Presence Of Ions Research Articles

Facile and One Pot Synthesis of Gold Nanoparticles Using Tetraphenylborate and Polyvinylpyrrolidone for Selective Colorimetric Detection of Mercury Ions in Aqueous Medium

In this work, we reported for the first time, a facile and one step synthesis of gold nanoparticles from HAuCl4, employing tetraphenylborate as the reducing agent. The synthesis is not only facile but also yields “dumb-bell-shaped”particles. This shape appears to arise from a possible emulsion of the products of oxidation/decomposition of tetraphenylborate by HAuCl4, surrounding the particle. The size and shape of the AuNPs were characterized by Transmission electron microscopy (TEM) and UV-visible Spectroscopy. Interestingly, the addition of polyvinylpyrrolidone (PVP) during the synthesis was found to enhance the stability of the nanoparticle dispersion. The particles synthesized under these conditions assume “spherical” shape with the appearance of only transverse surface plasmon resonance band. The highlight of the observations is that the gold nanoparticles synthesized using tetraphenylborate as reducing agent and PVP as stabilizer are highly stable in alkaline medium, in contrast to the synthesis wherein borohydride is used as reducing agent. The AuNPs synthesized using tetraphenylborate and PVP show their mercury sensing behavior only in the alkaline medium. The color of the nanoparticle dispersion undergoes distinct color change from pink to blue with the addition of mercury ions. They also show dramatic selectivity to mercury ions in presence of other interfering ions, Pb2+, Zn2+ and Ca2+.

Studies on testing and evaluation of platinum plated titanium electrode for production of uranous nitrate

Partitioning of plutonium from uranium is an important step in the reprocessing of spent fuel by PUREX process of solvent extraction using 30% TBP-dodecane. This is achieved by selectively reducing the Pu in solution to least extractable trivalent state by uranous nitrate as the reductant. The latter is conventionally produced by electrolytic reduction of uranyl ion in presence of hydrazine nitrate as uranous nitrate stabilizer using Pt-coated titanium as the anode. The anode plating wears out after period of operation thus affecting the process efficiency and hence the quality control testing of platinum plated electrode becomes important. This article describes the use of Beta backscattering method with strontium-90 radioisotope as non-destructive testing tool for measuring the coating thickness of the sample Ti electrode. The surface characteristics and coating morphology were also examined by scanning electron microscope and the micrographs are presented.

Preparation and characterization of silver‐chitosan nanocomposite particles with antimicrobial activity

AbstractA nanocomposite of silver nanoparticles (AgNPs) embedded in chitosan (Cts) matrix was successfully synthesized by crosslinking technology. Colloidal AgNPs formed in situ by chemical reduction of silver ions in presence of Cts showed a good stability. Transmission electron micrographs, X‐ray diffraction patterns, and UV‐visible spectra of Ag‐Cts composite particles confirmed the formation of silver nanocrystals. Fourier transform infrared spectroscopy verified the presence of Cts as a stabilizing agent surrounded AgNPs. Thermogravimetric‐differential scanning calorimeter analysis revealed Ag‐Cts nanocomposite had a higher thermal stability than Cts. X‐ray photoelectron spectroscopy suggested that the Ag‐O bond in the nanocomposite coule lead to the tight combination between silver and Cts. Microbial experiments showed the nanocomposite had excellent and wide spectrum antibacterial properties, and were more efficient than either AgNPs or Cts alone for inactivating bacteria. Therefore, the resultant nanocomposite could be used as antimicrobial materials for medical and biological applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Ion transport in the polyamide layer of RO membranes: Composite membranes and free-standing films

The permeability of the composite ESPA1 membrane to ferro- and ferricyanide ions without and with an excess of supporting buffer was analyzed by three different methods: filtration followed by phenomenological analysis, and electrochemical impedance spectroscopy and chronoamperometry using free polyamide films isolated from the membrane. Appropriate relations were developed that relate the observed permeability to actual permeability of the trace redox ions and correct for concentration polarization of the trace ion in presence of a more concentrated (dominant) electrolyte. Within the uncertainties associated with polarization correction, coupling of ionic fluxes, and ion association in solution and within the membrane, consistent values of permeabilities, of about 0.03–0.05 μm/s, were obtained by all methods. The results validate that (a) the contribution of convection to salt permeation through the active layer of thin-film composite membranes is small; (b) the procedures used to isolate the active polyamide layer from commercial membranes has a minimal impact on the transport properties of the polyamide films; the isolated free films may then adequately represent the properties of the original active layer in characterization studies. This information may have important implications for studying transport, modeling and characterization of thin-film composite membranes.

Novel Perchlorate Selective Electrode Based on Neutral Surfactant Ion-Pair Complex of Dodecyltrimethylammonium-Perchlorate

Novel perchlorate selective polymeric membrane electrode based on recently synthesized neutral ion-pair complex dodecyltrimethylammonium-perchlorate () has been reported to be exhibiting Nernstian slope (−57.34 mV/dec) for perchlorate ions over a wide concentration range (1.00 × 10−1 M–5.00 × 10−6 M) with lower detection limit of 2.51 × 10−6 M. Proposed electrode has fast response time (10 s) and wide pH range (1.40–6.05). Selectivity coefficient values indicate its ability to preferentially sense perchlorate ions in presence of various secondary anions. Application of the proposed electrode has been studied by potentiometric estimation of perchlorate ions in synthetic water samples.

Decameter structure in heater‐induced airglow at the High frequency Active Auroral Research Program facility

On 28 October 2008, small‐scale rayed artificial airglow was observed at the High frequency Active Auroral Research Program (HAARP) heating facility by the HAARP telescopic imager. This airglow occurred during an experiment at twilight from 0255–1600 UT (1855–2000 LT) and with estimated scale sizes of 100 m (at assumed 225 km altitude) constitutes the smallest structure observed in artificial airglow to date. The rays appeared to be oriented along the geomagnetic field lines. During this period, other instruments, SuperDARN, GPS receivers, stimulated electromagnetic emissions receivers, also recorded unusual data sets with the general characteristic of time scales longer than anticipated for features to form. The experiment took place at the commencement of a small geomagnetic disturbance (Kp of 4.3). This unique observation is as yet unexplained. The airglow features start as large scale structures and then become smaller as heating continues in apparent contradiction to current theories on irregularity development. A thermal gradient instability at boundary of the ionospheric footprint of the plasmapause may be responsible for causing the small‐scale structuring. Observations of 427.8 nm N2+ (first negative group) emissions indicate the presence of ionization.

Competitive modeling for the biosorptive removal of copper and lead ions from aqueous solution by Mansonia wood sawdust

Mansonia wood sawdust is applied as a biosorbent for the removal of copper and lead ions from single and binary aqueous solution. The effect of solution pH, electrolyte, metal ion competition and temperature were examined to obtain insight of its application for industrial waste water treatment. The Langmuir isotherm provided a better fit to experimental data for lead ion sorption with a higher monolayer capacity, while copper ion sorption was best described by the Freundlich and BET isotherms. The combined effect of adsorbing one metal ion in the presence of the other metal ion reduced the adsorption capacity of either metal ion. In a binary solution, removal of lead ions in the presence of copper ions followed the Langmuir isotherm model while the removal of copper ions in presence of lead ions followed both the Langmuir and BET isotherm models.

Effect of trapped electrons on soliton energy in an inhomogeneous magnetized multicomponent plasma

Energy carried by ion acoustic solitons are estimated in an inhomogeneous plasma containing negative ions and a group of hot and cold nonisothermal electron species in addition to positive ions in presence of external magnetic field. On the basis of Reductive Perturbation Technique (RPT), a relevant Korteweg-de Vries (KdV) equation is obtained and solved for its solitary wave solution. The profile of the propagating soliton is used to obtain an expression of the soliton energy. The characteristics of soliton and the energy carried by it are investigated under the effects of nonisothermal electrons trapped by wave potential, negative ions concentration, strength of the magnetic field and its obliqueness.

The effect of coherent phase control in (e, 2e) process of a hydrogenic ion in presence of a two colour laser field

We study the coherent phase control (CPC) of ionization (TDCS) of a hydrogenic ion under the action of a bichromatic laser field consisting of a fundamental frequency and one of its harmonics by varying the phase difference between the two components. A significant reduction is noted particularly in the recoil peak (dominant for the ionic target) with the two color field as compared to the monochromatic one, while the modification of the binary peak is comparatively less. The CPC is found to be more effective for the odd harmonics than the even one.

Analysis of oilfield waters by ion chromatography to determine the composition of scale deposition

Large amounts of water are produced during the production of crude oil and natural gas. This water has to be analyzed to realize the correct geological formation. In this work, an extensive analysis of oil field water delivered from Gulf of Suez was carried out to determine the composition of the precipitate formed before starting waterflood operation. Cation and anions are the main interest of this analysis and are carried out using ion chromatography (IC). The data of water analysis have been used as an input data for computer software program. The scale precipitation processes in the bulk solution as well as the tendency rate and inhibitor effectiveness have been determined using jar test methods. The data arising from jar test are compared with the output of the software program to evaluate and quantify the scale precipitation. Also, the mixing waters are analyzed after precipitation to determine the consumed calcium and sulfate ions in presence and absence of inhibitor. It was found that mixing of the injection water and formation water leads to calcium carbonate and barium sulfate scaling at 60% formation water in absence of scale inhibitor.

Ion-acoustic shock waves with negative ions in presence of dust particulates

Dust acoustics shock waves have been investigated experimentally in a homogeneous unmagnetized dusty plasma device containing negative ions. When the negative ion density larger than a critical concentration ‘ r c ’ negative shock waves were observed instead of positive shock waves. Again when it is nearly equal to ‘ r c ’ both positive and negative shock waves propagate. The experimental findings are compared with modified KdV–Burgers equation. The velocity of the shock waves are also measured and compared with the numerical integration of modified KdV–Burgers equation.

Resonant interaction of femtosecond radiation with a cloud of cold 87Rb atoms

The resonant interaction of 87Rb atoms in a magneto-optical trap with femtosecond laser radiation in the spectral range 760–820 nm has been investigated experimentally. It has been demonstrated that femtosecond laser radiation with a spectral width of 10 nm interacts with an atomic ensemble as a set of spectrally narrow modes and as an ionizing laser field simultaneously. The dynamics of trap loading in the presence of ionization by femtosecond radiation has been studied, and the 5D5/2 level population produced by an additional weak laser field has been measured.

Preparation of calix[4]arene methylene crosslinked resins with 2-pyridyl pendant group and their adsorption behavior towards silver ion

Three different resins namely 1:5 MC-resin, 1:3 MC-resin and 1:1 MC-resin have been synthesized by methylene crosslinking of 2-pyridylcalix[4]arene. Adsorption behavior of these resins towards the metal ions existing in photographic waste was investigated. The resins show absolute efficiency for adsorption of silver ion with no affinity for other coexisting ions. First two resins form 1:1 complex whereas the third one forms 2:1 complex with silver ion. Maximum loading capacity of silver ion on the present resins was found to be 1.15, 1.29 and 0.69 mol kg−1, respectively. Column chromatographic separation of silver ion in presence of excess of sodium ions was also carried out with 1:5 MC-resin. Selective adsorption of silver ions over excess of sodium ions was achieved.

Lanthanide Recognition: Determination of Thulium(III) Ions in Presence of Other Rare Earth Elements by a Thulium(III) Sensor Based on 4-Methyl-1,2-Bis(2-Pyridinecarboxamido)benzene as a Sensing Material

In this research, a novel thulium(III) potentiometric membrane sensor based on 4-methyl-1,2-bis(2-pyridinecarboxamido) benzene (MPB) is described. The sensor exhibits a Nernstian response over a concentration range of 1.0 × 10−7 M to 1.0 × 10−1 M, with a detection limit of 9.0 × 10−8 M. The best performance was achieved with a membrane composition of 30% PVC, 60% nitrobenzene (NB), 6% MPB, and 4% sodium tetraphenylborate (NaTPB). It was found that at the pH range of 3.6 to 9.0, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presents satisfactory reproducibility, very fast response time (15 s), and relatively good discriminating ability for Tm(III) ions with respect to many common cations and lanthanide ions. The validation of the proposed electrode was tested by using Coal and Fuel Ash (FFA 1 Fly Ash) as a Certified Reference Material (CRM).

Tb 3+ ions in presence of ZnS:Mn 2+ nanocrystals immobilized on silica: Energy transfer ZnS→Tb 3+ and coordination state of Mn 2+ ions

Three-component luminescent material consisting of silica xerogel as a support with immobilized ZnS:Mn 2+ nanocrystals and Tb 3+ ions was compared with such two-component materials as the silica support with ZnS:Mn 2+ as well as the support with Tb 3+. In each case the nanocrystals and the lanthanide ions were immobilized at silica surface by impregnation procedure. Size of the ZnS quantum dots doped with Mn 2+ were estimated by Scherrer method from the X-ray diffraction (XRD) pattern. The materials have been characterized by EPR and optical spectroscopy techniques. EPR spectra allow to distinguish two different Mn 2+ sites: the first is assigned to isolated Mn 2+ substitutionally and incorporated into cubic ZnS lattice and the second is ascribed to the Mn 2+ situated near the nanocrystal surface. From the optical spectra we have found that in the three-component material, energy transfer from excited ZnS:Mn 2+ nanocrystals to Tb 3+ ions takes place. The different mechanisms of such transfer are discussed.

Adsorption of Pb(II) and Pb(II)-citric acid on sawdust activated carbon: Kinetic and equilibrium isotherm studies

The removal of Pb(II) and Pb(II)-citric acid (Pb(II)-CA) from aqueous solutions by sawdust activated carbon (SDAC) was investigated. The higher adsorptive removal of Pb(II) from aqueous solutions containing Pb(II)-CA than Pb(II) only was observed due to the presence of CA in the former system. The mechanism of adsorption process was studied by conducting pH as well as kinetic studies. Batch adsorption experiments were conducted to study the effect of adsorbent dose, initial concentration and temperature for the removal of Pb(II) from Pb(II) only and Pb(II)-CA aqueous systems. The adsorption was maximum for the initial pH in the range of 6.5–8.0 and 2.0–5.0 for Pb(II) and Pb(II)-CA, respectively. The solution pH, zero point charge (pH zpc) and species distribution of Pb(II) and Pb(II)-CA were found to play an important role in the adsorption of Pb(II) and Pb(II)-CA onto SDAC from water and wastewaters. SDAC exhibited very high adsorption potential for Pb(II) ions in presence of CA than when Pb(II) ions alone were present. The kinetic and equilibrium adsorption data were well modeled using pseudo-first-order kinetics and Langmuir isotherm model, respectively.

Extraction of metal ions in aqueous polyethylene glycol–inorganic salt two-phase systems in the presence of inorganic extractants: Correlation between extraction behaviour and stability constants of extracted species

The use of aqueous polyethylene glycol–inorganic salt two-phase systems for the extraction of metal ions has a great potential due to their durability, non-toxicity and relative low cost. The aqueous phases can be easily separated by centrifugation, and the operation is possible in a range of experimental conditions. The experimental results have shown that for a given aqueous two-phase system, the extraction behaviour of metal ions in presence of inorganic extractants is mainly dependent on the stability of extracted species. In this paper we review our results obtained at metal ion extraction using inorganic extractants and discuss three major types of extraction behaviours.

Kinetics of Simultaneous Photocatalytic Degradation of Phenolic Compounds and Reduction of Metal Ions with Nano-TiO2

The simultaneous photocatalytic degradation of phenol and 4-nitrophenol and reduction of metal ions like copper (Cu2+) and chromium (Cr6+) was studied with solution combustion synthesized nanoanatase TiO2 (CS TiO2) and commercial titania, Degussa P-25. The presence of metal ion reduces the rate of degradation of phenol and 4-nitrophenol. It was found that Cu2+ reduction to Cu+ is accelerated in the presence of phenol. In the case of Cr6+, CS TiO2 enhances the initial adsorption of Cr6+ and complete reduction is achieved within the first 10 min of UV irradiation. The presence of phenol or 4-nitrophenol also enhances the initial adsorption of Cr6+ and its reduction. The metal ion reduction in the presence of CS TiO2 is compared with that of Degussa P-25. The rate of reduction of metal ions in presence of Degussa P-25 is twice as slow as that of CS TiO2 in presence of both phenol and 4-nitrophenol. The presence of Cu2+ and Cr6+ also induces the formation of the intermediates which were not observed for the phenol-CS TiO2 system. The formation and consumption of the intermediates are modeled with a simple series reaction mechanism. A detailed dual-cycle, multistep reaction mechanism of TiO2 photocatalysis for the simultaneous degradation and reduction is proposed and the model is developed following the network reduction technique. The kinetic rate constants in the model are evaluated for the systems studied.

SPECTROPHOTOMETRIC STUDIES TO DETERMINE THE DISTRIBUTION COEFFICIENT OF SOME METAL IONS ON ANION EXCHANGE RESIN IN PRESENCE OF E.B.T. DYE.

The absorption spectra of various concentrations of some metal nitrate salts; Co(II), Ni(II), Cu(II) and Cr(III) nitrate, with different concentrations of Eriochrome Black T (E.B.T) dye solutions were studied in the presence and absence of Dowex – S.B.R. anion exchange resin ( nitrate form ) . The calculated values of distribution coefficient kd illustrate the importance of the E.B.T dye solution as complexing agent for the removal of different metal ions on the Dowex – S.B.R. anion exchange resin. The same studies have been performed for samples in different molarities of nitric acid at constant concentration of E.B.T. and metal ion solution for only Co (II ) and Ni ( II ) ions since Cu ( II ) and Cr ( III ) ions precipitate in the presence of E.B.T. The nitric acid imported also a marked influence on Co and Ni ions complex formation and consequently on their kd values. Ethanol and acetone were used in different proportions to evaluate the effect of changing the dielectric constant of the medium on the kd values of the Co and Ni with E.B.T. in the studied solutions. The kd values are markedly higher in acetone – dye – metal ion - water media as compared with those obtained in aqueous – ethanol – dye – metal ion mixture at the same concentrations. The effects of pH on the absorption and kd behavior for Co (II) and Ni (II) ions in presence of E.B.T. dye on the Dowex – S.B.R. anion exchange resin were studied and discussed.

Preparation of Ag nanoparticles termini‐protected side‐chain liquid crystalline azobenzene polymers by RAFT polymerization

AbstractA new synthetic approach to prepare Ag nanoparticles protected side‐chain liquid crystalline (LC) azobenzene polymers was reported. It is based on the reduction of silver ions in presence of a LC polymer polymerized by RAFT. The formation of Ag colloidal nanoparticles was confirmed by TEM and UV analysis. At the same time, according to the results of DSC, XPS, and FTIR spectra, Ag nanoparticles were protected by the side‐chain LC azobenzene polymers through surface attachment interactions between thiol groups and Ag. The out‐plane orientation of side‐chain LC is confirmed by surface‐enhanced Raman spectra analysis and scanning near‐field optical microscope, resulting from the large electromagnetic field arising from the excitation of surface plasmon polariton of Ag nanoparticles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5380–5386, 2007