RESUMO
The treatment of metal-polluted wastes is a challenging issue of environmental concern. Metals can be removed using microbial biomass, and this is an interesting approach towards the design of eco-friendly technologies for liquid waste treatment. The study reported here aimed to optimize nickel and cobalt biosorption from aqueous solutions using three native metal-resistant Serratia marcescens strains. Ni(II) and Co(II) biosorption by S. marcescens strains was found to fit better to Langmuir's model, with maximum uptake capacities of 13.5 mg g-1 for Ni(II) ions and 19.9 mg g-1 for Co(II) ions. Different experimental conditions of initial metal concentration, pH, initial biomass, and temperature were optimized using the Plackett-Burman method, and, finally, biomass and metal concentration were studied using the response surface methodology (RSM) to improve biosorption. The optimum uptake capacities for Co(II) ions by the three biosorbents used were obtained for initial metal concentrations of 35-40 mg L-1 and an initial biomass of 6 mg. For Ni(II) ions, the optimum uptake capacity was achieved with 1 mg of initial biomass for S. marcescens C-1 and C-19, and with 7 mg for S. marcescens C-16, with initial concentrations of 20-50 mg L-1. The results obtained demonstrate the viability of native S. marcescens strains as biosorbents for Ni(II) and Co(II) removal. This study also contributes to our understanding of the potential uses of serpentine microbial populations for the design of environmental cleanup technologies.
Assuntos
Cobalto , Níquel , Adsorção , Biomassa , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Cinética , Serratia marcescensRESUMO
The metallurgical industry is one of the main sources of heavy metal pollution, which represents a severe threat to life. Metals can be removed from aqueous solutions by using microbial biomasses. This paper analyses the heavy metal biosorption capacity of Serratia marcescens strain 16 in single and multimetallic systems. The results obtained show that Co(II), Ni(II) and Zn(II) biosorption in monometallic systems is two to three times higher than in the presence of bi-metallic and multimetallic solutions. Fourier transform infrared spectroscopy confirmed that carbonyl, carboxyl and hydroxyl were the main functional groups, as well as the amide bands I and II involved in metal uptake, which are present in external structures of the bacterial cell. The results obtained demonstrated the viability of S. marcescens strain 16 as a biosorbent for the design of eco-friendly technologies for the treatment of waste liquor.
Assuntos
Metais Pesados , Níquel , Adsorção , Biodegradação Ambiental , Cobalto/análise , Cobre , Concentração de Íons de Hidrogênio , Íons/análise , Cinética , Serratia marcescens , Zinco/análiseRESUMO
An artificial neural network technique has been applied to the optimization of a hydride generation-inductively coupled plasma-atomic emission spectrometry (HG-ICP-AES) coupling for the determination of Ge at trace levels. The back propagation of errors net architecture was used. Experimental parameters and their relationship have been studied, obtaining a surface response of the system. The results and optimization aspects achieved with the neural network approach have been compared to the "one variable at time" and SIMPLEX methods.
RESUMO
We prepared synthetic hydroxyapatite [HAP; Ca5(PO4)(3-x)(CO3)x(OH)(1+x) (x = 0.3)] and then investigated this material's ability to remove trivalent antimony [Sb(III)] from water. The HAP was characterized by X-ray diffraction analysis, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. The sorption of Sb(III) to HAP was measured over an Sb(III) concentration range of 0.05-50 mg L(-1), at constant ionic strength (I = 0.01 mol dm(-3)) in equilibrated aqueous suspensions (34 g dm(-3)) for 5 < pH < 8 in vessels that were closed to the atmosphere. Under these conditions, we found that HAP particles were enriched in Ca after incongruent dissolution of the solid. More than 95% of the Sb(III) in solution adsorbed to the solid-phase HAP in <30 min. The equilibrium distribution of Sb(III) (solid vs liquid phase) was characterized by a Langmuir model with gamma(max) = 6.7 +/- 0.1 x 10(-8) mol m(-2) (1.4 +/- 0.2 x 10(-4) mol dm(-3) g(-1)) and K(ads) = 1.5 +/- 0.2 x 10(3) dm3 mol(-1). As Sb adsorption occurred, the pH of the isoelectric point (pH(iep)) of the HAP suspensions declined from 7.7 to 6.9. This finding supports the idea that the negative surface potential of the HAP increased due to the adsorption of Sb as a charged species. The decline in pH(iep) during Sb adsorption plus the thermodynamic description of the Sb(III)-HAP-H2O system suggest likely surface reactions for the interaction of Sb with HAP. We discuss the efficiency of Sb removal from water by HAP in the context of phosphate enrichment.
Assuntos
Antimônio/química , Durapatita/química , Poluição da Água/prevenção & controle , Adsorção , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Modelos Teóricos , Termodinâmica , Purificação da Água/métodos , Difração de Raios XRESUMO
A retrospective longitudinal study of 99 patients who underwent Highly Selective Vagotomy for duodenal ulcer was done. The follow-up period was two years. A 41-question survey, made for this purpose, was conducted. The survey meets the requirements of this investigation. The study assessed the effect of this technique. The patients stayed in the hospital for a short period of time after surgery. They did not need any blood transfusion. The recurrence percent was very low
Assuntos
Feminino , Adulto , Pessoa de Meia-Idade , Humanos , Masculino , Vagotomia Gástrica Proximal , Estudos RetrospectivosRESUMO
A retrospective longitudinal study of 99 patients who underwent Highly Selective Vagotomy for duodenal ulcer was done. The follow-up period was two years. A 41-question survey, made for this purpose, was conducted. The survey meets the requirements of this investigation. The study assessed the effect of this technique. The patients stayed in the hospital for a short period of time after surgery. They did not need any blood transfusion. The recurrence percent was very low.
Assuntos
Vagotomia Gástrica Proximal , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
Two 28 and 25 year old female patients were studied. Endoscopic analysis of their stomachs showed an hyperemic mammillation picture, neoplasia compatible, in the first patient, and an ulcerous lesion in the second one. Both findings were the result of a positive serological test to discard syphilis. All this, together with a cutaneous and epidemiological history, represented an assumed diagnosis of a secondary stage syphilis with gastric disorders. Although it was not necessary, one case was submitted to a specific spirochaeta stain, but results were negative. The true diagnosis resulted from a penicillin treatment, which provoked a cutaneous-visceral history regression as well as a diminishing in V.D.R.L. titles
Assuntos
Humanos , Feminino , Adulto , Gastropatias/diagnóstico , Sífilis/diagnóstico , Diagnóstico Diferencial , Gastropatias/tratamento farmacológico , Gastropatias/patologia , Penicilinas/uso terapêutico , Sorodiagnóstico da Sífilis , Sífilis/tratamento farmacológico , Sífilis/patologiaRESUMO
Two 28 and 25 year old female patients were studied. Endoscopic analysis of their stomachs showed an hyperemic mammillation picture, neoplasia compatible, in the first patient, and an ulcerous lesion in the second one. Both findings were the result of a positive serological test to discard syphilis. All this, together with a cutaneous and epidemiological history, represented an assumed diagnosis of a secondary stage syphilis with gastric disorders. Although it was not necessary, one case was submitted to a specific spirochaeta stain, but results were negative. The true diagnosis resulted from a penicillin treatment, which provoked a cutaneous-visceral history regression as well as a diminishing in V.D.R.L. titles.
Assuntos
Gastropatias/diagnóstico , Sífilis/diagnóstico , Adulto , Diagnóstico Diferencial , Feminino , Humanos , Penicilinas/uso terapêutico , Gastropatias/tratamento farmacológico , Gastropatias/patologia , Sífilis/tratamento farmacológico , Sífilis/patologia , Sorodiagnóstico da SífilisAssuntos
Neoplasias/epidemiologia , Sistema de Registros , Feminino , Humanos , Masculino , Porto Rico/epidemiologiaRESUMO
[Introducción] En este trabajo se presenta un estudio general del comportamiento de la incidencia de la estomatitis vesicular (EV) en la población animal en la dimensión espacio-temporal de los cuatro países de América del Sur donde ella se presenta con frecuencia.
[Introduction] This paper presents a general study of the bhavoir of the incidence of vesicular stomatitis (VS) in the animal population in the space-time dimension of the four South American countries in which the isease frequently occurs.