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1.
影响反胶束体系萃取蛋白能力的因素及机理 总被引：4，自引：0，他引：4
该文对影响二-（2-乙基已基）琥珀酸酯磺酸钠（AOT）反胶束萃取蛋白能力的因素与机理进行了研究,可以用来解释AOT/异辛烷反胶束溶液分离萃取蛋白与油脂时,萃取率变化的原因,进一步了解反胶束分离萃取蛋白质分子的机理。试验结果表明随着反胶束体系中黏度增加,微乳液增溶水量即水的物质的量与表面活性剂物质的量之比（W0）增大时,使得反胶束萃取蛋白质与油脂的能力增强,从而使萃取率升高。根据Gibbs吸附公式,得出AOT浓度在0.08 g/mL时,反胶束液具有较高的界面活性,W0值也较大,有利于提取蛋白质。利用荧光光谱法和电导法研究AOT反胶束体系的结构,可知W0为11～14时,AOT浓度大于0.06 g/mL,反胶束体系较稳定,该体系是由渗透型和非渗透型的结合,从而可以了解反胶束体系的相行为变化。 相似文献
2.
用Aspen Plus模拟反胶束萃取大豆蛋白过程中毛油脱溶操作 总被引：1，自引：1，他引：0
利用反胶束技术萃取大豆蛋白的同时可以提取出大豆毛油,但毛油中含有有机溶剂,它们可以循环回收利用。在工业生产中,为了获得回收有机溶剂所用脱溶操作的相关工艺参数,该文基于Aspen Plus11.1软件模拟了反胶束萃取大豆蛋白过程中毛油的脱溶操作。利用Aspen Plus模块化分析功能,对油脂和溶剂的纯度、精馏塔的塔板数、再沸器和冷凝器的热负荷进行了分析,结果显示:减压蒸馏的回流比为0.352,塔顶馏出物流量为10.348kg/h时,油脂和溶剂的纯度分别可以达到98.9%和99.7%,此时再沸器和冷凝器的实际热负荷分别为1398.824W和1626.226W。灵敏度分析模块显示:随着塔板数的增加,油脂和溶剂的浓度分别增大,并确定了最佳塔板数为5。在模拟计算的基础上,进行成本分析,每年可节约成本127.2万元,并初步探讨了工业化装置设计的技术关键点,以期为工业设计放大脱溶装置提供可靠的数据。 相似文献
3.
没食子酸烷基酯是一类优良的抗氧化剂，具有潜在的药用价值。为了避免化学合成方法带来的弊端，建立了生物合成没食子酸烷基酯的方法。利用单宁酶在有机相可成功地催化没食子酸烷基酯的合成。在合成没食子酸丙酯(PG)、没食子酸丁酯(BG)和没食子酸戊酯(AG)的反胶束(reverse micelle, RM)催化合成体系中，反胶束组成为双(2-乙基己基)磺基琥珀酰钠(AOT)、异辛烷和水。单宁酶浓度为0.6 mg/mL；pH值为6； W0(水与表面活性剂的摩尔比)分别为15、15和12.5；反应温度分别为30、40和45℃；AOT浓度分别为0.1、0.2和0.2 mol/L时，没食子酸转化率分别为87.4%、90.3%和92.5%。3个体系中由于底物脂肪醇的不同，致使各种因素对单宁酶催化活力的影响不同。 相似文献
4.
盐效应辅助水相萃取油茶籽油的工艺 总被引：6，自引：4，他引：2
为克服油脂水相萃取时乳化严重而清油得率低的问题,采取了盐效应辅助水相萃取油茶籽油的新工艺。以碳酸钠溶液为萃取剂,考察液料比、提取时间、提取温度和振荡速度对油茶籽油清油得率的影响,并采用Box-Behnken试验设计对主要影响因素进行了优化,得到利用碳酸钠的盐效应水相萃取油茶籽油的优化工艺参数为：液料比为3.39 mL/g,提取时间1 h,提取温度65℃,震荡速度140 r/min。在该最优条件下,油茶籽油清油得率可达96.33%。由此说明,盐效应可明显防止油茶籽油水相萃取时乳液的形成,显著提高其清油得率,同时也为提高其他油脂水相萃取时的清油得率提供了一种新思路。 相似文献
5.
寒区多年冻土斜坡内部存在的下卧冰层对多年冻土斜坡稳定有着重要影响。为探究冰-冻土界面力学特性对斜坡稳定的影响,该研究以冰-冻土界面为研究对象,在低温环境（-3℃）下开展了不同冻土初始孔隙比和含水率下的冰-冻土界面及对应的冰-土颗粒界面直接剪切试验,建立了考虑冰晶胶结特性的冰-冻土界面非线性弹性损伤模型,结合试验结果对模型进行了验证,并分析了界面在剪切过程中切线刚度的变化规律。结果表明：冰-土颗粒界面的剪切应力表现为应变硬化特性,而冰-冻土界面的剪应力在峰值强度之后迅速下降,表现为应变软化特性。冰-冻土界面结构系数峰值点对应的剪切位移随着含水率的增大而增大,当冻土初始孔隙比为1.0、0.8和0.6,冻土初始含水率从14%增大至18%时剪切位移分别增大了32.7%、41.3%和52.1%。在-3℃下,冻土的初始含水率越大,则界面处的胶结冰越多,黏聚强度对界面的抗剪强度贡献也就越大。当结构系数达峰值点后,界面开始产生损伤,并随着剪切位移的增加进入加速损伤阶段。剪切过程中界面的切线刚度呈先增大后减小的趋势,在结构系数峰值点处为0,之后切线刚度随着剪切位移的增加逐渐减小。此外,界面的峰值切线刚度随着法向应力的增大而增大,当冻土初始孔隙比1.0、初始含水率为18%,法向应力从50 kPa增大至200 kPa时,则界面的峰值切线刚度增加了63.7%。在冰-冻土界面力学模型中考虑冰晶胶结特性更加合理,研究结果可为寒区斜坡稳定性分析提供参考。 相似文献
6.
7.
利用反胶束技术萃取大豆蛋白的同时可以提取出大豆毛油,但毛油中含有有机溶剂,它们可以循环回收利用。在工业生产中,为了获得回收有机溶剂所用脱溶操作的相关工艺参数,该文基于Aspen Plus 11.1软件模拟了反胶束萃取大豆蛋白过程中毛油的脱溶操作。利用Aspen Plus模块化分析功能,对油脂和溶剂的纯度、精馏塔的塔板数、再沸器和冷凝器的热负荷进行了分析,结果显示：减压蒸馏的回流比为0.352,塔顶馏出物流量为10.348 kg/h时,油脂和溶剂的纯度分别可以达到98.9%和99.7%,此时再沸器和冷凝器的实际热负荷分别为1 398.824W和?1 626.226 W。灵敏度分析模块显示：随着塔板数的增加,油脂和溶剂的浓度分别增大,并确定了最佳塔板数为5。在模拟计算的基础上,进行成本分析,每年可节约成本127.2万元,并初步探讨了工业化装置设计的技术关键点,以期为工业设计放大脱溶装置提供可靠的数据。 相似文献
8.
氢自养反硝化修复地下水中的硝酸盐污染以其清洁、环保又经济而受到广泛重视。利用全自动恒温振荡仪,以NaHCO3为碳源驯化氢自养反硝化细菌,并对影响氢自养反硝化速率的因素进行了研究。结果表明,以NaHCO3作为唯一的无机碳源,不仅可以高效驯化氢自养反硝化细菌,而且可以控制体系的pH值,效果优于单独以CO2或以CO2和NaHCO3共同为碳源的系统;当单独以NaHCO3为碳源时,其浓度为2g·L-1时可以满足氢自养反硝化细菌的生长,并使体系pH保持在8.5±0.2;当初始NO3--N浓度〈135.6mg·L-1时,反硝化速率随着NO3--N浓度的升高而增大,当NO3--N浓度过高时（〉135.6mg·L-1）,会抑制氢自养反硝化的进行;当pH在6.0～9.0时,氢自养反硝化可以进行,但其最适pH为7.0～8.0,而当pH〈6.0或pH〉9.0时,反硝化基本停滞;温度为35℃时反硝化速率最大,为2.83mg·L-·1h-1,当温度为15℃时,有明显的亚硝酸盐积累。 相似文献
9.
设施菜田土壤pH和初始C/NO3– 对反硝化产物比的影响 总被引：1，自引：0，他引：1
10.
包气带土体反硝化作用对NO3^—转化的试验研究 总被引：2，自引：0，他引：2
就河北平原山前地区包气带土体中的氮素循环转化及污染地下水的过程、包气带土体中反硝化细菌对硝酸盐转化的作用强度进行了试验研究。结果表明，生物反硝化作用是土壤包气带氮素转化的主要作用之一。该区包气带土体中由于有机物较少并随深度增加而减少，因此对NO3^-细菌的反硝化作用强度也随深度加大而减弱，从而造成包气带土体中硝酸盐积累，进而污染地下水。如对包气带的有机碳源加以调控，可阻止地下水的污染。 相似文献
11.
Ruíz-Henestrosa VP Sanchez CC Rodríguez Patino JM 《Journal of agricultural and food chemistry》2007,55(15):6339-6348
In this contribution, we have analyzed the effect of different strategies, such as change of pH (5 or 7) or ionic strength (at 0.05 and 0.5 M), and addition of sucrose (at 1 M) and Tween 20 (at 1 x 10(-4) M) on interfacial characteristics (adsorption, structure, dynamics of adsorption, and surface dilatational properties) and foam properties (foam capacity and stability) of soy globulins (7S and 11S at 0.1 wt %). We have observed that (1) the adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depends on the modification in the 11S/7S ratio and on the level of association/dissociation of these proteins by varying the pH and ionic strength (I), the effect of sucrose on the unfolding of the protein, and the competitive adsorption between protein and Tween 20 in the aqueous phase. The rate of adsorption increases at pH 7, at high ionic strength, and in the presence of sucrose. (2) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior but do not have the capacity to form a gel-like elastic film. The surface dilatational modulus increases at pH 7 and at high ionic strength but decreases with the addition of sucrose or Tween 20 into the aqueous phase. (3) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface plays an important role in the formation of foams generated from aqueous solutions of soy globulins. However, the dynamic surface pressure and dilatational modulus are not enough to explain the stability of the foam. 相似文献
12.
Ruíz-Henestrosa VP Sánchez CC Rodríguez Patino JM 《Journal of agricultural and food chemistry》2008,56(7):2512-2521
In this contribution, we have analyzed the effect of sucrose on dynamic interfacial (dynamic surface pressure and surface dilatational properties) and foaming (foam capacity and foam stability) characteristics of soy globulins (7S and 11S). The protein (at 1 x 10(-3), 1 x 10(-2), 0.1, and 1 wt %) and sucrose (at 0, 0.25, 0.5, and 1.0 M) concentrations in aqueous solution and the pH (at 5 and 7), and ionic strength (at 0.05 and 0.5 M) were analyzed as variables. The temperature was maintained constant at 20 degrees C. We have observed the following. (i) The dynamics of adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depend on the peculiar molecular features of proteins (7S or 11S soy globulin) and the level of association/dissociation of these proteins by varying the pH and ionic strength, as well as the effect of sucrose in the aqueous phase on the unfolding of the protein. The rate of adsorption increases with the protein concentration in solution, at pH 7 compared to pH 5, at high ionic strength, and in the absence of sucrose. (ii) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior. The surface dilatational modulus increases at pH 7 compared to pH 5, but decreases with the addition of sucrose into the aqueous phase. (iii) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface play an important role in the formation of foams generated from aqueous solutions of soy globulins. (iv) The increased interfacial adsorption (at high surface pressures) and the combined effects of interfacial adsorption and interfacial interactions between adsorbed soy globulin molecules (at high surface dilatational modulus) can explain the higher stability of the foam, with few exceptions. 相似文献
13.
Seuvre AM Espinosa Diaz MA Voilley A 《Journal of agricultural and food chemistry》2002,50(5):1106-1110
The transfer kinetics of aroma compounds from the aqueous phase to the lipidic phase (miglyol) and from miglyol to the aqueous phase have been studied in the presence or absence of a protein, beta-lactoglobulin, and at different pH values. In the presence of beta-lactoglobulin, the transfer at the interface from the aqueous to the lipidic phase decreases, with a greater effect of the presence of the protein at pH 3 than at pH 6. This barrier effect of the protein plays a role in the transfer of the aroma compounds between the different phases of the matrix. 相似文献
14.
Rogacheva S Espinosa-Diaz MA Voilley A 《Journal of agricultural and food chemistry》1999,47(1):259-263
Interactions of volatile aroma compounds with protein in aqueous solutions, especially whey proteins, have received significant attention in recent years. This work attempts to improve our understanding of the mass transfer in multiphasic systems, such as emulsions at the lipid-water interface, and to reveal the role of beta-lactoglobulin in the release rate of solutes. For this purpose the rotating diffusion cell has been used. From a practical point of view it enables evaluation of the transfer through the aqueous phase, through the oil and the interfacial transfer. The effect of beta-lactoglobulin, medium pH, and solute concentration has been investigated. Benzaldehyde and 2-nonanone have been studied, and miglyol has been chosen as an oil phase. It has been demonstrated that mass transfer has a rate-limiting step, which depends on physicochemical parameters such as hydrophobicity of the volatile, diffusion and partition coefficients, and rheological properties of the aqueous phase. 相似文献
15.
Cao Y Xing H Yang Q Bao Z Su B Yang Y Ren Q 《Journal of agricultural and food chemistry》2012,60(13):3432-3440
The separation of a compound of interest from its structurally similar homologues is an important and challenging problem in producing high-purity natural products, such as the separation of genistein from other soybean isoflavone aglycone (SIA) homologues. The present work provided a novel method for separating genistein from its structurally similar homologues by ionic liquid (IL)-based liquid-liquid extraction using hydrophobic IL-water or hydrophilic IL/water-ethyl acetate biphasic systems. Factors that influence the distribution equilibrium of SIAs, including the structure and concentration of IL, pH value of the aqueous phase, and temperature, were investigated. Adequate distribution coefficients and selectivities over 7.0 were achieved with hydrophilic IL/water-ethyl acetate biphasic system. Through a laboratory-scale simulation of fractional extraction process containing four extraction stages and four scrubbing stages, genistein was separated from the SIA homologues with a purity of 95.3% and a recovery >90%. 相似文献
16.
《Communications in Soil Science and Plant Analysis》2012,43(9):999-1007
Abstract Cation exchange capacity (CEC) of the 0–5 cm depth of forest soils increased with the square root of solution ionic strength over the experimental range of 6 to 96 mM. Percentage increases in CEC were positively correlated with percentage organic carbon; for mixed hardwood forest soils, increases were 38% for soils with 3.3% carbon, and 105% for soils with 7.4% carbon when ionic strength was varied over the full experimental range. When analyzing soils with constant‐potential surfaces, both pH and ionic strength must be controlled, preferably at or near levels found in the field, in order to provide interpretable measures of CEC. 相似文献
17.
Mohamed Salleh MR Maruyama N Adachi M Hontani N Saka S Kato N Ohkawa Y Utsumi S 《Journal of agricultural and food chemistry》2002,50(25):7380-7385
Rapeseeds contain cruciferin (11S globulin), napin (2S albumin), and oleosin (oil body protein) as major seed proteins. The effects of oil expression and drying conditions on the extraction of these proteins from rapeseed meal were examined. The conditions strongly affected the extraction of oleosin and only weakly affected the extraction of cruciferin and napin. The protein chemical and physicochemical properties of cruciferin, the major protein present, were compared with those of glycinin (soybean 11S globulin) under various conditions. In general, cruciferin exhibited higher surface hydrophobicity, lower thermal stability, and lower and higher solubility at mu= 0.5 and mu = 0.08, respectively, than did glycinin. At the pHs (6.0, 7.6, and 9.0) and ionic strengths (mu= 0.08 and 0.5) examined, the emulsifying ability of cruciferin was worse than that of glycinin, except at mu= 0.08 and pH 7.6. The emulsifying abilities of cruciferin and glycinin did not correlate with thermal stability and surface hydrophobicity. Higher protein concentration, higher heating temperature, higher pH, and lower ionic strength were observed to produce harder gels from cruciferin. Gel hardness partly correlated with the structural stability of cruciferin. 相似文献
18.
Martijn P. J. Smit Tim Grotenhuis Harry Bruning Wim H. Rulkens 《Journal of Soils and Sediments》2008,8(2):80-85
Background, Aim and Scope
With the predicted climate change, it is expected that the chances of flooding may increase. During flood events, sediments will resuspend and when the sediments are polluted, contaminants can be transferred to the surrounding water. Mass transfer of organic compounds like Persistent Organic Pollutants (POPs) from soils and sediments to the surrounding aqueous phase are essential regarding fate and transport of these chemicals in the aqueous environment. The distribution of POPs between sorbed and aqueous phases and the time needed to obtain equilibrium are required to calculate the exposure to potential receptors. A reactor was designed in which the water flow is controlled and low POP concentrations could be measured by tenax extraction outside the reactor vessel. This reactor design named SPEED (Solid Phase Extraction with External Desorption) was used to study desorption from aged contaminated sediment in relation to sediment particle size.Materials and Methods
In the newly developed SPEED (Solid Phase Extraction with External Desorption) reactor, the water flow rate was set and controlled, and low aqueous POP concentrations were measured by sorption to Tenax® outside the reaction vessel. The effect of particle size on desorption rate was studied using a widely used Tenax® solid phase extraction method.Results
The experiments, by specific measurement of the aqueous dieldrin concentration at different HRT, show that desorption of dieldrin in time is faster when short HRTs were applied. However, the mass of dieldrin desorbed per liter refreshed water is higher for longer HRTs. Therefore, the mass transfer of dieldrin within the sediment particles is the rate determining process in contaminant desorption. This observation was confirmed by Tenax® solid phase extractions which were applied for different particle size fractions. Desorption rates of POPs from the sediment fraction with small particles were faster than desorption rates from the sediment fraction with large particles. Organic matter was present as separate particles in the sediment sample. All experiments demonstrated biphasic desorption. The fluxes calculated for both phases are supportive of non-stationary diffusion as the main process of mass transfer.Discussion
In the literature, the relation between particle size and desorption of organic contaminants from soils and sediments is contradictory. Most often this seems to be due to overlooking the spatial configuration of organic matter in the soils and sediments. In several papers the presence of organic matter as a thin coating around mineral particles has been overlooked. There-fore, milling had no effect on desorption behavior of contaminants, as the diffusion length will not be affected. In our opinion, both the particle size and spatial configuration of organic matter are rate determining parameters of the desorption process.Conclusions
Flood events will result in an increase of desorption rate of POPs from sediments to the surrounding water. HRT and particle size determine the concentration gradient and, thereby, the desorption rate. Furthermore, the diffusion length will be smaller when sediment particles are suspended and more water is present to decrease the aqueous concentration. We conclude that non-stationary diffusion within organic matter is the main process of mass transfer. The combination of simulated in-situ measurements of desorption from sediments with generic measurable parameters like flow rate and particle size distribution results in a quantitative measurable flux of contaminants, which resembles the in-situ (bio)availability as the result of dynamic processes in the sediment/water system.Recommendations and Perspectives
The results obtained provided a sound basis for mechanistic modeling of POP mass transfer from sediment to water. The modeling results will be presented in a separate paper. Besides the HRT, also mixing conditions can be changed to assess the desorption from sediment layers. The possibility to combine flow rate and mixing intensity enables the study of the effect of hydraulically different river systems on desorption of contaminants. In a long term perspective we foresee a link with hydrology and sediment transport with desorption in water bodies. 相似文献19.
Yugao Guo Xia Liu Yelin Han Xihui Bian Qingyin Zhang 《Water, air, and soil pollution》2017,228(8):317
An efficient and stable preconcentration method for ionic and ionizable analytes, named radical electric focusing solid phase extraction (REFSPE), was proposed here for enriching trace Cu(II), Ni(II), and Co(II) from water samples. In REFSPE, radical electric field was introduced into solid phase extraction system to enhance the mass transfer rate of heavy metal ions in aqueous solution and shorten the extraction time obviously. The concentration of mixed heavy metal ions were predicted using partial least squares (PLS) regression by analyzing ultraviolet and visible spectrum efficiently. By optimizing chromogenic agent, pH values, extraction voltage, extraction time, and PLS parameters, the proposed method had higher figures of merit. The comparison of the determination data and the calculation results showed that the proposed method can provide a favorite quantitative precision with expanded measuring range. The limit of detection (LOD) for Cu(II), Ni(II), and Co(II) were 0.10, 0.13, and 0.15 μg L?1, respectively. The reliability was confirmed by the RSD lower than 5% and the recovery of 95–102%. The novel enrichment method has a great potential for applications in detecting different ionic and ionizable analytes with the help of spectrometry determination and chemometrics calculation. 相似文献
20.
Puls Robert W. Powell Robert M. Clark Donald Eldred Cynthia J. 《Water, air, and soil pollution》1991,57(1):423-430
Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal concentration, kaolinite concentration and time. The organic acids used were p-hydroxybenzoic acid, o-toluic acid, and 2,4-dinitrophenol. Titrations were used to derive previously unavailable aqueous conditional stability constants for the organometallic complexes. Batch results showed that aqueous lead-organic complexation reduced sorption of Pb by kaolinite. Cadmium behavior was similar, except for 2,4-dinitrophenol, where Cd sorption was increased. Metal sorption increased with increasing pH and decreasing ionic strength. Distribution ratios (K d 's) decreased with increasing solid/solution ratio. The subsurface transport of lead and cadmium may be enhanced via complex interactions with organic wastes or their degradation products and sorbent mineral surfaces.
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