O uso de técnicas espectroscópicas para o estudo de questões ambientais é uma área de pesquisa que vem experimentando importante desenvolvimento em tempos recentes. Essas técnicas abrangem métodos espectroscópicos intensificados, que proporcionam grande sensibilidade e seletividade para a detecção de espécies químicas em baixas concentrações. Nesta dissertação, propomos a introdução de uma nova metodologia aplicada ao estudo da fotodegradação de moléculas de interesse ambiental. Utilizamos técnicas de espectroscopia Raman intensificada pela superfície (SERS) para a análise dos processos de fotodegradação de azo-corantes mediados por dióxido de titânio. Nosso primeiro passo para o desenvolvimento dessa metodologia foi realizar um estudo comparativo acerca de diferentes métodos para preparação de um substrato SERS-ativo - sobre cuja superfície viríamos a proceder a fotodegradação de corantes e simultaneamente o estudo espectroscópico desse processo. A dificuldade na preparação do substrato reside no fato de que é necessário produzir uma superfície simultaneamente fotocatalítica (pela presença do semicondutor TiO2) e com atividade SERS (pela presença de partículas de Ag nanoestruturadas). Assim, três diferentes métodos para a preparação do substrato foram estudados, buscando obter atividade SERS aliada à reprodutibilidade. Escolhido o método mais satisfatório, utilizamos o substrato para realizar estudos SERS dos processos de fotodegradação de dois corantes: vermelho do Congo e verde de Janus. Considerando que a degradação fotocatalítica pode envolver oxidação e redução das moléculas, foi realizado também o estudo espectroeletroquímico dos dois corantes, buscando correlações que ajudassem a esclarecer as transformações envolvidas nas etapas iniciais da fotodegradação dessas substâncias. Nossos estudos revelaram que as primeiras etapas dos processos de fotodegradação dos dois corantes seguem mecanismos diferentes: enquanto no caso do vermelho do Congo há evidências de oxidação, no caso do verde de Janus as evidências apontam para um processo de redução. A combinação de dados da fotodegradação de corantes com seu estudo via eletroquímica - utilizando técnicas de espectroscopia intensificada para a identificação e caracterização de produtos - mostrou-se bastante promissora, no sentido de oferecer informações relevantes sobre os complexos mecanismos envolvidos nos processos de fotodegradação. / The use of spectroscopic techniques for the study of environmental questions is a research area has been experiencing important developments in recent years. These techniques embrace intensified spectroscopic methods, which offer great sensibility and selectivity for the detection of chemical species in low concentrations. In this work, we propose the introduction of a new methodology to be applied to the study of photodegradation of environmentally relevant molecules. We employed surface-enhanced Raman spectroscopy to the analysis of photodegradation of azo-dyes mediated by titanium dioxide. First, we performed a comparative study concerning the different methods for the preparation of SERS-active substrate, onto which we would carry out simultaneously the photodegradation of dyes and the spectroscopic study of the process. The difficulty in the preparation of such substrates resides in the fact that it is necessary to produce a surface which is all together photocatalytic (by the presence of the semiconducting TiO2) and SERS-active (by the presence of nanostructured silver). In this context, three different preparation methods were investigated, with the purpose of achieving good SERS activity and reproducibility. The optimized SERS-active substrate was employed to study the photodegradation of two azo-dyes: Congo red and Janus green. Considering that the photocatalitic degradation process might involve either the oxidation or the reduction of molecules, the spectroelectrochemical study of both dyes was also performed, in order to in order to search for important correlations that would help to clarify the transformations involved in the initial steps of the photochemical decomposition of these substances. The obtained results revealed that the first steps of the degradation processes of both dyes followed different routes: whereas for Congo red there are evidences of an oxidation process, for Janus green the evidences point to a reduction mechanism. The combination of the data relative to the photochemical behavior of the dyes and their electrochemical study - using enhanced spectroscopic techniques for identification and characterization of products - has proven to be very promising, in the sense of offering relevant information with respect to the complex mechanisms that are involved in photodegradation processes.

PhD (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Anaerobic digestion (AD) is usually applied in the treatment of distillery effluent due to the fact that it is effective in chemical oxygen demand (COD) reduction and bioenergy recovery. However, due to the presence of biorecalcitrant melanoidins present in distillery effluent, AD is ineffective in colour reduction. For this reason, ultraviolet (UV) photodegradation, which is effective in melanoidins’ degradation, can be integrated with AD to achieve high efficiency in colour and COD reduction. However, the UV process is energy intensive, majorly due to the electricity requirement of the UV lamp. In contrast, the AD process has high potential of renewable energy production in the form of biomethane, which can be transformed into electrical energy and applied to supplement the energy requirement of the UV process. The aim of this study was to evaluate the efficiency of a combined AD-UV system in colour and COD reduction for the treatment of distillery effluent in fluidised bed reactors. The potential of the application of the bioenergy produced by the AD process to supplement the energy intensive UV process was evaluated and modelled using response surface methodology. In the first place, the optimal hydrodynamic conditions of the fluidised bed reactors were determined using optical attenuation technique. The best homogeneity in the bioreactor, in which zeolite was used as microbial support, was found to be at a superficial liquid velocity of 0.6 cm/s while the best catalyst and gas hold up in the photoreactor were found to be 0.077 and 0.003, respectively. At these conditions, it was found that the initial biological step removed about 90% of COD and only about 50% of the colour while photodegradation post-treatment removed 98% of the remaining colour. Kinetic analysis of the bioreactor showed that ~ 9% of the feed total organic carbon (TOC) was non-biodegradable and this was attributed to the biorecalcitrant melanoidins. Photodegradation post-treatment mineralized the biorecalcitrant melanoidins via a reductive pathway as was indicated by the formation of NH4+ in large quantity compared to NO3-. Kinetic analysis further showed that the rate of substrate utilization in the bioreactor increased with an increase in organic loading rate and it was inversely proportional to the rate of photodegradation post-treatment. Modeling using response surface methodology (RSM) was applied to predict the effects of the operating parameters of the initial AD step on the performance of the photodegradation post-treatment process and the energy efficiency. Energy analysis of the integrated system showed that the AD process could produce 59 kWh/m3 of electricity which could supplement the electricity demand of the UV lamp by 30% leading to operation cost reduction of about USD 4.8/m3. This led to a presumed carbon dioxide emission reduction (CER) of 28.8 kg CO2e/m3.

This research combines observation, experimentation, and modeling to evaluate the influence of lakes on dissolved organic matter (DOM) quantity, quality and export in subalpine watersheds of the Sawtooth Mountain Lake District, central Idaho. First, I conducted an empirical study of the hydrologic and biogeochemical controls on DOM dynamics in stream-lake fluvial networks. I hypothesized that lakes would decrease temporal variability (i.e., buffer) and alter the characteristics of DOM from inflow to outflow. I tested these hypotheses by evaluating DOM temporal patterns and measuring annual export in seven-paired lake inflows and outflows. I then evaluated how ultraviolet (UV) exposure affected DOM characteristics during snowmelt and baseflow, and how UV alters baseflow DOM bioavailability and nutrient limitation. Given that increased water residence time increases UV exposure, I hypothesized that lake outflow DOM would be more photorecalcitrant than DOM from lake inflows. I further hypothesized that UV exposure would increase DOM quality, heterotrophic processing, and nutrient demand. Results indicate that lakes can buffer stream temporal variability by acting as a DOM sink during snowmelt and a DOM source during baseflow. Lake outflow DOM photodegradation was similar to lake inflows during snowmelt (p=0.66). Conversely, outflow DOM was 2X more photorecalcitrant than inflow DOM during baseflow (ANOVA, p=0.03) and was strongly related to water residence time (WRT). During baseflow, light exposure increased inflow and outflow DOM bioavailability (p=0.059 and 0.024, respectively) and nutrient limitation (p=0.03 and 0.09, respectively). Combined, these results indicate that WRT in subalpine lakes strongly influences DOM temporal variability and DOM degradation and processing. Thus, lakes can provide temporal stability of DOM and potentially increase both carbon and nutrient uptake by heterotrophs in lake outflows. I then evaluated how global changes could alter hydrologic and nutrient dynamics in a subalpine lake. Model results indicate that the magnitude and timing of snowmelt runoff can have a substantial effect on water and nutrient exports. In phosphorus (P)-limited lakes, increases in inorganic N concentrations within and exported from lakes are likely to occur with increased temperatures and lake WRT. Increases in atmospheric N deposition will further enhance inorganic N exports in P-limited subalpine lakes.

No description available.

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Petroleum wastewater is highly contaminated with toxic organic pollutants that are harmful to the environment. The heterogeneous photocatalytic oxidation (HPO) process has shown the ability to remove these pollutants through the application of a fluidized bed reactor (FBR). The purpose of the study was to apply response surface modelling (RSM) and computational fluid dynamics (CFD) to optimize the operating conditions for the photodegradation process in an FBR. This was done by investigating the hydrodynamics, photodegradation efficiency and reaction kinetics; that gave a holistic view on the performance of the FBR. The hydrodynamic study focused on modelling the axial liquid velocity, gas hold-up and turbulence quantities due to their substantial impact on the design and performance of the FBR. This was done by implementing the Eulerian-Eulerian approach which solves the continuity and momentum equations for each phase. In addition, the standard k-ε turbulence model was used to capture the turbulent characteristics in the liquid phase. A numerical optimization technique (desirability) was used to determine the optimal simulation setting methods; that were found to be a fine grid size (500 000 cells), 2nd Order Upwind discretization scheme and a small time step size (0.001) and gave the best desirability (0.985). The axial liquid velocity was maximal towards the centre of the reactor and decreased towards the wall. The same trend was seen with the local gas hold-up, where it was high towards the centre and low near the wall region. This was an indication that the bubbles tended to gather towards the central region as they move up. Furthermore, the bubbles had a spherical–like shape due to the low superficial gas velocity and operating within the homogeneous regime. The turbulent kinetic energy increased at distances away from the distributor region, due to the bubbles accelerating, and it balanced well with the energy introduced by the bubbles. Central composite design (CCD), which is a type of response surface modelling technique, was used to investigate and optimize the photodegradation operating parameters. The maximal degradation efficiency in the current study was found to be 65.9%, which was relatively low when compared to literature (80.84%). This was attributed to the increase in the catalyst particle size from nanometer to micrometer. Furthermore, the second-order empirical model that was developed, using the analysis of variance (ANOVA), presented a sufficient correlation to the photodegradation experimental data. The optimal photodegradation operating conditions were found to be: superficial gas velocity of 17.32 mm/s, composite catalyst loading of 1.0 g/L, initial pH level of 3.5 and reaction time being 210 min. Using the Langmuir-Hinshelwood model, it was found that the photocatalytic degradation of petroleum wastewater follows pseudo first-order reaction kinetics. Since the photocatalytic degradation mechanism of phenol follows three stages whereby the second stage is the photocatalytic degradation on the surface of the catalyst to form by-products. This is the rate dominant stage and follows the pseudo firstorder reaction kinetics.

No description available.

L’objectif principal de cette thèse était de mieux comprendre le comportement photochimique des pesticides pulvérisés dans les serres agricoles à Menyeh-Liban Nord. La première partie du travail a été consacrée à l’analyse des échantillons de poivrons verts, concombres, tomates, des films de plastique et de l’air récupérés dans ces serres agricoles. Nous avons quantifié et suivi par HPLC-HR-MS les résidus de 4 pesticides: bifénazate (BIF), acétamipride, imidaclopride et thiophanate méthyl (TM) dans les échantillons de légumes extraits par la méthode QUECHERS. Les quantités retrouvées durant les 6 jours suivant la pulvérisation étaient bien supérieures aux MRLs imposées pour chaque pesticide. Par ailleurs, des photoproduits de TM, BIF et de l’imidaclopride ont été détectés dans les solutions de rinçage de la surface des tomates, des concombres et des poivrons verts, démontrant ainsi la possibilité de photodégradation des pesticides à l’intérieur d’une serre agricole. L’analyse de la phase gazeuse par GC-MS a révélé la libération de terpènes, d’alcanes et d’aldéhydes comme réponse des plantes au stress de température et de pulvérisation. Dans une deuxième partie, on a détaillé les mécanismes de transformation photochimique du BIF et du TM sous irradiations simulées. La photodégradation de TM avait un caractère autoaccéléré qui n’a jamais été rapporté dans la littérature. Une étude détaillée nous a permis de démontrer que cette auto-accélération est due à la formation d’un photoproduit photosensibilisateur dérivé de la quinoxaline. Quant au BIF, sa vitesse de dégradation et la nature des produits dépendaient du milieu (ACN, eau, cire et poivron verts). Ces travaux ont mis en évidence l’effet de support et de mélange sur le comportement photochimique des pesticides. / The main purpose of this work was to better understand the photochemical behavior of pesticides used in agricultural greenhouses in Menyeh-North Lebanon. The first part was dedicated to the analysis of green peppers, cucumbers, tomatoes, plastic films and air samples from these agricultural greenhouses. HPLC-HR-MS was used to quantify and monitor the residues of 4 pesticides: bifenazate (BIF), acetamiprid, imidacloprid and thiophanate methyl (TM) after QUECHERS extraction of the vegetables samples. The quantities of pesticides found within 6 days after spraying were well above the MRLs imposed for each one. Then, the photoproducts of TM, BIF and imidacloprid were identified after rinsing the surface of tomatoes, cucumbers and green peppers. This demonstrated the possibility of photodegradation of pesticides even inside an agricultural greenhouse. Gas phase analysis by GC-MS revealed the presence of terpenes, alkanes and aldehydes as the response of plants to temperature and spraying stresses. In a second part, we studied the photochemical mechanisms of BIF and TM in the laboratory under simulated irradiation. The auto-accelerated photodegradation of TM was reported for the first time. A detailed study enabled us to demonstrate that this auto-acceleration was due to the formation of a photosensitizing photoproduct derived from quinoxaline. The rate of degradation of BIF and the nature of the products were dependent on the medium (ACN, water, wax and green peppers). These results highlighted the effect of support and mixture on the photochemical behavior of pesticides.

Os corantes sintéticos são amplamente empregados em indústrias têxteis, de cosméticos, alimentícia, farmacêutica, dentre diversas outras. Entretanto, vários destes compostos apresentam elevada toxicidade intrínseca, e são precursores de intermediários tóxicos e/ou mutagênicos gerados durante a metabolização. Portanto, o emprego de corantes naturais destaca-se como uma alternativa aos sintéticos, na busca por compostos seguros para a saúde humana e ambiental. Neste contexto, no presente trabalho nós investigamos o potencial toxicológico e ecotoxicológico do corante natural eritrostominona (Ery), uma naftoquinona extraída de micro-organismo, utilizando modelos alternativos à experimentação animal. Adicionalmente, foi avaliada a ecotoxicidade do Basic Red 51 (BR51), um corante sintético azo utilizado em indústrias têxteis e de cosméticos, e do Ery degradado (EryD) após a exposição à luz, visando uma alternativa simples para o tratamento de efluentes industriais contendo o corante. As avaliações ecotoxicológicas foram realizadas em diferentes níveis tróficos: nos microcrustáceos Daphnia magna e nos estágios iniciais de desenvolvimento de zebrafish (Danio rerio). As avaliações toxicológicas do Ery foram realizadas em linhagem hepatocelular humana (HepG2) como órgão-alvo de metabolização de xenobióticos, e em epiderme humana equivalente (EHE), um modelo 3D construído com queratinócitos humanos imortalizados (HaCaT), visto que é esperado o contato dérmico devido ao potencial uso como corante de cosmético. Nossos resultados mostraram que o Ery e o BR51 são tóxicos para D. magna e zebrafish. O BR51 induziu alterações na imobilidade, na reprodução, no consumo de oxigênio e no comportamento de D. magna em concentrações até 200 vezes superiores às do Ery capazes de alterar a imobilidade, reprodução e comportamento. Todavia, para embriões e larvas de zebrafish ambos os corantes apresentaram efeitos tóxicos em concentrações próximas, com alterações do desenvolvimento embrionário e do comportamento, indução de efeitos pró-oxidantes e alterações no balanço energético dos organismos. O EryD interessantemente não apresentou nenhum efeito tóxico para os organismos aquáticos, demonstrando que a luz foi capaz de reduzir e/ou inativar a toxicidade da estrutura inicial. Para as linhagens celulares humanas, o Ery foi citotóxico para HepG2, tendo a apoptose como a principal causa de morte celular. O Ery também causou um atraso no ciclo celular de HepG2, em particular na fase da mitose (G2/M), diminuindo a proliferação das células. Por outro lado, o Ery não apresentou potencial genotóxico e mutagênico para HepG2 e não induziu citotoxicidade e genotoxicidade após exposições por períodos curtos em EHE. Em conclusão, o Ery e o BR51 são classificados como tóxicos e muito tóxicos para o ambiente aquático, respectivamente. O Ery também induz efeitos pró-apoptóticos, o qual pode estar ligado à estrutura química das quinonas. No entanto, o Ery apresenta potencial aplicabilidade industrial como um corante eco-friendly, com destaque para a simples e rápida fotodegradação, e como um corante não genotóxico e mutagênico para células humanas. Avaliações adicionais sobre os mecanismos de apoptose devem ser realizadas para assegurar a segurança à saúde humana / Synthetic dyes are widely used by textiles, cosmetic, food and pharmaceutical industries. However, several compounds have high inherent toxicity, and many are precursors of mutagenic and/or carcinogenic intermediates produced during metabolism. Thereby, the use of natural dyes became an alternative to the synthetic ones, in search of safe compounds for human and environmentl health. In this context, we aimed to investigate the toxicological and ecotoxicological potential of the natural dye erythrostominone (Ery), a naphthoquinone compound extracted from microorganism, using alternative methods to animal experimentation. Additionally, it was assessed the ecotoxicity of the Basic Red 51 (BR51), an azo synthetic dye used bu cosmetic and textile industries, and the Ery degraded (EryD) after exposure to light, aiming an easy alternative to industrial effluent treatments containing the dye. Ecotoxicological assessment was performed at different trophic levels: in the microcrutaceans Daphnia magna and in zebrafish (Danio rerio) early life stages. Toxicological assessment of Ery was also performed in human hepatocellular line (HepG2) as target organ of xenobiotic metabolism, and in equivalent human epidermis (EHE), a 3D model constructed with immortalized human keratinocytes (HaCaT), since dermal contact is expected due to potential use as cosmetic dye. Our results showed that Ery and BR51 are toxic for D. magna and zebrafish. BR51 induced alterations in immobility, reproduction, oxygen uptake and behavior of D. magna at concentrations up to 200-fold higher than those of Ery able to impair immobility, reproduction and behavior. However, for zebrafish embryos and larvae, both dyes showed toxic effects at close concentrations, with changes in embryo development and behavior, induction of pro-oxidant effects and changes in the energy balance of organisms. Interestingly, EryD showed no toxic effect on aquatic organisms, demonstrating that light was able to reduce and/or inactivate the toxicity of the initial chemical structure. For human cell lines, Ery showed to be cytotoxic to HepG2, with apoptosis being the main source of cell death. Ery also induced a delay in HepG2 cell cycle, particularly in the mitosis phase (G2/M), decreasing cell proliferation. On the other hand, Ery presented no genotoxic and mutagenic potential for HepG2 and did not induce cytotoxicity and genotoxicity after short-term exposure to EHE. In conclusion, Ery and BR51 are classified as toxic and very toxic to the aquatic environment, respectively. Ery also induces pro-apoptotic effects, which may be linked to the chemical structure of quinones. Therefore, Ery presents potential industrial applicability as an eco-friendly dye, highlighting the easy and rapid photodegradation, and the non-genotoxic and mutagenic effects for human cells. Further assessment of apoptosis mechanisms should be performed to ensure safety to human health

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2019-01-25T12:11:45Z No. of bitstreams: 1 Vinicius_Carvalho_2018.pdf: 2139357 bytes, checksum: 24497f5a37afd82fb7a7bb75a202949e (MD5) / Made available in DSpace on 2019-01-25T12:11:45Z (GMT). No. of bitstreams: 1 Vinicius_Carvalho_2018.pdf: 2139357 bytes, checksum: 24497f5a37afd82fb7a7bb75a202949e (MD5) Previous issue date: 2018-07-30 / The heterogeneous photocatalysis process is one of the treatment options for pollutants, which has presented excellent results. In this work, zinco oxide and Cu doped zinc oxide were synthesized by sol-gel method and applied as a catalyst in the degradation of the antibiotic ciprofloxacin hydrochloride (CIP) in aqueous medium, also using UV. The synthesized and comercial zinc oxide were analyzed by XRD. The mean crystallite size of sintethsized zinc oxide was 13-18 nm, estimated by the Scherrer’s equation, lower than the commercial zinc oxide that presented an average size of 35 nm. It was possible to observe that the sol-gel method was able to decrease the average size of the zinc oxide crystallite. The synthesized zinc oxides were able to decrease the concentration of ciprofloxacin around 24 to 31%, higher than the values found for the commercial oxide that was of 18%. However, it was noticed that with the increase of copper doping, the photocatalytic activity decreased.The results obtained by SEM showed that the sol-gel method was not effective in the reduction of the particles, however, it was able to form oxides with a surface area of 19,083 m².g-1 higher than the value of 12,202 m².g-1 found for commercial zinc oxide. TGA and FTIR demonstrate that there may still be amount of PVA in the synthesized oxides. The analyzed photocatalysts follow a first order reaction, for the more efficient photocatalyst a percentage of absorbance reduction (%RedAbs) at 272 nm of 66.49% was reported in 120 min, while commercial zinc oxide, this %RedAbs was 33.44% the same time interval. / O processo de fotocatálise heterogênea é uma das opções de tratamento para poluentes, a qual têm apresentado ótimos resultados. Neste trabalho foram sintetizados óxido de zinco e óxidos de zinco dopados com cobre em diversas proporções e com diferentes temperaturas de calcinação utilizando o método sol-gel e aplicá-los como catalisadores na degradação do antibiótico cloridrato de ciprofloxacino (CIP) em solução aquosa, empregando-se também luz UV. As amostras sintetizadas foram analisadas por DRX e comparadas com uma amostra de óxido de zinco comercial. O tamanho médio dos cristalitos obtidos foi de aproximadamente 13-18 nm, estimado pela equação de Scherrer, sendo inferiores ao óxido de zinco comercial que apresentou um tamanho médio de 35 nm. Foi possível observar que o método sol-gel foi capaz de diminuir o tamanho médio do cristalito de óxido de zinco. Os óxidos de zinco sintetizados foram capazes de diminuir a concentração de ciprofloxacino em torno de 24 a 31%, superior aos valores encontrados para o óxido comercial que foi de 18%, entretanto foi notado que com o aumento da dopagem de cobre ocorreu a diminuição da atividade fotocatalítica. Os resultados obtidos por MEV demonstram que o método sol-gel não foi efetivo na diminuição das partículas, entretanto, foi capaz formar óxidos com área superficial de 19.083 m².g-1 superior ao valor de 12.202 m².g-1 encontrado para o óxido de zinco comercial. Análises de TGA e FTIR demonstram que ainda pode haver quantidade de PVA nos óxidos sintetizados. Os fotocatalisadores avaliados seguem uma reação de primeira ordem, no qual para o melhor fotocatalisador foi verificado um percentual de redução da absorbância (%RedAbs) em 272 nm de 66,49% em 120 min, enquanto que para o óxido de zinco comercial, este %RedAbs foi de 33,44% no mesmo intervalo de tempo.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-04-12T20:41:07Z No. of bitstreams: 1 2012 - Juliana de Oliveira Lopes.pdf: 1518311 bytes, checksum: 21fc297e17199bf911f4cf85812c2694 (MD5) / Made available in DSpace on 2017-04-12T20:41:07Z (GMT). No. of bitstreams: 1 2012 - Juliana de Oliveira Lopes.pdf: 1518311 bytes, checksum: 21fc297e17199bf911f4cf85812c2694 (MD5) Previous issue date: 2012-04-26 / CAPES / The teak wood (Tectona grandis L. f.) from young plantations (12 years old) has some undesirable characteristics in terms of color uniformity as well as presenting a high proportion of sapwood, which is distinguished from heartwood by the lower durability and light color. In addition, teak wood has color change when exposed to ultraviolet (UV) radiation, which depreciates the product over time. Heat treatments can be applied to change, standardize and stabilise the color of the wood, thus adding more value to the final product. In this context, the objectives of this study were: (1) to determine the effect of spacing between trees on the physical properties (density and moisture content) and the original color of wood, (2) to determine the color change of wood after heat treatments, (3) to evaluate the color uniformity of the wood (pieces containing heartwood and sapwood) after heat treatments and (4) to evaluate the color stability of heat-treated wood after UV radiation in accelerated aging conditions. Nine trees from three different levels of spacing (4 x 2 m, 5 x 2 m and 6 x 2 m) were used, with three trees per spacing. Samples of 150 x 75 x 20 mm were produced and divided into three groups: I: samples with a predominance of heartwood (? 75% heartwood in relation to sapwood), II: samples with 100% of sapwood and III: samples with approximately 50% heartwood and 50% sapwood. The groups I and II were used to determine the physical properties, wood color changes before and after heat treatments and color stability after exposure to UV radiation, whereas those of group III were used to determine the color uniformity after heat treatments. Heat treatments were performed in a laboratorial electric oven from Linn Elektro Therm under two temperatures: 180 and 200?C. Color measurements were performed using the portable spectrophotometer CM 2600d in the CIE-L*a*b* space. The accelerated aging test was performed in a QUV/Spray from Q-Lab chamber. The total cycle of exposure to UV radiation was 168 hours, and color measurements were taken to every 42 hours. The spacing affected the physical properties and the original color of wood. The heat treatment affected more the density of heartwood than sapwood. Heartwood and sapwood presented an average decrease of the 52% in equilibrium moisture content after heat treatments. Heartwood and sapwood had the same lightness pattern at the different spacings. After the heat treatment, wood had a loss of lightness, becoming darker, and this was more pronounced in the treatment at 200?C. Heartwood and sapwood presented different behavior for the coordinates a* and b* depending of spacing, before and after heat treatments. There was a greater formation of red hue and loss on yellow hue of heartwood and sapwood treated at 200?C. Heat treatments caused a higher color change on sapwood than heartwood, which provided greater uniformity to the pieces of wood with heartwood and sapwood. The color of sapwood heat-treated at 180oC woods had higher stability at UV radiation, thus demonstrating the potential of heat treatment to obtain products of higher added value. / A madeira de teca (Tectona grandis L. f.) proveniente de plantios jovens (12 anos de idade) apresenta algumas caracter?sticas indesej?veis em termos de uniformidade de cor al?m de apresentar alta propor??o de alburno, o qual distingue-se do cerne pela menor durabilidade e cor clara. Al?m disso, a madeira de teca apresenta altera??o de cor quando exposta ? radia??o ultravioleta (UV), o que acaba depreciando o material ao longo do tempo. Tratamentos termorretificadores podem ser aplicados para alterar, uniformizar e estabilizar a cor da madeira, agregando assim maior valor ao produto final. Neste contexto, os objetivos deste estudo foram: (1) determinar o efeito do espa?amento entre ?rvores nas propriedades f?sicas (densidade e teor de umidade) e na cor original da madeira, (2) determinar a altera??o da cor da madeira ap?s a termorretifica??o, (3) avaliar a uniformidade da cor da madeira (pe?as contendo cerne e alburno) ap?s os tratamentos termorretificadores e (4) avaliar a estabilidade da cor da madeira termorretificada ? radia??o UV em condi??es de envelhecimento acelerado. Foram utilizadas nove ?rvores de teca provenientes de tr?s espa?amentos (4 x 2 m, 5 x 2 m e 6 x 2 m), sendo 3 ?rvores para cada espa?amento. Amostras de 150 x 75 x 20 mm foram produzidas e divididas em tr?s grupos: I: amostras com predomin?ncia de madeira do cerne (? 75% de cerne em rela??o ao alburno), II: amostras com 100% de alburno e III: amostras com aproximadamente 50% de cerne e 50% de alburno. Os grupos I e II foram utilizados para determinar as propriedades f?sicas, a varia??o da cor da madeira antes e ap?s a termorretifica??o e a estabilidade da cor ap?s ? radia??o UV, enquanto que o grupo III foi utilizado para determinar a uniformidade da cor ap?s a termorretifica??o. A termorretifica??o foi realizada em um forno mufla el?trico laboratorial Linn Elektro Therm sob duas temperaturas: 180 e 200?C. As medi??es de cor foram realizadas atrav?s do espectrofot?metro port?til CM 2600d no espa?o CIE-L*a*b*. O ensaio de envelhecimento acelerado foi realizado em uma c?mara QUV/Spray da Q-Lab. O ciclo total de exposi??o ? radia??o UV foi de 168 horas, sendo realizadas medi??es de cor ? cada 42 horas. O espa?amento afetou as propriedades f?sicas e a cor original da madeira. A termorretifica??o afetou mais a densidade do cerne que do alburno. As madeiras de cerne e alburno apresentaram uma redu??o m?dia de 52% no teor de umidade de equil?brio ap?s a termorretifica??o. O cerne e o alburno apresentaram o mesmo padr?o de luminosidade nos diferentes espa?amentos. Ap?s a termorretifica??o, a madeira teve perda de luminosidade, tornado-se mais escura, sendo isso mais acentuado para o tratamento ? 200?C. As madeiras de cerne e alburno apresentaram comportamentos diferentes para as coordenadas a* e b* dependendo do espa?amento, antes e ap?s a termorretifica??o. Ocorreu uma maior forma??o de pigmento vermelho e perda de pigmento amarelo nas madeiras de cerne e alburno tratadas ? 200?C. A termorretifica??o proporcionou uma maior altera??o ? cor do alburno, o que resultou em uma maior uniformidade ?s pe?as de madeira contendo cerne e alburno. A cor da madeira de alburno termorretificada ? 180?C apresentou maior estabilidade ? radia??o UV, mostrando assim o potencial da termorretifica??o para obten??o de produtos de maior valor agregado.