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Photooxidation of 4-chlorophenol sensitised by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin in aqueous solution

Silva, Eliana; Pereira, Mariette M.; Burrows, Hugh D.; Azenha, M. E.; Sarakha, Mohamed; Bolte, Michèle
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
ENG
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The photosensitised degradation of 4-chlorophenol (4-CP) by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin (FeTDCPPS) has been studied in aerated aqueous solution, and is shown to lead to formation of p-benzoquinone (BQ) and p-hydroquinone (HQ) as main photoproducts. In deaerated solution no p-benzoquinone was formed. The photolysis products were identified by high performance liquid chromatography (HPLC) and UV-visible spectroscopy. The photodegradation in aerated solution was also carried out in the presence of sodium azide (NaN3) as a singlet oxygen [1O2(1g)] quencher, and showed a significant decrease in the rate of photolysis, suggesting under these conditions, that Type II sensitisation is one of the dominant mechanisms of 4-CP degradation. Support for this comes from laser flash photolysis and time-resolved singlet oxygen phosphorescence measurements. However, these also show direct reaction between the excited porphyrin and 4-CP, indicating that there are two mechanisms involved in the chlorophenol photodegradation.; http://dx.doi.org/10.1039/b308975d; Clermont-Ferrand; ICCTI/GRICES; CNRS; FCT; POCTI; FEDER

Thermodynamic Stabillity of Hydrogen-Bonded Systems in Polar and Nonpolar Environments

PASALIC, Hasan; AQUINO, Adelia J. A.; TUNEGA, Daniel; HABERHAUER, Georg; GERZABEK, Martin H.; Georg, Herbert de Castro; Moraes, Tatiane Faustino de; Coutinho, Kaline Rabelo; Canuto, Sylvio Roberto Accioly; LISCHKA, Hans
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
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The thermodynamic properties of a selected set of benchmark hydrogen-bonded systems (acetic acid dimer and the complexes of acetic acid with acetamide and methanol) was studied with the goal of obtaining detailed information on solvent effects on the hydrogen-bonded interactions using water, chloroform, and n-heptane as representatives for a wide range in the dielectric constant. Solvent effects were investigated using both explicit and implicit solvation models. For the explicit description of the solvent, molecular dynamics and Monte Carlo simulations in the isothermal isobaric (NpT) ensemble combined with the free energy perturbation technique were performed to determine solvation free energies. Within the implicit solvation approach, the polarizable continuum model and the conductor-like screening model were applied. Combination of gas phase results with the results obtained from the different solvation models through an appropriate thermodynamic cycle allows estimation of complexation free energies, enthalpies, and the respective entropic contributions in solution. Owing to the strong solvation effects of water the cyclic acetic acid dimer is not stable in aqueous solution. In less polar solvents the double hydrogen bond structure of the acetic acid dimer remains stable. This finding is in agreement with previous theoretical and experimental results. A similar trend as for the acetic acid dimer is also observed for the acetamide complex. The methanol complex was found to be thermodynamically unstable in gas phase as well as in any of the three solvents. (C) 2010 Wiley Periodicals...

A stable liquid-liquid extraction system for clavulanic acid using polymer-based aqueous two-phase systems

Pereira, Jorge F. B.; Santos, Valeria C.; Johansson, Hans-Olof; Teixeira, Jose A. C.; Pessoa, Adalberto, Jr.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
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The partitioning of Clavulanic Acid (CA) in a novel inexpensive and stable aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The aqueous two-phase systems are formed by mixing both polymers with a salt (NaCl or Na2SO4) and an aqueous solution of CA. The stability of CA on the presence of both polymers was investigated and it was observed that these polymers do not degrade the biomolecule. The effect of PEG-molecular size, polymer concentrations on the commercial CA partitioning has been studied, at 25 degrees C. The data showed that commercial CA was preferentially partitioned for the PEG-rich phase with a partition coefficient (K-CA) between 1 and 12 in the PEG/NaPA aqueous two phase systems supplemented with NaCl and Na2SO4. The partition to the PEG phase was increased in the systems with high polymer concentrations. Furthermore, Na2SO4 caused higher CA preference for the PEG-phase than NaCl. The systems having a composition with 10 wt.% of PEG4000, 20 wt.% of NaPA8000 and 6 wt.% of Na2SO4 were selected as the optimal ones in terms of recovery of CA from fermented broth of Streptomyces clavuligerus. The partitioning results (K-CA = 9.15 +/- 1.06) are competitive with commercial extraction methods of CA (K-CA = 11.91 +/- 2.08) which emphasizes that the system PEG/NaPA/Na2SO4 can be used as a new process to CA purification/concentration from fermented broth. (C) 2012 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)...

Electrochemical investigation of the dimeric oxo-bridged ruthenium complex in aqueous solution and its incorporation within a cation-exchange polymeric film on the electrode surface for electrocatalytic activity of hydrogen peroxide oxidation

Teixeira, Marcos F. S.; Cincotto, Fernando H.; Raymundo-Pereira, Paulo A.
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 6804-6811
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 05/01296-4; Processo FAPESP: 08/07298-7; Electrochemical behavior of oxo-bridged dinuclear ruthenium(III) complex ([(bpy)2(H(2)O)Ru(III)-O-Ru(III)(H(2)O)(bpy)2](4+)) has been studied in aqueous solution (KCl 0.5 mol L(-1)) by both cyclic and rotating disk electrode (ROE) voltammetry in order to identify and elucidate the reaction mechanism. Modified electrode containing the oxo-bridged ruthenium complex incorporated into a cation-exchange polymeric film deposited onto platinum electrode surface was studied. Cyclic voltammetry at the modified electrode in KCl solution showed a single-electron reduction/oxidation of the couple Ru(III)-O-Ru(III)/Ru(III)-O-Ru(IV). The modified electrode exhibited electrocatalytic property toward hydrogen peroxide oxidation in KCl solution with a decrease of the overpotential of 340 mV compared with the platinum electrode. The Tafel plot analyses have been used to elucidate the kinetics and mechanism of the hydrogen peroxide oxidation. The first at low overpotential region there is no significant change in the Tafel slope (similar to 0.130 V dec(-1)) with varying peroxide concentration. The second region at higher overpotential the slope values (0.91-0.47V dec(-1)) were depended on the peroxide concentration. The apparent reaction order for H(2)O(2) varies from 0.16 to 0.50 in function of the applied potential. The apparent reaction order (at constant potential) with respect to H. concentration of 10(-5) to 10(-1) mol L(-1) was 0.25. A plot of the anodic current vs. the H(2)O(2) concentration for chronoamperometry (potential fixed = +0.61 V) at the modified electrode was linear in the 1.0 x 10(-5) to 2.5 x 10(-4) mol L(-1) concentration range. (C) 2011 Elsevier Ltd. All rights reserved.

Determination of Cu, Ni and Pb in Aqueous Medium by FAAS after Pre-Concentration on 2-Aminothiazole Modified Silica Gel

De Alcântara, Ilton Luiz; Dos Santos Roldan, Paulo; Margionte, Maurício A. L.; Castro, Gustavo R.; Padilha, Cilene C. F.; De Oliveira Florentino, Ariovaldo; De Magalhães Padilha, Pedro
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 366-371
ENG
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This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT), and the results of a study of the adsorption and pre-concentration (in batch and using a flow-injection system coupled to an absorption atomic spectrometer) of Cu(II), Ni(II) and Pb(II) in aqueous medium. The adsorption capacities for each metal ions in mmol g -1 were: Cu(II)= 1.18, Ni(II)= 1.15 and Pb(II)= 1.10. The results obtained in the flow experiments showed a recovery of practically 100% of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L -1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the application of a flow-injection system for the pre-concentration and quantification by FAAS of metal ions at trace level in natural water samples digested and not digest by an oxidizing UV photolysis.

A stable liquid–liquid extraction system for clavulanic acid using polymer-based aqueous two-phase systems

Pereira, Jorge F. B.; Santos, Valéria Carvalho; Johansson, Hans-Olof; Teixeira, J. A.; Pessoa Júnior, Adalberto
Fonte: Pergamon Press Ltd. Publicador: Pergamon Press Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2012 ENG
Relevância na Pesquisa
467.5939%
The partitioning of Clavulanic Acid (CA) in a novel inexpensive and stable aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The aqueous two-phase systems are formed by mixing both polymers with a salt (NaCl or Na2SO4) and an aqueous solution of CA. The stability of CA on the presence of both polymers was investigated and it was observed that these polymers do not degrade the biomolecule. The effect of PEG-molecular size, polymer concentrations on the commercial CA partitioning has been studied, at 25 C. The data showed that commercial CA was preferentially partitioned for the PEG-rich phase with a partition coefficient (KCA) between 1 and 12 in the PEG/NaPA aqueous two phase systems supplemented with NaCl and Na2SO4. The partition to the PEG phase was increased in the systems with high polymer concentrations. Furthermore, Na2SO4 caused higher CA preference for the PEG-phase than NaCl. The systems having a composition with 10 wt.% of PEG4000, 20 wt.% of NaPA8000 and 6 wt.% of Na2SO4 were selected as the optimal ones in terms of recovery of CA from fermented broth of Streptomyces clavuligerus. The partitioning results (KCA = 9.15 ± 1.06) are competitive with commercial extraction methods of CA (KCA = 11.91 ± 2.08) which emphasizes that the system PEG/NaPA/Na2SO4 can be used as a new process to CA purification/concentration

Mercury Removal from Aqueous Solution and Flue Gas by Adsorption on Activated Carbon Fibres

Nabais, Joao; Carrott, Peter; Ribeiro Carrott, Manuela
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 28711 bytes; application/pdf
ENG
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The use of two activated carbon fibres, one laboratorial sample prepared from a commercial acrylic textile fibre and one commercial sample of Kynol1, as prepared/received and modified by reaction with powdered sulfur and H2S gas in order to increase the sulfur content were studied for the removal of mercury from aqueous solution and from flue gases from a fluidized bed combustor. The sulfur introduced ranged from 1 to 6 wt.% depending on the method used. The most important parameter for the mercury uptake is the type of sulfur introduced rather than the total amount and it was found that the H2S treatment of ACF leads to samples with the highest mercury uptake, despite the lower sulfur amount introduced. The modified samples by both methods can remove HgCl2 from aqueous solutions at pH 6 within the range 290–710 mg/g (ACF) which can be favourably compared with other studies already published. The use of a filter made with an activated carbon fibre modified by powdered sulfur totally removed the mercury species present in the flue gases produced by combustion of fossil fuel.

Real-time monitoring of the heat of transfer of a homologous series of m-alkoxy phenols from isotonic aqueous solution to bacterial cells

Volpe,P. L. O.; Beezer,A. E.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
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Heats of dissolution of a homologous series of m-alkoxy phenols in an osmotically stable isotonic solution and in the same media containing a suspension of Escherichia coli cells were obtained by a differential heat conduction batch calorimeter at 298 K. The calorimetric curves show an initial rapid endothermic dissolution of the solute, followed by an exothermic process. From the heats of solution, the heat of transfer (Qtrs) of these compounds from the aqueous solution to the cells was calculated. The heat of transfer is exothermic and increases with the hydrophobicity of the compounds due to the biological consequences of the interaction process with the lipidic phase.

Degradation of the insecticides Thiamethoxam and Imidacloprid in aqueous solution as promoted by an innovative Feº/Fe3O4 composite

Urzedo,Ana P. F. M. de; Nascentes,Clésia C.; Augusti,Rodinei
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
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The performance of an innovative Feº/Fe3O4 composite to degrade the insecticides Thiamethoxam and Imidacloprid in aqueous solution was evaluated. Factorial designs were built to investigate the influence of a number of crucial variables on such degradation processes: H2O2 concentration, solution pH, and composite mass. The solution pH was the most influential variable; hence, significant degradation rates (> 90%) was accomplished exclusively in acidic solutions (pH=2). In addition, the composite was highly efficient in promoting the degradation of both insecticides either in the presence or unpredictably in the absence of H2O2. These results thus indicated that the composite possess a dual behavior, acting as either an oxidizing or a reducing agent.

Removal of lead from aqueous solution using waste tire rubber ash as an adsorbent

Mousavi,H. Z.; Hosseynifar,A.; Jahed,V.; Dehghani,S. A. M.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 EN
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The purpose of this study was to investigate the possibility of the utilization of waste tire rubber ash (WTRA) as a low cost adsorbent for removal of lead (II) ion from aqueous solution. The effect of different parameters (such as contact time, sorbate concentration, adsorbent dosage, pH of the medium and temperature) were investigated. The sorption process was relatively fast and equilibrium was reached after about 90 min of contact. The experimental data were analyzed by the Freundlich isotherm and the Langmuir isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 22.35 mg/g. The adsorption kinetics was investigated and the best fit was achieved by a first-order equation. The results of the removal process show that the Pb (II) ion adsorption on WTRA is an endothermic and spontaneous process. The procedure developed was successfully applied for the removal of lead ions in aqueous solutions.

Removal of cadmium and nickel from aqueous solution using expanded perlite

Torab-Mostaedi,M.; Ghassabzadeh,H.; Ghannadi-Maragheh,M.; Ahmadi,S. J.; Taheri,H.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
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The adsorption characteristics of cadmium and nickel onto expanded perlite from aqueous solution have been investigated with respect to changes in pH of solution, adsorbent dosage, contact time and temperature of the solution. The maximum removal efficiency of Cd (II) is 88.8% at pH 6 and exposure to 10 g/L expanded perlite, while for Ni (II), it is 93.3% at the same pH and exposure to 8 g/L adsorbent. For the adsorption of both metals, the Freundlich isotherm model fitted the equilibrium data better than the Langmuir isotherm model. Experimental data are also evaluated in terms of kinetic characteristics of adsorption and it was found that the adsorption process for both metal ions follows well pseudo-second-order kinetics. Thermodynamic functions, the change of free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of adsorption are also calculated for each metal ion. The results show that the adsorption of these metal ions on expanded perlite is feasible and exothermic at 20-50°C.

High-efficiency liquid-scintillation counting of 14C-labelled material in aqueous solution and determination of specific activity of labelled proteins

Hall, T. C.; Cocking, E. C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1965 EN
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1. Inexpensive scintillation mixtures are described which enable the detection of as little as 40μμc of 14C in aqueous solution with an efficiency of counting of over 80%. 2. A rapid method for the counting of alkaline, acidic and neutral aqueous solutions of up to 1ml. volume is described. Ethanol or 2-ethoxyethanol is used as blending agent. 3. The scintillation counting of alkaline solutions is applied to the accurate determination of the specific activity of 14C-labelled proteins from plant tissues. 4. Attention has been paid to the importance of a standardized washing procedure for the removal of all traces of radioactive material from glassware.

Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution

Tossell, JA
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 11/11/2003 EN
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Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides Sn2-, n = 2–6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, SnH2, n = 2–5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As...

Directly Relating Reduction Energies of Gaseous Eu(H2O)n3+, n = 55–140, to Aqueous Solution: The Absolute SHE Potential and Real Proton Solvation Energy

Donald, William A.; Leib, Ryan D.; Demireva, Maria; O’Brien, Jeremy T.; Prell, James S.; Williams, Evan R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 23/09/2009 EN
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In solution, half-cell potentials are measured relative to other half-cells resulting in a ladder of thermodynamic values that is anchored to the standard hydrogen electrode (SHE), which is assigned an arbitrary value of exactly 0 V. A new method for measuring the absolute SHE potential is introduced in which reduction energies of Eu(H2O)n3+, from n = 55 to 140, are extrapolated as a function of the geometric dependence of the cluster reduction energy to infinite size. These measurements make it possible to directly relate absolute reduction energies of these gaseous nanodrops containing Eu3+ to the absolute reduction enthalpy of this ion in bulk solution. From this value, an absolute SHE potential of +4.11 V and a real proton solvation energy of −269.0 kcal/mol are obtained. The infrared photodissociation spectrum of Eu(H2O)119-1243+ indicates that the structure of the surface of the nanodrops is similar to that at the bulk air–water interface and that the hydrogen bonding of interior water molecules is similar to that in aqueous solution. These results suggest that the environment of Eu3+ in these nanodrops and the surface potential of the nandrops are comparable to those of the condensed phase. This method for obtaining absolute potentials of redox couples has the advantage that no explicit solvation model is required...

Biosorption of methyl blue onto tartaric acid modified wheat bran from aqueous solution

Yao, Shuhua; Lai, Hong; Shi, Zhongliang
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 05/12/2012 EN
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Tartaric acid modified wheat bran was utilized as adsorbent to remove methyl blue, a basic dye from aqueous solution. Batch experiments were carried out to study the effect of various experimental parameters such as initial solution pH, contact time, initial dye concentration and adsorbent dosage, on dye adsorption. The results showed that the modification of wheat bran by tartaric acid significantly improved its adsorption capacity, and made this material a suitable adsorbent to remove methyl blue. The adsorption capacity of modified wheat bran was about 1.6 times higher than that of unmodified one. The amount of methyl blue adsorbed was found to vary with initial solution pH, adsorbent dosage, contact time and initial methyl blue concentration. Kinetics study showed that the overall adsorption rate of methyl blue was illustrated by pseudo-second-order kinetic model. The applicability of the Langmuir and Freundlich models for the data was tested. Both models adequately described the experimental data of the biosorption of methyl blue. The maximum adsorption capacity for methyl blue calculated from Langmuir model was 25.18 mg/g. The study has shown the effectiveness of modified wheat bran in the removal of methyl blue, and that it can be considered as an attractive alternative to the more expensive technologies used in wastewater treatment.

Silica encapsulation of thiol-stabilized lead selenide (PbSe) quantum dots in aqueous solution

Primera-Pedrozo, Oliva M.; Ates, Mehmet; Arslan, Zikri
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/07/2013 EN
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Silica encapsulation of lead selenide quantum dots (PbSe QDs) in aqueous solution is reported. Thioglycolic acid (TGA) stabilized PbSe QDs were modified with 3-mercaptopropyl trimethoxysilane (MPS) through vigorous stirring in water for 18–24 h in alkaline solution (pH 10.4–10.6). Silica shell was developed by controlled deposition and precipitation of silicates from sodium silicate solution onto MPS modified QDs surfaces. TEM images showed multiple PbSe QDs encapsulated in silica shell. The size of PbSe-SiO2 core-shell nanocrystals was estimated to be 25–30 nm by TEM. Elemental compositions (Pb, Se and Si) were investigated by EDX analysis. The purified colloids of PbSe-SiO2 QDs were stable for months when kept at 4 °C.

Geometric consequences of electron delocalization for adenine tautomers in aqueous solution

Raczyńska, Ewa D.; Makowski, Mariusz
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Artigo de Revista Científica
EN
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Geometric consequences of electron delocalization were studied for all possible adenine tautomers in aqueous solution by means of ab initio methods {PCM(water)//DFT(B3LYP)/6-311+G(d,p)} and compared to those in the gas phase {DFT(B3LYP)/6-311+G(d,p)}. To measure the consequences of any type of resonance conjugation (π-π, n-π, and σ-π), the geometry-based harmonic oscillator model of electron delocalization (HOMED) index, recently extended to the isolated (DFT) and hydrated (PCM//DFT) molecules, was applied to the molecular fragments (imidazole, pyrimidine, 4-aminopyrimidine, and purine) and also to the whole tautomeric system. For individual tautomers, the resonance conjugations and consequently the bond lengths strongly depend on the position of the labile protons. The HOMED indices are larger for tautomers (or their fragments) possessing the labile proton(s) at the N rather than C atom. Solvent interactions with adenine tautomers slightly increase the resonance conjugations. Consequently, they slightly shorten the single bonds and lengthen the double bonds. When going from the gas phase to water solution, the HOMED indices increase (by less than 0.15 units). There is a good relation between the HOMED indices estimated in water solution and those in the gas phase for the neutral and ionized forms of adenine. Subtle effects...

Adsorption and Desorption of Nickel(II) Ions from Aqueous Solution by a Lignocellulose/Montmorillonite Nanocomposite

Zhang, Xiaotao; Wang, Ximing
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 03/02/2015 EN
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A new and inexpensive lignocellulose/montmorillonite (LNC/MMT) nanocomposite was prepared by a chemical intercalation of LNC into MMT and was subsequently investigated as an adsorbent in batch systems for the adsorption-desorption of Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the LNC/MMT nanocomposite were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and time. The results indicated that the maximum adsorption capacity of Ni(II) reached 94.86 mg/g at an initial Ni(II) concentration of 0.0032 mol/L, a solution pH of 6.8, an adsorption temperature of 70°C, and adsorption time of 40 min. The represented adsorption kinetics model exhibited good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir isotherm equation best fit the experimental data. The structure of the LNC/MMT nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas the adsorption mechanism was discussed in combination with the results obtained from scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy analyses (FTIR). The desorption capacity of the LNC/MMT nanocomposite depended on parameters such as HNO3 concentration...

Effects of surface functional groups of activated carbon on adsorption of triclosan from aqueous solution

Fang, S.; Pendleton, P.; Badalyan, A.
Fonte: Inderscience Publishers; United Kingdom Publicador: Inderscience Publishers; United Kingdom
Tipo: Conference paper
Publicado em //2009 EN
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We report adsorption of triclosan by using activated carbons as a potential method to improve the discharge water purification process. Commercially available activated carbons, P1300, Picazine HP and Hydrodarco C, display different levels of affinity for triclosan from aqueous solution. Surface chemistry of these adsorbents were modified via reduction, oxidation and nitridation, to improve and better understand the adsorption process. The adsorption capacity was greatly influenced by surface group changes, with a decrease in relative affinity on oxidation. Nitridation enhanced the amounts adsorbed over the thermally reduced samples. Surface analysis via X-ray Photoelectron Spectroscopy (XPS) helped us identify the introduced surface functional group changes. Overall, nitridation resulted in an increased basic character of the surface exploiting the Lewis acidic nature of triclosan when it is dissolved in solution. The surface chemistry modified adsorbents suggest that adsorption from solution is a viable methodology for triclosan control during wastewater treatment.; Sheng Fu Fang, Phillip Pendleton and Alexander Badalyan

Structural Properties of High and Low Density Water in a Supercooled Aqueous Solution of Salt

Corradini, D.; Rovere, M.; Gallo, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/01/2011
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We consider and compare the structural properties of bulk TIP4P water and of a sodium chloride aqueous solution in TIP4P water with concentration c = 0.67 mol/kg, in the metastable supercooled region. In a previous paper [D. Corradini, M. Rovere and P. Gallo, J. Chem. Phys. 132, 134508 (2010)] we found in both systems the presence of a liquid-liquid critical point (LLCP). The LLCP is believed to be the end point of the coexistence line between a high density liquid (HDL) and a low density liquid (LDL) phase of water. In the present paper we study the different features of water-water structure in HDL and LDL both in bulk water and in the solution. We find that the ions are able to modify the bulk LDL structure, rendering water-water structure more similar to the bulk HDL case. By the study of the hydration structure in HDL and LDL, a possible mechanism for the modification of the bulk LDL structure in the solution is identified in the substitution of the oxygen by the chloride ion in oxygen coordination shells.; Comment: 10 pages, 10 figures, 2 tables. Accepted for publication on J. Phys. Chem B