Determination of lead in paints by electro-oxidation in cationic surfactant—aqueous sodium hydroxide suspensions

It was shown that anodic voltammetry can be used to determine lead in paint samples by solubilizing the sample in an aqueous solution using a cationic surfactant (Hyamine 2389, prdominantly methyldodecylbenzyltrimethylammonium chloride). In addition to solubilizing the solid paint particles, the cationic surfactant increased the oxidation potential of water to the point where one could observe, in concentrated sodium hydroxide solutions, an anodic peak for the oxidation of lead monoxide to lead dioxide. If the surfactant was below the critical micelle concentration, the height of the peak was linearly proportional to the concentration of lead oxide in the paint. The technique was experimentally verified by comparing the concentration of lead in a commercial paint sample, as determined by x-ray fluorescence, with the concentration determined voltammetrically.     

On the nature of decrease in the particles size of nanostructured nickel oxide obtained by the sol-gel method in the presence of surfactants

A processes of formation of nanostructured powders of nickel oxide by annealing in the temperature range of 200–700°C of the nickel hydroxide obtained by the sol-gel method at 80°C from solutions of nickel nitrate by precipitation with alkali in the presence of surfactant AF-12 (polyethylene oxide alkylphenyl ether) was investigated. The formation of nanostructured powders of nickel oxide in the presence of a surfactant reduces the size of nanoparticles to 20–25 nm, which is 1.5 times smaller than the particles obtained without a surfactant. The effective influence of surfactant on the particle size begins in the temperature range of its decomposition and evaporation equal 350–400°C.     

Effect of microemulsion variables on copper oxide nanoparticle uptake by AOT microemulsions

Ultradispersed metal oxide nanoparticles have applications as heterogeneous catalysts for organic reactions. Their catalytic activity depends primarily on their surface area, which in turn, is dictated by their size, colloidal concentration and stability. This work presents a microemulsion approach for in situ preparation of ultradispersed copper oxide nanoparticles and discusses the effect of different microemulsion variables on their stability and highest possible time-invariant colloidal concentration (nanoparticle uptake). In addition, a model which describes the effect of the relevant variables on the nanoparticle uptake is evaluated. The preparation technique involved solubilizing CuCl(2) in single microemulsions followed by direct addition of NaOH. Upon addition of NaOH, copper hydroxide nanoparticles stabilized in the water pools formed in addition to a bulk copper hydroxide precipitate at the bottom. The copper hydroxide nanoparticles transformed with time into copper oxide. After reaching a time-independent concentration, mixing had limited effect on the nanoparticle uptake and particle size. Particle size increased with increasing the surfactant concentration, concentration of the precursor salt, and water to surfactant mol ratio; while the nanoparticle uptake increased linearly with the surfactant concentration, displayed an optimum with R and a power function with the concentration of the precursor salt. Surface areas per gram of nanoparticles were much higher than literature values. Even though lower area per gram of nanoparticles was obtained at higher uptake, higher surface area per unit volume of the reverse micellar system was attained. A model based on water uptake by Wisor type II microemulsions, and previously used to describe iron oxide nanoparticle uptake by the same microemulsions, agreed well with the experimental results.     

Electrochemical deposition of mesoporous nickel hydroxide films from dilute surfactant solutions

A series of micelle-templated mesoporous nickel hydroxide films were prepared by electrochemical deposition from dilute surfactant solutions by using different types of template and by varying plating solvent composition. Lamellar mesostructured Ni(OH)2 films are obtained with only anionic surfactant sodium dodecyl sulfate (SDS) as the template. In particular, a unique cooperative assembly fashion, that is, the combination between Ni2+ and a complex composed of the primary template SDS and a cosurfactant, such as triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) copolymers and poly(ethylene glycol), was explored, by which two-dimensional hexagonal mesoporous Ni(OH)2 films were electrodeposited. Meanwhile, the deposition medium also plays a crucial role in determining the mesostructure of Ni(OH)2 films. For the composite nickel hydroxide films deposited from aqueous solution or dilute aqueous solution of ethylene glycol (<20 wt %) in the presence of SDS or the SDS-poly(alkylene oxide) polymer complexes, a mixed lamellar phase with d(001) = 37.4 A and d(001) = 28.5 A was obtained. However, single lamellar phase with d(001) = 37.4 A was electrodeposited from concentrated aqueous solutions of ethylene glycol (> or = 20 wt %). Furthermore, such deposition baths have access to hexagonal mesoporous nickel hydroxide films with d(100) = 37.4 A at 70 degrees C with the SDS-poly(alkylene oxide) polymer complexes as the templates. Within the potential window for Ni(OH)2, the morphology and quality of mesostructured films are significantly dependent on the deposition potential, while the mesostructures of the composite films always remain unchanged.     

Colloidal particles derived from a complex of phosphotungstic Acid and ethoxylated surfactants

Stable, colloidal sols of submicron size were prepared by titration of aqueous solutions of alkylene oxide surfactants with phosphotungstic acid, H(3)PW(12)O(40) (PTA), followed by neutralization with ammonium or potassium hydroxide. The stoichiometry of the complex between phosphotungstic acid and the ethoxylated surfactant was determined by (1)H and (31)P NMR and was dependent upon the degree of ethoxylation. For example, in the ethoxylated octylphenol having 9-10 ethylene oxide units, Triton X-100, the mole ratio of surfactant to PTA was 4.5. In the ethoxylated octylphenol having 70 ethylene oxide units, Triton X-705, the mole ratio of surfactant to PTA was 1. Prior to nucleation of particles, phosphotungstic acid forms an apparent yellow charge transfer complex with ethoxylated alkylphenol surfactants, typified by Triton X-405. This complex is characterized by an absorption spectrum that is the sum of the spectra of Triton X-405 and PTA with a very weak shoulder at 400-500 nm. Particles were nearly monodisperse and their size was dependent on the nonionic surfactant employed, the heteropolyacid, and the rate of addition of heteropolyacid solution.     

Removal of phosphate by aluminum oxide hydroxide

The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The adsorption of phosphate onto aluminum oxide hydroxide was influenced by pH in solution: the amount adsorbed was greatest at pH 4, ranging with pH from 2 to 9. The optimum pH for phosphate removal by aluminum oxide hydroxide is 4. The selectivity of phosphate adsorption onto aluminum oxide hydroxide was evaluated based on the amount of phosphate ion adsorbed onto aluminum oxide hydroxide from several anion complex solutions. It is phosphate that aluminum oxide hydroxide can selectively adsorb. The selectivity of phosphate onto aluminum oxide hydroxide was about 7000 times that of chloride. This result indicated that the hydroxyl groups on aluminum oxide hydroxide have selective adsorptivity for phosphate and could be used for the removal of phosphate from seawater.     

Surfactant-resisted assembly of Fe-containing nanoparticles for site-specific growth of SWNTs on Si surface

This paper describes a facile approach to the site-specific growth of single-walled carbon nanotubes (SWNTs) on silicon surfaces by chemical vapor deposition (CVD). The approach is based on the use of a surfactant as a resist to define patterns of silicon oxide nanodomains onto which nanoparticles of iron hydroxide (Fe(OH)3), 1-5 nm diameter, could be deposited. In base growth mode, the SWNTs can grow from the oxide nanodomains. By controlling the location of oxide nanodomains, site-specific growth could be obtained. The iron hydroxide nanoparticles were prepared by hydrolysis of ferric chloride (FeCl3). Patterned hydroxylated silicon oxide nanodomains were created by scanning probe oxidation (SPO) of silicon substrates modified with aminopropyltrimethoxysilane (APTMS, H2N(CH2)3Si(OCH3)3). Due to electrostatic interaction, Fe(OH)3 nanoparticles can be selectively deposited on hydroxyl groups present on silicon oxide nanodomains. To inhibit the assembly of the nanoparticles on a APTMS-coated silicon surface, sodium dodecyl sulfate (SDS) was introduced, which restricted deposition to the hydroxylated nanodomains. A model mechanism for the selective deposition mechanism has been proposed. It was possible to convert the patterned Fe(OH)3 nanoparticles to iron oxide, which served as a catalyst for the site-specific growth of SWNTs. Raman spectroscopy and AFM were used to characterize the nanotubes on the Si substrate. This will offer the possibility for future integration with conventional microelectronics as well as the development of novel devices.     

近二维结构的六边形金属镍纳米片的水热合成

片状二维镍纳米材料具有较高的形状各异性,在催化、磁记录以及生物探测方面具有重要的应用价值,因此寻找一种简单,成本低的方法制备表面无活性剂的片状镍纳米材料显得尤为重要。在没有有机表面活性剂和形貌控制剂的条件下,在氟掺杂氧化铟锡(FTO)导电玻璃表面,通过水热制备得到金属镍纳米薄片。系统地研究了反应条件对产物形貌的影响,发现镍源、氢氧化钠、氨水的浓度以及反应温度对纳米镍的形貌有较大的影响。只有在合适的氨水和氢氧化钠浓度共同存在下,才能获得具有较大的特征长度以及较薄的近二维结构的六边形镍金属钠米薄片。经过条件优化,制备得到的厚度约为10 nm,横向特征长度超过1μm金属镍纳米薄片。经过分析认为,体系的p H值及温度影响了反应速度,最终导致产物的形貌受到影响,在p H值约为10的条件下,氨水对镍离子的络合作用对镍纳米薄片的二维生长具有一定的促进作用。     

Adsorption and heterocoagulation of nonionic surfactants and latex particles on cement hydrates

The adsorption of nonionic surfactants of the alkyl-phenol-poly(ethylene oxide) family and of acrylic latex particles on several anhydrous (but hydrating) or fully hydrated mineral phases of Portland cement was studied. No or negligible adsorption of the surfactant was observed. This was assigned to the ionized character of the surface silanol groups in calcium-silicate-hydrates and to the strongly ionic character of the OH groups in calcium hydroxide and in the calcium-sulfoaluminate-hydrates, which prevents the formation of surface-ethoxy hydrogen bonds. In contrast, provided they are properly stabilized by the surfactant, the latex particles form a loose monolayer on the surface of hydrating tricalcium silicate particles. The attractive interaction between the positive mineral surface and the negative latex surface appears to be the driving force for adsorption. In line with this, adsorption is reduced by sulfate anions, which adsorb specifically onto the silicate surface. Compared to tricalcium silicate, portlandite and gypsum interact only marginally with the latex particles. Our results show that the stability of the nonionic surfactant/latex/cement systems is essentially controlled by the latex colloidal stability and the latex-cement interactions, the surfactant having little direct interaction, if any, with the mineral surfaces.     

Experimental Study of the Effect of Strong Alkali on Lowering the Interfacial Tension of Oil/Heavy Alkylbenzene Sulfonates System

Experimental studies were conducted to explore the fundamental mechanisms of alkali to lower the interfacial tension of oil/heavy alkylbenzene sulfonates (HABS) system. Sodium hydroxide was used as the strong alkali chemical to investigate the interfacial tension (IFT) of oil/HABS system. The influences of salt and alkali on the interfacial activity were studied by the measurement of interfacial tension and partition coefficient. Moreover, the alkali/surfactant solutions were measured by dynamic laser scattering. The results showed that compared with the salt, the function of alkali to lower the interfacial tension and improve partition coefficient is more significant. The micelles formed by surfactants could be disaggregated because of adding alkali, so the size of micelles decreases and the number of mono‐surfactants increases, then more surfactant molecules move to the interface of oil/surfactant system and the adsorption of surfactants at oil‐water interfaces increases, which can lead to the decrease of IFT.     

Growth and surface properties of boehmite nanofibers and nanotubes at low temperatures using a hydrothermal synthesis route

The growth of boehmite nanostructures at low temperature using a soft chemistry route with and without (PEO) surfactant is presented. Remarkably long boehmite 1D nanotubes/nanofibers were formed within a significantly short time by changing the reaction mechanism of aluminum hydroxide. By using the PEO surfactant as a templating agent, boehmite nanotubes up to 170 nm in length with internal and external diameters of 2-5 and 3-7 nm, respectively, were formed at 100 degrees C. A slightly higher temperature (120 degrees C) resulted in the formation of lath-like nanofibers with an average length of 250 nm. Using the cationic surfactant CTAB, nanotubes rather than nanofibers were formed at 120 degrees C. Without surfactant, nanotubes counted for around 20% of the entire sample. A regular interval supply of fresh boehmite precipitate resulted in a larger crystallite size distribution of nanotubes. The morphology of nanotubes was more uniform in samples without the regular addition of aluminum hydroxide. Moreover, for the same hydrothermal time, the final nanotubes for nanomaterials without a regular interval supply of fresh aluminum hydroxide precipitate were longer than those with a regular aluminum hydroxide precipitate supply, which is in contrast to previously published results. Higher Al/PEO concentrations resulted in the formation of shorter nanotubes. A detailed characterization and mechanism are presented.     

Large-scale, surfactant-free, hydrothermal synthesis of lithium aluminate nanorods: optimization of parameters and investigation of growth mechanism

Lithium aluminate nanorods were successfully synthesized from Al2O3 nanoparticles and lithium hydroxide by a simple, large-scale hydrothermal process without any surfactant or template. The various reaction parameters were optimized to achieve the maximum yield. The as-obtained nanorods had orthorhombic beta-lithium aluminate structure with edges in the range of 40-200 nm and lengths of 1-2 mum confirmed by SEM, TEM, XRD, and NMR. Upon calcination at 1273 K for 12 h it transformed to gamma-lithium aluminate, yet maintained the initial morphology, demonstrating the thermal stability. The ratio of lithium hydroxide to aluminum oxide showed a significant effect on the morphology as Li/Al = 1 gives "microroses", whereas Li/Al = 3 and Li/Al = 15 gave "microbricks" and "nanorods", respectively. Investigation of the mechanism showed that the nanorods were formed via a "rolling-up" mechanism. As we used all-inorganic raw materials and a simple synthetic procedure under mild conditions, the scale-up of this process for large-scale production should be very easy.     

Alkylation of methyl 4,6-O-benzylidene-α-D-galactopyranoside

The partial alkylation of methyl 4,6-O-benzylidene-α-D-galactopyranoside in dimethylformamide and dimethyl sulfoxide in the presence of barium oxide and hydroxide is described. It has been shown that methylation and benzylation lead predominantly to the 3-alkyl derivatives with yields of 30–40%, benzylation taking place more selectively than methylation. The compounds synthesized have been characterized by their melting points and specific rotations.     

Adsorptive bubble separation of zinc and cadmium cations in presence of ferric and aluminum hydroxides

The adsorptive bubble separation of zinc and cadmium cations from solution in the presence of ferric and aluminum hydroxides was carried out by means of Tween 80 (nonionic surfactant), and sodium laurate and stearate (anionic surfactants). The mechanism of metal removal is different depending on the nature of the surfactant used. The removal of zinc cations by adsorbing colloid flotation is higher than that of cadmium cations. It increases with increases in the amount of hydroxide precipitate and the concentration of Tween 80. The removal of zinc cations by ion flotation is lower than that of cadmium cations. It does not change with increases in the hydroxide amount. It increases, however, with increased sodium laurate or stearate concentration. Both separation methods turned out to be helpful for studying both the solution's structure and the interactions at the solution-solid interface.     

Synthesis of arsenic sorbent by the reaction of magnesium hydroxide with aqueous iron(III) chloride solution

The reaction of magnesium hydroxide with a concentrated aqueous solution of iron(III) chloride yields a mixture of magnesium–iron layered double hydroxide and iron oxide–hydroxide in the akaganeite form. The content of these phases depends on the Mg/Fe atomic ratio in the starting reactant mixture. Iron oxide–hydroxide is the major reaction product at the Mg/Fe atomic ratio in the interval 1.5–1.75, and layered magnesium–iron layered double hydroxide, at Mg/Fe = 3–4. The ability of the synthesized products to take up As(III) from aqueous solutions was studied. These sorbents allow the arsenic concentration to be decreased from 3–5 mg L^–1 to values below MPC (0.01 mg L^–1).     

Selective desorption and analysis of humic substances on suspended particles in river water

The elemental analysis and morphology of individual particles indicate that the dominant suspended particles in river water are kaolin covered with hydrated iron(III) oxide which strongly sorbs humic substances. Suspended particles, about 1 mg, collected from 250 ml of water by centrifugation, are treated with 0.7 ml of 0.1M sodium hydroxide to desorb humic substances. Approximately 60% of copper and 30% of lead on or in suspended particles exist as humic complexes.     

Lead oxide solubility in molten NaOH and NaOH–Na2CO3

Using the method of isothermal saturation, the solubility of lead oxide in NaOH and NaOH–30%Na₂CO₃ melts was studied under an inert helium atmosphere in the temperature range 673–873 K. The temperature dependence of the lead oxide solubility m_s (mole fractions) in the given melts is described by the equations: ln m_s = 12.174–13,490 1/Т for the molten NaOH and ln m_s = 15.536–16,680 1/Т for the molten NaOH–30%Na₂CO₃. The heterogeneous equilibrium between solid lead oxide and its saturated solution in the alkali and alkali-carbonate melts can occur according to the reaction: PbO_s = Pb²⁺ + O^2?. The model mechanism of dissolution is discussed. Thermodynamic parameters for the dissolution of lead oxide in the melts are calculated. The addition of sodium carbonate to the molten sodium hydroxide decreases the solubility of lead oxide in the melt. As the temperature of the melt rises, the lead oxide solubility in it increases.     

Self-organization of surfactant-metal-ion complex nanofibers on graphite surfaces and their application to fibrously concentrated platinum nanoparticle formation

We report the fabrication of self-organized surfactant nanofibers containing platinum ions on a highly oriented pyrolytic graphite (HOPG) surface from mixed solutions of hexadecyltrimethylammonium hydroxide (C16TAOH) and hydrogen hexachloroplatinate (IV) (H2PtCl6). The fibrous surfactant self-assembly was stable in air, even after being soaked in water, in contrast to surfactant hemicylindrical micelles, which are stable only at graphite/solution interfaces. The results show that the graphite surface served as an essential template for the specific formation of fibrous surfactant self-assemblies. In addition, when surfactant nanofibers containing metal ions were treated with hydrazine, platinum nanoparticles concentrated in the nanofibers formed on the HOPG surface. We also prepared surfactant nanofibers containing gold ions on HOPG surfaces and formed gold nanoparticles in the nanofibers.     

Rigid organic nanodisks of controlled size: A catanionic formulation

We show that organic rigid nanodisks of controlled size can be produced using a balanced pair of ionic surfactant molecules in a catanionic system. The counter-ion for the cationic surfactant is hydroxide. The counter-ion of the anionic surfactant is the hydronium ion. Close to equimolarity, counter-ions from water molecules: fluid solutions of ultra-low conductivity are obtained. This is solution contains rigid disks of thickness 4 nm: chains are frozen and surfaces are covered by ion pairs formed by the headgroups. The overall size of the disks is continuously adjustable from micrometer to nanometer size and is controlled by the excess of one of the two single chain surfactants involved. Unbound dispersed, nematic and lamellar structures are detected and located in the ternary equilibrium phase diagram at room temperature.