Solution Of Tween Research Articles

Universal functions and exactly solvable chaotic systems

A universal differential equation is a nontrivial differen- tial equation the solutions of which approximate to arbitrary accuracy any continuous function on any interval of the real line. On the other hand, there has been much interest in exactly solvable chaotic maps. An important problem is to generalize these results to continuos sys- tems. Theoretical analysis would allow us to prove theorems about these systems and predict new phenomena. In the present paper we discuss the concept of universal functions and their relevance to the theory of universal differential equations. We present a connection be- tween universal functions and solutions to chaotic systems. We will show the statistical independence between X(t) and X(t + �) (when � is not equal to zero) and X(t) is a solution to some chaotic systems. We will construct universal functions that behave as delta-correlated noise. We will construct universal dynamical systems with truly noisy solutions. We will discuss physically realizable dynamical systems with universal-like properties.

Is Lipid Peroxidation Induced by the Aqueous Suspension of Fullerene C60 Nanoparticles in the Brains of Cyprinus carpio?

This study aimed to clarify whether fullerene C60 nanoparticles induced lipid peroxidation in Cyprinus carpio brains. A stable well-characterized aqueous suspension of C60 nanoparticle (diameter: 50th and 95th percentiles, 36 and 95 nm respectively) with 0.1% Tween80 solution was prepared by bead milling. Lipid hydroperoxides (LPO) were measured in vitro in homogenized fish brain tissues containing 33 microg/mg-protein dispersed C60 nanoparticles under light and dark conditions to verify the lipid peroxidation ability of C60 and the interference of light exposure by using a commercial assay kit The LPO concentration significantly increased under the light condition but not under the dark condition. This suggests that C60 has the lipid peroxidation ability under light condition, and the light exposure that occurs during the dissection and preparation of fish brain samples containing C60 for the LPO assay interferes with the measurements of the in vivo LPO levels. Therefore, dissection and assay in the in vivo experiment were conducted under a yellow lamp or dark condition to avoid the interference of light. Moreover, the result of the in vitro test suggests that the LPO assay with irradiation might be a good method for detecting C60 in brain tissues. In the in vivo experiment, C. carpio was exposed to 4.5 mg/L nano C60 suspension for 48 h, following which the brain LPO concentration was measured. In the in vivo experiment, no fish died or exhibited abnormal symptoms during exposure. LPO assay of the C. carpio brain samples confirmed the absence of lipid peroxidation after exposure to 4.5 mg/L aqueous C60 nanoparticle suspension for 48 h. Additional LPO assay under irradiation showed that C60 did not reach the brain.

First Report of Leaf Rust of Blueberry Caused by Pucciniastrum vaccinii in Hawaii.

Blueberries (Vaccinium corymbosum L.) are a potential high-value, niche market crop for Hawaii. In May of 2007, rust-like symptoms were observed on multiple blueberry plants in a private nursery in Waimea, HI. In September of 2007, a similar leaf rust was observed on one bush of V. corymbosum cv. Sharpblue in the corner of a 36.6 × 9.1-m experimental plot at Mealani Research Station in Waimea. Within a month, rust was observed throughout the plot on 'Biloxi', 'Emerald', 'Jewel', 'Misty', 'Sapphire', and 'Sharpblue'. Preliminary field observations suggest that 'Sharpblue' and 'Sapphire' are highly susceptible to the rust and 'Biloxi' shows some tolerance. Leaf lesions began as approximately 1-mm2 chlorotic flecks that expanded and developed into reddish brown, necrotic spots with a chlorotic halo. New lesions and uredinia kept appearing over the course of 4 months. Defoliation occurred on plants where infection was severe. Yellowish orange pustules containing urediniospores first appeared on the abaxial side of older leaves and later appeared on new leaves. Urediniospores were elliptical to obovate (19.4 to 24.8 × 15.2 to 19.8 μm) with a thick, slightly roughened wall and a well-developed pore. Urediniospore morphology and dimensions were consistent with the description of Pucciniastrum vaccinii (G. Wint.) (1). A pathogenicity test was conducted with two 18-month-old 'Sharpblue' plants. Fully expanded leaves were sprayed with freshly collected urediniospores (3.8 × 105 spores per ml) suspended in a 0.05% solution of Tween 20 in water. The control plant was sprayed with sterile distilled water (SDW). Plants were covered with plastic bags for 48 h and held in a growth chamber at 20 to 22°C under continuous fluorescent lighting. The plastic bags were then removed and the plants were maintained in the growth chamber. Yellowish orange pustules that were identical to the original symptoms developed on 100% of inoculated leaves after 10 days. The plant inoculated with SDW remained symptomless. While leaf rust caused by P. vaccinii has been reported on Ohelo berry (V. reticulatum) (2), it has not been reported on V. corymbosum in Hawaii. To our knowledge, this is the first report of P. vaccinii on blueberry plants in Hawaii. This rust disease may pose a threat to the potential blueberry industry in Hawaii.

Algal extracts improve antioxidant defense abilities and salt tolerance of wheat plant irrigated with sea water

Effect of irrigation bread wheat plants (Triticum aestivum L., cv. Giza 94) with sea water (10 and 20% v/v), spraying with microalgae extracts obtained from Chlorella ellipoida and Spirulina maxima (5 gL-1 dry weight in 0.1% Tween solution) cultivated under normal and stress conditions were studied. Some plant bioregulators (BRGs, ascorbic acid and benzyl adenine, at 200 ppm) at the vegetative growth stage on photosynthetic pigments, antioxidant components, activity of some antioxidant enzymes, lipid peroxidation products, growth parameters, mineral content and economic yield were estimated. Irrigation of wheat plants with sea water led to an increase in Na+ ion, activities of antioxidant enzymes, superoxide dismutase, ascorbate peroxidase and total peroxidase, and TBARs components. In contrast, the contents of photosynthetic pigments and yield components were reduced. Furthermore, the overall growth of wheat plants was interrupted by irrigation with sea water (10 and 20%) and the effect was pronounced at higher level (20%). Application of BRGs had a slight effect on plant growth, antioxidant behaviour and activity of antioxidant enzymes in plants irrigation with sea water compared with that in stressed wheat plants. Application of algal extracts significantly increased the contents of total chlorophyll and antioxidant phenomenon. In additional, application of algal extracts exhibited strong positive correlation with increase in fresh weight (FW), grain weight and yield components. It is concluded that productive purpose of wheat crop by mean of brackish water (at 20 v/v level) is possible under a level of economical value through its application of algal extracts. Key words: Microalgae, sea water, wheat, salinity stress, antioxidant systems.

Effect of succinic acid and Tween-80 on glucuronidation of 2-ethyl-6-methyl-3-hydroxypyridine

We studied the effect of succinic acid on the process of glucuronidation of 2-ethyl-6-methyl-3-hydroxypyridine after peroral and intraperitoneal administration in the form of succinate or a base. Since the basic form of 2-ethyl-6-methyl-3-hydroxypyridine is insoluble in water, it was administered in 5% Tween-80. It was necessary to evaluate also the effect of Tween-80 on glucuronidation of 2-ethyl-6-methyl-3-hydroxypyridine in different administration routes. Quantitative assay of glucuronidated fractions was performed by the method of reversed-phase HPLC with fluorometrical detection. The detection limit for this method was 10 ng/ml. We confirmed that the major excretion pathway for 2-ethyl-6-methyl-3-hydroxypyridine is conjugation with glucuronic acid. It was found that succinic acid increased excretion of glucuronidated metabolite after both peroral and intraperitoneal administration of 2-ethyl-6-methyl-3-hydroxypyridine in the form of succinate and base in 5% Tween-80. The effect of Tween-80 was detected only after peroral administration, which was probably related to its effect on absorption of this compound. Tween-80 increased excretion of glucuronate after peroral administration of 2-ethyl-6-methyl-3-hydroxypyridine in the form of succinate and in 5% Tween solution.

New cell extraction procedure applied to deep subsurface sediments

A new method is presented for the separation of cells from a marine sediment matrix. Different methods and reagents were tested for detaching microbial cells from sediment particles; the highest yields were achieved in a solution of EDTA, Tween 80, sodium‐pyrophosphate, and methanol plus gentle ultrasonic treatment, followed by density centrifugation through a cushion of Nycodenz. If present, carbonates were dissolved before extraction. Comparison with untreated sediments and pure cultures verified that this technique minimizes cell lysis. The new procedure was tested on seafloor sediment from several locations and water depths (<1 to >4000 m) and subseafloor sediment from the Arctic Ocean (IODP Expedition 302). Cell extraction efficiency was relatively high (65% to 100%) and consistent for each sediment type, with significantly (P < 0.01) lower variability of counts of separated cells compared with conventional counts on slurried sediments. Concentrating cells before enumeration allows for a much lower minimum detection limit and lower uncertainty than the conventional approach of simply slurrying sediment. Resolving relatively small differences in the distribution of microorganisms will allow for comparisons to other parameters (porewater chemistry, lithology, etc). Additionally, this method has potential for the use of molecular techniques that were previously difficult owing to coelution of interfering compounds from the sediment matrix.

Effect of surfactant Tween on induction time of gas hydrate formation

Acceleration of gas hydrate formation is important in preventing coal and gas outbursts and is based on a hydration mechanism. It becomes therefore necessary to investigate the effect of surfactants, acting as accelerants for hydrate formation, on induction time. We experimented with three types of a Tween solution with equal concentrations of 0.001 mol/L (T40, T40/T80 (1:1), T40/T80 (4:1)). By means of visual experimental equipment, developed by us, we measured generalized induction time using a Direct Observation Method. The experimental data were analyzed combined with a mass transfer model and a hydrate crystal nuclei growth model. Our major conclusions are as follows: 1) solubilization of surfactants produces supersaturated gas molecules, which promotes the mass transfer from a bulk phase to hydrates and provides the driving force for the complexation between host molecules (water) and guest molecules in a gas hydrate formation process; 2) when the solution of the surfactant concentration exceeds the critical micelle concentration (CMC), the surfactant in an aqueous solution will transform to micelles. Most of the gas molecules are bound to form clusters with water molecules, which promotes the formation of crystal nuclei of gas hydrates; 3) the surfactant T40 proved to have more notable effects on the promotion of crystal nuclei formation and on shortening the induction time, compared with T40/T80 (1:1) and T40/T80 (4:1).

Improvement of the in vitro dissolution rate of mebendazole via crystallization in aqueous surfactant solutions

The technique of crystallization from different aqueous surfactant solutions has been employed in the present study for the purpose of enhancing the solubility and dissolution rate of mebendazole (MBZ), thereby; the limited systemic availability could be improved. Crystallization was carried out using aqueous solutions of non-ionic surfactants (Tween 20, 40, 60 and 80) and ionic surfactants (sodium lauryl sulfate and cetrimide). The in vitro dissolution rates were determined for the untreated drug, the drug crystallized in water [0% surfactant] (control) and that treated with 1, 2, 3 and 4% w/v aqueous surfactant solutions. The dissolution was performed in 0.1N HCl at 37°C for 2 h. Certain factors affecting the dissolution rate enhancement namely, type and concentration of surfactant, concentration of MBZ in solution (saturated or supersaturated solution) and temperature of the crystallization medium were all investigated. The results showed higher dissolution rates for the treated samples as compared to the untreated drug with the exception of samples crystallized from cetrimide solutions which had no enhancing effect towards the dissolution rate. Samples precipitated with the non-ionic surfactants showed higher dissolution rates over those precipitated with the ionic surfactants. Moreover, samples crystallized with 3% aqueous solution of Tween 60 showed the highest dissolution rates among all the preparations. A study on the effect of aging on the dissolution rate of the sample crystallized with Tween 60 (3%) over a period of 7 months showed a slight decrease in the amount dissolved from 66.7 to 49.8% after a dissolution period of 2 h. Further evaluation was performed to study the physicochemical properties of the crystallized drug using IR spectroscopy, differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and microscopic examination.

Evaluation of trichloroethene recovery processes in heterogeneous aquifer cells flushed with biodegradable surfactants

The ability of two biodegradable surfactants, polyoxyethylene (20) sorbitan monooleate (Tween® 80) and sodium dihexyl sulfosuccinate (Aerosol® MA), to recover a representative dense non-aqueous-phase liquid (DNAPL), trichloroethene (TCE), from heterogeneous porous media was evaluated through a combination of batch and aquifer cell experiments. An aqueous solution containing 3.3% Aerosol MA, 8% 2-propanol and 6 g/l CaCl 2 yielded a weight solubilization ratio (WSR) of 1.21 g TCE/g surfactant, with a corresponding liquid–liquid interfacial tension (IFT) of 0.19 dyn/cm. Flushing of aquifer cells containing a TCE-DNAPL source zone with approximately two pore volumes of the AMA formulation resulted in substantial (> 30%) mobilization of TCE-DNAPL. However, a TCE mass recovery of 81% was achieved when the aqueous-phase flow rate was sufficient to displace the mobile TCE-DNAPL toward the effluent well. Aqueous solutions of Tween 80 exhibited a greater capacity to solubilize TCE (WSR = 1.74 g TCE/g surfactant) and exerted markedly less reduction in IFT (10.4 dyn/cm). These data contradict an accepted empirical correlation used to estimate IFT values from solubilization capacity, and indicate a unique capacity of T80 to form concentrated TCE emulsions. Flushing of aquifer cells with less than 2.5 pore volumes of a 4% T80 solution achieved TCE mass recoveries ranging from 66 to 85%, with only slight TCE-DNAPL mobilization (< 5%) occurring when the total trapping number exceeded 2 × 10 − 5 . These findings demonstrate the ability of Tween 80 and Aerosol MA solutions to efficiently recover TCE from a heterogeneous DNAPL source zone, and the utility of the total trapping number as a design parameter for a priori prediction of DNAPL mobilization and bank angle formation when flushing with low-IFT solutions. Given their potential to stimulate microbial reductive dechlorination at low concentrations, these surfactants are well-suited for remedial action plans that couple aggressive mass removal followed by enhanced bioremediation to treat chlorinated solvent source zones.

Wormlike micelles in Tween-80/C mEO 3 mixed nonionic surfactant systems in aqueous media

Formation and rheological behaviour of viscoelastic wormlike micellar solution in aqueous mixed system of nonionic surfactants, polyoxyethylene sorbitan monooleate (Tween-80) and trioxyethylene alkyl ether (C m EO 3, m = 12 , 14, and 16) was studied. The semi-dilute aqueous solution of Tween-80, in presence of C m EO 3 shows a sharp increase in viscosity leading to the formation of a gel-like highly viscoelastic solution reaching a maximum, but decreases beyond an intermediate concentration and finally phase separates. When C 12EO 3 is replaced by C 14EO 3 the micellar growth occurs more effectively. However, with further increase in alkyl chain length, i.e. with C 16EO 3, phase separation occurs before a viscoelastic solution is formed. The effect of temperature on the water/Tween-80/C 14EO 3 mixed surfactant system was also studied. With increase in temperature, viscosity increases more promptly and the viscosity maximum is attained at relatively lower concentration of C 14EO 3. Enhanced one dimensional micellar growth with increase in the temperature is mainly attributed to the decrease in the spontaneous curvature of the aggregates. Structural investigation by means of small-angle X-ray scattering (SAXS) technique of micelles in aqueous solution of Tween-80 and mixed water/Tween-80/C m EO 3 systems confirmed the one dimensional micellar growth in the above system.

Glycinebetaine-induced modulation of antioxidant enzymes activities and ion accumulation in two wheat cultivars differing in salt tolerance

Modulation of water relations, activities of antioxidant enzymes and ion accumulation was assessed in the plants of two wheat cultivars S-24 (salt tolerant) and MH-97 (moderately salt sensitive) subjected to saline conditions and glycinebetaine (GB) applied foliarly. Different levels of GB, i.e., 0 (unsprayed), 50 and 100 mM (in 0.10% Tween-20 solution) were applied to the wheat plants at the vegetative growth stage. Leaf water potential, leaf osmotic potential and turgor potential were decreased due to salt stress. Salt stress increased the Na + and Cl − accumulation coupled with a decrease in K + and Ca 2+ in the leaves and roots of both cultivars thereby decreasing tissue K +/Na + and Ca 2+/Na + ratios. Furthermore, salt stress decreased the activities of superoxide dismutase (SOD), whereas it increased the activities of catalase (CAT) and peroxidase (POD) in both wheat cultivars. However, accumulation of GB in the leaves of both wheat cultivars was consistently increased with an increase in concentration of exogenous GB application under both non-saline and saline conditions. Accumulation of Na + was decreased with an increase in K + accumulation upon a consistent increase in GB accumulation under salt stress conditions thereby resulting in better K +/Na + and Ca 2+/Na + ratios in the leaves and roots. High accumulation of GB and K + mainly contributed to osmotic adjustment, which is one of the factors known to be responsible for improving growth and yield under salt stress. The activities of all antioxidant enzymes, SOD, CAT and POD were enhanced by GB application in cv. MH-97 under saline conditions, whereas all these except SOD were reduced in cv. S-24. It is likely that both applied GB and intrinsic SOD scavenged ROS in the tolerant cultivar thereby resulting into low activities of CAT and POD enzymes under salt stress. In conclusion, the adverse effects of salt stress on wheat can be alleviated by the exogenous application of 100 mM GB by modulating activities of antioxidant enzymes and changes in water relations and ion homeostasis. Furthermore, effectiveness of GB application on regulation of activities of antioxidant enzymes was found to be cultivar-specific.

A Partition Equilibrium Study of Sulfonephthalein Dyes in Nonionic Surfactant Systems at High pH

The acid base equilibria of two sulfonephthalein dyes, viz., bromothymol blue (BTB) and bromocresol green (BCG) in aqueous nonionic micellar solutions of Triton X100, Tween 20, Tween 40, Tween 60 and Tween 80 have been investigated spectroscopically using a partition equilibrium method. A red shift in the λ max of the visible absorption band corresponding to the base forms of the dyes with increase in surfactant concentration was observed at and above pH 9.0. For a particular dye-surfactant system the red shift increases with the increase in pH and was found to be greater for TX 100 than for the Tween surfactants. Red shift of the λ max of BTB was observed to be greater than that of BCG in all of the nonionic micellar systems investigated in buffered medium. The observed red shift has been attributed to stabilization of the base form of the dye by the polyoxyethylene (POE) head groups. The stabilization effect was found to decrease with increase in the number of carbon atom and unsaturation in the hydrophobic tail of the surfactant molecules. The equilibrium constant of the partition of the dyes between micellar and aqueous pseudophases (K ass ) was found to be greater for the more hydrophobic BTB than the less hydrophobic BCG. With the surfactants the K ass increases in the order Tween 80 < Tween 60 < Tween 40 < Tween 20 < TX 100. The pK a2 of the dyes were predicted using a partition equilibrium model and found to be in good agreement with the experimental values.

Direct encapsulation of BSA and DNA into silica microcapsules (hollow spheres)

We reported before that silica hollow spheres (microcapsules) are prepared by interfacial reaction method that W/O emulsion with the aqueous solution of sodium silicate and n-hexane solution of Tween 80 and Span 80 is combined with another aqueous solution of silica precipitant such as NH(4)HCO(3) and NH(4)Cl. This procedure using W/O/W emulsion fabricates the hollow structures of silica particles directly, and additional steps such as the removal of core parts, that are often essential for the preparation of hollow particles via core-shell materials, are not required. When biomacromolecules such as protein and nucleic acid are mixed in the aqueous solution of sodium silicate, these macromolecules can be encapsulated into the microcapsules. We succeeded the direct encapsulation of bovine serum albumin (BSA) and duplex DNA. Most of encapsulated BSA and DNA cannot be released from the microcapsules without the destruction of microcapsule shell. These microcapsule materials encapsulating biomacromolecules will be applied to biotechnologies such as immobilized enzyme and so on.

A Novel peroxy Radical Based Oxidative Stressing System for Ranking the Oxidizability of Drug Substances

A novel oxidative stressing system is described which generates high levels of peroxy radicals in solution at room temperature, without the use of azonitrile initiators. The oxidative stressing system is composed of a 10% solution of Tween 80 in water to which FeCl3 x 6H2O is added. The Tween 80 acts as a solubilizing agent for drug compounds, and also contains substantial amounts of organic hydroperoxides. It is shown that the Fe III/ Fe II couple operates on the hydroperoxide concentration to effectively generate new peroxy radicals, which then propagate in the Tween 80 solution. Key features of the Tween 80/Fe III system are investigated, and the oxidizability of seven known compounds and ten developmental compounds are examined. Relative reaction rates span a 300-fold range, from benzoic acid (nonreactive, defined as <0.5% reacted per day) to Vitamin D3 (7% reacted per hour). Oxidizability "rankings" thus generated are shown to agree well with azonitrile initiated oxidative stress. The potential for general correlations between this type of oxidizability data and actual oxidative performance in LFC and solid oral dosage forms is discussed.

Solubilization of non-steroidal anti-inflammatory drugs in the presence of tween series surfactants

The aqueous solubility of non-steroidal anti-inflammatory drugs (NSAIDs) Ketoprofen, Ibuprofen, Diflunisal and Naproxen were measured in the presence of the Tween series surfactants at 37°C. Results showed that the solubility of NSAIDs in the Tween solutions was approximately proportional to Tween concentration; the ability of Tween series surfactants to solubilize NSAIDs in the present study was Tween-80 > Tween-60 > Tween-40 > Tween-20; the order of increased solubility of NSAIDs in Tween series surfactants at a constant Tween series and concentration was Ibuprofen > Ketoprofen > Diflunisal > Naproxen. Under suitable conditions Tween series surfactants can be highly effective used to enhance the solubility of NSAIDs.

Crystal modification of dipyridamole using different solvents and crystallization conditions

Dipyridamole crystals having different types of habits, improved dissolution rate were prepared by recrystallization from selected solvents, such as acetonitrile, benzene and methanol (Method I); crystals have also been made by solvent change using methanolic solution of dipyridamole in the presence of 2% solutions of Tween-80, Povidone K 30 and polyethylene glycol (PEG) 4000 (Method II). Scanning electron microscopy, X-ray powder diffractometry, IR spectrometry and differential scanning calorimetry were used to investigate the physicochemical characteristics of the crystals. The comparative dissolution behavior of the newly developed crystals and that of the untreated dipyridamole were also studied. It was found that the newly developed crystals were different from each other with respect to physical properties but are chemically identical. The crystals, obtained (Method I) from benzene and acetonitrile, produced needle shaped crystals and that obtained from methanol produced rectangular shaped crystals. But the crystals obtained (Method II) with the methanolic solution of the drug in the presence of Tween-80, Povidone K 30 and PEG-4000 produced smooth needle shaped crystals. X-ray diffraction spectra and differential scanning calorimetry study of the newly developed crystals, clearly indicate that dipyridamole exist in different crystal modification. The dissolution rate of newly developed crystals was found to be greater than the pure drug dipyridamole. Stability studies at 40 °C (75% RH) for 1 month for the modified crystals as well as the pure drug did show some changes in the XRD and DSC but not in IR studies.

Solubility of Rofecoxib in the Presence of Aqueous Solutions of Glycerol, Propylene Glycol, Ethanol, Span 20, Tween 80, and Sodium Lauryl Sulfate at (298.15, 303.15, and 308.15) K

The solubility data of rofecoxib in various mass fraction compositions of cosolvents (glycerol, propylene glycol, and ethanol) + water and surfactants (Span 20, Tween 80, and sodium lauryl sulfate) + water at (298.15, 303.15, and 308.15) K are presented. The analysis of rofecoxib was done by high-performance liquid chromatography. The solubility of rofecoxib increased with increasing mass fraction of cosolvents and surfactants at (298.15, 303.15, and 308.15) K. For ethanol + water mixtures, the solubility of rofecoxib was higher when compared to the glycerol + water and propylene glycol + water mixtures. The solubilization power of glycerol, propylene glycol, and ethanol at (298.15, 303.15, and 308.15) K was 0.81, 0.87, and 0.88; 2.2, 2.3, and 2.4; and 3.4, 3.6, and 3.8, respectively. In case of surfactants, sodium lauryl sulfate exhibited higher solubilizing efficiency at (298.15, 303.15, and 308.15) K than Span 20 and Tween 80.

New approach for the control of size and surface characteristics of mesoporous silica particles by using mixed surfactants in W/O emulsion

Mesoporous silica micro-spheres have been prepared using an emulsion-gel method in W/O emulsion consisting of aqueous solution of SDS or Tween 20 and n-octanol of hydroxypropyl cellulose (HPC) and Span 80. The morphology of water droplets in W/O emulsion was controlled by the concentration of the water-soluble surfactants of SDS and Tween 20 and the oil-soluble surfactant of Span 80. Since water droplets serve as a supporting structure for particle growth and aggregation, their morphology influences the shape, size, and size distribution of particles. When 3 wt.% and 5 wt.% of Span 80 were employed in our system, the effect of surfactant on the particle size distribution was more prominent than when 7 wt.% was used. Anionic surfactants were hardly used in aqueous phase to make mesoporous silica particles and one or more water-soluble surfactants were only used in aqueous phase to control the shape of particles. Interestingly, the particles of mesophase structure were synthesized when the anionic surfactant, SDS, was added to the water phase and the nonionic surfactant, Span 80, was employed in the oil phase. As the concentration of SDS and Tween 20 increases, the pore size of samples is altered from 7.2 nm up to 44.4 nm. This change of surface morphology occurred due to the solubilization ability of water-soluble surfactants. Moreover, depending on whether the anionic surfactant or nonionic surfactant is used, the degree of the change in pore size distribution of silica particles is relatively different. When SDS is used, the maximum peaks of the pore size distribution are located on the right rather than those in silica particles prepared using Tween 20. The structure of these materials was characterized by optical microscope, field-emission scanning electron microscopy, and nitrogen adsorption and desorption (BET isotherms and BJH pore size distribution measurements).

Preparation and Formation Mechanism of Silica Microcapsules (Hollow Sphere) by Water/Oil/Water Interfacial Reaction

Silica microcapsules (hollow spheres) were readily prepared by an interfacial reaction using a water/oil/water (W/O/W) emulsion system. A W/O emulsion consisting of an aqueous solution of sodium silicate (WP-1) and an n-hexane solution of Tween 80 and Span 80 (OP) was added to another aqueous solution of a precipitant (WP-2). The reaction of sodium silicate with a precipitant to form silica on this W/O/W emulsion system (WP-1/OP/WP-2) forms the hollow structure spontaneously. Therefore, no core material often utilized in silica hollow sphere fabrication was required in this process. The formation and the particle size of the silica microcapsule depended on the precipitant employed. When NH4HCO3 was used as precipitant, the particle size of the silica microcapsule was successfully controlled by the volume ratio of WP-1/OP/WP-2, the rotation number of the homogenizer, and the concentration of sodium silicate in WP-1. However, this control of the particle size was not achieved when other precipitants such as...

Stimulated Microbial Reductive Dechlorination following Surfactant Treatment at the Bachman Road Site

A pilot-scale demonstration of surfactant-enhanced aquifer remediation (SEAR) was conducted in July 2000 at the Bachman Road site located in Oscoda, MI. The Bachman aquifer is a shallow, relatively homogeneous, unconfined aquifer formation composed primarily of sandy glacial outwash with relatively low organic carbon content (0.02 wt %). A 6 wt % aqueous solution of Tween 80 (a nonionic, food-grade surfactant) was flushed through a localized dense nonaqueous phase liquid (DNAPL) source zone to recover approximately 19 L of tetrachloroethene (PCE). Post-treatment monitoring revealed PCE concentrations were reduced by up to 2 orders of magnitude within the source zone, and there was no evidence of concentration rebound after more than 450 d. Concentrations of PCE dechlorination products (trichloroethene, cis-1,2-dichloroethene) 450 d after SEAR operations ceased were more than 2 orders of magnitude greater than pretreatment values, suggesting stimulation of native dechlorination activity. Post-treatment monitoring detected increased concentrations of volatile fatty acids generated from the fermentation of residual-level Tween 80 surfactant. These field data suggest that Tween 80 not only induced and maintained anaerobiosis but also provided reducing equivalents to reductively dechlorinating populations present in the oligotrophic Bachman aquifer. Experience from this site supports application of staged treatment strategies that couple SEAR and microbial reductive dechlorination to enhance mass removal and reduce contaminant mass flux emanating from treated source zones.