-halloysite floc, at extremely low concentrations of GX solution at pH 6.5. In contrast to GX, in the presence of sodium polyacrylate, there was a complete lack of deflocculation of the flocculated allophane at pH 6.5. This fact suggests that effective deflocculation is due to the double-stranded wormlike structure of the GX chain with a small but finite flexibility. The fact that flocculated allophane by GX at pH 4.5 still exhibited a positive electrophoretic mobility can be ascribed to the flocculation of allophane particles by bridging with this biopolymer. The relationship between FC of GX and the allophane content in soil clays was also examined. 相似文献
19.
A hard white spring wheat was milled to yield three patent flours with different starch damage levels by manipulating reduction grinding conditions, and each flour was sieved to give three different particle sizes (85–110, 110–132, 132–183 μm). Raw alkaline noodles were prepared using either 1% w/w kansui (sodium and potassium carbonates in 9:1 ratio) or 1% w/w sodium hydroxide. Noodles prepared with sodium hydroxide were significantly brighter, less red, and more yellow than those made with kansui. Differences in noodle color among flour treatments were evident but were attributable to differences in flour refinement rather to than particle size or starch damage. Noodles were rested for 1 hr after processing before cooking. Alkaline reagent was the main factor associated with cooking loss, being ≈50% greater for sodium hydroxide noodles because of higher pH compared with kansui noodles. Cooked sodium hydroxide noodles were thicker than kansui noodles, and cooked strands for both noodle types became thicker as starch damage increased and as particle size became coarser. Instrumental assessment of cooked noodle texture showed that maximum cutting stress (MCS), resistance to compression (RTC), recovery (REC), stress relaxation time (SRT), chewiness (CHE), and springiness (SPR) were influenced by the type of alkaline reagent. Flour particle size and starch damage also influenced noodle texture but the magnitude of the effects and the trends were dependent on alkaline reagent. MCS of kansui noodles was much greater than for sodium hydroxide noodles. MCS of kansui noodles increased as starch damage increased but, in contrast, MCS of sodium hydroxide noodles decreased with increasing starch damage. REC of kansui noodles increased with increasing starch damage and decreased with larger particle size, whereas for sodium hydroxide noodles REC decreased with increasing starch damage and declined dramatically with larger particle size. Kansui noodles exhibited significantly shorter SRT than sodium hydroxide noodles. SRT of kansui noodles was only moderately affected by starch damage and particle size, whereas for sodium hydroxide noodles, SRT became much shorter as flour became coarser and starch damage became higher. CHE of kansui noodles was greater than for sodium hydroxide noodles. CHE of kansui noodles increased as starch damage increased. In contrast, CHE of sodium hydroxide noodles decreased as starch damage increased and also decreased as flour became coarser. SPR of both noodle types decreased as flour became coarser and starch damage became greater. On the basis of these experiments, flour of smaller particle size is an asset to the cooking quality of sodium hydroxide noodles, but high starch damage is to be avoided. For kansui noodles, the impact of flour particle size on cooked noodle texture was less evident and low starch damage, rather than high starch damage, was an asset. 相似文献
20.
Aisha Mhashhash Bettina Bockelmann-Evans Shunqi Pan 《Journal of Soils and Sediments》2018,18(10):3094-3103