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Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

A series of economic and political changes that occurred in the 1980s and the beginning of the 1990s have had major impacts on the small-scale agricultural sector in Mexico. The debt crisis of the 1980s led the government to adopt the neoliberal model. Reforms brought by the adoption of this model including trade liberalization, privatization of state-owned enterprises, reduction and cancellation of credits and social programs, along with the relative abandonment of the agricultural sector and focus on the manufacturing and services industries have caused economic, social and environmental harm to corn producers in the Totonacapan region of the state of Veracruz. In order to respond to the impacts of these large-scale policies, farmers coped by migrating to cities and U.S., and by taking advantage of the emergence of alternative markets, such as the corn husk, or totomoxtle, industry. The objective of this study is to explain the context in which totomoxtle emerged and evolved, and determine the importance and impact that this market has had on corn producers, intermediaries and exporters, men, women and children. Based on qualitative data gathered during 2011 using semi-structured interviews, participant observation, and the examination of secondary sources, I found that the totomoxtle trade has expanded considerably in the last decade becoming the main source of income and employment for many marginal households in the Totonacapan. The study questions, however, its ability to be used as a tool for poverty alleviation. Findings suggest that intermediaries and exporters obtain larger profits than farmers thus elucidating the need for more access to capital and infrastructure to achieve higher benefits for growers. At the same time, research also found evidence of the different participation of women and men during the production and manufacturing of totomoxtle. Moreover, research show that women were paid less, work for more hours and they labor in small and crowed places. Finally, data also suggests that the growth of totomoxtle production can be attributed to the increased demand and consumption by Mexican/Latino immigrant populations in the U.S., a shift in the American palate, and its overall availability in new immigrant destinations. / text

In this thesis work, it was aimed to optimize the conditions to produce silicon carbide (SiC), from rice husks from Turkish Thrace Region, via pyrolysis. Rice husks, coked at 500oC, were high energy ball-milled prior to pyrolysis, in order to investigate the effects of ball-milling on pyrolysis temperature, pyrolysis time and morphology of the SiC produced. Samples of rice husks subjected to different ball milling conditions, were pyrolyzed at temperatures varying from 1500oC to 1600oC and for times varying from &frac12 / hour to 2 hours. Results of experiments showed that, ball-milling reduced the pyrolysis temperature and pyrolysis time to some extent. It was also experimentally shown that ball-milling favored the formation of SiC particles rather than formation of SiC whisker.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O uso de polímeros e de compósitos biodegradáveis se apresenta como uma solução para o problema gerado pelo descarte de grandes quantidades de resíduos plásticos no ambiente. Os polímeros convencionais, além de não biodegradáveis, tem como fonte um material não-renovável, o petróleo. Os polímeros biodegradáveis, produzidos a partir de materiais renováveis, frequentemente apresentam como desvantagem o alto custo e propriedades nem sempre satisfatórias. Neste contexto, os compósitos poliméricos se apresentam como uma alternativa, pela possibilidade de incorporar cargas, tanto de origem vegetal como mineral, para alterar propriedades, adequando-as à finalidade do material. Além disso, para viabilizá-los economicamente, há o uso de cargas de baixo custo, como resíduos agrícolas. Neste estudo foram elaborados compósitos de poli(adipato-co-tereftalato de butileno) e amido (ECOBRAS) com palha de milho, em diferentes concentrações. Foi utilizada a palha de milho in natura, resíduo agrícola abundante, como forma de reduzir os custos e aumentar a proporção de produtos naturais usados, considerando que o ECOBRAS já possui amido em sua composição. O ensaio de tração e análises de DSC, TGA, FTIR, MO e MEV foram utilizadas para caracterizar e avaliar as propriedades dos compósitos. A matriz polimérica e os compósitos foram submetidos ao ensaio de biodegradabilidade através do enterro em solo simulado, segundo a norma ASTM G 160-03, por períodos variando de 2 a 15 semanas. Após cada período de enterro, foram determinadas a perda de massa e a morfologia dos corpos de prova e foram realizadas análises de TGA e FTIR. Os compósitos apresentaram menor resistência à tração que a matriz polimérica. No ensaio de biodegradabilidade, todos os compósitos foram considerados biodegradáveis, embora o acréscimo de palha tenha aumentado o tempo de degradação / The use of polymers and biodegradable composites is presented as a solution for the problem created by the discarding of a high amount of plastic residue in the environment. The conventional polymers, besides being non-biodegradable, have a non-renewable source: oil. The biodegradable polymers produced via renewable materials often present as downsides the high cost and not always satisfactory properties. In this context, the polymeric composites can be an alternative, due to the possibility of incorporation of fillers, both of vegetable and mineral origins, to alter properties, making them adequate to the destined use of this material. Other than that, there is the use of low cost fillers, such as agricultural residues, to make them economically viable. In this study, composites of poly (butylene adipate-co-terephthalate) and starch (ECOBRAS) were elaborated, with corn husks, in different concentrations. Corn husks in natura, being an abundant agricultural residue, were used in order to lower costs and increase the proportion of natural materials utilized, considering ECOBRAS already has starch in its composition. The stress strength tests and DSC, TGA, FTIR, MO e MEV analysis were used to characterize and evaluate the properties of the composites. The polymer matrix and the composites were submitted to biodegradability trials through burying in simulated soil, according to the ASTM G 160-03 norm, for periods varying between 2 and 15 weeks. After each trial period, the mass loss and morphology of each test subject were determined, and analysis of DSC, TGA and FTIR were made. The composites presented a higher resistance to stress strength tests than the polymer matrix. In the biodegradability trial, all composites were considered biodegradable, although the addition of corn husks increased the deterioration time

Spelt (Triticum spelt L.) is commonly processed to wholegrain flour, especially in organic quality. Even this type of flour does not usually contain husks which are removed before milling. This thesis aims to evaluate a possibility of utilizing whole grains including husks in the bakery industry and its effect on the quality from the nutritional as well as technological point of view. Quality control analyses were conducted in 17 samples. These included whole meal flour of common wheat, whole meal flour of spelt without husks, white flour of spelt with husks, white flour of common wheat and white flour of spelt. Remaining samples were made of soft four and coarse meal mixed in various proportions. The alpha and omega for the quality of bread and other bakery products is the quality of ingredients, especially the flour. Therefore, it was necessary to determine quality values and conduct corresponding analyses (Zeleny sedimentation test, falling number, wet gluten content, protein content, etc.). All samples were also subject to measuring rheological characteristics of dough using Mixolab II. In whole grain meals, in which there is the highest risk of mycotoxin contamination, incidence of such contamination was surveyed using the ROSA Mycotoxin Strips method. In the end, the bakery test was conducted with selected 11 samples after which the volume of the baked products was evaluated. This was followed by sensory evaluation by respondents following a presented questionnaire. The bakery experiment showed that it is possible to use spelt grains with husks, but this was reflected in the sensory test by the respondents. They preferred products which are more common and they did not positively evaluate the new taste and texture.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The beginning of the 21st century has been characterized by a great interest about the use of renewable raw materials for the production of industrial feedstocks and technological products. This trend is followed by the concern about the huge amount of waste generated by the always increasing agricultural production. In this sense, the reuse of the residual rice husks (RH) of the rice production, which by inadequate management affects negatively the environment in several ways, can constitute an environmental solution and a source of income. In this work, it was used RH as a source of cellulose for the production of levulinic acid (AL), a versatile chemical intermediate with many industrial applications, produced usually via chemical synthesis. The cellulose hydrolysis in acidic medium releases glucose monomers, which by heating under pressure dehydrate and form the intermediary 5-hydroxymethyl-2-furfural (5-HMF) - that, in turn, degraded generating AL. For the AL production, a 1.00 g of RH previously comminuted, selected, washed and dried in an oven, was hydrolyzed with 10.0 mL of HCl 4.5% (v/v) or 4% H2SO4 (v/v) in a batch reactor under pressure (51 to 62 atm). The concentration of AL, as well as of 5-HMF, present in the acidic hydrolysate, were analyzed by HPLC-UV. The solid residue of the hydrolysis was characterized by SEM and FTIR. In order to evaluate the effect of the variables temperature, pressure and hydrolysis time on the yield of the process of AL production, two factorial designs were performed: one, for the process using HCl, and another for the process using H2SO4, keeping constant the mass of RH and the used acid volume. After optimization of the time, pressure and temperature of hydrolysis, it was studied the effects of the acid concentration and of the RH pre-treatment on the production of AL. It was investigated, therefore, the pre-treatment with hydrogen peroxide, sodium hypochlorite, oxalic acid, Soxhlet extraction in aqueous medium and Soxhlet extraction with a mixture of benzene-ethanol 1:1 (v/v). It was verified that the AL production is maximum when the hydrolytic process was carried out at temperatures 160 °C, under pressure of 53 atm and reaction time of 70 min. The best catalyst for the process was hydrochloric acid at a concentration of 4.5% (v/v). Among the pre-treatments applied to the RH, the Soxhlet aqueous extraction provided the best yield of AL (59.4%, w/w). / O início do século 21 tem se caracterizado por um grande interesse na utilização de matérias-primas renováveis para a produção de insumos e produtos tecnológicos. A esta tendência soma-se à preocupação com a enorme quantidade de resíduos gerada pela sempre crescente produção agrícola. Neste sentido, o aproveitamento das cascas residuais da produção de arroz (CA) - cuja disposição inadequada leva a prejuízos ao meio ambiente, de várias maneiras pode constituir uma solução ambiental e possível fonte adicional de renda. Neste trabalho utilizou-se a CA como fonte de celulose para o processo de produção de ácido levulínico (AL), intermediário químico muito versátil, com diversas aplicações industriais, produzido, em geral, via síntese química. A hidrólise da celulose em meio ácido leva à liberação de monômeros de glicose, que, por aquecimento à pressão, se desidrata e forma o intermediário 5-hidroximetil-2-furfural (5-HMF) que, por sua vez, se degrada gerando o AL. Para o processo de produção do AL, uma fração de 1,00 g de CA, previamente cominuída, selecionada, lavada e seca em estufa, foi hidrolisada com 10,0 mL de HCl 4,5% (v/v) ou de H2SO4 4% (v/v), em batelada, em reator à pressão (51 a 62 atm). A concentração de AL, bem como de 5-HMF, presente no hidrolisado ácido, foram analisadas por HPLC-UV. Já, o resíduo sólido da hidrólise foi caracterizado por meio de MEV e FTIR. Os efeitos da temperatura, pressão e tempo de hidrólise no processo de produção de AL foram avaliados através de planejamento fatorial utilizou-se metodologia de superfície resposta. Foram feitos dois planejamentos: um para o processo com HCl e outro para o processo com H2SO4, mantendo-se constantes a massa da CA e o volume de ácido utilizado. Após otimização do tempo, da pressão e da temperatura reacional, foram estudados os efeitos da concentração de ácido e do pré-tratamento inicial da CA na produção de AL. Foram investigados, assim, os prétratamentos com peróxido de hidrogênio, clorito de sódio, ácido oxálico, extração por soxhlet em meio aquoso e extração por soxhlet com mistura benzeno-etanol 1:1 (v/v). Verificou-se que a produção de AL é máxima quando o processo hidrolítico foi realizado em temperatura de 160 °C, sob pressão de 53 atm e tempo reacional de 70 min. O melhor catalisador para o processo foi o ácido clorídrico, na concentração de 4,5% (v/v). Entre os prétratamentos aplicados à biomassa, a extração aquosa da CA, em soxhlet, levou ao melhor rendimento em AL (59,4%, m/m).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O uso de polímeros e de compósitos biodegradáveis se apresenta como uma solução para o problema gerado pelo descarte de grandes quantidades de resíduos plásticos no ambiente. Os polímeros convencionais, além de não biodegradáveis, tem como fonte um material não-renovável, o petróleo. Os polímeros biodegradáveis, produzidos a partir de materiais renováveis, frequentemente apresentam como desvantagem o alto custo e propriedades nem sempre satisfatórias. Neste contexto, os compósitos poliméricos se apresentam como uma alternativa, pela possibilidade de incorporar cargas, tanto de origem vegetal como mineral, para alterar propriedades, adequando-as à finalidade do material. Além disso, para viabilizá-los economicamente, há o uso de cargas de baixo custo, como resíduos agrícolas. Neste estudo foram elaborados compósitos de poli(adipato-co-tereftalato de butileno) e amido (ECOBRAS) com palha de milho, em diferentes concentrações. Foi utilizada a palha de milho in natura, resíduo agrícola abundante, como forma de reduzir os custos e aumentar a proporção de produtos naturais usados, considerando que o ECOBRAS já possui amido em sua composição. O ensaio de tração e análises de DSC, TGA, FTIR, MO e MEV foram utilizadas para caracterizar e avaliar as propriedades dos compósitos. A matriz polimérica e os compósitos foram submetidos ao ensaio de biodegradabilidade através do enterro em solo simulado, segundo a norma ASTM G 160-03, por períodos variando de 2 a 15 semanas. Após cada período de enterro, foram determinadas a perda de massa e a morfologia dos corpos de prova e foram realizadas análises de TGA e FTIR. Os compósitos apresentaram menor resistência à tração que a matriz polimérica. No ensaio de biodegradabilidade, todos os compósitos foram considerados biodegradáveis, embora o acréscimo de palha tenha aumentado o tempo de degradação / The use of polymers and biodegradable composites is presented as a solution for the problem created by the discarding of a high amount of plastic residue in the environment. The conventional polymers, besides being non-biodegradable, have a non-renewable source: oil. The biodegradable polymers produced via renewable materials often present as downsides the high cost and not always satisfactory properties. In this context, the polymeric composites can be an alternative, due to the possibility of incorporation of fillers, both of vegetable and mineral origins, to alter properties, making them adequate to the destined use of this material. Other than that, there is the use of low cost fillers, such as agricultural residues, to make them economically viable. In this study, composites of poly (butylene adipate-co-terephthalate) and starch (ECOBRAS) were elaborated, with corn husks, in different concentrations. Corn husks in natura, being an abundant agricultural residue, were used in order to lower costs and increase the proportion of natural materials utilized, considering ECOBRAS already has starch in its composition. The stress strength tests and DSC, TGA, FTIR, MO e MEV analysis were used to characterize and evaluate the properties of the composites. The polymer matrix and the composites were submitted to biodegradability trials through burying in simulated soil, according to the ASTM G 160-03 norm, for periods varying between 2 and 15 weeks. After each trial period, the mass loss and morphology of each test subject were determined, and analysis of DSC, TGA and FTIR were made. The composites presented a higher resistance to stress strength tests than the polymer matrix. In the biodegradability trial, all composites were considered biodegradable, although the addition of corn husks increased the deterioration time

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The generation of residual materials and its unavoidable disposal in the environment has been a reason of great concern, not only environmentally but also economically. The use of these renewable residual feedstocks, not only for the production of heat and energy, but also for the generation of technological products, has become a priority. In this study, it was investigated the physico-chemical and fermentative processes for the good use of the agro-industrial residue rice husks. The husks, resulting from the rice processing, has been also used, even incipiently, for the generation of heat to dry grains and electrical energy. As a result of this process, rice husk ash (RHA) is available, very rich in silica (sílica), representing a potential future source of industrial raw material. Micronized RHA, obtained from micro grinding process, was used to produce three types of silica xerogels, which were tested as additives for rice cultivation. The good results demonstrated the feasibility of the use of the xerogel silicas in substitution of agrochemical products. The influence of the process parameters (pH, time, concentration) was determined by means of the response surface methodology (RSM). The maximum production yields of sodium, potassium and calcium silica xerogels were 98%, 95% and 75%, respectively. The silica produced was characterized and analyzed by the following techniques: X-ray fluorescence and X-ray diffractometry (XRF, XRD), Fourier-transform infrared spectrometry (FTIR), scanning electronic microscopy (SEM), particle size distribution determined by laser diffraction, specific surface area by BET method (Brunauer, Emmett e Teller), and determination of metals by inductively coupled plasma emission optical pectrometry (ICP-OES). The production of xylose was studied by acid hydrolysis of rice husk, under pressure, in autoclave. Then, the xylose was converted into xylitol by fermentation. The process parameters, temperature and reaction time, were adjusted by RSM. Fermentations were performed using the yeast species Candida guilliermondii and Candida tropicalis, with maximum yields of 40% and 8%, respectively. The influence of various types of pretreatment of the sample was evaluated, demonstrating the potential yields of 66% and 64%, respectively, when the husk was treated with hydrogen peroxide and ammonium hydroxide solutions. When using physical pretreatment (ultrasound), yields up to 62% can be obtained. The influence of the variation of acid concentration and pH of the hydrolyzate on the yields was also evaluated. The contact time and amount of activated carbon added to the hydrolyzate exerts great influence on the process yield. The products obtained - xylose and xylitol - were identified and quantified by liquid chromatography coupled to mass spectrometer (LC-MS/MS) with electrospray ionization in positive mode. Results of the second order RSM applied to obtain silica xerogel as well as xylitol were evaluated by analysis of variance (ANOVA). The efficiency of the processes studied here shows that they may be interesting alternatives of use of biomass residue rice husk, with considerable economic potential and positive environmental impact. / A geração de materiais residuais e o seu descarte no ambiente têm sido motivo de grande preocupação, tanto ambiental quanto econômica. O aproveitamento destas matérias-primas residuais renováveis, não apenas para a produção de energia e calor, mas também para a geração de produtos tecnológicos, tornou-se uma prioridade. Neste trabalho, investigaram-se processos físico-químicos e fermentativos para o aproveitamento do resíduo agroindustrial casca de arroz (CA). A casca, resultante do beneficiamento do arroz, tem sido utilizada, ainda que incipientemente, na produção de calor para secagem de grãos e produção de energia elétrica. Em consequência deste processo, tem-se a formação de cinza da casca de arroz (CCA), muito rica em sílica (SiO2), apresentando grande potencial como futura matéria-prima industrial. A CCA micronizada, obtida a partir do processo de micromoagem, foi utilizada na obtenção de três tipos de sílicas xerogéis, que foram testadas como aditivos para o cultivo de arroz. Os bons resultados alcançados demonstram a viabilidade do aproveitamento da sílica xerogel em substituição a derivados agroquímicos. A influência dos parâmetros de processo (pH, tempo, concentração) foi determinada por meio de metodologia de superfície de resposta (RSM). Os rendimentos máximos de produção das sílicas xerogéis base sódio, potássio e cálcio foram de 98%, 95% e 75%, respectivamente. As sílicas produzidas foram caracterizadas e analisadas por meio de técnicas de fluorescência e difração de raios-X (XRF, XRD), espectrometria no infravermelho com transformada de Fourier (FTIR), microscopia eletrônica de varredura (SEM), distribuição do tamanho de partículas segundo a técnica de difratometria a laser, área de superfície específica pelo método BET (Brunauer, Emmett e Teller) e determinação de metais pela técnica de espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-OES). A produção de xilose foi estudada por meio de hidrólise ácida à pressão da CA. A xilose, por sua vez, foi convertida em xilitol por meio de processo fermentativo. Os parâmetros de processo, temperatura e tempo reacional, foram ajustados por meio de RSM. As fermentações foram feitas com auxílio das leveduras das espécies Candida guilliermondii e Candida tropicalis, com rendimentos máximos de 40% e 8%, respectivamente. Avaliou-se a influência de diversos tipos de pré-tratamento da amostra, evidenciando-se rendimentos de 66% e 64%, respectivamente, quando a CA foi tratada com solução de peróxido de hidrogênio e com solução de hidróxido de amônio. Quando se utiliza pré-tratamento físico (ultra-som), rendimento de até 62% pode ser obtido. A influência da variação da concentração de ácido e do pH do hidrolisado sobre o rendimento também foi avaliada. Comprovou-se, ainda, que o tempo de contato e a quantidade de carvão ativado adicionado ao hidrolisado, exercem grande influência sobre o rendimento. Os produtos obtidos - xilose e xilitol - foram identificados e quantificados por cromatografia líquida acoplada a espectrômetro de massas (LC-MS2) com ionização eletrospray, no modo positivo. Os resultados do modelo de superfície de resposta de segunda ordem, aplicado tanto ao processo de obtenção de sílicas xerogéis como ao de produção de xilitol, foram avaliados por meio de análise de variância (ANOVA). A eficiência dos processos estudados demonstra que estes podem constituir interessante alternativa para o aproveitamento da biomassa residual CA, com apreciável potencial econômico e positiva repercussão ambiental.