Kinetics of photocatalytic reduction of Pb(II) on nanocrystalline TiO2 coatings: A quartz crystal microbalance study

Pb(II) is a highly toxic substance, exposure to which can cause various diseases. To better understand the application of TiO₂ as a photocatalyst for removing Pb(II) from wastewater, quartz crystal microbalance (QCM) technique was employed to in situ investigate the reduction behavior of Pb(II) on nanocrystalline TiO₂ coatings under N₂. The processes of Pb(II) reduction at various concentrations of HCOOH and in the presence of different organic additives were monitored, and the corresponding kinetics was proposed. The obtained results showed that the kinetics of Pb(II) reduction on TiO₂ coatings was closely related to the organic additives. The HCOOH showed a higher efficiency for Pb(II) reduction in comparison with other organic additives, and the reduction-rate constant reached 0.54 × 10⁻³ s⁻¹ which was two times higher than that exhibited in the presence of C₂H₅OH. QCM measurement provides an useful method for monitoring the reduction process of Pb(II) on TiO₂ coatings.     

The Cluster Mechanism in Sulphur Sensitization

. The production of silver sulphide on two cubic silver halide emulsions has been followed using sodium thiosulphate sensitizer with the outer sulphur atom labelled ³⁵S. It is found that the position of sensitizer adsorption on the silver halide grain has an effect upon its rate of breakdown to yield silver sulphide. The concentration of sensitizer added to the emulsion affects the photographic response. At optimum sensitivity the quantity of silver sulphide present depends upon the initial sensitizer level, the silver sulphide becoming less efficient with increasing sensitizer. Clusters of silver sulphide are probably produced as a result of preferential adsorption of sensitizer by silver sulphide.     

Determination of the oxidizing ability of HTSC materials containing two elements with a variable degree of oxidation

The presence of mixed valence states of elements is supposed to be a common characteristic feature of the high-T _c superconductors, based on copper oxides. Methods have been suggested for the determination of Cu(III) in the Y-Ba-Cu-O ceramics and separate determination of two oxidants: Bi(V) and Cu(III), Tl(III) and Cu(III) in the corresponding materials. Compounds of Bi(V) oxidize in the ions of Mn(II) to MnO ₄ ⁻ in the acidic medium. Active oxygen, bound to Cu(III) is isolated, not oxidizing Mn(II). MnO ₄ ⁻ is titrated then with a solution of Fe(II) sulphate. For the determination of Tl(III) the sample is dissolved in the acid, Cu(III) is reduced to Cu(II) and Tl(III) is titrated with the hydroquinone solution. The compounds of Bi(V), Tl(III) and Cu(III), having high oxidation-reduction potentials can oxidize the complex Co(II)-EDTA to Co(III)-EDTA. The colour intensity of the latter is proportional to the content of Cu(III) or to the sum of Bi(V) and Cu(III) or Tl(III) and Cu(III). The content of Cu(III) in Bi- and Tl-containing materials is determined by the difference.     

Optical and spectroscopic properties of soda lime alumino-silicate glasses doped with erbium and silver

Spectroscopic properties of Ag/Er co-doped soda lime silicate glasses have been studied with the aim of assessing the effective role of silver as a sensitizer for erbium. Changes in spectroscopic properties of Er³⁺ as a function of silver addition to the base composition have been measured. Transmission electron microscopy (TEM), absorption as well as photoluminescence measurements in the visible and infrared spectral region, particularly ⁴I_13/2 → ⁴I_15/2 transition of the Er³⁺ ion were performed; excitation wavelengths in the range from 325 to 808 nm were used. Enhancement of the Er³⁺ luminescence at 1.54 μm was observed when Ag was added.     

Development and validation of a one-step immunoassay for determination of cadmium in human serum.

A sensitive and simple one-step immunoassay was developed and validated for quantitative determination of Cd(II) in human serum. In this method, a monoclonal antibody that recognizes Cd(II)-EDTA complexes was directly immobilized onto microwell plates. The serum sample containing metallothionein(MT)-bound and non-MT-bound Cd(II) was acidified to displace the Cd(II) from MT. The sample was then treated with metal-free EDTA to convert Cd(II) to Cd(II)-EDTA complexes. A mixture of Cd(II)-EDTA complexes derived from serum samples and Cd(II)-EDTA conjugated with peroxidase enzyme was incubated in the wells to compete for binding sites of the immobilized antibody. After addition of peroxidase substrate, the bound fraction of the enzyme conjugate was measured by a microplate reader, and the signal was inversely proportional to the concentration of the Cd(II) in the sample. The assay limit of detection was 0.24 microg/L, and the effective working range at coefficient of variation of < or = 10% was 0.24-100 microg/L. Analytical recovery of spiked Cd(II), in the concentration range between 0.8 and 50 microg/L, was 97.8 +/- 4.0%. The assay was selective for Cd(II); other metal ions (Mn, Co, Cu, Zn, Mg, Hg, Ca, Ni, Fe, and Pb), tested at concentrations considerably higher than those present in human serum, did not significantly interfere with the assay. The assay results correlated well with those obtained by graphite furnace atomic absorption spectrometry (r = 0.984).     

Formation of Photosensitive Layers in Alkali Germanate Glasses

The induced optical absorption spectra of 70GeO₂ ⋅ 10Ga₂O₃ ⋅ 20Li₂O glasses are measured. A process is described for producing photosensitive layers on alkali germanate glasses using ion-exchange diffusion from salt melts containing silver nitrate. The effects of the sensitizer (Ce³⁺, Fe³⁺, and Fe²⁺) and preparation, UV irradiation, and heat treatment conditions on the mechanisms of silver reduction in the surface layer of germanate glasses are examined. The results demonstrate that colloidal silver particles can be produced via ion exchange at 350°C in glasses containing 0.1 wt % Fe₂O₃. The particle diameter in a glass prepared under reducing conditions is estimated at 2.5 nm.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 6, 2005, pp. 753–761.Original Russian Text Copyright © 2005 by Bocharova.     

Removal of Pb(II) ions from aqueous solution by adsorption using bael leaves (Aegle marmelos)

Biosorption of Pb(II) on bael leaves (Aegle marmelos) was investigated for the removal of Pb(II) from aqueous solution using different doses of adsorbent, initial pH, and contact time. The maximum Pb loading capacity of the bael leaves was 104 mg g^?1 at 50 mg L^?1 initial Pb(II) concentration at pH 5.1. SEM and FT-IR studies indicated that the adsorption of Pb(II) occurs inside the wall of the hollow tubes present in the bael leaves and carboxylic acid, thioester and sulphonamide groups are involved in the process. The sorption process was best described by pseudo second order kinetics. Among Freundlich and Langmuir isotherms, the latter had a better fit with the experimental data. The activation energy E_a confirmed that the nature of adsorption was physisorption. Bael leaves can selectively remove Pb(II) in the presence of other metal ions. This was demonstrated by removing Pb from the effluent of exhausted batteries.     

Chemically modified activated carbon with 1-acylthiosemicarbazide for selective solid-phase extraction and preconcentration of trace Cu(II), Hg(II) and Pb(II) from water samples

A new sorbent 1-acylthiosemicarbazide-modified activated carbon (AC-ATSC) was prepared as a solid-phase extractant and applied for removing of trace Cu(II), Hg(II) and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 3, the maximum static adsorption capacity of Cu(II), Hg(II) and Pb(II) onto the AC-ATSC were 78.20, 67.80 and 48.56 mg g⁻¹, respectively. The adsorbed metal ions were quantitatively eluted by 3.0 mL of 2% CS(NH₂)₂ and 2.0 mol L⁻¹ HCl solution. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3σ) of this method for Cu(II), Hg(II) and Pb(II) were 0.20, 0.12 and 0.45 ng mL⁻¹, respectively. The relative standard deviation under optimum conditions is less than 4.0% (n = 8). The prepared sorbent was applied for the preconcentration of trace Cu(II), Hg(II) and Pb(II) in certified and water samples with satisfactory results.     

Tl-based high-Tc superconducting films prepared by aerosol deposition

The deposition of aqueous aerosols of nitrates led to precursor films with a thickness of 3–5 μm. The Ba–Ca–Cu–O and Pb–Sr–Ba–Ca–Cu–O as-deposited layers were calcined at 850–870°C. Thallination of Ba–Ca–Cu–O precursors at relatively high Tl₂O partial pressure resulted in Tl-2212 films with preferred c-axis orientation. Partial substitution of Pb for Tl and of Sr for Ba yielded randomly oriented Tl-1212 films. Deposition of Ba(II)-, Ca(II)- and Cu(II)-bis(2,4-pentanedionates) on polycrystalline silver tapes produced — after subsequent thallination — textured Tl-2223 films with a thickness of about 1 μm. Some aspects of the chemical reactions proceeding during the aerosol deposition and in the thallination step are discussed on the basis of thermogravimetric measurements.     

Magnetic and electrical properties of new inorganic complex based materials derived from bis(1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolato)metalate(II) ions

Magnetic and electrical properties of a series of new inorganic complex based materials [n-Pr₄N]₂[Pb(ecda)₂], [Et₄N]₄[Hg₂(ecda)₄] and M[M′(ecda)₂] (M=Co(II), Ni(II), Cu(II), Cd(II) or Pb(II); M′=Hg(II) or Pb(II); ecda²⁻=1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate) have been investigated using molecular spectroscopic (IR, Raman, EPR, electronic and mass) and conducting properties. Complete quenching of paramagnetism indicates strong Cu–Cu interaction in the layered polymeric array of Cu[Hg(ecda)₂] and Cu[Pb(ecda)₂] in the solid state. The ¹H NMR spectrum of Ni[Pb(ecda)₂] in DMSO-d₆ gives narrow unshifted peaks due to diamagnetic, square-planar geometry around Ni(II) and shows absence of some octahedral units (μ_eff=1.49 BM) present in the solid state of this product. While the peak broadening indicates paramagnetic nature and absence of dominant Cu–Cu interaction in solution for Cu[Hg(ecda)₂] and Cu[Pb(ecda)₂]. The temperature dependent (305–373 K) compressed pellet conductivity together with activation energy (0.36–1.23 eV), show semiconducting behaviour of some of the bimetallic derivatives.     

SERS property of Co complex on boron nitride nanosheets/silver nanoparticles aggregates and photophysical characterisation of interactions among Co complex ion-exchanged within zirconium phosphate

ABSTRACT

The Co(II) complex of [Co(bpy)₂(NO₃)]Cl·3H₂O, bpy = 2,2'-bipyridine, has been synthesised by the solution crystallisation method. The boron nitride nanosheets/silver nanoparticles/[Co(bpy)₂(NO₃)]Cl·3H₂O nanoaggregate was prepared in order to better analyse the adsorption orientation of the cobalt complex on the surface of silver nanoparticles. The result of the surface-enhanced Raman scattering measurement indicates that the molecular plane of the cobalt complex presents a tilted orientation with respect to the surface of silver nanoparticles. The luminescence property of [Co(bpy)₂(NO₃)]⁺ two-dimensional arrangements within the layers of zirconium phosphate (ZrP) was also investigated. Steady-state luminescence spectra of the [Co(bpy)₂(NO₃)]⁺-exchanged ZrP materials show an increase in the luminescence intensity.     

The use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate as precursor in the deposition of thin silver layers on float glass by the atmospheric pressure combustion chemical vapor deposition process

The innovative use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate ([AgO₂C(CH₂OCH₂)₃H], 3) as precursor for the deposition of silver on float glass by applying the atmospheric pressure combustion chemical vapor deposition process is described. As nucleation layer tungsten oxide was utilized, conformal, closed and dense silver layers of ca. 70 nm thickness were obtained. They are adhesive and high reflective with a resistivity of 5 ? 10⁻⁸ Ωm.     

Inkjet printing of conductive patterns with an aqueous solution of [AgO2C(CH2OCH2)3H] without any additional stabilizing ligands

The use of silver(I)-2-[2-(2-methoxyethoxy)ethoxy]acetate, [AgO₂C(CH₂OCH₂)₃H], and its application as an aqueous metal-organic decomposition (MOD) inkjet ink is reported. The chemical and physical properties of the silver carboxylate and the ink formulated thereof are discussed. The ink meets all requirements of piezo driven inkjet printing. The printed features were converted into electrically conducting silver patterns by thermal or photo-thermal treatment. The conversion of [AgO₂C(CH₂OCH₂)₃H] to elemental silver follows a two-step decomposition as demonstrated by thermogravimetry-mass spectrometry (TG-MS) measurements. The measured conductivities of the printed features on glass and polyethylene-terephthalate (PET) are 2.7 × 10⁷ S m⁻¹ and 1.1 × 10⁷ S m⁻¹, respectively, which correspond to 43% (glass) and 18% (PET) of the bulk silver conductivity.     

Magnetic nanobiosorbent (MG‐Chi/Fe3O4) for dispersive solid‐phase extraction of Cu(II), Pb(II), and Cd(II) followed by flame atomic absorption spectrometry determination

Trace amounts of Cu (II), Pb (II), and Cd (II) in a wastewater sample were preconcentrated with a novel cross‐linked magnetic chitosan modified with a new synthesised methionine‐glutaraldehyde Schiff''s base (MG‐Chi/Fe₃O₄) as a dispersive solid‐phase extraction (DSPE) adsorbent. The adsorbed metal ions were then eluted with a specific volume of suitable solution and determined by flame atomic absorption spectrometry (FAAS). Various parameters affecting the extraction efficiency of the metal ions were investigated and optimised, including pH, amount of adsorbent, extraction time, type and volume rate of eluent, elution time, sample volume, and effect of interfering ions. The adsorption kinetics are more consistent with the pseudo‐second order model. The results were statistically interpreted and the analytical performance of the proposed method was found to have preconcentration factors of 55, 60, and 50 μg L⁻¹ for Cu(II), Pb(II), and Cd(II), respectively, limits of detection were 0.22, 0.24, and 0.10 μg L⁻¹ for Cu(II), Pb(II), and Cd(II), respectively, with a relative standard deviation (1.5%‐2.8 %), and the liner range was 5–1000 for Cu(II) and Pb(II) and 2.5–1000 for Cd(II). It was concluded that this method was suitable for successful simultaneous determination of Cu(II), Pb(II), and Cd(II) in industrial wastewater samples.     

Preparation, characterization and analytical applications of a new and novel electrically conducting fibrous type polymeric-inorganic composite material: polypyrrole Th(IV) phosphate used as a cation-exchanger and Pb(II) ion-selective membrane electrode

‘Polymeric-inorganic’ composite type of cation-exchanger ‘polypyrrole Th(IV) phosphate’ was prepared by mixing polypyrrole into fibrous inorganic precipitate of Th(IV) phosphate. This type of composite possesses a new class of hybrid ion-exchangers with good ion-exchange capacity (I.E.C.), higher stability, reproducibility and selectivity for heavy metals. The physicochemical properties of the material were determined using AAS, CHN elemental analysis, ICP-MS, UV-VIS spectrophotometry, FTIR, thermogravimetric analyses-differential thermal analysis (TGA-DTA), XRD and SEM studies. Ion-exchange capacity, pH-titrations, elution and distribution behavior etc. were also carried out to characterize the material. On the basis of distribution studies, the material was found to be highly selective for Pb(II), a heavy metal pollutant in the environment. Its selectivity was examined by achieving some important binary separations like Pb(II)-Zn(II), Pb(II)-Ni(II), Pb(II)-Cu(II) and Pb(II)-Cd(II) on its column that indicate its utility in environmental pollution control in one-way or other. This electroactive material also showed the DC electrical conductivity in the range of 10⁻⁶ to 10⁻⁴ S cm⁻¹. A new heterogeneous precipitate based selective ion-sensitive membrane electrode was developed by using this composite cation-exchanger for the determination of Pb(II) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.     

Chelating agent-free solid phase extraction (CAF-SPE) of uranium,cadmium and lead by Fe-Al-Mn nanocomposite from aqueous solution

Fe-Al-Mn nanocomposite has been synthesized by impregnating MnO₂ with Fe and Al nitrate aqueous solution for preconcentration and determination of Pb (II), Cd (II) and U (VI) ions from aqueous solution. Fourier Transform Infrared spectroscopy (FTIR), X-Ray-diffraction (XRD) and Scanning electron microscopy coupled with energy dispersive&nbsp;X-ray detector (SEM–EDX) were employed to characterize the as-synthesized nanocomposite. The XRD result indicates that the as-synthesized nanocomposite had a crystal size with rhombohedral structure and size of 30.81 nm. FTIR results confirmed the presence of hydroxyl group and Metal–Oxygen vibration in the adsorbent. A sensitive and simple solid-phase preconcentration procedure for the determination of trace amounts of Pb(II) and Cd(II) ions by FAAS and U(VI) ions by Uv–Vis was developed. The adsorption isotherm was formally described by both Langmuir and Freundlich equation with a maximum adsorption capacity of 12.5 (Pb), 12.8(Cd) and 14.9(U) mg g^?1 respectively with preconcentration factor of 15. The limits of detection were 0.09, 0.05 and 0.0097 mg L^?1 and the relative standard deviation for ten replicate measurements were 2.47, 0.979 and 2.04%, for Pb (II), Cd(II) and U(VI) ions, respectively. The recovery of Pb(II), Cd(II) and U(VI) ions were found to be 92.7, 91.3, and 81.76%, respectively. On the basis of these findings, the as-synthesized Fe-Al-Mn nanocomposite was successfully applied as a solid phase extraction for preconcentration and determination of Pb(II), Cd(II) and U(VI) ions in aqueous solution.

     

Large-scale synthesis of silver nanowires via a solvothermal method

Silver nanostructures have been synthesized through a simple solvothermal method by reducing silver nitrate (AgNO₃) with ethylene glycol (EG) and using poly(vinylpyrrolidone) (PVP) as an adsorption agent. Different concentrations of ferric chloride (FeCl₃) are added into the solution. It is found that AgCl colloids formed in the initial stage greatly influence the final morphologies of the products. When a low-concentration FeCl₃ solution is used, there is a mixture of silver nanoparticles and nanowires. However, when a high-concentration FeCl₃ solution (100 μM) is used, large amounts of AgCl colloids appear, resulting in decreasing free Ag⁺ during initial formation of silver seeds and slowly releasing of Ag⁺ to the solution in the subsequent reaction. This leads to the formation of silver nanowires. Furthermore, an increase in the concentration of FeCl₃ from 100 to 300 μM results in the synthesis of silver nanowires with larger sizes. In addition, Fe(III) is reduced to Fe(II) form which in turn reacts with and removes adsorbed atomic oxygen from the surface of silver seeds. In this case, uniform silver nanowires can be obtained.     

Selective extraction and detection of noble metal based on ionic liquid immobilized silica gel surface using ICP-OES

In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf₂) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf₂ was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf₂ phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf₂ phase followed the Langmuir model with adsorption capacity of 59.48 mg g^?1, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g^?1). Furthermore, SG–ClPrNTf₂ phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results.     

Fabrication and Properties of Ag–Ni Bimetallic Sheathed (Bi,Pb)-2223 Tapes

10-meter-long Ag?CNi bimetallic sheathed (Bi,Pb)-2223 tapes with outer nickel sheath and inner silver sheath have been successfully fabricated by the ??Powder in tube?? technique. Microstructure and phase evolution studies by means of SEM and XRD, as well as critical current density (J _c ) measurements have been performed. It is found that the nickel sheath and dwell time in the first sintering process have great influences on the texture evolution, phase transformation and J _c of the Bi-2223/Ag/Ni tapes. Mono-filament (Bi,Pb)-2223 tape with a J _c of 6656?A?cm^?2 and 61-filament tape with a J _c of 12420?A?cm^?2 are obtained. Although using composite bimetallic sheaths can reduce production costs and improve mechanical properties of the Bi-2223 tapes, the Bi-2223 content and J _c of Bi-2223/Ag/Ni tapes are relatively lower than that of traditional Bi-2223/Ag tapes. Meanwhile, due to higher Bi-2223 content and better alignment of Bi-2223 grains, tapes with 61-filament have higher J _c than mono-filament tapes.     

Development of a hexavalent chromium ISFET sensor with a polymeric membrane including tributylphosphate

This paper presents a first report on chromium ISFET (ion-sensitive field effect transistor) based on a polymeric membrane (siloprene) including an ionophore (tributylphosphate) sensitive for hexavalent chromium. The sensor sensitivity as a function of the pH was studied; its value is minimum in a pH interval from 5.5 to 7.5. The sensitivity for hexavalent chromium was found to be 15 mV/loga_Cr⁶⁺ in the range of 10^− 4 to 10^− 2 M. The detection limit was found to be 10^− 5 M. The studied interfering ions are Pb(II) and Cd(II) that do not represent a great perturbation upon the response for hexavalent chromium.