RESUMO
Pseudomonas aeruginosa UFPEDA 614 produced a rhamnolipid biosurfactant when grown on sugarcane bagasse impregnated with a solution containing glycerol. Biosurfactant levels reached 40 g of rhamnolipid per kilogram of dry initial substrate after 12 days. On the basis of the volume of liquid used, the biosurfactant levels were similar to those obtained in submerged liquid culture of a medium identical to the impregnating solution. The properties of the biosurfactant were very similar to those obtained with rhamnolipids produced in submerged culture, with a critical micelle concentration of 46.8 mg/L and an emulsification index at 24 h of over 90% against gasoline. The surface properties were maintained after autoclaving of the fermented solids, meaning that it is possible to minimize safety risks by killing the producing organism with a heat treatment of the solids prior to product extraction. The biosurfactant was used in the washing of soils contaminated with gasoline. An aqueous biosurfactant solution was 3.2-fold more efficient than water in leaching organic material from the soil, demonstrating the viability of application of rhamnolipids in the bioremediation of soils contaminated with gasoline.
Assuntos
Biodegradação Ambiental , Glicolipídeos/metabolismo , Pseudomonas aeruginosa/metabolismo , Poluentes do Solo/metabolismo , Tensoativos/metabolismo , Reatores Biológicos , Celulose/metabolismo , Estabilidade de Medicamentos , Gasolina , Glicolipídeos/química , Cinética , Micelas , Propriedades de Superfície , Tensoativos/química , TemperaturaRESUMO
Two advanced oxidative processes (Fe2+/H2O2/UV and H2O2/UV systems) were used for the pre-treatment of mature landfill leachate with the objective of improving its overall biodegradability, evaluated in terms of BOD5/COD ratio, up to a value compatible with biological treatment. At optimized experimental conditions (2000 mgL(-1) of H2O2 and 10 mgL(-1) of Fe2+ for the photo-Fenton system, and 3000 mgL(-1) of H2O2 for the H2O2/UV system), both methods showed suitability for partial removal of chemical oxygen demand (COD), total organic carbon (TOC) and color. The biodegradability was significantly improved (BOD5/COD from 0.13 to 0.37 or 0.42) which allowed an almost total removal of COD and color by a sequential activated sludge process. In addition, gel permeation chromatography (GPC) has showed a substantial agreement on the cleavage of large organic compound into smaller ones.
Assuntos
Biodegradação Ambiental , Eliminação de Resíduos/métodos , Catálise , Peróxido de Hidrogênio , Oxirredução , Fotoquímica/métodos , Raios UltravioletaRESUMO
A liberação de fluoreto da resina Fluroshied (Dentsply) foi influenciada pela presença de íons e pelo valor do pH. Os íons presentes num regulador de pH e de força iônica (acetato, sódio, cloreto) provocaram uma pequena redução na capacidade total de dessorção de fluoreto. O fluoreto foi dessorvido em água e em tampões de acetato e fosfato, atingindo teor máximo com cerca de 0,18 a 0,36 ppm/17 mm³ de resina. A velocidae de liberação foi maior para o tampão fosfato e foi menor para o tampão acetato. Assim, a liberação de íons fluoreto pela resina ocorre no meio bucal nos diversos valores de pH que possam ser encontrados fisiologicamente, embora possa variar o grau de dessorção. A resina quase não demonstrou capacidade de adsorver íons fluoreto de uma solução a 1 ppm (img/L), o que sugere que ela deveria ser substituída de tempos em tempos para manter sua capacidade de liberar fluoreto
