Adsorption of fluoride from aqueous solution by graphene

A batch adsorption system was applied to investigate the adsorption of fluoride from aqueous solution by graphene. The adsorption capacities and rates of fluoride onto graphene at different initial pH, contact time, and temperature were evaluated. The experimental results showed that graphene is an excellent fluoride adsorbent with an adsorption capacity of up to 17.65 mg/g at initial fluoride concentration of 25 mg/L and temperature of 298 K. The isotherm analysis indicated that the adsorption data can be well described by Langmuir isotherm model. Thermodynamic studies revealed that the adsorption reaction was a spontaneous and endothermic process.     

A thermodynamic study of the aggregation process of oxacillin sodium salt in aqueous solution

The aggregation characteristics of oxacillin in aqueous solutions have been examined by means of conductivity measurements over the temperature range 288.15-313.15 K and by static light scattering measurements at 298.15 K. Two critical concentrations were detected in conductivity and light scattering over the concentration range 0-0.35 mol kg^-1. Light scattering measurements indicate the formation of dimers at the first critical concentration (0.024 mol kg^-1) and the subsequent formation of aggregates with an aggregation number of 8 at the second critical concentration (0.104 molkg^-1). The thermodynamic parameters of aggregation were derived from the critical concentration data using a mass-action model that has been modified for application to systems of low aggregation number. Values for the enthalpy of aggregate formation calculated by this method showed that the aggregation became increasingly exothermic with increasing temperature. The values of the two critical concentrations show that this penicillin, oxacillin, is more hydrophobic than other molecules of similar structure.     

Reaction of gaseous hydrogen fluoride with aluminium and its compounds

The reaction of metallic aluminium surfaces, aluminium oxides, hydrated oxides and sulphate with gaseous anhydrous hydrogen fluoride was studied at 470°C and pressures between 10 and 100 torr. The complementary analytical techniques of X-ray induced photoelectron spectra, X-ray and electron diffraction, and electron microscopy were used for identifying the (frequently unexpected) products.     

Homogeneous precipitation of basic aluminium benzoate with a buffer solution

Addition of an ammonium benzoate-benzoic acid buffer solution to a solution of aluminium ions gives a homogeneous precipitation of basic aluminium benzoate. This has advantages over the urea method for the gravimetric determination of aluminium in the presence of large quantities of manganese, calcium, cadmium, nickel, cobalt, copper, and zinc ions.     

Rare earth element complexation by fluoride ions in aqueous solution

Rare earth fluoride stability constants for Ce, Eu, Gd, Tb and Yb at 25°C have been determined by examining the influence of fluoride ions on the distribution of rare earths between tributyl phosphate (TBP) and 0.68M NaClO₄. Our results indicate that rare earth mono and difluoro complexation constants show a steady increase as a function of atomic number from La to Tb but remain relatively constant after Dy. This behavior is similar to that which has been observed for dicarboxylic acids. Stepwise stability constant ratios, K₂/K₁, obtained in our work (where K₁=[MF²⁺][M³⁺]^–1[F^–]^–1 and K₂=[MF ₂ ⁺ ]^–1[MF²⁺]^–1[F^–]^–1) indicated that, for all rare earths, K₂/K₁=0.09±0.03.     

The determination of aluminium in aqueous solution by atomic absorption spectroscopy

A special burner is proposed for the atomic absorption spectrophotometric determination of aluminium. With a suitable mixture of nitrogen, oxygen and acetylene, a limit of detection of less than 2 p.p.m. was achieved in aqueous solution. The experimental variables and potential interferences were studied. Iron and chloride interfered in high concentrations, and must be either absent or allowed for in the preparation of standards. Several standard samples of various types were analysed for aluminium with satisfactory results.     

Adsorption and precipitation processes at cadmium oxide/sodium sulfate aqueous solution interface

The results of experimental studies of the adsorption of ions at the cadmium oxide/electrolyte solution interface are presented. On the basis of kinetic changes in the concentration of cadmium, hydroxide, and sulfate ions in the solution, the processes occurring in this system are discussed. It was found that cadmium oxide is transformed into the hexagonal form of cadmium hydroxide. The surface charge data for cadmium oxide/aqueous Na₂SO₄ are presented.     

铝在氢氧化钠溶液中的电化学行为研究

铝是地壳中含量丰富的元素 ,分布广泛 ,由于其具有价格低、能量密度高、导电性良好及无毒性等优点 ,因而是阳极材料的首选物质 ,铝电池的研究也已经成为近年来研究开发的热点课题之一[1～ 3] 。探讨铝在强碱性溶液中的溶解机理 ,对铝电池的研究和开发将具有一定的理论指导意义。1　实验部分1 1　仪器与试剂ＢＡＳ 1 0 0Ａ电化学系统 (美国ＢＡＳ仪器公司 ) ;ＣＳ5 0 1型恒温槽 ;工作电极为直径是 0 .3ｍｍ的铂圆盘电极 ,参比电极是标准甘汞电极 (ＳＣＥ)。铝( 99.99% ) (天津化学试剂厂 ) ,氢氧化钠为分析纯(上海化学试剂厂 ) ,水为二次蒸…     

Copolymerization of acrylamide with sodium acrylate in aqueous salt solutions

Kinetic relationships in homogeneous radical copolymerization of acrylamide with sodium acrylate, initiated by potassium peroxosulfate in concentrated aqueous solutions at 60°C, were examined in relation to the ionic strength of the solution and pH of the medium.     

Dissolution of copper oxide by the ethanolamine and ammonium fluoride in aqueous solution

Dissolution properties of copper oxide in aqueous solutions containing ethanolamine and/or ammonium fluoride have been evaluated at various pH ranges. The dissolution rate was strongly affected by the pH of the solution. The solution of ammonium fluoride showed good properties for the dissolution of copper oxide in the range of acidic conditions, whereas the solution containing ethanolamine showed a dissolution property within the basic condition. A mixture solution of ethanolamine and ammonium fluoride displayed enhanced dissolution property of copper oxide at acidic and basic conditions only. An expected synergy effect on the dissolution rate and selectivity could not be produced through a mixture of ethanolamine and ammonium fluoride in an aqueous solution. Copyright © 2011 John Wiley & Sons, Ltd.     

Solubility of sodium soaps in aqueous salt solutions

The solubility of sodium soaps in dilute aqueous salt solutions has been systematically investigated by direct visual phase behavior observations. The added electrolytes, including simple inorganic salts and bulky organic salts, influence the solubility of sodium soaps in water, as represented by the varied soap Krafft point. Two inorganic salts, sodium chloride and sodium perchlorate, demonstrate a "salting-out" property. On the other hand, tetraalkylammonium bromides show an excellent ability to depress the soap Krafft point and enhance the soap solubility in water. With increasing the tetraalkylammonium ionic size, the degree of "salting-in" of soaps in water increases. However, solubility of pure tetraalkylammonium bromide in water decreases as the length of the alkyl chains increases. Furthermore, in the ternary water-tetrapentylammonium bromide (TPeAB)-sodium myristate (NaMy) system, we observed an upper cloud point phenomenon, which greatly shrinks the 1-phase micellar solution region in the phase diagram. This miscibility gap, together with the organic salt solubility limitation, restricts the use of tetraalkylammonium bromides with alkyl chains longer than 4 carbon atoms as effective soap solubility enhancement electrolytes. We also found that for sodium soap with a longer hydrocarbon chain, more tetrabutylammonium salt is required to reduce the soap Krafft point to room temperature.     

Unusual visible luminescence of aluminium polyoxocations in aqueous solution

Identification of aluminium polyoxocations, MO(4)Al(12)(OH)(24)(H(2)O)(12)(7/8+) (M = Al, Ga and Ge) (K-MAl(12)) and Al(30)O(8)(OH)(56)(H(2)O)(26)(18+) (Al(30)), by their luminescence is reported. The fluorescence behavior of K-Al(13) has been found to differ with different metal ions and anions, implying a new discovery of a potential ion sensor.     

Corrosion mechanism of pure aluminium in aqueous alkaline solution

The corrosion of pure aluminium in alkaline solution has been explored using an open circuit potential transient, potentiodynamic polarization experiment and a.c. impedance spectroscopy. The steady-state value of the open circuit potential (E _ocp ^ss ) of pure aluminium in alkaline solution was observed to decrease with increasing rotation rate of the specimen, which is ascribed to the enhanced anodic reaction. The extent of anodic polarization for the aluminium dissolution reaction on pure aluminium at E _ocp ^ss was found to be greater than that of cathodic polarization for the water reduction reaction. This indicates that the rate of corrosion of pure aluminium is mainly determined by the anodic reaction in alkaline solution. Based upon the experimental results, a corrosion mechanism for pure aluminium has been proposed in the presence of the native surface oxide film in alkaline solution, involving consecutive oxide film formation and dissolution, and simultaneous water reduction.     

Electric polarizability of DNA in aqueous salt solution

Monte Carlo simulations are performed to determine the anisotropy of the electric polarizability of a model DNA fragment in aqueous salt solution. By taking into consideration the participation of coions in the electroneutrality condition, at every simulation step, we obtain a list of counterions constituting the net charge arranged in increasing order of their distance from the DNA and calculate the contribution to the dipole moment from the first n counterions in the list. We define a partial polarizability tensor due to these n counterions to understand the origin of the polarizability in close relation to the solution structure. The ionic distributions are described by the counterion condensation theory. Characteristic features of the electric properties of polyelectrolytes are reproduced. The anisotropy of the electric polarizability Deltaalpha of DNA decreases with the addition of salt, yielding values comparable to experiment. The effect of electrophoretic motion of the polyion is examined by estimating its upper limit.     

Decomposition of sodium dodecyl sulfate with ozone in aqueous solution

Decomposition of sodium dodecyl sulfate with ozone in aqueous solution in the presence of high concentrations of sodium nitrate was studied. The factors affecting ozone interaction with a dissolved compound were determined.