RESUMO
Biodiesel and diesel-like have been obtained from soybean oil by transesterification and thermal cracking process, respectively. These biofuels were characterized as according to ANP standards by using specific ASTM methods. Ethanol, gasoline, and diesel were purchased from a gas station. Deacetylation degree of chitosan was determined by three distinct methods (conductimetry, FTIR and NMR), and the average degree was 78.95%. The chitosan microspheres were prepared from chitosan by split-coating and these spheres were crosslinked using glutaraldehyde. The surface area of microspheres was determined by BET method, and the surface area of crosslinked microspheres was 9.2m(2)g(-1). The adsorption isotherms of cooper, nickel and zinc on microspheres of chitosan were determined in petroleum derivatives (gasoline and diesel oil), as well as in biofuels (alcohol, biodiesel and diesel-like). The adsorption order in all fuels was: Cu>Ni>Zn. The elution tests presented the following preconcentration degrees: >4.5 to ethanol, >4.4 to gasoline, >4.0 to diesel, >3.8 to biodiesel and >3.6 to diesel-like. The application of chitosan microspheres in the metal ions preconcentration showed the potential of this biopolymer to enrich fuel sample in order to be analyzed by flame atomic absorption spectrometry.
Assuntos
Biocombustíveis/análise , Cátions Bivalentes/química , Quitosana/química , Etanol/análise , Gasolina/análise , Metais/química , Adsorção , Calorimetria , Esterificação , Espectroscopia de Ressonância Magnética , Microesferas , TermodinâmicaRESUMO
The compound 2-mercaptobenzimidazole (MBI) was attached onto a silica gel surface by homogeneous and heterogeneous routes. Both silica modification methodologies resulted in similar products, named SiM(hom) and SiM(het), respectively. These materials were characterized by surface area, infrared, thermogravimetry, and 13C and 29Si NMR spectroscopy. The ability of these materials to remove divalent mercury from aqueous solution was followed by a series of adsorption isotherms adjusted to a modified Langmuir equation. The maximum number of moles adsorbed was determined to be 1.35+/-0.3 and 1.42+/-0.17 mmolg-1 for SiMhet and SiMhomt, respectively. These interactions were calorimetrically followed and the thermodynamic data showed the following exothermic enthalpic values: -23.04+/-1.4 and -20.08+/-1.2 kJmol-1 for SiMhom and SiMhet, respectively. All liquid/solid interface adsorptions were spontaneous in nature and enthalpically driven.