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Search Results: 1 - 10 of 176390 matches for " Kely Viviane de;Peralta-Zamora "
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Spectrophotometric determination of phenol in the presence of congeners by multivariated calibration
SOUZA, KELY VIVIANE DE;PERALTA-ZAMORA, PATRICIO;
Anais da Academia Brasileira de Ciências , 2001, DOI: 10.1590/S0001-37652001000400005
Abstract: the generation of poly-hydroxilated transient species during the photochemical treatment of phenol usually impedes the spectrophotmetric monitoring of its degradation process. frequently, the appearance of compounds such as pyrocatechol, hydroquinone and benzoquinone produces serious spectral interference, which hinder the use of the classical univariate calibration process. in this work, the use of multivariate calibration is proposed to permit the spectrophotometric determination of phenol in the presence of these intermediates. using 20 synthetic mixtures containing phenol and the interferents, a calibration model was developed by using a partial least square regression process (plsr) and processing the absorbance signal between 180 and 300 nm. the model was validated by using 3 synthetic mixtures. in this operation, typical errors lower than 3% were observed. close correlation between the results obtained by liquid chromatography and the proposed method was also observed.
Spectrophotometric determination of phenol in the presence of congeners by multivariated calibration
SOUZA KELY VIVIANE DE,PERALTA-ZAMORA PATRICIO
Anais da Academia Brasileira de Ciências , 2001,
Abstract: The generation of poly-hydroxilated transient species during the photochemical treatment of phenol usually impedes the spectrophotmetric monitoring of its degradation process. Frequently, the appearance of compounds such as pyrocatechol, hydroquinone and benzoquinone produces serious spectral interference, which hinder the use of the classical univariate calibration process. In this work, the use of multivariate calibration is proposed to permit the spectrophotometric determination of phenol in the presence of these intermediates. Using 20 synthetic mixtures containing phenol and the interferents, a calibration model was developed by using a partial least square regression process (PLSR) and processing the absorbance signal between 180 and 300 nm. The model was validated by using 3 synthetic mixtures. In this operation, typical errors lower than 3% were observed. Close correlation between the results obtained by liquid chromatography and the proposed method was also observed.
Imobiliza??o de ferro (II) em matriz de alginato e sua utiliza??o na degrada??o de corantes têxteis por processos Fenton
Souza, Kely Viviane de;Peralta-Zamora, Patricio;Zawadzki, S?nia Faria;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000500041
Abstract: in this work fenton and photo-fenton processes for textile dye degradation were investigated using iron (ii) immobilized in alginate spheres. photomicrographs obtained by scanning electron microscopy showed an irregular and porous surface with a homogeneous distribution of iron. the fenton process was used to evaluate the degradation efficiency of reactive dyes and this procedure showed a low degradation effect. the association of artificial visible light or solar radiation in the fenton process (foto-fenton process) showed degradation ratios of 70 and 80% respectively in 45 min. it was also observed that the iron-alginate matrix can be reused.
Degrada??o redutiva de azo-corantes utilizando-se ferro metálico
Souza, Cláudio Lima de;Peralta-Zamora, Patricio;
Engenharia Sanitaria e Ambiental , 2006, DOI: 10.1590/S1413-41522006000100003
Abstract: azo dyes are extensively used in textile dying processes and are characterized by extreme resistance to biodegradation and consequently persistence during conventional wastewater treatment processes. in this work the reductive degradation of azo dyes was studied using zero-valent iron. at optimized experimental conditions (ph 7 and 10 g of commercial iron wool) complete decolorization of the model dye (reactive black 5) was afforded in a continuous system operating with hydraulic retention time of 6 min. at these conditions the released total soluble iron reaches a concentration compatible with the limits imposed by the current brazilian legislation (12 mg l-1). that is a very promising result, mainly taking into account the high recalcitrant character of azo dyes and the simplicity of the proposed system.
Por que otimiza??o multivariada?
Peralta-Zamora, Patricio;Morais, Josmaria Lopes de;Nagata, Noemi;
Engenharia Sanitaria e Ambiental , 2005, DOI: 10.1590/S1413-41522005000200003
Abstract: studies aiming at the optimization of experimental variables are generally carried out by procedures that evaluate the effect of just one variable on time. however, this approach does not allow the establishment of true optimal values, mainly due to close connections that may exist among the studied variables. in this paper some practical applications based upon factorial design systems are used to demonstrate the convenience of multivariate procedures. the three examples described here entail the optimization of degradation processes related to the experimental design as well as interpretation of results.
Photocatalytic degradation of camphor by suspended and immobilized photocatalysts
Sirtori, Carla;Freitas, Adriane M. de;Fujiwara, Sérgio Toshio;Peralta-Zamora, Patricio;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012005000020
Abstract: in this work, the degradation of aqueous solution of camphor by heterogeneous photocatalysis was study using suspended and supported tio2 and zno. the supported catalysts (tio2/borosilicate reaching ring, tio2/calcium alginate and zno/calcium alginate) were characterized by scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (sem/edx), x-ray diffractometry (xrd), energy dispersive x-ray fluorescence (edxrf) and raman spectroscopy, techniques that permitted to confirm the porosity of the material as well as the characteristic crystalline forms (anatase and wurtzite). the degradation efficiency of the supported photocatalysts was compared with the performance of free tio2 and zno, observing comparable results between conventional degussa p25 tio2 and tio2 immobilized in glass-rings. on the other hand, the use of calcium alginate beads leads to lower degradation efficiency probably due to the significant area reduction observed in immobilized systems.
Estudo de sor??o de herbicidas pelos argilominerais vermiculita e montmorilonita
Rezende, Edivaltrys Inayve Pissinati de;Peralta-Zamora, Patricio Guillermo;Abate, Gilberto;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000100005
Abstract: the clay minerals montmorillonite (mt) and vermiculite (vt), previously treated with ca2+, k+ and na+, were employed in a sorption study with herbicides. the herbicides 2,4-d, diuron, alachlor and metolachlor showed no interaction with mt and vt. on the other hand, the triazines presented a good sorption process, close to 100% for ametrine removal and near to 56 and 69% for atrazine and simazine, respectively, by mt. these results suggest that the mt specie may be a good material for triazines removal from aqueous medium and an alternative phase to preconcentration process, besides to exhibit a good selectivity.
Degrada??o de espécies nitroaromáticas e remedia??o de efluentes da indústria de explosivos, utilizando-se processos redutivos-oxidativos fundamentados no uso de ferro metálico
Cavalotti, Luiz Fernando Rocha;Peralta-Zamora, Patricio;Rodrigues, Marcio Barreto;Paiva, Teresa Cristina Brazil de;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000600027
Abstract: in this work the potentiality of reductive-oxidative processes based on zero-valent iron was studied aiming the degradation of nitroaromatic compounds and the remediation of residues from the explosive industry. the reductive process was applied as a continuous treatment system, using steel-wool as zero-valent iron source. the process permitted an almost total degradation of nitrobenzene, nitrophenol, nitrotoluene, dinitrotoluene and trinitrotoluene, probably with generation of the respective amine-derivative. the yellow-water residue, containing soluble trinitrotoluene, was notably modified by the reductive process, a fact that permitted a substantial enhancement of its biodegradability. furthermore, the subsequent photo-fenton process allowed toc removal of about 80%.
Previs?o das propriedades físicas do papel kraft por espectroscopia no infravermelho próximo (NIR) e regress?o por mínimos quadrados parciais (PLS)
Samistraro, Gisely;Muniz, Graciela I. B. de;Peralta-Zamora, Patricio;Cordeiro, Gilcélia A.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000600011
Abstract: the main objective of the present work is represented by the characterization of the physical properties of industrial kraft paper (i.e. transversal and longitudinal tear resistance, transversal traction resistance, bursting or crack resistance, longitudinal and transversal compression resistance (sct (compressive strength tester) and compression resistance (rct-ring crush test)) by near infrared spectroscopy associated to partial least squares regression. several multivariate models were developed, many of them with high prevision capacity. in general, low prevision errors were observed and regression coefficients that are comparable with those provided by conventional standard methodologies.
Avalia??o do potencial de processos oxidativos avan?ados para remedia??o de águas contaminadas com geosmina e 2-MIB
Freitas, Adriane Martins de;Sirtori, Carla;Peralta-Zamora, Patricio G.;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000100016
Abstract: in this work, the efficiency of some homogeneous advanced oxidation processes (uvc/h2o2, fe2+/h2o2, uvc/fe2+/h2o2, uva/fe2+/h2o2, solar/fe2+/h2o2) was investigated toward the degradation of geosmin and 2-methylisoborneol (2-mib). the effect of relevant experimental parameters (ie. ph, fe2+ and h2o2 concentration) was first investigated by factorial design, using camphor as a model substrate. in the geosmin and 2-mib degradation studies the fenton processes assisted by solar and uva radiation offered the most promising results, mainly on account of high degradation capacity (higher than 80% at a reaction time of 60 min), high operational simplicity and low cost.
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