Retention characteristics of Cu2+, Pb2+, and Zn2+ from aqueous solutions by two types of low lime fly ashes

The technical feasibility of utilization of fly ash as a low-cost adsorbent for the removal of metals from water has been studied. For two types of fly ashes, the retention capacities of copper, lead, and zinc metal ions have been studied. Contact time, initial concentration, and pH have been varied and their effect on retention mechanism has been studied. The dominant mechanisms responsible for retention are found to be precipitation due to the presence of calcium hydroxide, and adsorption due to the presence of silica and alumina oxide surfaces in the fly ash. First-order kinetic plots have revealed that the rate constant increases with increase in the initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions considered under different conditions. X-ray diffraction studies revealed the formation of new peaks corresponding to respective metal ions precipitates under alkaline conditions.

Atom localization in a four-level alkaline earth atomic system

We propose an atom localization scheme for a four-level alkaline earth atom via a classical standing-wave field, and give the analytical expressions of the localization peak positions as well as the widths versus the parameters of the optical fields. We show that the probability of finding the atom at a particular position can be increased from 1/4 to 1/3 or 1/2 by adjusting the detuning of the probe field and the Rabi frequencies of the optical fields. Furthermore, the localization precision can be dramatically enhanced by increasing the intensity of the standing-wave field or decreasing the detuning of the probe field. The analytical results are quite accordant to the numerical solutions.

Kinetic study of the 2-methyl-3-methoxy-4-phenylbutanoic acid produced by oxidation of microcystin in aqueous solutions

Microcystins (MCs) are a family of related cyclic hepatotoxic heptapeptides, of which more than 70 types have been identified. The chemically unique nature of the C20 beta-amino acid, (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca4,6-dienoic acid (Adda), portion of the MCs has been exploited to develop a strategy to analyze the entirety. Oxidation of MCs causes the cleavage of MC Adda to form 2-methyl-3-methoxy-4-phenylbutanoic acid (MMPB). In the present study, we investigated the kinetics of MMPB produced by oxidation of the most-often-studied MC variant, MC-LR (L = leucine, R = arginine), with permanganate-periodate. This investigation allowed insight regarding the influence of the reaction conditions (concentration of the reactants, temperature, and pH) on the conversion rate. The results indicated that the reaction was second order overall and first order with respect to both permanganate and MC-LR. The second-order rate constant ranged from 0.66 to 1.35 M/s at temperatures from 10 to 30 degrees C, and the activation energy was 24.44 kJ/mol. The rates of MMPB production can be accelerated through increasing reaction temperature and oxidant concentration, and sufficient periodate is necessary for the formation of MMPB. The initial reaction rate under alkaline and neutral conditions is higher than that under acidic conditions, but the former decreases faster than the latter except under weakly acidic conditions. These results provided new insight concerning selection of the permanganate-periodate concentration, pH, and temperature needed for the oxidation of MCs with a high and stable yield of MMPB.

Study on the hydrolysis/precipitation behavior of Keggin Al-13 and Al-30 polymers in polyaluminum solutions

The hydrolysis/precipitation behaviors of Al3+, Al-13 and Al-30 under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl3, PAC(A113) and PAC(A130) were 6.5-7.5, 8.5-9.5, and 7.5-9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl3 >> PAC(A130) > PACA113. The precipitates' size increased when the dosage increased from 50 mu M to 200 mu M, but it decreased when the dosage increased to 800 AM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The isoelectric points of the freshly formed precipitates for AlCl3, PAC(A113) and PAC(A130) were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl3 hydrolysis precipitates were lower than those of PAC(A113) and PAC(A130) when pH > 5.0. The Zeta potential of PAC(A130) hydrolysis precipitates was higher than that of PACA113 at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al-Ferron research indicated that the hydrolysis precipitates of AlCl3 were composed of amorphous AI(OH)3 precipitates, but those of PACA113 and PACA130 were composed of aggregates of Al-13 and Al-30, respectively. Al3+ was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al-13 and Al-30 species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al-Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al--Ferron method. The chemical composition of Al-a, Al-b and Al-c depended on coagulant and solution pH. The Al-b measured in the current case was different from Keggin Al-13, and the high Alb content in the AlCl3 hydrolysis precipitates could not used as testimony that most of the Al3+ Was converted to highly charged Al-13 species during AlCl3 coagulation.

The electrochemical reduction reaction of dissolved oxygen on Q235 carbon steel in alkaline solution containing chloride ions

Cyclic voltammetry, electrochemical impedance spectroscopy, and rotating disk electrode voltammetry have been used to study the effect of chloride ions on the dissolved oxygen reduction reaction (ORR) on Q235 carbon steel electrode in a 0.02 M calcium hydroxide (Ca(OH)(2)) solutions imitating the liquid phase in concrete pores. The results indicate that the cathodic process on Q235 carbon steel electrode in oxygen-saturated 0.02 M Ca(OH)(2) with different concentrations of chloride ions contain three reactions except hydrogen evolution: dissolved oxygen reduction, the reduction of Fe(III) to Fe(II), and then the reduction of Fe(II) to Fe. The peak potential of ORR shifts to the positive direction as the chloride ion concentration increases. The oxygen molecule adsorption can be inhibited by the chloride ion adsorption, and the rate of ORR decreases as the concentration of chloride ions increases. The mechanism of ORR is changed from 2e(-) and 4e(-) reactions, occurring simultaneously, to quietly 4e(-) reaction with the increasing chloride ion concentration.

Transesterification of vegetable oils on basic large mesoporous alumina supported alkaline fluorides-Evidences of the nature of the active site and catalytic performances

KF, LiF and CsF/A(2)O(3) catalysts with different loadings from 1 to 20 wt% were prepared using aqueous solutions of the alkaline fluoride compounds by wet impregnation of basic mesoporous MSU-type alumina. The catalysts were activated under At at 400 degrees C for 2 h and monitored by in situ XRD measurements. The catalysts were also characterized using several techniques: N-2 adsorption/desorption isotherms at -196 degrees C, FTIR, DR-UV-vis, CO2-TPD, XRD, Al-27 CP/MAS NMR. These characterizations led to the conclusion that the deposition of alkaline fluorides on the alumina surface generates fluoroaluminates and aluminate species. The process is definitivated at 400 degrees C. The fluorine in these structures is less basic than in the parent fluorides, but the oxygen becomes more basic. The catalysts were tested for the transesterification of fatty esters under different experimental conditions using conventional heating, microwave and Ultrasound irradiation. Recycling experiments showed that these catalysts are stable for a limited number of cycles. (C) 2009 Elsevier Inc. All rights reserved.

Kinetics and mechanism of a macrocyclic chromium(III) complex oxidation to chromium(IV) by hexacyanoferrate(III) in strongly alkaline media

Oxidation of the macrocyclic Cr(III) complex cis-[Cr(cycb)(OH)(2)](+), where cycb = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by an excess of the hexacyanoferrate( III) in basic solution, slowly produces Cr(V) species. These species, detected using e.p.r. spectroscopy, are stable under ambient conditions for many hours, and the hyperfine structure of the e.p.r. spectrum is consistent with the interaction of the d-electron with four equivalent nitrogen nuclei. Electro-spray ionization mass spectrometry suggests a concomitant oxidation of the macrocyclic ligand, in which double bonds and double bonded oxygen atoms have been introduced. By comparison basic chromate(III) solutions are oxidized rapidly to chromate(VI) by hexacyanoferrate(III) without any detectable generation of stable Cr(V) intermediates.

Crystal structures and thermal behavior of alkaline earth tricyanomethanides

The alkaline earth tricyanomethanides Mg(tcm)(2) center dot 2H(2)O, Ca(tcm)(2), Sr(tcm)(2) - H2O and Ba(tcm)(2) center dot 2H(2)O were prepared from aqueous solutions of the respective chlorides and silver tricyanomethanide. Their IR spectra and thermal behavior are described. The crystal structures of Ca(tcm)(2) and Ba(tcm)(2) center dot 2H(2)O were determined by single crystal X-ray diffraction. The structure of Ca(tcm)(2) is of the type found for several transition metal tricyanomethanides [1], containing two independent interpenetrating networks. Ba(tcm)(2) center dot 2H(2)O has a unique crystal structure corresponding to a three-dimensional coordination polymer with nine fold coordinated Ba atoms connected by water molecules and tricyanomethanide anions.

Bismuth Modified Gold Microelectrode for Pb(II) Determination in Wine Using Alkaline Medium

Electrodeposition of bismuth on gold microelectrodes for determination of Pb(II) by square wave anodic stripping voltammetry (SWASV) was accomplished by an in situ procedure in alkaline solution. A linear calibration plot for Pb(II) in the concentration range 40 to 6700 nmol L(-1) (r=0.998) was obtained, the detection limit was found to be 12.5 nmol L(-1) (S/N = 3) and the relative standard deviation in Solutions containing 1 mu mol L(-1) Pb(II) was 4% (n = 12). The analytical performance of the proposed sensor wits tested by measuring the Pb(II) concentration in a wine sample. The result Was in good agreement with the one obtained by GFAAS.

Ex Situ Scanning Electrochemical Microscopy (SECM) Investigation of Bismuth- and Bismuth/Lead Alloy Film-Modified Gold Electrodes in Alkaline Medium

Scanning electrochemical microscopy (SECM) in feedback mode was employed to characterise the reactivity and microscopic peculiarities of bismuth and bismuth/lead alloys plated onto gold disk substrates in 0.1 molL(-1) NaOH solutions. Methyl viologen was used as redox mediator, while a platinum microelectrode was employed as the SECM tip. The metal films were electrodeposited ex situ from NaOH solutions containing either bismuth ions only or both bismuth and lead ions. Approach curves and SECM images indicated that the metal films were conductive and locally reactive with oxygen to provide Bi(3+) and Pb(2+) ions. The occurrence of the latter chemical reactions was verified by local anodic stripping voltammetry (ASV) at the substrate solution interface by using a mercury-coated platinum SECM tip. The latter types of measurements allowed also verifying that lead was not uniformly distributed onto the bismuth film electrode substrate. These findings were confirmed by scanning electron microscopy images. The surface heterogeneity produced during the metal deposition process, however, did not affect the analytical performance of the bismuth coated gold electrode in anodic stripping voltammetry for the determination of lead in alkaline media, even in aerated aqueous solutions. Under the latter conditions, stripping peak currents proportional to lead concentration with a satisfactory reproducibility (within 5% RSD) were obtained.

Effects of acetylsalicylic acid and acetic acid solutions on VX2 liver carcinoma in rabbits: in vivo analysis

OBJETIVO: Analisar os efeitos das soluções de aspirina e de ácido acético, in vivo, em fígado de coelhos portadores de tumor hepático VX2, verificando o efeito histolítico e anatomo-patológico das soluções e eventuais alterações bioquímicas hepáticas. MÉTODOS: Utilizou-se 48 coelhos, divididos em 2 protocolos experimentais(3 e 4), subdivididos em 3 grupos cada. Após 4 dias da implantação do tumor no fígado, procedeu-se a laparotomia mediana, com injeção de 0,4 ml da solução de aspirina (5,0%), de ácido acético (5,0%) e solução salina; o sacrifício ocorreu apos 24 horas (protocolo 3) e 11 dias (protocolo 4); avaliou-se o peso, evolução clinica, dosagens bioquímicas, cavidade abdominal e torácica e microscopia do fígado. RESULTADOS: Não foram observadas alterações na evolução clinica, peso e nas dosagens bioquímicas, apenas elevação da fosfatase alcalina no grupo controle do protocolo 4. Observamos desaparecimento do tumor em ambos os protocolos. CONCLUSÃO: As soluções de ácido acético e ácido acetilsalicílico acarretam destruição do tumor hepático experimental.

PRODUCTION OF MICROBIAL ALKALINE CELLULASE AND STUDIES OF THEIR CHARACTERISTICS

In order to obtain cellulases that improve the detergency of laundry detergent products, two alkalophilic microorganims, Bacillus sp B38-2 and Streptomyces sp S36-2, were isolated from soil and compost by incubating samples in enrichment culture medium containing CMC and Na2CO3 at pH9.6. It was found that they secrete a constitutive extracellular alkaline carboxymethyl cellulase (CMCase) in high quantity. The maximum enzyme activity was observed between 48hr to 72 hr at 30-degrees-C for the Streptomyces and between 72hr to 96hr at 35-degrees-C for the Bacillus. The optimum pH and temperature of the crude enzyme activities ranged from 6.0 to 7.0 at 55-degrees-C for the Streptomyces and 7.0 to 8.0 at 60-degrees-C for the Bacillus. Two crude CMCases activities were termostable at 45-degrees-C for 1hr and the both crude enzyme activities of the Bacillus as of the Streptomyces were stable at pH 5.0 to 9.0 after pH treatments in various buffer solutions at 30-degrees-C for 24hr.

Electrochemical studies with copper-based alloys: open-circuit potential oscillations in alkaline media

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

An infection control protocol: effectiveness of immersion solutions to reduce the microbial growth on dental prostheses

This investigation evaluated the effectiveness of an infection control protocol for cleansing and disinfecting removable dental prostheses. Sixty-four dentures were rubbed with sterile cotton swab immediately after they had been taken from patients' mouths. Samples were individually placed in the culture medium and immediately incubated at 37 +/- 2 degreesC. The dentures were scrubbed for 1 min with 4% chlorhexidine, rinsed for 1 min in sterile water and placed for 10 min in one of the following immersion solutions: 4% chlorhexidine gluconate, 1% sodium hypochlorite, Biocide (iodophors) and Amosan (alkaline peroxide). After the disinfection procedures, the dentures were immersed in sterile water for 3 min, reswabbed and the samples were incubated. All samples obtained in the initial culture were contaminated with micro-organisms. All the lower dentures immersed in Biocide showed positive growth, and the upper dentures were positive for growth in six of eight dentures. The 4% chlorhexidine gluconate, 1% sodium hypochlorite and Amosan solutions have been proved effective to reduce the growth of the micro-organisms in the 10 min immersion period. The protocol evaluated in this study seems to be a viable method to prevent cross-contamination between dental personnel and patients.

Structural study of a series of synthetic goethites obtained in aqueous solutions containing cadmium(II) ions

The capacity of goethite for Cd-II substitution has been explored in a series of synthetic samples prepared from Fe-III and Cd-II nitrate solutions aged 21 days in alkaline media. The total metal content ([ Fe] + [ Cd]) was 0.071 M in all preparations. The samples have been characterized by chemical and X-ray diffraction analysis; the morphology of the solids is described. The cell parameters for all samples were obtained by the Rietveld fits to the X-ray diffraction data. Refined structures show that for samples prepared at the final molar ratio mu(Cd)less than or equal to5.50 (expressed as mu(Cd) = 100X[Cd]/[Cd] + [Fe]), a (Cd, Fe)-goethite is the only crystalline product. In these samples, the unit cell parameters increased as a function of Cd concentration, indicating Cd incorporation in the structural frame. At the preparative ratio, mu(Cd)=7.03, the incorporation of Cd in the goethite structure is drastically reduced and a probable Cd-substituted hematite is formed together with the Fe,Cd-goethite. (C) 2003 International Centre for Diffraction Data.