Organometallic catalysis: some contributions to organic synthesis

In the present paper some general aspects of metal complex catalysis and its applications for oxyfunctionalization of various olefins, including naturally occurring ones, via selective oxidation, hydroformylation and alkoxycarbonylation are discussed.

Use of the EPR technique to determine thermal stability of some humified organic substances found in soil organic-mineral fractions

In this work, using the EPR spectroscopy, we analysed the thermal stability of some organic-mineral compounds found in a Gleysoil from Rio Janeiro. It was observed a complete disappearance of the EPR signal around 600 °C for the < 2 µm fraction and a residual EPR signal of semiquinone free radical for the 2-20 µm and 20-53 µm fractions at the same temperature. Also, the experiments showed that the 2-20 µm fraction had a larger concentration of semiquinone free radical per g of carbon and a smaller line width indicated a larger humification of this fraction. This is an evidence that the soil organic matter of this fraction (2-20 µm) is more stable than the other ones.

Organic chicken product authentication: state-of-the-art and future perspectives

Organic food products are highly susceptible to fraud. Currently, administrative controls are conducted to detect fraud, but having an analytical tool able to verify the organic identity of food would be very supportive. The state-of-the-art in food authentication relies on fingerprinting approaches that find characteristic analytical patterns to unequivocally identify authentic products. While wide research on authentication has been conducted for other commodities, the authentication of organic chicken products is still in its infancy. Challenges include finding fingerprints to discriminate organic from conventional products, and recruiting sample sets that cover natural variability. Future research might be oriented towards developing new authentication models for organic feed, eggs and chicken meat, keeping models updated and implementing them into regulations. Meanwhile, these models might be very supportive to the administrative controls directing inspections towards suspicious fraudulent samples.

Contaminação de águas por BTXs e processos utilizados na remediação de sítios contaminados

After decades of polluting actions the environment manifests serious and global consequences. The contamination of soils and groundwater by organic compounds is a widespread problem mainly on account of contamination by leakage from underground storage tanks, which often results in the release of gasoline or other chemicals. The main problem about groundwater contamination is due to the toxicity of water-soluble components such as benzene, toluene and xylene (BTX). In the present work a study about classical and modern methods for remediation of BTX is reported.

Análise sistemática de reagentes e resíduos sem identificação

This work presents a detailed routine applied to the identification of unknown chemicals and wastes. 786 specimens were analyzed during 20 months. Unknown materials fell into three basic classes: (i) commercial chemicals without labels or illegible ones; (ii) laboratory synthesis products; (iii) used solvents (including mixtures). Uranium and thorium were recovered form their wastes. Unknown chemicals were mainly inorganic compounds, many of which had never been opened. Alkaline salts were dominant, but also precious metal compounds were identified. Laboratory synthesis products were organic compounds. The final destination depended on the nature of the chemical. Most organic compounds were sent to incineration; inorganic salts were distributed among several public organizations, including secondary and technical schools. The work described in this paper greatly reduced the amount of wastes that had to be sent to disposal.

The influence of substratum type and nutrient supply on biofilm organic matter utilization in streams

We investigated the effect of benthic substratum type (sand and rocks) and nutrient supply (N and P) on biofilm structure and heterotrophic metabolism in a field experiment in a forested Mediterranean stream (Fuirosos). Rock and sand colonization and biofilm formation was intensively studied for 44 d at two stream reaches: control and experimental (continuous addition of phosphate, ammonia, and nitrate). Structural (C, N, and polysaccharide content and bacterial and chlorophyll density) and metabolic biofilm parameters (b-glucosidase, peptidase, and phosphatase enzyme activities) were analyzed throughout the colonization process. The epilithic biofilm (grown on rocks) had a higher peptidase activity at the impacted reach, together with a higher algal and bacterial biomass. The positive relationship between the peptidase activity per cell and the N content of the epilithic biofilm suggested that heterotrophic utilization of proteinaceous compounds from within the biofilm was occurring. In contrast, nutrient addition caused the epipsammic biofilm (grown on sand) to exhibit lower b-glucosidase and phosphatase activities, without a significant increase in bacterial and algal biomass. The differential response to nutrient addition was related to different structural characteristics within each biofilm. The epipsammic biofilm had a constant and high C:N ratio (22.7) throughout the colonization. The epilithic biofilm had a higher C:N ratio at the beginning of the colonization (43.2) and evolved toward a more complex structure (high polysaccharide content and low C:N ratio) during later stages. The epipsammic biofilm was a site for the accumulation and degradation of organic matter: polysaccharides and organic phosphorus compounds had higher degradation activities

Hydrology, light and the use of organic and inorganic materials as structuring factors of biological communities in Mediterranean streams

Hydrological disturbances, light availability and nutrients are the most relevant factors determining the structure of the biological communities in Mediterranean rivers. While some hydrological disturbances are able to induce catastrophic effects, which may cause a complete reset in physical and biological conditions, continued enrichment or changes in light availability are factors leading to the progressive shift in the communities of autotrophs and heterotrophs in the systems. Primary production in Mediterranean streams shows relevant seasonal changes which mainly follows the variations in light availability. In most forested streams, the algal community is shade-adapted. Nutrient enrichment (especially phosphorus) leads to marked increases in primary production, but this increase is not lineal and there is a saturation of algal biomass even in the most enriched systems. The heterotrophs (bacteria, fungi) are related to the pattern of DOC availability (which most depends on the seasonal discharge and leaf fall dynamics) and to the available substrata in the stream. It has been repeatedly observed that shorttime increases of extracellular enzyme activities are related to the accumulation of autochthonous (algal) and/or allochthonous (leaves) organic matter on the streambed during spring and summer, this being more remarkable in dry than in wetter years. Flow reduction favours detritus concentration in pools, and the subsequent increase in the density and biomass of the macroinvertebrate community. In Mediterranean streams collectors are accounting for the highest density and biomass, this being more remarkable in the least permanent systems, in accordance with the effect of floods on the organic matter availability. Nutrients, through the effect on the primary producers, also affect the trophic food web in the streams by favouring the predominance of grazers

Organic carbon and nutrient (P, N) concentrations of water and sediment in several aquatic environment types of a Mediterranean coastal wetland (Empordà Wetlands, NE Iberian Peninsula)

Total sediment and water organic carbon and nutrient (nitrogen and phosphorus) concentrations of different environment types of a Mediterranean coastal wetland (temporary and brackish, temporary and freshwater, semi-permanent and brackish, and permanent and brackish basins) were analysed during two hydroperiods. A nitrogen limitation was found for both sediment and water. The total organic carbon concentration of the water was significantly related to the water level, which varies throughout the hydroperiods. In contrast, the total organic carbon concentration of the sediment was not related to water level. However, significant differences in total organic carbon of the sediment were found between hydroperiods. On the other hand, total organic carbon of the sediment varied spatially, being higher in temporary brackish basins with lower sand content, and lower in permanent and semi-permanent brackish basins with higher sand content

Persistent organic pollutants in two reservoirs along the Paraíba do Sul-Guandu River system, Rio de Janeiro, Brazil

Sediment contamination is evaluated by determining organic micropollutants (organochlorine compounds - OCs and polycyclic aromatic hydrocarbons - PAHs) in two important Brazilian water reservoirs. Trace levels of OCs were observed in the Santana reservoir (44.8 ng g-1 d.w. of p,p'-DDT), while in the Funil reservoir the levels were below detection level. Forty-eight percent of the found sigmaocs were polychlorinated biphenyls, 29% dichlorodiphenyltrichloroethane (DDT), 18% Drins, and 5% other pesticides (HCB, Heptachlor, Heptachlor-epoxide, gamma-HCH and a-Endosulfan). We observed lower levels of sigmaPAH in the Funil reservoir (1 to 275 ng g-1d.w.) than in the Santana reservoir (2.2 to 26.7 µg g-1 d.w.).

Nanoparticle-coated organic-inorganic microparticles: experimental design and gastrointestinal tolerance evaluation

The influences of the spray-drying parameters and the type of nanoparticles (nanocapsules or nanospheres) on the characteristics of nanoparticle-coated diclofenac-loaded microparticles were investigated by using a factorial design 3². Gastrointestinal tolerance following oral administration in rats was evaluated. Formulations were selected considering the best yields, the best encapsulation efficiencies and the lowest water contents, presenting surfaces completely coated by nanostructures and a decrease in the surface areas in relation to the uncoated core. In vitro drug release demonstrated the influence of the nanoparticle-coating on the dissolution profiles of diclofenac. Nanocapsule-coated microparticles presented a protective effect on the gastrointestinal mucosa.

Water circulations for effective bleaching of high-brightness mechanical pulps

The amount of water available is usually restricted, which leads to a situation where a complete understanding of the process, including water circulations and the influence of water components, is essential. The main aim of this thesis was to clarify the possibilities for the efficient use of residual peroxide by means of water circulation rearrangements. Rearranging water circulations and the reduction of water usage may cause new problems, such as metal induced peroxide decomposition that needs to be addressed. This thesis introduces theoretical methods of water circulations to combine two variables; effective utilization of residual peroxide and avoiding manganese in the alkaline peroxide bleaching stage. Results are mainly based on laboratory and mill site experiments concerning the utilization of residual peroxide. A simulation model (BALAS) was used to evaluate the manganese contents and residual peroxide doses. It was shown that with optimum recirculation of residual peroxide the brightness can be improved or chemical costs can be decreased. From the scientific perspective, it was also very important to discover that recycled peroxide was more effective pre-bleaching agent compared to fresh peroxide. This can be due to the organic acids i.e. per acetic acid in wash press filtrate that have been formed in alkaline bleaching stage. Even short retention time was adequate and the activation of residual peroxide using sodium hydroxide was not necessary. There are several possibilities for using residual peroxide in practice regarding bleaching. A typical modern mechanical pulping process line consist of defibering, screening, a disc filter, a bleach press, high consistency (HC) peroxide bleaching and a wash press. Furthermore there usually is not a particular medium consistency (MC) pre-bleaching stage that includes additional thickening equipment. The most advisable way to utilize residual peroxide in this kind of process is to recycle the wash press filtrate to the dilution of disc filter pulp (low MC pre-bleaching stage). An arrangement such as this would be beneficial in terms of the reduced convection of manganese to the alkaline bleaching stage. Manganese originates from wood material and will be removed to the water phase already in the early stages of the process. Recycling residual peroxide prior to the disc filter is not recommended because of low consistencies. Regarding water circulations, the novel point of view is that, it would be beneficial to divide water circulations into two sections and the critical location for the division is the disc filter. Both of these two sections have their own priority. Section one before the disc filter: manganese removal. Section two after the disc filter: brightening of pulp. This division can be carried out if the disc filter pulp is diluted only by wash press filtrate before the MC storage tower. The situation is even better if there is an additional press after the disc filter, which will improve the consistency of the pulp. This has a significant effect on the peroxide concentration in the MC pre-bleaching stage. In terms of manganese content, it is essential to avoid the use of disc filter filtrate in the bleach press and wash press showers. An additional cut-off press would also be beneficial for manganese removal. As a combination of higher initial brightness and lower manganese content, the typical brightness increase varies between approximately 0.5 and 1% ISO units after the alkaline peroxide bleaching stage. This improvement does not seem to be remarkable, but as it is generally known, the final brightness unit is the most expensive and difficult to achieve. The estimation of cost savings is not unambiguous. For example in GW/TMP mill case 0.6% ISO units higher final brightness gave 10% savings in the costs of bleaching chemicals. With an hypothetical 200 000 ton annual production, this means that the mill could save in the costs of bleaching chemicals more than 400 000 euros per year. In general, it can be said that there were no differences between the behavior of different types of processes (GW, PGW, TMP and BCTMP). The enhancement of recycling gave a similar response in all cases. However, we have to remember that the utilization of residual peroxide in older mills depends a great deal on the process equipment, the amount of water available and existing pipeline connections. In summary, it can be said that processes are individual and the same solutions cannot be applied to all cases.

Preparation, spectroscopic and acidity properties of two hydrazones: an organic lab experiment

An undergraduate organic lab experiment is described based on the preparation of two readily accessible hydrazones. The UV-visible spectra of these N-H acids and of their conjugate bases are employed to illustrate the importance of through-conjugation in determining their acid strength and their internal charge-transfer-band transitions.

Comparison of GC and HPLC for quantification of organic acids in two jaboticaba (Myrciaria) fruit varieties

Gas chromatography (GC) with trimethylsilyl derivative formation was compared to high-performance liquid chromatography (HPLC) for quantification of organic acids (OAs) in two jaboticaba (Myrciaria) fruit (pulp and pericarp) varieties (Sabará and Açu Paulista). Succinic and citric acids were the major OAs found in all the samples analyzed. Besides being much more tedious, the results obtained with GC were significantly lower than HPLC (p<0.05) when the data (acids, variety, two parts and flowering days) were considered together. The presence of both acids was confirmed by gas chromatography-mass spectrometry (GC-MS).

Recovery of organic acids with liquid-liquid extraction contactors

Liquid-liquid extraction is a mass transfer process for recovering the desired components from the liquid streams by contacting it to non-soluble liquid solvent. Literature part of this thesis deals with theory of the liquid-liquid extraction and the main steps of the extraction process design. The experimental part of this thesis investigates the extraction of organic acids from aqueous solution. The aim was to find the optimal solvent for recovering the organic acids from aqueous solutions. The other objective was to test the selected solvent in pilot scale with packed column and compare the effectiveness of the structured and the random packing, the effect of dispersed phase selection and the effect of packing material wettability properties. Experiments showed that selected solvent works well with dilute organic acid solutions. The random packing proved to be more efficient than the structured packing due to higher hold-up of the dispersed phase. Dispersing the phase that is present in larger volume proved to more efficient. With the random packing the material that was wetted by the dispersed phase was more efficient due to higher hold-up of the dispersed phase. According the literature, the behavior is usually opposite.

Rhizodeposition of organic carbon by plants with contrasting traits for resource acquisition: responses to different fertility regimes

Background and aims Rhizodeposition plays an important role in mediating soil nutrient availability in ecosystems. However, owing to methodological difficulties (i.e., narrow zone of soil around roots, rapid assimilation by soil microbes) fertility-induced changes in rhizodeposition remain mostly unknown. Methods We developed a novel long-term continuous 13C labelling method to address the effects of two levels of nitrogen (N) fertilization on rhizodeposited carbon (C) by species with different nutrient acquisition strategies. Results Fertility-induced changes in rhizodeposition were modulated by root responses to N availability rather than by changes in soil microbial biomass. Differences among species were mostly related to plant biomass: species with higher total leaf and root biomass also had higher total rhizodeposited C, whereas species with lower root biomass had higher specific rhizodeposited C (per gram root mass). Experimental controls demonstrated that most of the biases commonly associated with this type of experiment (i.e., long-term steady-state labelling) were avoided using our methodological approach. Conclusions These results suggest that the amount of rhizodeposited C from plants grown under different levels of N were driven mainly by plant biomass and root morphology rather than microbial biomass. They also underline the importance of plant characteristics (i.e., biomass allocation) as opposed to traits associated with plant resource acquisition strategies in predicting total C rhizodeposition.