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X-ray Diffraction and 1H NMR in Solution: Structural Determination of Lanthanide Complexes of a Py2N6Ac4 Ligand

Valencia, L.; Martinez, J.; Macías, A.; Bastida, R.; Carvalho, R. A.; Geraldes, C. F. G. C.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
ENG
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Complexes between the Py2N6Ac4 (H4L) ligand containing four carboxylate pendant arms and trivalent lanthanide ions have been synthesized, and structural studies have been made both in the solid state and aqueous solution. The crystal structures of the La, Ce, Sm, Tb, Dy, Ho, Er, Tm, and Lu complexes, with chemical formulas [LaH2L](NO3)·3H2O (1), [Ce4L2](NO3)4·30H2O (2), [SmHL]·EtOH·3H2O (5), [TbHL]·EtOH·3H2O (8), [DyHL]·2EtOH·2H2O (9), [HoHL]·3H2O (10), [ErHL]·EtOH·3H2O (11) [TmHL]·EtOH·3H2O (12), and [LuHL]·3H2O (14), have been determined by single-crystal X-ray crystallography. In the solid state, the complexes of the lighter lanthanide ions La3+−Dy3+ show a 10-coordinated geometry close to a distorted bicapped antiprism, where the carboxylate pendants are situated alternatively above and below the best plane that contains the nitrogen donor atoms. The complexes of the heavier ions, Ho3+−Lu3+, have a 9-coordinated geometry close to distorted tricapped trigonal prism, with one of the pendant carboxylate groups uncoordinated. The ligand is in a “twist−fold” conformation, where the twisting of the pyridine units is accompanied by an overall folding of the major ring of the macrocycle so that the pyridine nitrogen atoms and the metal are far from linear. The aqueous solution structures of the complexes were thoroughly characterized...

Study of spectroscopic properties of Europium (III) Tris(beta-diketonate) complex and alpha-Cyclodextrin in aqueous medium

RIBEIRO, Anderson O.; SERRA, Osvaldo A.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
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The solubilization of an europium (III) beta-diketonate chelate in aqueous medium and the changes in its photophysical properties upon its inclusion into an alpha-cyclodextrin hydrophobic cavity are described. The complex [Eu(tta)(3)center dot(H(2)O)(2)] (tta = 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione) was synthesized, characterized, and incorporated into the hydrophobic cavity by stirring in an alpha-cyclodextrin aqueous solution. The inclusion was confirmed by (1)H NMR, and the stoichiometry of association was obtained by the Job method. The maximum in the excitation spectrum of the alpha-CD inclusion compound in aqueous solution was shifted 28 nm compared with the maximum of non alpha-CD complex. The emission spectrum of the association is similar to that of the free solid complex and displays the characteristic (5)D(0) -> (7)F(0-4) Eu(3+) transitions.; FAPESP; CAPES; CNPq

Sistemas micelares de duas fases aquosas aplicados à purificação de enzimas; Aqueous two-phase micellar system for enzyme purification

Rangel-Yagui, Carlota de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/07/2003 PT
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A partição das enzimas glicose-6-fosfato desidrogenase (G6PD) e uroquinase (UK) em sistemas micelares de duas fases aquosas foi investigada, teórica e experimentalmente. Inicialmente, a partição de G6PD em sistema micelar de duas fases aquosas composto pelo tensoativo não-iônico C10E4 (óxido de n-deciltetraetileno) foi estudada. Observou-se uma partição governada primariamente por interações repulsivas estéricas, do tipo "volume de exclusão", sendo a G6PD recuperada preferencialmente na fase inferior do sistema, pobre em micelas, resultando em valores de KG6PD inferiores a 1,0. Os tensoativos catiônicos CnTAB (brometos de alquiltrimetilamônio, n = 8, 10 e 12) foram adicionados ao tensoativo C10E4, de modo a formar sistemas micelares mistos (não-iônico/catiônico) de duas fases aquosas e atrair a G6PD de carga efetiva negativa para a fase superior, rica em micelas positivamente carregadas. Os coeficientes de partição obtidos nos sistemas C10E4/CnTAB/tampão foram no mínimo 2,5 vezes maiores que os correspondentes no sistema C10E4/tampão mantendo-se o volume de exclusão constante. De uma forma geral, o sistema micelar misto C10E4/C10TAB/tampão forneceu o melhor KG6PD = 7,7, com um rendimento de G6PD na fase superior de 71%. A adição de ligantes de afinidade (inibidores enzimáticos) ao sistema de duas fases aquosas C10E4/tampão para purificação de UK e G6PD também foi estudada. Não foram observadas diferenças significativas no perfil de partição da UK na presença ou não do ligante p-aminobenzamidina...

Avaliações bioquímicas séricas e hepáticas do extrato de yacon (Polymnia sonchifolia) Poepp. & Endl.

Fernandes, A. A H; Bordon, J. G.; Batistella, R. F.; Nascimento, S. M.; Silva, M. S.; Alves, M. J Q F
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 30-34
POR
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Yacon is a medicinal plant, the tuberous roots of which have been thought to contain a large amount of fructan (oligosaccharides). Purpose - The aim of paper was to study the effect of aqueous extracts of yacon on biochemical parameters of clinical importance in rats. The animals (male, wistar, weighing approximately 300g) were divided in 3 groups: G1(n=8)= water control; G2(n=8)= aqueous extract of roots (0,17g/100g/day); G3(n=8)= aqueous extract of leaves (25mg/100g/day). The serum samples were obtained after 30 days, and the biochemical parameters were measured. The livers were removed and homogenized in 0,01M phosphate buffer pH 7,0 and then the supernatant fractions were used for enzyme assay. Significantly increased serum glucose was observed in G2 (206,72±91,27 mg/dL). The groups G2 and G3 rats had higher (p<0,05) urea concentration, while creatinin level decreased (p<0,05). The serum albumin concentration showed a tendency to remain in G2 (2,44±0,45 g/dL) and G3 (2,84±0,50 g/dL). Aqueous extracts administration markedly decreased (p<0,05) the activities of ALT in the liver and greatly increased these enzymatic activities in blood. The serum alkaline phosphatase activity increased (p<0,05) in rats receiving the aqueous extract of root (192...

Treatment of aqueous effluents contaminated with ionic liquids; Tratamento de efluentes aquosos contaminados com líquidos iónicos

Neves, Catarina Maia Seco Seiça
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
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Ionic liquids are a class of solvents that, due to their unique properties, have been proposed in the past few years as alternatives to some hazardous volatile organic compounds. They are already used by industry, where it was possible to improve different processes by the incorporation of this kind of non-volatile and often liquid solvents. However, even if ionic liquids cannot contribute to air pollution, due to their negligible vapour pressures, they can be dispersed thorough aquatic streams thus contaminating the environment. Therefore, the main goals of this work are to study the mutual solubilities between water and different ionic liquids in order to infer on their environmental impact, and to propose effective methods to remove and, whenever possible, recover ionic liquids from aqueous media. The liquid-liquid phase behaviour of different ionic liquids and water was evaluated in the temperature range between (288.15 and 318.15) K. For higher melting temperature ionic liquids a narrower temperature range was studied. The gathered data allowed a deep understanding on the structural effects of the ionic liquid, namely the cation core, isomerism, symmetry, cation alkyl chain length and the anion nature through their mutual solubilities (saturation values) with water. The experimental data were also supported by the COnductor-like Screening MOdel for Real Solvents (COSMO-RS)...

RECOVERY OF CARBOXYLIC ACIDS FROM AQUEOUS SOLUTIONS BY LIQUID-LIQUID EXTRACTION WITH A TRIISOOCTYLAMINE DILUENT SYSTEM

Malmary,G.; Albet,J.; Putranto,A.M.H.; Molinier,J.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2001 EN
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Tertiary alkylamines in solution with organic diluents are attractive extractants for the recovery of carboxylic acids from dilute aqueous phases. The aim of this study was to investigate the mechanism for extraction of organic acids from water by a long-chain aliphatic tertiary amine. In order to attain this objective, we studied the liquid-liquid equilibria between the triisooctylamine + 1-octanol + n-heptane system as solvent and an aqueous solution of an individual carboxylic acid such as citric, lactic and malic acids. The experiments showed that the partition coefficient for a particular organic acid depends on the kind of solute, notably when the acid concentration in the aqueous phase is low. A mathematical model, where both chemical association and physical distribution are taken into consideration, is proposed. The model suggests that the various complexes obtained between amine and organic acids contribute to the distribution of the solute between the coexisting phases in equilibrium.

Dermal absorption of a dilute aqueous solution of malathion

Scharf, John E; Johnson, Giffe T; Harbison, Stephen Casey; McCluskey, James D; Harbison, Raymond D
Fonte: Medknow Publications Publicador: Medknow Publications
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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Malathion is an organophosphate pesticide commonly used on field crops, fruit trees, livestock, agriculture, and for mosquito and medfly control. Aerial applications can result in solubilized malathion in swimming pools and other recreational waters that may come into contact with human skin. To evaluate the human skin absorption of malathion for the assessment of risk associated with human exposures to aqueous solutions, human volunteers were selected and exposed to aqueous solutions of malathion. Participants submerged their arms and hands in twenty liters of dilute malathion solution in either a stagnant or stirred state. The “disappearance method” was applied by measuring malathion concentrations in the water before and after human exposure for various periods of time. No measurable skin absorption was detected in 42% of the participants; the remaining 58% of participants measured minimal absorbed doses of malathion. Analyzing these results through the Hazard Index model for recreational swimmer and bather exposure levels typically measured in contaminated swimming pools and surface waters after bait application indicated that these exposures are an order of magnitude less than a minimal dose known to result in a measurable change in acetylcholinesterase activity. It is concluded that exposure to aqueous malathion in recreational waters following aerial bait applications is not appreciably absorbed...

Ion clustering in aqueous solutions probed with vibrational energy transfer

Bian, Hongtao; Wen, Xiewen; Li, Jiebo; Chen, Hailong; Han, Suzee; Sun, Xiuquan; Song, Jian; Zhuang, Wei; Zheng, Junrong
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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Despite prolonged scientific efforts to unravel the hydration structures of ions in water, many open questions remain, in particular concerning the existences and structures of ion clusters in 1∶1 strong electrolyte aqueous solutions. A combined ultrafast 2D IR and pump/probe study through vibrational energy transfers directly observes ion clustering in aqueous solutions of LiSCN, NaSCN, KSCN and CsSCN. In a near saturated KSCN aqueous solution (water/KSCN molar ratio = 2.4/1), 95% of the anions form ion clusters. Diluting the solution results in fewer, smaller, and tighter clusters. Cations have significant effects on cluster formation. A small cation results in smaller and fewer clusters. The vibrational energy transfer method holds promise for studying a wide variety of other fast short-range molecular interactions.

Influence of Simple Electrolytes on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

Carlton, Rebecca J.; Gupta, Jugal K.; Swift, Candice L.; Abbott, Nicholas L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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We report orientational anchoring transitions at aqueous interfaces of a water-immiscible, thermotropic liquid crystal (LC; nematic phase of 4′-pentyl-4-cyanobiphenyl) that are induced by changes in pH of the aqueous solution and the addition of simple electrolytes (NaCl) to the aqueous phase. Whereas measurements of the zeta potential on the aqueous side of the interface of LC-in-water emulsions prepared with 5CB confirm pH-dependent formation of an electrical double layer extending into the aqueous phase, quantification of the orientational ordering of the LC leads to the proposition that an electrical double layer is also formed on the LC-side of the interface with an internal electric field that drives the LC anchoring transition. Further support for this conclusion is obtained from measurements of the dependence of LC ordering on pH and ionic strength, as well as a simple model based on the Poisson-Boltzmann equation from which we calculate the contribution of an electrical double layer to the orientational anchoring energy of the LC. Overall, the results presented herein provide new fundamental insights into ionic phenomena at LC-aqueous interfaces, and expand the range of solutes known to cause orientational anchoring transitions at LC-aqueous interfaces beyond previously examined amphiphilic adsorbates.

Solution reaction design: electroaccepting and electrodonating powers of ions in solution

Li, Keyan; Li, Min; Xue, Dongfeng
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 05/01/2012 EN
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By considering a first-order variation in electroaccepting and electrodonating powers, ω±, induced by a change from gas to aqueous solution phase, the solvent effect on ω± for charged ions is examined. The expression of electroaccepting and electrodonating powers in the solution phase, ω±s, is obtained through establishing the quantitative relationship between the change of the ω± due to the solvation and the hydration free energy. It is shown that cations are poorer electron acceptors and anions are poorer electron donors in solution compared to those in gas phase. We have proven that the scaled aqueous electroaccepting power, ω+s, of cations can act as a good descriptor of the reduction reaction, which is expected to be applied in the design of solution reactions.

Conformation Types of Ubiquitin [M+8H]8+ Ions from Water:Methanol Solutions: Evidence for the N and A States in Aqueous Solution

Shi, Huilin; Pierson, Nicholas A.; Valentine, Stephen J.; Clemmer, David E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Ion mobility and mass spectrometry measurements are used to examine the gas-phase populations of [M+8H]8+ ubiquitin ions formed upon electrospraying 20 different solutions: from 100:0 to 5:95 water:methanol that are maintained at pH = 2.0. Over this range of solution conditions, mobility distributions for the +8 charge state show substantial variations. Here we develop a model that treats the combined measurements as one data set. By varying the relative abundances of a discrete set of conformation types, it is possible to represent distributions obtained from any solution. For solutions that favor the well-known A-state ubiquitin, it is possible to represent the gas-phase distributions with seven conformation types. Aqueous conditions that favor the native structure require four more structural types to represent the distribution. This analysis provides the first direct evidence for trace amounts of the A state under native conditions. The method of analysis presented here should help illuminate how solution populations evolve into new gas-phase structures as solvent is removed. Evidence for trace quantities of previously unknown states under native solution conditions may provide insight about the relationship of dynamics to protein function as well as misfolding and aggregation phenomena.

A Valence Bond Model for Aqueous Cu(II) and Zn(II) Ions in the AMOEBA Polarizable Force Field

Xiang, Jin Yu; Ponder, Jay W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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A general molecular mechanics (MM) model for treating aqueous Cu2+ and Zn2+ ions was developed based on valence bond (VB) theory and incorporated into the AMOEBA polarizable force field. Parameters were obtained by fitting molecular mechanics energies to that computed by ab initio methods for gas phase tetra- and hexa-aqua metal complexes. Molecular dynamics (MD) simulations using the proposed AMOEBA-VB model were performed for each transition metal ion in aqueous solution and solvent coordination was evaluated. Results show the AMOEBA-VB model generates the correct square-planar geometry for gas phase tetra-aqua Cu2+ complex and improves the accuracy of MM model energetics for a number of ligation geometries when compared to quantum mechanical (QM) computations. On the other hand, both AMOEBA and AMOEBA-VB generate results for Zn2+-water complexes in good agreement with QM calculations. Analyses of the MD trajectories revealed a 6-coordination first solvation shell for both Cu2+ and Zn2+ ions in aqueous solution, with ligation geometries falling in the range reported by previous studies.

Phytodegradation potential of bisphenolA from aqueous solution by Azolla Filiculoides

Zazouli, Mohammad Ali; Mahdavi, Yousef; Bazrafshan, Edris; Balarak, Davoud
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 02/04/2014 EN
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Many organic hazardous pollutants such as bisphenolA (BPA) which are toxic and not easily biodegradable can concerns for environmental pollution worldwide. The objective of this study was to examine whether Azolla Filiculoides is able to remove BPA from aqueous solutions. In this study, the Azolla with different biomass (0.3, 0.6, 0.9, 1.2 g) has been cultured in solution that was contained 5, 10, 25 and 50 ppm BPA. Samples were collected every 2 days from all of containers. The analytical determination of BPA was performed by using of DR4000 uv-visible at λmax = 276 nm. The results indicated that Azolla has high ability to remove BPA from aqueous solutions. The BPA removal was 60-90%. The removal efficiency is increasing with decreasing of BPA concentration and increasing of biomass amount and vice versa. The removal efficiency was more than 90% when BPA concentration was 5 ppm and amount of biomass was 0.9gr. It is concluded that Azolla able remove BPA by Phytodegradation from the aqueous solutions. Since conventional methods of BPA removal need to high cost and energy, phytoremediation by Azolla as a natural treatment system can decrease those issues and it can be a useful and beneficial method to removal of BPA.

Size evolution of highly amphiphilic macromolecular solution assemblies via a distinct bimodal pathway

Kelley, Elizabeth G.; Murphy, Ryan P.; Seppala, Jonathan E.; Smart, Thomas P.; Hann, Sarah D.; Sullivan, Millicent O.; Epps, Thomas H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 07/04/2014 EN
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The solution self-assembly of macromolecular amphiphiles offers an efficient, bottom-up strategy for producing well--defined nanocarriers, with applications ranging from drug delivery to nanoreactors. Typically, the generation of uniform nanocarrier architecturesis controlled by processing methods that rely upon cosolvent mixtures. These preparation strategies hinge on the assumption that macromolecular solution nanostructures are kinetically stable following transfer from an organic/aqueous cosolvent into aqueous solution. Herein we demonstrate that unequivocal step-change shifts in micelle populations occur over several weeks following transfer into a highly selective solvent. The unexpected micelle growth evolves through a distinct bimodal distribution separated by multiple fusion events and critically depends on solution agitation. Notably, these results underscore fundamental similarities between assembly processes in amphiphilic polymer, small molecule, and protein systems. Moreover, the non-equilibrium micelle size increase can have a major impact on the assumed stability of solution assemblies, for which performance is dictated by nanocarrier size and structure.

Experiment and Optimization for Simultaneous Carbonation of Ca2+ and Mg2+ in A Two-phase System of Insoluble Diisobutylamine and Aqueous Solution

Wang, Wenlong; Wang, Man; Liu, Xin; Wang, Peng; Xi, Zhenqian
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 03/06/2015 EN
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An optimized approach of CO2 fixation in Ca2+/Mg2+-rich aqueous solutions using insoluble amine as an enhancing medium was reported. Apparent basicity was verified to be an effective indicator for the selection and optimization of organic amine systems and finally the diisobutylamine + n-octanol system was selected to enhance the carbonation reactions of CO2 in an artificial Ca2+/Mg2+-rich solution. In our experiments, when the volume ratio of insoluble organic phase to aqueous one was 2:1 and the reaction temperature was 28 °C, 92% of Ca2+ and 80% of Mg2+ could be converted to calcium and magnesium carbonate precipitates within 5 min of reaction with the bubbling-in of CO2. The organic amine system could be regenerated by using carbide slag as the regeneration agent and could still show attractive enhancement performances after 7 rounds of carbonation-regeneration experiments. In this way, the CO2 capture and sequestration was realized within one single process, with value-added Ca/Mg carbonates being the byproducts. In view of the vast availability of Ca2+/Mg2+-rich aqueous solutions and the feasible technical coordination with desalination industry, this novel process may have a good application potential in the future.

Responses of Dendrobium 'darrenn glory' and Mokara 'calypso jumbo' orchids to 1-methylcyclopropene and aqueous ozone postharvest treatments

Almasi,Parviz; Mohamed,Mahmud Tengku Muda; Anwar,Parvez; Ahmad,Siti Hajar; Kadir,Jugah
Fonte: Instituto Agronômico de Campinas Publicador: Instituto Agronômico de Campinas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2015 EN
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AbstractOrchids possess a very special place amongst ornamental plants. But high ethylene sensitivity and early flower senescence of orchid result in a short vase life and rapid quality deterioration which is of great concern for the growers, traders and consumers. An attempt was made to study the influence of 1-methylcyclopropene (1-MCP) (0 and 300 nL L–1) and аquеous ozone (0 and 5.2 nL L–1) in prolonging vase life and maintaining quality of two cut orchid hybrids Dendrobium 'Darren Glory' (DDG) and Mokara “Calypso Jumbo” (MCJ). Results showed that orchid hybrids exhibited differences in their ethylene sensitivity, vase life, 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC oxidase activities. Pre-treatment with 1-MCP resulted in reduced ethylene production, vase life, ACC content and ACC oxidase activities, but increased bud opening %. Pre-treatment with аquеous ozone failed to influence all those parameters except bud opening %. Interaction effects of hybrid and 1-MCP were significant for ethylene production, hybrid and ozone for vas life, 1-MCP and ozone for bud opening %, and hybrid, 1-MCP and ozone for ethylene production and vase life. Aqueous ozone markedly contributed to the inhibition of microbial growth in vase solution. Pre-treatment of the cut orchid flowers with 300 nL L–11-MCP...

Absolute Standard Hydrogen Electrode Potential Measured by Reduction of Aqueous Nanodrops in the Gas Phase

Donald, William A.; Leib, Ryan D.; O'Brien, Jeremy T.; Bush, Matthew F.; Williams, Evan R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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In solution, half-cell potentials are measured relative to those of other half cells, thereby establishing a ladder of thermochemical values that are referenced to the standard hydrogen electrode (SHE), which is arbitrarily assigned a value of exactly 0 V. Although there has been considerable interest in, and efforts toward, establishing an absolute electrochemical half-cell potential in solution, there is no general consensus regarding the best approach to obtain this value. Here, ion-electron recombination energies resulting from electron capture by gas-phase nanodrops containing individual [M(NH3)6]3+, M = Ru, Co, Os, Cr, and Ir, and Cu2+ ions are obtained from the number of water molecules that are lost from the reduced precursors. These experimental data combined with nanodrop solvation energies estimated from Born theory and solution-phase entropies estimated from limited experimental data provide absolute reduction energies for these redox couples in bulk aqueous solution. A key advantage of this approach is that solvent effects well past two solvent shells, that are difficult to model accurately, are included in these experimental measurements. By evaluating these data relative to known solution-phase reduction potentials, an absolute value for the SHE of 4.2 ± 0.4 V versus a free electron is obtained. Although not achieved here...

Extraction of cadmium from aqueous solutions by emulsion liquid membranes using a stirred transfer cell contactor

Marchese, José; Valenzuela, Fernando; Ochoa, Ariel; Sapag Hagar, Jaime; Acosta, Adolfo; Poblete, Maritza; Basualto Flores, Carlos Alfonso
Fonte: SOC BRASILEIRA QUIMICA Publicador: SOC BRASILEIRA QUIMICA
Tipo: Artículo de revista
EN
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It is studied the extraction of cadmium( II) ions from acidic aqueous solutions using a stirred transfer cell-type emulsion liquid membrane ( ELM) prepared by dissolving in kerosene, with D2EHPA ( an alkylphosphoric acid) as mobile carrier and Span-80 as surfactant. The ELM allowed efficient metal transport from the feed solution to the stripping liquor in experiments carried out at 25 C. The significant variables on cadmium transport through the membrane were extractant concentration and metal content in the feed metal-donor solution. Concentration of HCl as stripping agent affected only the initial metal extraction rate but not the extraction extent. The surfactant content used in this study stabilized the membrane adequately, but the use of a higher content produced a smaller initial extraction rate due to higher interfacial resistance. The experimental results suggest the possibility of recovering or removing valuable or toxic metals from dilute aqueous solution in an extractor based on emulsified liquid membranes.

Computational Study of Copper(II) Complexation and Hydrolysis in Aqueous Solutions Using Mixed Cluster/Continuum Models

Bryantsev, Vyacheslav S.; Diallo, Mamadou S.; Goddard, William A., III
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 27/08/2009
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We use density functional theory (B3LYP) and the COSMO continuum solvent model to characterize the structure and stability of the hydrated Cu(II) complexes [Cu(MeNH_2)(H_2O)_(n−1)]^(2+) and [Cu(OH)_x(H_2O)_(n−x)]^(2−x) (x = 1−3) as a function of metal coordination number (4−6) and cluster size (n = 4−8, 18). The small clusters with n = 4−8 are found to be the most stable in the nearly square-planar four-coordinate configuration, except for [Cu(OH)_3(H_2O)]^−, which is three-coordinate. In the presence of the two full hydration shells (n = 18), however, the five-coordinate square-pyramidal geometry is the most favorable for Cu(MeNH_2)^(2+) (5, 6) and Cu(OH)^+ (5, 4, 6), and the four-coordinate geometry is the most stable for Cu(OH)_2 (4, 5) and Cu(OH)_3^− (4). (Other possible coordination numbers for these complexes in the aqueous phase are shown in parentheses.) A small energetic difference between these structures (0.23−2.65 kcal/mol) suggests that complexes with different coordination numbers may coexist in solution. Using two full hydration shells around the Cu^(2+) ion (18 ligands) gives Gibbs free energies of aqueous reactions that are in excellent agreement with experiment. The mean unsigned error is 0.7 kcal/mol for the three consecutive hydrolysis steps of Cu^(2+) and the complexation of Cu^(2+) with methylamine. Conversely...

Minerals in Aqueous Extract of the Coproducts Myrciaria dubia (Kunth.) McVaugh, Myrtaceae; Sais Minerais em Extrato Aquoso de Coprodutos da Myrciaria dubia (Kunth.) McVaugh, Myrtaceae

Rita de Cassia P. de Sousa; Empresa Brasileira de Pesquisa Agropecuária; Edvan A. Chagas; Empresa Brasileira de Pesquisa Agropecuária; Pedro Vitor P. Guimarães; Universidade Estadual de Roraima; Wilson B. Nascimento Filho; Universidade Federal de Rorai
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 08/07/2015 PT
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The camu-camu of fruits (Myrciaria dubia (HBK) McVaugh, Myrtaceae) arising from Amazonia, are considered a major source of vitamin C in the world. There are still important sources of different bioactive compounds and good source of minerals such as sodium, potassium, calcium, zinc, magnesium, manganese and copper. However, the processing of these fruits for extraction of the pulp, the product of greatest interest to many consumption, creates an effective quantity of different wastes, solid and liquid, capable of utilization for various uses its technological potential is studied. Thus, this work aimed at determining, quickly, via direct condutometric electroanalytical method, the amount of dissolved minerals contained in the aqueous extract of processed seeds and peels, coproducts of Myrciaria dubia, with potential use in the area of biotechnology development. The samples used for the study come from the experimental processing of fruit camu-camu. Three coproducts (byproducts/waste) named: CF, CS and SSC also processed via Standard Operating Procedure (SOP) created in our own laboratory for the study of organic waste. Analyzing the results obtained it was found that the samples CF and SSC showed higher electrical conductivity, which characterizes them as a rich source of electrolytes...