Estudo de titanatos nanoestruturados obtidos por tratamento hidrotérmico de óxido de titânio em meio alcalino

TiTanate NanoTubes (TTNT) were synthesized by hydrothermal alkali treatment of TiO2 anatase followed by repeated washings with distinct degrees of proton exchange. TTNT samples with different sodium contents were characterized, as synthesized and after heattreatment (200-800ºC), by X-ray diffraction, scanning and transmission electron microscopy, electron diffraction, thermal analysis, nitrogen adsorption and spectroscopic techniques like FTIR and UV-Vis diffuse reflectance. It was demonstrated that TTNTs consist of trititanate structure with general formula NaxH2−xTi3O7·nH2O, retaining interlayer water in its multiwalled structure. The removal of sodium reduces the amount of water and contracts the interlayer space leading, combined with other factors, to increased specific surface area and mesopore volume. TTNTs are mesoporous materials with two main contributions: pores smaller than 10 nm due to the inner volume of nanotubes and larger pores within 5-60 nm attributed to the interparticles space. Chemical composition and crystal structure of TTNTs do not depend on the average crystal size of the precursor TiO2-anatase, but this parameter affects significantly the morphology and textural properties of the nanostructured product. Such dependence has been rationalized using a dissolution-recrystallization mechanism, which takes into account the dissolution rate of the starting anatase and its influence on the relative rates of growth and curving of intermediate nanosheets. The thermal stability of TTNT is defined by the sodium content and in a lower extent by the crystallinity of the starting anatase. It has been demonstrated that after losing interlayer water within the range 100-200ºC, TTNT transforms, at least partially, into an intermediate hexatitanate NaxH2−xTi6O13 still retaining the nanotubular morphology. Further thermal transformation of the nanostructured tri- and hexatitanates occurs at higher or lower temperature and follows different routes depending on the sodium content in the structure. At high sodium load (water washed samples) they sinter and grow towards bigger crystals of Na2Ti3O7 and Na2Ti6O13 in the form of rods and ribbons. In contrast, protonated TTNTs evolve to nanotubes of TiO2(B), which easily convert to anatase nanorods above 400ºC. Besides hydroxyls and Lewis acidity typical of titanium oxides, TTNTs show a small contribution of protonic acidity capable of coordinating with pyridine at 150ºC, which is lost after calcination and conversion into anatase. The isoeletric point of TTNTs was measured within the range 2.5-4.0, indicating behavior of a weak acid. Despite displaying semiconductor characteristics exhibiting typical absorption in the UV-Vis spectrum with estimated bandgap energy slightly higher than that of its TiO2 precursor, TTNTs showed very low performance in the photocatalytic degradation of cationic and anionic dyes. It was concluded that the basic reason resides in its layered titanate structure, which in comparison with the TiO2 form would be more prone to the so undesired electron-hole pair recombination, thus inhibiting the photooxidation reactions. After calcination of the protonated TTNT into anatase nanorods, the photocatalytic activity improved but not to the same level as that exhibited by its precursor anatase

Vermiculitas tratadas quimicamente na obtenção de sólidos microporosos como precursores para híbridos inorgânico-orgânicos com aplicações adsortivas

ALVES, Ana paula Melo. Vermiculitas tratadas quimicamente na obtenção de sólidos microporosos como precursores para híbridos inorgânico-orgânicos com aplicações adsortivas. 2009. 124 f. Tese (Doutorado em Quimica) - Centro de Ciências Exatas e da Natureza, Universidade Federal da Paraíba, João Pessoa, PB, 2009.

O sistema de certificação do etanol brasileiro sob a ótica do princípio constitucional do desenvolvimento sustentável

The gradual inclusion of biofuels is a necessary change that countries must include in their energy mixes. Energy sources still widely used in the world, such as oil and coal, are endowed with a high pollution load to the environment, bringing damages to the water, to the air and to humans as well. In addition, although there are conflicting studies, they are also identified as major causes of the greenhouse effect and the global warming phenomenon. They are, moreover, finite sources of energy, given that its reserves will surely run out. However, even if the introduction of biofuels, such as ethanol, in the energy mix is crucial for the survival of the present and future populations, this insertion cannot settle so disorderly and, thus, one must ensure the quality of these resources and promote transparency in international trade. In this manner, a certification process for ethanol is essential to attest that this biofuel meets the sustainable requirements defined for its production. Hence, this study sought to address the importance of the adoption of certification in the ethanol industry, according to the principle of sustainable development, by analyzing the evolution of its concept, its combination with the fundamental objectives sculptured in the Constitution of 1988, its regulation under Brazilian laws and the need for a balance between economic activities and the mentioned principle. The work also encompassed the criteria used to establish certification standards and their participating actors, combined with a study of ongoing initiatives. Finally, the consequences of the adoption of a certification process for ethanol in Brazil were presented, both in terms of sustainable development and in international trade

Remoção de corantes utilizando tensoativos: extração por ponto de nuvem e floculação iônica

The textile sector is one of the main contributors to the generation of industrial wastewaters due to the use of large volumes of water, which has a high organic load content. In these, it is observed to the presence of dyes, surfactants, starch, alcohols, acetic acid and other constituents, from the various processing steps of the textiles. Hence, the treatment of textile wastewater becomes fundamental before releasing it into water bodies, where they can cause disastrous physical-chemical changes for the environment. Surfactants are substances widely used in separation processes and their use for treating textile wastewaters was evaluated in this research by applying the cloud point extraction and the ionic flocculation. In the cloud point extraction was used as surfactant nonylphenol with 9.5 ethoxylation degree to remove reactive dye. The process evaluation was performed in terms of temperature, surfactant and dye concentrations. The dye removal reached 91%. The ionic flocculation occurs due to the presence of calcium, which reacts with anionic surfactant to form insoluble surfactants capable of attracting the organic matter by adsorption. In this work the ionic flocculation using base soap was applied to the treatment of synthetic wastewater containing dyes belonging to three classes: direct, reactive, and disperse. It was evaluated by the influence of the following parameters: surfactant and electrolyte concentrations, stirring speed, equilibrium time, temperature, and pH. The flocculation of the surfactant was carried out in two ways: forming the floc in the effluent itself and forming the floc before mixing it to the effluent. Removal of reactive and direct dye, when the floc is formed into textile effluent was 97% and 87%, respectively. In the case where the floc is formed prior to adding it to the effluent, the removal to direct and disperse dye reached 92% and 87%, respectively. These results show the efficience of the evaluated processes for dye removal from textile wastewaters.

Vermiculitas tratadas quimicamente na obtenção de sólidos microporosos como precursores para híbridos inorgânico-orgânicos com aplicações adsortivas

ALVES, Ana paula Melo. Vermiculitas tratadas quimicamente na obtenção de sólidos microporosos como precursores para híbridos inorgânico-orgânicos com aplicações adsortivas. 2009. 124 f. Tese (Doutorado em Quimica) - Centro de Ciências Exatas e da Natureza, Universidade Federal da Paraíba, João Pessoa, PB, 2009.

Eutrofização do reservatório Engenheiro Armando Ribeiro Gonçalves, no Rio Grande do Norte: implicações para o abastecimento público e para a piscicultura intensiva em tanques-rede

This study aimed to describe the spatial and temporal patterns of variation in trophic state and its relation with the structure and dynamics of planktonic community of a large reservoir located in semi-arid tropical region of Northeast Brazil. The reservoir Armando Ribeiro Gonçalves is the biggest reservoir of the Rio Grande do Norte State and is responsible for about 53% of all surface water accumulated in the State. The samples of water and plankton were taken monthly in 10 points distributed throughout the longitudinal axis of the reservoir and over a full hydrological cycle. The samples were collected to determine concentrations of total phosphorus, total nitrogen, chlorophyll a and suspended solids (fixed and volatile) and for determining the composition and abundance of phytoplanktonic and zooplanktonic species. During the study period, the reservoir was characterized as eutrophic and there was no trend of increasing the trophic state of the reservoir in the period of drought. The concentrations of total phosphorus and suspended fixed solids decreased towards the dam while the N:P ratios increased in the same direction due to the reduction in the phosphorus concentrations and relative constancy in the nitrogen concentrations. The N:P ratios observed were indicative of greater limitation by phosphorus than by nitrogen. However, as concentrations of both nutrients were high and the water transparency was very low, with secchi depth usually lower than one meter, it seems likely that the planktonic primary production of the reservoir is more limited by the availability of light than the availability of nutrients. High nutrient concentrations coupled with low availability of light may explain the continuing dominance of filamentous cyanobacteria such as Cylindrospermopsis raciborskii in the plankton of the reservoir.These cyanobacteria are potentially toxic and pose a serious environmental problem because it compromises the water quality for public supply, recreation and fishing when present in high densities as in this study. The mesozooplankton of the reservoir was dominated by the calanoid Notodiaptomus cearensis and the cladoceran Diaphanosoma spinulosum. In general, the structure of zooplankton community seems to be particularly influenced by the spatial variation of cyanobacteria. The results of the regression analyses show that both the chlorophyll a concentrations and the cyanobacteria biovolume were more strongly correlated with the nitrogen than with phosphorus and that the water transparency was more strongly correlated with algal biomass than with other sources of turbidity. The maximum load of phosphorus to attain the maximum permissible concentration of total P in the reservoir was estimated in 63.2 tonnes P/ year. The current external P load to the reservoir is estimated in 324 tonnes P / year and must be severely reduced to improve the water quality for water supply and allow the implementation of aquaculture projects that could contribute to the socio-economic development of the region

Eutrofização e capacidade de carga de fósforo de seis reservatórios a bacia do Rio Seridó, região semi-árida do Estado do RN

The eutrofization is a natural process of accumulation of nutrients in aquatic´s body that it has been accelerated for the human´s actives, mainly the related with the activities of camp, industrial and the inadequate disposition of the domestic sewage. The enrichment of the aquatic´s body with nutrients, mainly the nitrogen and the phosphorus, and the consequent proliferation of algae and Cyanobacteria can commit the quality of the water for the public provisioning, for the fish farming and for other ends. The problem becomes more critical when there is a shortage of water naturally as in the semi-arid area of the Brazilian northeast. Before that problem this work had as objective evaluates the trophic state of six reservoirs of the basin of River Seridó of Rio Grande of Norte and also estimate the capacity of load of match of the reservoir and risk probabilities based on the established limits by the resolution Conama 357/05. The results demonstrate that the six reservoirs are eutrofization, with concentration of total phosphorus and cloro a in the water upster to 50 e 12 μg l-1. The results show that space homogeneity exists in the state trophic of the reservoirs, but a significant variation interanual in function of the increase of the concentrations of nutrients and decrease of the transparency of the water with the reduction of the body of water accumulated in the reservoirs.The results of the simulation risk estocastic show that the reservoirs could receive annually from 72 to 216 Kg of P, assuming a risk of 10% of increasing in more than 30 μg l-1 the annual medium concentrations of total match in the water of these reservoirs. This load could be high in until 360 kg of P a year in case the managers assume a risk of 10% of increasing in more than 50 μg l-1 the annual medium concentrations of total phosphorus in the waters of these reservoirs

Nitrificação de efluentes de reatores anaeróbicos em filtros submersos aerados

Although the good performance in organic matter and suspended solids removal, the anaerobic reactors are unable to remove ammonia nitrogen from sewage, which makes indispensable to include a step of post-treatment for removal of ammonia or nitrate as necessary. This paper presents the performance of a new variant technology, where the nitrification unit, preceded by anaerobic units, is a submerged aerated biological filter, without continuous sludge discharge in their daily operation. The oxygenation system is very simple and inexpensive, consisting of perforated hoses and compressors. The anaerobic reactors are a septic tank with two chambers followed (8.82 m³) and two parallel anaerobic filters (36 m³ each) filled with ceramic bricks and conics plastic parts. Both followed aerated filters were filled with cut corrugated conduit. The study evaluated the behavior of the system with constant domestic sewage flow (10 m³/d) and different aeration conditions, are these: stage 01, when applied air flow of 0.01 m³ air/min in both aerated filter; stage 02, remained in the initial air flow rate in the second aerated filter and increased at the first to 0.05 m³ air/min; at last, at last, in stage 03, the air flow rate of first aerated filter was 0.10 m³ air/min and on the second remained at 0.01 m³ air/min. The filter FA1 received load of 0.41 kg COD/m³.d, 0.37 kg COD/m³.d and 0.26 kg COD/m³.d on phases 01, 02 and 03, respectively. The FA2 received loads of 0.25 kg COD/m³.d, 0.18 kg COD/m³.d and 0.14 kg COD/m³.d on phases 01, 02 and 03, respectively. During stage 01, were found the following results: 98% removals of BODtotal and 92% of CODtotal, with effluent presenting 9 mg/L of BODtotal final average and 53 mg/L of CODtotal average; suspended solids removals of 93%, with a mean concentration of 10 mg/L in the final effluent; 47% reduction of ammonia of FA2 to FAN 's, presenting average of 28 mg NNH3/ L of ammonia in the effluent with; the dissolved oxygen levels always remained around 2.0 mg/L. During stage 02, were found removals of 97% and 95% to BODtotal and suspended solids, respectively, with average final concentrations of 8 and 7 mg/L, respectively; was removed 60% of ammonia, whose final concentration was 16.3 mg NNH3/ L, and nitrate was increased to a final average concentration of 16.55 mg N-NO3/L. Finally, the stage 03 provided 6 mg/L of DBOtotal (98% removal) and 23 mg/L of CODtotal (95% removal) of final effluent concentrations average. At this stage was identified the higher ammonia oxidation (86%), with final effluent showing average concentration of 6.1 mg N-NH3/L, reaching a minimum of 1.70 mg N-NH3/L. In some moments, during stage 03, there was a moderate denitrification process in the last aerated filter. The average turbidity in the effluent showed around 1.5 NTU, proving the good biomass physical stability. Therefore, the results demonstrate the submerged biological filters potential, filled with high void ratio material (98%), and aerated with hoses and compressor adoption, in the carbonaceous and nitrogenous matter oxidation, also generating an effluent with low concentration of solids

Eutrofização do reservatório Engenheiro Armando Ribeiro Gonçalves, no Rio Grande do Norte: implicações para o abastecimento público e para a piscicultura intensiva em tanques-rede

This study aimed to describe the spatial and temporal patterns of variation in trophic state and its relation with the structure and dynamics of planktonic community of a large reservoir located in semi-arid tropical region of Northeast Brazil. The reservoir Armando Ribeiro Gonçalves is the biggest reservoir of the Rio Grande do Norte State and is responsible for about 53% of all surface water accumulated in the State. The samples of water and plankton were taken monthly in 10 points distributed throughout the longitudinal axis of the reservoir and over a full hydrological cycle. The samples were collected to determine concentrations of total phosphorus, total nitrogen, chlorophyll a and suspended solids (fixed and volatile) and for determining the composition and abundance of phytoplanktonic and zooplanktonic species. During the study period, the reservoir was characterized as eutrophic and there was no trend of increasing the trophic state of the reservoir in the period of drought. The concentrations of total phosphorus and suspended fixed solids decreased towards the dam while the N:P ratios increased in the same direction due to the reduction in the phosphorus concentrations and relative constancy in the nitrogen concentrations. The N:P ratios observed were indicative of greater limitation by phosphorus than by nitrogen. However, as concentrations of both nutrients were high and the water transparency was very low, with secchi depth usually lower than one meter, it seems likely that the planktonic primary production of the reservoir is more limited by the availability of light than the availability of nutrients. High nutrient concentrations coupled with low availability of light may explain the continuing dominance of filamentous cyanobacteria such as Cylindrospermopsis raciborskii in the plankton of the reservoir.These cyanobacteria are potentially toxic and pose a serious environmental problem because it compromises the water quality for public supply, recreation and fishing when present in high densities as in this study. The mesozooplankton of the reservoir was dominated by the calanoid Notodiaptomus cearensis and the cladoceran Diaphanosoma spinulosum. In general, the structure of zooplankton community seems to be particularly influenced by the spatial variation of cyanobacteria. The results of the regression analyses show that both the chlorophyll a concentrations and the cyanobacteria biovolume were more strongly correlated with the nitrogen than with phosphorus and that the water transparency was more strongly correlated with algal biomass than with other sources of turbidity. The maximum load of phosphorus to attain the maximum permissible concentration of total P in the reservoir was estimated in 63.2 tonnes P/ year. The current external P load to the reservoir is estimated in 324 tonnes P / year and must be severely reduced to improve the water quality for water supply and allow the implementation of aquaculture projects that could contribute to the socio-economic development of the region

Eutrofização e capacidade de carga de fósforo de seis reservatórios a bacia do Rio Seridó, região semi-árida do Estado do RN

The eutrofization is a natural process of accumulation of nutrients in aquatic´s body that it has been accelerated for the human´s actives, mainly the related with the activities of camp, industrial and the inadequate disposition of the domestic sewage. The enrichment of the aquatic´s body with nutrients, mainly the nitrogen and the phosphorus, and the consequent proliferation of algae and Cyanobacteria can commit the quality of the water for the public provisioning, for the fish farming and for other ends. The problem becomes more critical when there is a shortage of water naturally as in the semi-arid area of the Brazilian northeast. Before that problem this work had as objective evaluates the trophic state of six reservoirs of the basin of River Seridó of Rio Grande of Norte and also estimate the capacity of load of match of the reservoir and risk probabilities based on the established limits by the resolution Conama 357/05. The results demonstrate that the six reservoirs are eutrofization, with concentration of total phosphorus and cloro a in the water upster to 50 e 12 μg l-1. The results show that space homogeneity exists in the state trophic of the reservoirs, but a significant variation interanual in function of the increase of the concentrations of nutrients and decrease of the transparency of the water with the reduction of the body of water accumulated in the reservoirs.The results of the simulation risk estocastic show that the reservoirs could receive annually from 72 to 216 Kg of P, assuming a risk of 10% of increasing in more than 30 μg l-1 the annual medium concentrations of total match in the water of these reservoirs. This load could be high in until 360 kg of P a year in case the managers assume a risk of 10% of increasing in more than 50 μg l-1 the annual medium concentrations of total phosphorus in the waters of these reservoirs