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Aracaju, Brazil

Hydrilla verticillata (Hydrocharitaceae) is a highly prolific, rooted submerged macrophyte native to Asia that has invaded aquatic systems worldwide, causing many ecological and human-related problems. Hydrilla recently invaded the Paraná River basin in Brazil, making other ecologically and socially important Brazilian watersheds more susceptible to invasion by this plant. Here, I summarize the relevant information about Hydrilla, focusing on its biotic attributes, abiotic tolerance and effects on ecosystems. The aim of this review is to provide background information to assist with planning for the potential impacts of this species in the Neotropical region (particularly in Brazil) and the development of research, monitoring and management strategies. A wide ecological amplitude, resistance organs, and high growth rates and dispersion ability provide Hydrilla with great potential to invade and infest a variety of habitats, often resulting in important physico-chemical and biotic effects on the environment. Hydrilla is similar in its morphological and ecological aspects to Egeria najas and Egeria densa (South American Hydrocharitaceae), but this non-native species is a superior competitor and can be expected to exert significant pressure in habitats colonized by these native Hydrocharitaceae. Socially important rivers (such as the São Francisco River) have a high risk of being infested with Hydrilla, especially in stretches affected by dams, which could prejudice important human activities like hydropower generation. Important wetlands for biodiversity conservation (such as the Pantanal) may also be invaded, but they seem to be more resistant to infestations as long as their natural hydrologies are preserved. Before investing substantial effort to control Hydrilla, managers should weigh the potential costs and benefits of available techniques and consider the potential benefits of Hydrilla in providing ecosystem services. © 2011 Springer Science+Business Media B.V.

Pereira J.F.B.,University of Aveiro | Lima A.S.,Tiradentes University | Freire M.G.,University of Aveiro | Coutinho J.A.P.,University of Aveiro
Green Chemistry | Year: 2010

The potential use of ionic liquids (ILs) as adjuvants in typical polymer-salt aqueous systems for the separation and purification of vital biomolecules is investigated. An innovative study involving the addition of various imidazolium-based ILs to conventional PEG/inorganic salt aqueous biphasic systems (ABS), aiming at controlling their phase behaviour and extraction capability for l-tryptophan, is carried out here. For this purpose, phase diagrams and respective tie-lines for PEG 600/Na2SO4 ABS with the addition of small quantities of IL were established. In addition, the partition coefficients of l-tryptophan were determined in those systems. The results obtained indicate that the addition of small amounts of IL to the typical PEG/inorganic salt aqueous systems could largely control the extraction efficiency for l-tryptophan, and that efficiency depends on the IL employed. Salting-in inducing ILs enhance the partition coefficient of l-tryptophan for the PEG-rich phase while salting-out inducing ILs decrease the partitioning of the amino acid. These results are an interesting advance in biotechnological separation processes regarding the extraction of biomolecules that could be used instead of the common approach of PEG functionalization. © 2010 The Royal Society of Chemistry.

Freitas S.V.D.,University of Aveiro | Pratas M.J.,University of Aveiro | Ceriani R.,University of Campinas | Lima A.S.,Tiradentes University | Coutinho J.A.P.,University of Aveiro
Energy and Fuels | Year: 2011

Viscosity is an important biodiesel parameter, subject to specifications and with an impact on the fuel quality. A model that could predict the value of viscosity of a biodiesel based on the knowledge of its composition would be useful in the optimization of biodiesel production processes and the planning of blending of raw materials and refined products. This work aims at evaluating the predictive capability of several models previously proposed in the literature for the description of the viscosities of biodiesels and their blend with other fuels. The models evaluated here are Ceriani's, Krisnangkura's, and Yuan's models, along with a revised version of Yuan's model proposed here. The results for several biodiesel systems show that revised Yuan's model proposed provides the best description of the experimental data with an average deviation of 4.65%, as compared to 5.34% for Yuan's model, 8.07% for Ceriani's model, and 7.25% for Krisnangkura's model. The same conclusions were obtained when applying these models to predict the viscosity of blends of biodiesel with petrodiesel. © 2010 American Chemical Society.

Freitas S.V.D.,University of Aveiro | Oliveira M.B.,University of Aveiro | Lima A.S.,Tiradentes University | Coutinho J.A.P.,University of Aveiro
Energy and Fuels | Year: 2012

Vapor pressure directly affects the quality of ignition, atomization, and combustion of a fuel. Lower values lead to delayed ignition, poor atomization, and problematic combustion. Biodiesel fuels might present these problems because they have lower vapor pressure compared to that of petrodiesel. Similar to other properties, however, the magnitude of this property depends upon the composition of fatty acid alkyl esters in biodiesel; therefore, the knowledge of the relationship between these two variables is of great importance. This work reports the vapor pressures of 3 pure methyl esters and 10 biodiesel fuels. The experimental data were used to evaluate the predictive ability of Yuan's, Ceriani's, and cubic-plus-association equation of state (CPA EoS) models for its description. The results underline the good capacity of Yuan's and CPA models for describing the experimental data for all biodiesel fuels studied here, presenting an overall average temperature difference (OΔT m) of 1.12 and 1.25 K, while the overall average deviations (OARDs) in vapor pressure are 3.41 and 0.80%, respectively. © 2012 American Chemical Society.

Garcia-Segura S.,University of Barcelona | Cavalcanti E.B.,Tiradentes University | Brillas E.,University of Barcelona
Applied Catalysis B: Environmental | Year: 2013

Chloramphenicol is a widely used broad-spectrum antibiotic, which has been detected as emerging pollutant in natural waters. The mineralization of this drug in a synthetic sulfate solution of pH 3.0 has been studied by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF), UVA photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF). Comparative electrolyses carried out with 100mL stirred tank reactors equipped with a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode at constant current density showed the superiority of the processes with BDD because of the higher oxidation ability of ™OH formed from water oxidation at the BDD surface. Total mineralization was rapidly reached for the most potent treatment of SPEF with BDD due to the additional oxidation by ™OH produced from Fenton's reaction between added Fe2+ (0.5mM) and H2O2 generated at the cathode, together the synergistic photolytic action of sunlight, much more intense than the 6W UVA lamp used in PEF. Chloramphenicol decay always followed a pseudo-first-order kinetics. The influence of current density and substrate concentration on SPEF with BDD was examined. Nine aromatic products, thirteen hydroxylated derivatives and seven carboxylic acids were identified by different chromatographic techniques. While the initial Cl of the drug was released as chloride ion, its initial N was lost as nitrate ion and, in smaller proportion, as ammonium ion. From the detected products, a general reaction pathway for chloramphenicol mineralization is proposed. The viability of SPEF was confirmed in a 10L pre-pilot plant with a Pt/air-diffusion filter-press reactor coupled to a solar CPCs photoreactor. After 180min of electrolysis at 100mAcm-2, a 245mgL-1 chloramphenicol solution in 0.05M Na2SO4 with 0.5mM Fe2+ at pH 3.0 underwent 89% mineralization with 36% current efficiency and 30.8kWhm-3 energy cost. © 2013 Elsevier B.V.

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