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1.
McClements DJ 《Journal of agricultural and food chemistry》2000,48(11):5604-5611
Isothermal titration calorimetry (ITC) was used to measure enthalpy changes resulting from injection of anionic (sodium dodecyl sulfate, SDS) or cationic (dodecyl trimethylammonium bromide, DTAB) surfactants into aqueous 1 wt % pectin solutions (30, 60, or 90% methoxylated). In the absence of pectin, the critical micelle concentrations (cmc) determined by ITC were 14.7 mM for DTAB and 7.7 mM for SDS. Binding of DTAB to pectin was endothermic and was attributed to electrostatic attraction between the cationic surfactant and anionic biopolymer. Binding of SDS to pectin was exothermic and was attributed to hydrophobic interactions. Pectin reduced the cmc of SDS, probably because of long-range electrostatic repulsion between the molecules. Above a particular concentration, which depended on pectin and surfactant type, both ionic surfactants promoted pectin aggregation (monitored by turbidity increase). This study demonstrates the potential of ITC for providing valuable information about interactions between polysaccharides and amphiphiles. 相似文献
2.
Pentachlorophenol (PCP) adsorption and desorption equilibrium was studied with two Menfro silt loam soils — upper horizon and lower horizon. For the adsorption studies the variables were: temperature (10 and 30 °C) and the amount of organic matter. The variables for the desorption studies were: temperature (10 and 30 °C), pH and the presence of an anionic and a cationic surfactant. The results from these studies confirmed the importance of soil organic matter for adsorption of PCP on the soils. The adsorption data at different temperatures indicated the physical nature of the adsorption process. The desorption data produced non-singularity and some PCP was irreversibly adsorbed onto the soil despite repeated washings. Increased pH increased the desorption of PCP from the soil. The anionic surfactant, sodium dodecylbenzene sulfonate (SDS) was able to desorb significant amounts of PCP from the soil at doses equal to critical micelle concentration (CMC). But, the nonionic surfactant, surfactant, Triton X-405 required a much higher dose (twice the CMC) to cause a significant desorption of PCP from the soil. 相似文献
3.
The binding processes of thearubigin, which is one of the two major polyphenols (the other one is theaflavin) that gives black tea its characteristic color and taste, to the bovine serum albumin (BSA) surface have been investigated by quartz crystal microbalance with dissipation monitoring (QCM-D). The mass and thickness of the thearubigin adlayer on BSA surfaces at various thearubigin concentrations, salt concentrations, and pH values have been determined by QCM-D using the Voigt model. Our results show that the adsorption isotherm of thearubigin on the BSA surface can be better described by the Langmuir model than the Freundlich model, suggesting that the thearubigin adsorption on the BSA surface is dominated by specific interactions, such as electrostatic interaction and hydrogen bonding, as evidenced by the stronger thearubigin adsorption at pH below the isoelectric point (pI) of BSA and shifts in the positions of both amide bands in the FTIR spectra of the BSA surface with and without thearubigin adsorption. The addition of salt can also influence the thearubigin binding to BSA surfaces. The salt concentration-enhanced effect at a salt concentration lower than 0.1 M is explained as that an increase of salt concentration can screen the electrostatic repulsion to a larger extent than the electrostatic attraction between thearubigin and BSA. On the other hand, when the salt concentration is higher than 0.1 M, both electrostatic repulsion and attraction can be significantly screened by the higher salt concentration, resulting in the salt concentration-reduced effect. However, when the salt concentration is further increased to 0.4 M, the addition of thearubigin may promote the formation of a certain type of complex with BSA, resulting in the increases of both thickness and mass of the thearubigin adlayer. 相似文献
4.
Removal of Nickel by Means of Micellar-Enhanced Ultrafiltration (MEUF) Using Two Anionic Surfactants
Encarnacion Samper Manuel Rodríguez Irene Sentana Daniel Prats 《Water, air, and soil pollution》2010,208(1-4):5-15
Micellar-enhanced ultrafiltration (MEUF) is an effective separation technique for removing metal ions from aqueous environments. The critical micellar concentration (CMC) of two anionic surfactants, sodium dodecyl sulfate (SDS) and linear alkylbenzene sulfonate (LAS), was determined by means of conductometry. The effects of pH, conductivity, and surfactant concentration on the permeate flow, retention of surfactants and nickel by MEUF, was studied. Results showed that for surfactant concentrations beyond the CMC, Ni(II) retention with SDS was slightly higher than with LAS (S/M?=?45: Ni(II) retention was 70% and 55% for SDS and LAS, respectively). LAS surfactant was always retained in higher quantities than SDS. An increase in conductivity produced large reduction in Ni(II) retention and slightly increased surfactant retention. pH values between 4 and 8 did not affect nickel retention but enhanced the SDS and LAS surfactant retentions. 相似文献
5.
Wangsakan A Chinachoti P McClements DJ 《Journal of agricultural and food chemistry》2001,49(10):5039-5045
Interactions between maltodextrin (DE = 10) and an anionic surfactant (sodium dodecyl sulfate, SDS) were studied in a buffer solution (pH 7.0, 10 mM NaCl, 20 mM Trizma, 30.0 degrees C) using isothermal titration calorimetry (ITC), surface tension, differential scanning calorimetry (DSC), and turbidity techniques. ITC measurements indicated that the binding of SDS to maltodextrin was exothermic and that, on average, one SDS monomer bound per 24 glucose units of maltodextrin at saturation. Surface tension measurements indicated that there was a critical surfactant concentration ( approximately 0.05 mM SDS) below which surfactant and maltodextrin did not interact and that the amount of surfactant bound to the maltodextrin above this concentration increased with increasing maltodextrin concentration. Turbidity measurements indicated that the solutions remained transparent at all maltodextrin (0-1 wt %) and SDS (0-20 mM) concentrations studied, which suggested that phase separation did not occur. DSC measurements indicated that no phase transitions occurred between 10 and 110 degrees C for maltodextrin solutions (0.5 wt %) in the presence or absence of surfactant. A phase diagram was developed to describe the interactions between SDS and maltodextrin. 相似文献
6.
Chitosan is a cationic biopolymer that has many potential applications in the food industry because of its unique nutritional and physiochemical properties. Many of these properties depend on its ability to interact with anionic surface-active molecules, such as phospholipids, surfactants, and bile acids. The purpose of this study was to characterize the interaction between chitosan and a model anionic surfactant (sodium dodecyl sulfate, SDS) using isothermal titration calorimetry (ITC), surfactant-selective electrode (SSE), and turbidity measurements. ITC and SSE indicated that SDS bound strongly to chitosan via a highly exothermic interaction. The turbidity measurements indicated that chitosan formed insoluble complexes with SDS that strongly scattered light. The chitosan bound approximately 4 mM of SDS per 0.1 wt % chitosan before becoming saturated with surfactant. The SDS-chitosan interaction was weakened appreciably by the presence of 100 mM NaCl, which suggested that it was electrostatic in origin. This study provides information about the origin and characteristics of molecular interactions between chitosan and anionic surface-active lipids that may be useful for the rational design of chitosan-based food ingredients with specific nutritional and functional characteristics, e.g., cholesterol lowering or fat replacement. 相似文献
7.
The sorption behavior of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, on marine sediments was systematically investigated. The experimental results showed that 100 min was required for the adsorption equilibrium. For the sediments treated by HCl and H2O, sorption behavior of SDBS was fit with linear isotherm very well over the concentration range studied at 298 K. The sorption occurred primarily due to partition function of hydrophobic chains into organic carbon of sediments. Sorption of SDBS on H2O2-treated sediments was satisfactorily fit with Freundlich isotherm model and mainly through surface function of clay minerals in the sediment. The sorption was favorably influenced by the increased salinity, deceased pH and decreased temperature of seawater. 相似文献
8.
Ziani K Chang Y McLandsborough L McClements DJ 《Journal of agricultural and food chemistry》2011,59(11):6247-6255
Thyme oil-in-water nanoemulsions stabilized by a nonionic surfactant (Tween 80, T80) were prepared as potential antimicrobial delivery systems (pH 4). The nanoemulsions were highly unstable to droplet growth and phase separation, which was attributed to Ostwald ripening due to the relatively high water solubility of thyme oil. Ostwald ripening could be inhibited by incorporating ≥75% of corn oil (a hydrophobic material with a low water solubility) into the nanoemulsion droplets. The electrical characteristics of the droplets in the nanoemulsions were varied by incorporating ionic surfactants with different charges after homogenization: a cationic surfactant (lauric arginate, LAE) or an anionic surfactant (sodium dodecyl sulfate, SDS). The antifungal activity of nanoemulsions containing positive, negative, or neutral thymol droplets was then conducted against four strains of acid-resistant spoilage yeasts: Zygosaccharomyces bailli, Saccharomyces cerevisiae, Brettanomyces bruxellensis, and Brettanomyces naardenensis. The antifungal properties of the three surfactants (T80, LAE, SDS) were also tested in the absence of thymol droplets. Both ionic surfactants showed strong antifungal activity in the absence of thymol droplets, but no antimicrobial activity in their presence. This effect was attributed to partitioning of the antimicrobial surfactant molecules between the oil droplet and microbial surfaces, thereby reducing the effective concentration of active surfactants available to act as antimicrobials. This study shows oil droplets may decrease the efficacy of surfactant-based antimicrobials, which has important consequences for formulating effective antimicrobial agents for utilization in emulsion-based food and beverage products. 相似文献
9.
Kanaji Masakorala Andrew Turner Murray T. Brown 《Water, air, and soil pollution》2011,218(1-4):283-291
The toxicities of three synthetic surfactants to the marine macroalga, Ulva lactuca, have been examined by monitoring chlorophyll a fluorescence quenching. The anionic surfactant, sodium dodecyl sulphate (SDS), exerted no measurable toxicity over the concentration range 0?C10 mg L?1, while presence of the non-ionic surfactant, Triton X-100 (TX), elicited a small reduction in photochemical efficiency that was independent of concentration. The cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA), incurred a dose-dependent response to ??3 mg L?1 (EC50?=?2.4 mg L?1), but a reduction in toxicity thereafter. Presence of TX had little effect on the toxicity of HDTMA but an equimolar concentration of SDS directly offset the impact of HDTMA on photochemical efficiency. Relative toxicities of the surfactants are attributed to differences in affinity for the algal surface and tendencies to disrupt cell membranes and interact with intracellular macromolecules. Non-linear dose responses and antagonistic effects are attributed to non-specific interactions between molecules of the same surfactant and electrostatic interactions between molecules of different amphiphilic character. 相似文献
10.
对 3种可变电荷土壤和 4种恒电荷土壤在陪伴阳离子分别为Na 、K 、NH 4 、Mg2 、Ba2 、Al3 和共存SO2 -4下Cl- 的吸附量进行了测定。结果表明 ,供试土壤的Cl-吸附量顺序均为AlCl3>BaCl2 和MgCl2 >KCl和NH4 Cl>NaCl,其中可变电荷土壤的差异较大。不同电解质溶液中Cl- 吸附量的顺序与土壤所带正电荷量的顺序一致。Langmuir方程的K值较小 ,且在不同介质中的差异不大。随SO2 -4浓度的增大 ,可变电荷土壤对Cl- 的吸附量减少 ,平衡液的pH值增大 ,而恒电荷土壤则变化甚微 ,说明共存的SO2 -4使可变电荷土壤的表面负电荷增加 ,但对恒电荷土壤则影响不大。这些结果说明 ,Cl- 以电性吸附的机理不因介质而变。可变电荷土壤在一价阳离子存在时 ,除土壤本身所带的正电荷外 ,还有一价阳离子吸附后产生的正电荷以及由此引起的对Cl- 的协同吸附。在二、三价阳离子存在时 ,还有Cl- 的离子对吸附 ,而恒电荷土壤在所有介质中 ,似乎总是以与Cl- 的协同吸附为主 相似文献
11.
Sorption of anionic surfactants Aerosol-OT (AOT) and Sodium Dodecyl Sulfate (SDS), as well as cationic surfactant Hyamine1622 on two soil surfaces were investigated. Batch equilibriumtechniques were used under laboratory conditions to observe the amount of surfactant adsorbed and desorbed to and from thesoil surfaces. Data obtained were fitted to two sorption isotherms in order to characterise the sorption process. The nature of the sorbate (i.e. the surfactant) was found to be important in the sorption process. Anionics adsorbed via hydrophobic bonding, whereas `cation-exchange' mechanism was dominant in the sorption of cationic Hyamine 1622. Anionic AOT,with a double chain, and hence a higher critical packing parameter, adsorbed more strongly onto the surface compared tothe singly-chained SDS. 相似文献
12.
A TiO2 photocatalyst was prepared by depositing silica and titanium dioxide on the surface of black sand that made the photocatalyst recoverable using a magnetic field. The magnetic photocatalyst was used to remove six aqueous dyes from water and the removal was attributed to both adsorption and photocatalytic oxidation. Removal by adsorption was more noticeable with the cationic dyes than with the anionic dyes. The difference was related to the electrostatic interaction between the charged dye molecular and the silica-occupied surface of the photocatalyst. Removal by photocatalytic oxidation occurred with anionic dyes, while it was not appreciable with cationic dyes. It was postulated that photocatalytic oxidation might have happened with cationic dyes as well, but the strong adsorption made the photocatalytic oxidation undetectable. 相似文献
13.
In this study, the formation of complexes between surfactants and the helical chains of amylopectins was confirmed. Nonionic surfactants with hydrophobic and hydrophilic groups of appropriate size and chemical structure enhanced the swelling and gelatinization processes of starch granules. Hydrophobic groups form complexes with the amylose and linear chains of amylopectin by becoming inserted into the hydrophobic inner area of the helical structures. The hydrophilic groups help the approach of the hydrophobic groups into the hydrated molecular chains and thus aid the formation of the complex. Among the anionic surfactants tested, SDS and sodium n‐decyl benzenesulfate caused maximum swelling and gelatinization peaks. The average length of the amylopectin exterior chains is almost the same as that of the hydrophobic chains of SDS (16.9 Å) and of sodium decyl benzenesulfate (18.2 Å). This suggests that these anionic surfactants form rigid complexes with the exterior of the amylopectin by fitting their hydrophobic chains to the hydrophobic inside of the helical structures of these short exterior chains. This process was clarified by NMR analysis and by a decrease in the complex with the addition of iodine. The hydrophobic alkyl chains of anionic and cationic surfactants fix to the edge of the starch molecular chains by forming inclusion complexes with the helical chains of the amylopectin. Cationic ions interact with the starch molecular chains, causing a negative charge that results in a more rapid and efficient swelling of the starch granules. A decrease in setback value occurs due to the inhibition of rearrangement among the starch molecular chains. With SDS, the complex molecular chains become more extensively developed through the repulsion effects of the anionic ions resulting in a larger swelling power and gelatinization peak. 相似文献
14.
以平衡吸附法研究了塿土对阴离子表面活性剂（SDS）、非离子表面活性剂（TritonX-100、Tween80和Brij35）的吸附特征,考察了pH、阴-非离子表面活性剂混合对塿土吸附表面活性剂的影响。结果表明,非离子表面活性剂在塿土上吸附等温线均呈L型,且均符合Freundlich和Langmuir方程;塿土对SDS的吸附等温线呈LS型,可用Freundlich方程来描述;塿土对4种表面活性剂吸附量的大小顺序为Tween80〉SDS〉Brij35〉TritonX-100。当阴-非离子表面活性剂一起进入土壤中,SDS-Brij35之间的相互影响不大;TritonX-100与SDS相互作用较大,无论二者以何种方式混合都会使TritonX-100在塿土上的吸附量增加,SDS的吸附量下降;SDS与Tween80之间的相互作用最大,混合后吸附量均下降,但Tween80吸附量降低的幅度最大。pH对非离子表面活性剂的吸附影响不大,而随着pH的增加,塿土对SDS的吸附百分率明显下降;在pH为8.0时,塿土对非离子表面活性剂的吸附百分率达到80以上。因此在选择合适的表面活性剂进行有机污染土壤修复和治理时,考虑土壤的特性和表面活性剂的结构是非常重要的。 相似文献
15.
Taheri-Kafrani A Bordbar AK Mousavi SH Haertlé T 《Journal of agricultural and food chemistry》2008,56(16):7528-7534
Bovine beta-lactoglobulin (beta-LG) in vivo (in milks) has been found in complexes with lipids such as butyric and oleic acids. To elucidate the still unknown structure-function relationship in this protein, the structural changes of beta-lactoglobulin variant A (beta-LG A) in the presence of anionic surfactant such as sodium n-dodecyl sulfate (SDS) and in the presence of nonionic surfactant such as Triton X-100 have been investigated. Subsequently, the retinol binding by beta-LG has been investigated in the presence of various amounts of these surfactants as its binding indicator. The results of UV-vis and fluorescence studies show a higher denaturating effect of SDS at acid pH that can be due to greater positive charges of beta-LG at this pH indicating also the nonspecific hydrophobic interactions of Triton X-100 with beta-LG at all studied pHs. Isothermal titration calorimetry (ITC) measurements indicate the endothermic nature of beta-LG/SDS interactions and the exothermic nature of Triton X-100/beta-LG interactions. The analysis of the binding data demonstrates the absence of considerable changes in retinol binding properties of beta-LG in the presence of various amounts of these surfactants. This implies that surfactant binding does not change the conformation of beta-LG in the regions defining the retinol-binding site. 相似文献
16.
Wangsakan A Chinachoti P McClements DJ 《Journal of agricultural and food chemistry》2003,51(26):7810-7814
Isothermal titration calorimetry (ITC) was used to study interactions between an anionic surfactant (sodium dodecyl sulfate, SDS) and maltodextrins with different dextrose equivalents (DE) in a buffer solution (pH 7.0, 10 mM NaCl, 20 mM Trizma, 30.0 degrees C). The interaction between SDS and maltodextrin was exothermic, which was attributed to incorporation of the hydrocarbon tail of the surfactant into a helical coil formed by the maltodextrin molecules. ITC measurements indicated that the number of SDS molecules bound per gram of maltodextrin increased with decreasing maltodextrin DE, i.e., increasing molecular weight. It was proposed that SDS only binds to maltodextrin molecules that have a DE greater than 10 glucose units. 相似文献
17.
研究离子交换中的离子特异性效应有助于揭示离子-带电表面相互作用机制。以蒙脱石Cu2+饱和样为研究对象,采用恒流法研究不同浓度碱金属离子Li+、Na+和K+的吸附动力学过程,并建立1︰1型(LiNO3、NaNO3、KNO3)电解质溶液中离子平衡吸附量与体系吸附活化能之间的关系。结果发现:(1)Li+、Na+和K+在蒙脱石-Cu2+表面的吸附过程仅呈现出弱静电力作用下的一级动力学特征,并存在明显的离子特异性效应。(2)离子非经典极化作用与体积效应共同决定了离子在双电层中的位置,从而导致表面电位存在差异;并且表面电位(绝对值)随着电解质浓度降低而增加,表现为Li+>Na+>K+。(3)根据新建立的模型可预测吸附离子在双电层中的位置,进而求出体系的吸附活化能,并发现离子特异性效应产生的根本原因是由活化能决定的,同时本研究表明建立的新模型在固/液界面反应中具有普适性。本研究将对固/液界面反应理论的完善提供新思路。 相似文献
18.
Wei WANG Xue ZHANG Yuhui ZHANG Xin MI Run WANG Huilan SHI Chunli LI Ziwen DU Youming QIAO 《土壤圈》2021,31(4):596-605
The widespread use of sodium p-perfluorous nonenoxybenzene sulfonate(OBS), a typical alternative to perfluorooctane sulfonate, has resulted in potential threats to the environment, but the adsorption behavior of OBS in soils has not yet been reported. In this study, the adsorption behaviors of OBS on five soils with different physicochemical properties were investigated. The rate of OBS adsorption was fast, and most of the OBS uptake was completed within 12 h. The good model fit of OBS adsorption to the pseudo-second-order and Elovich models indicated the occurrence of chemical adsorption. The adsorption isotherms of OBS on the soils were better described by the Freundlich model than by the Langmuir model, suggesting that the OBS adsorption sites on the soils were heterogeneous. This is possibly associated with various adsorption mechanisms including hydrophobic, π-π, hydrogen bonding, and electrostatic interactions,further confirmed by the good model fit to the D-R isotherm. Adsorption of OBS occurred on the soils, and the adsorption process was spontaneous and endothermic. In addition, the soils were more suitable for OBS adsorption at lower pH values due to the stronger electrostatic adsorption. The OBS adsorption on the soils decreased with the increase of soil depth from 0 to 30 cm. Moreover, the presence of organic matter and ammonia nitrogen in the soils was favorable for OBS adsorption, and these parameters decreased with increasing soil depth, making OBS adsorption less prominent in the deeper soil. This study indicates that OBS is easily enriched in surface soils, and that soil organic matter and ammonia nitrogen significantly affect OBS migration in soil. 相似文献
19.
Hai Nguyen Tran Chung-Kung Lee Mai Thi Vu Huan-Ping Chao 《Water, air, and soil pollution》2017,228(10):401
Spherical biochar derived from saccharides (glucose, sucrose, and xylose) was prepared through two steps: pre-hydrothermal carbonization at 190 °C and calcination at low temperatures (200–325 °C). The spherical biochar was characterized by Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy, zeta potential, scanning and transmission electron microscopies, and X-ray diffraction. The result indicated that the spherical biochar exhibited low S BET (15–22 m2/g), but abundant superficial active oxygen-containing functional groups. The spherical biochar possessed a negatively charged surface within solution pH 2.0–11. The adsorption process of Pb2+, Cu2+, and methylene green 5 (MG5) was strongly dependent on the solution pH and reached fast equilibrium at approximately 60 min. The maximum Langmuir adsorption capacity (Q°max) exhibited the following order: glucose-biochar > sucrose-biochar > xylose-biochar prepared at 300 °C. The selective adsorption order of glucose-biochar was Cu2+ (0.894 mmol/g) > Pb2+ (0.848 mmol/g) > MG5 (0.334 mmol/g). The electrostatic attraction played a determining role in the adsorption mechanism of pollutant cations. The adsorption of anionic dye (acid red 1) on the spherical biochar was negligible because of electrostatic repulsion. The spherical biochar can serve as a newer and promising adsorbent to remove toxic pollutant cations from water media. 相似文献
20.
The adsorption equation of Bowden et al. (I 977) was modified so that adsorption at a constant pH could be described by three parameters. One of these parameters represents the maximum adsorption. The second is the product of three characteristics. These are the binding constant for the adsorbing ion; the proportion of the adsorbate present as that ion; and the electrostatic potential in the plane of adsorption before adsorption had started. The third parameter indicates the rate at which the electrostatic potential in the plane of adsorption changes as adsorption increases. With these modifications, the adsorption equation may be linearized and graphs used to estimate the parameters. This simplification may be of value either when there is no data for the charge characteristics of the surface, or when there is insufficient computer expertise to fit more complex models. 相似文献