Navegando por Assunto "Copper (II)"

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Acesso aberto (Open Access)
Adsorção de cobre (II) presente em cachaça utilizando quitosana obtida por radiação micro-ondas: caracterização e estudo cinético
(Universidade Federal do Pará, 2020-02-27) SANTOS, Lucely Nogueira dos; FERREIRA, Nelson Rosa; http://lattes.cnpq.br/3482762086356570; https://orcid.org/0000-0001-6821-6199
Cachaça is a typical drink in Brazil and has been reaching more and more the national and international market. The cachaças produced in copper stills present unique characteristics, however they may be more susceptible to suffer contamination by copper (II). Adsorption by biopolymers has shown to be a very promising technique for the removal of metal ions. Chitosan is a biopolymer derived from the deacetylation of chitin and has free amino groups in its structure, which are strongly reactive to metal ions. Considering the aforementioned aspects, this work aimed to perform the deacetylation of chitosan using microwave irradiation technology and to evaluate the capacity of the chitosan obtained in adsorbing copper (II) from cachaça. Chitin was extracted from shrimp exoskeleton, chitosan was deacetylated and its adsorption capacity was evaluated through kinetic study using mathematical models. The copper (II) concentration remaining in the cachaça, in all kinetic experiments was estimated by the spectrophotometry technique in the visible region and confirmed by microwave-induced plasma optical emission spectrometry (MIP OES). Chitosan was characterized by infrared spectroscopy with attenuated reflectance (FTIR-ATR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and molecular mass The results of the characterization showed that the microwave deacetylation process it occurred efficiently, since the chitosan obtained had satisfactory properties in terms of its main characteristics observed, degree of deacetylation (above 85%), molecular weight, morphology and crystallinity. Regarding the adsorption kinetics, the best condition for copper adsorption was 6 mg of chitosan per mL of cachaça, in an equilibrium time of 60 min which resulted in a reduction rate of 84.09% of copper in the drink, according to results obtained by MIP OES. The kinetic analysis indicated the best fit of the data by the Elovich equation, suggesting that the chemisorption mechanism controls the kinetic process. Therefore, chitosan proved to be a good adsorbent for the removal of copper in cachaça and in this respect, a promising target for future technological investments.
Acesso aberto (Open Access)
Obtenção e caracterização de carvão ativado de caroço de buriti (Mauritia flexuosa L. f.) para a avaliação do processo de adsorção de cobre (II)
(Instituto Nacional de Pesquisas da Amazônia, 2013-03) PINTO, Marcos Vinicios de Souza; SILVA, Denilson Luz da; SARAIVA, Augusto Cesar Fonseca
In the Amazon region some industries discharges copper into watercourse that in high concentrations is toxic to the biota. The removal of copper from industrial effluent is performed by several processes such as adsorption. This work shows the result of copper (II) adsorption on activated carbon obtained from buriti kernel, carbonized at 400 °C and activated at 900 °C. The activated carbon was characterized according to specific area, pore size, apparent and real density, porosity, scanning electron microscopy, ash content, pH, moisture, fixed carbon and surface functional groups. The study of adsorption equilibrium evaluated the influence of the coal particles diameter, contact time adsorbent/adsorbate, pH and copper (II) solution initial concentration on copper (II) remotion. The results showed a higher removal efficiency of copper (II) to the diameter D < 0.595 mm, contact time of 300 minutes, pH of 4.01 and the copper (II) initial concentrations of 50 and 80 mg L-1. The mathematical model of Langmuir was the best fit to the adsorption equilibrium data. From the contact time of 15 minutes, all the equilibrium concentrations were below the allowed maximum of 1,0 mg L-1 provided by law for discharging effluents into receiving bodies.