Small-angle X-ray and nuclear-magnetic resonance study of siloxane-PMMA hybrids prepared by the sol-gel process

Transparent siloxane-polymethylmethacrylate (PMMA) hybrids were synthesized by the sol-gel process through hydrolysis of methacryloxyproyltrimethoxysilane (TMSM), tetramethoxysilane (TMOS) and polymerization of methylmethacrylate (MMA) using benzol peroxide (BPO) as catalyst. These composites have a good chemical stability due to the presence of covalent bonds between the inorganic (siloxane) and organic (PMMA) phases. The effects of siloxane content, pH of the initial sol and BPO content on the structure of the dried gels were analyzed by small-angle X-ray scattering (SAXS). SAXS results revealed the presence of an interference (or correlation) peak at medium q-range for all compositions, suggesting that siloxane groups located at the ends of PMMA chains form isolated clusters that are spatially correlated. The average intercluster distance - estimated from the q-value corresponding to the maximum in SAXS spectra - decreases for samples prepared with increasing amount of TMSM-TMOS. This effect was assigned to the expected increase in the number density of siloxane groups for progressively higher siloxane content. The increase of BPO content promotes a more efficient polymerization of MMA monomers but has no noticeable effect on the average intercluster distance. High pH favors polycondensation reactions between silicon species of both TMOS and TMSM silicon alcoxides, leading to a structure in which all siloxane clusters are bonded to PMMA chains. This effect was confirmed by Si-29 nuclear-magnetic resonance (NMR) measurements.

Degradation of the antibiotic amoxicillin by photo-Fenton process - Chemical and toxicological assessment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Monolithic diphasic gels of mullite by sol-gel process under ultrasound stimulation

Diphasic gel in the mullite composition was prepared from a colloidal sol of boehmite mixed with a hydrolyzed tetraethoxisilane (TEOS) solution. The boehmite sol was obtained by peptization of a poorly crystallized or very small mean crystallite size (∼34 Å) precipitate, resulting from the reaction between solutions of aluminum sulfate and sodium hydroxide. Ultrasound was utilized in the processes of the TEOS hydrolysis and the boehmite peptization, and also for complete homogenization of the mixture to gel. The wet gel is almost clear and monolithic. The gel transparency is lost on drying, when syneresis has ended, so that the interlinked pore structure starts to empty and is recovered upon water re-absorption. Cracking closely accompanies this critical drying process. Differential thermal analysis (DTA) and X-ray diffraction (XRD) show that the solid structure of the gel is composed of an amorphous silica phase, as a matrix, and a colloidal sized crystalline phase of boehmite. Upon heat treatment, the boehmite phase within the gel closely follows the same transition sequence as in pure alumina shifted towards higher temperatures. Orthorhombic mullite formation was detected at 1300°C. © 1998 Elsevier Science B.V. All rights reserved.

Formation of colloidal particles of hydrous iron oxide by forced hydrolysis

The mechanism of formation and growth of hydrous iron oxide (FeOOH) during the initial stages of forced hydrolyses of ferric chloride aqueous solution was studied by small angle X-ray scattering (SAXS). The effect of the hydrolysis temperature (60°C, 70°C and 80°C) and of the addition of urea on the formation of colloidal particles under isothermal conditions were investigated. Based on the experimental scattering functions in the Guinier range, we suggest the presence of elongated colloidal particles. The particle diameter and length, and their variation with time, were determined by fitting the form factor of prolate ellipsoids to the experimental scattering functions. We have assumed that our solutions are in a dilute state and that all colloidal particles are approximately of the same size. The colloidal particles have geometrical shapes similar to those of the subcrystals that build up the superstructure of β-FeOOH crystals, indicating that the formation of this hydrous iron oxide is governed by an aggregation process. Otherwise, the addition of urea hinders the growth and yields smaller particles, with a reduction in size greater than 50%. © 2000 Elsevier Science B.V. All rights reserved.

Optimization of neutral hydrolysis reaction of post-consumer PET for chemical recycling

The neutral hydrolysis reaction of post-consumer poly(ethylene terephthalate) in solid state was studied through the reaction of the polymer with water at the molar ratio 1:91 with autogenous pressure. Two sizes of post-consumer PET flakes and temperatures of 135 °C, 170°C and 205°C with pressures of 4.0 atm, 7.5 atm and 13.5 atm, respectively, were considered. With reaction time equal to 6h, the method reached 99% depolymerization at 205°C, 8.2% at 170 °C and 1.7% at 135°C. The reaction extension was measured by separating the terephthalic acid formed in the process and calculating by gravimetry how much material could still be reacted. Through the viscosimetry of diluted, solutions and the counting of carboxylic end groups in the remaining material from the gravimetric assay, it was possible to suggest that the reaction occurs randomly and in the whole volume of the polymeric particle and not solely on the surface. The terephthalic acid obtained and then purified was characterized by elemental analysis, magnetic nuclear resonance, size and panicle size distribution and spectrophotometry in the visible spectrum, and it was similar to the petrochemical equivalent, with purity recorded in carbon base equal to 99.9%.

Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improved pretreatments applied to the sugarcane bagasse and release of lignin and hemicellulose from the cellulose-enriched fractions by sulfuric acid hydrolysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Optimal control strategy for fed-batch enzymatic hydrolysis of lignocellulosic biomass based on epidemic modeling

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Production of alcoholic beverage from ginger: study of fermentation process and final product quality

Introduction: In Brazil part of the production of ginger is of inadequate quality for export. The production of spirit from felt-over rhizomes is an alternative of great interest to producers of these rhizomes. Aim: Aiming to increase the value of felt-over rhizomes, this work aimed to study the use of ginger as a raw material for alcoholic beverage production. It was evaluated the effect of fermentation conditions on the components of fermented alcoholic, as well as, the quality of alcoholic distilled beverage of ginger. Methods: Dehydrated ginger passed by enzymatic hydrolysis-saccharification processes. The hydrolysate obtained was analyzed for sugar profile in HPLC. The alcoholic fermentation process followed the central composite rotational design for three factors: fermentation temperature (23 to 37ºC), time of fermentation (17 to 33 h) and concentration of inoculum (0.22 to 3.00%). The fermented alcoholic obtained was analyzed in HPLC for the contents of ethanol, methanol, glycerol and residual sugars. The distillated alcoholic beverage of ginger was analyzed for ethanol, methanol, acetaldehyde, ethyl acetate and higher alcohols in the gas chromatography (GC). In addition, copper content and acidity were analyzed Results: Sugar profile of the ginger hydrolysate revealed the presence of 77.8% of glucose. Data analysis of fermentation process showed influence of temperature on ethanol and methanol content of the fermented alcoholic of ginger. Time of fermentation had effect on glycerol content. All parameters of process had influence on residual sugars contents. The HPLC analysis has shown presence of methanol, ethyl acetate, aldehyde, acids, higher alcohols and esters in distilled alcoholic beverage of ginger. Conclusion: Fermented alcoholic of ginger with higher levels of ethanol can be obtained under the conditions of 1.5% w/w of inoculum, 30°C of temperature and 24 hours of fermentation time. In this condition of fermentation process the beverage of ginger had good quality.

Saccharification of Brazilian sisal pulp: evaluating the impact of mercerization on non-hydrolyzed pulp and hydrolysis products

Cultivation of sisal, a plant with a short growth cycle, is highly productive in Brazil. This work is part of extensive research in which sisal is valued. In these studies, sisal fibers are used in the preparation of bio-based composites and in the derivatization of the pulp, including posterior preparation of films. This study aimed to examine the use of sisal pulp in the production of bioethanol, which can potentially be a high efficiency process because of the cellulose content of this fiber. A previous paper addressed the hydrolysis of sisal pulp using sulfuric acid as a catalyst. In the present study, the influence of the mercerization process on the acid hydrolysis of sisal pulp was evaluated. Mercerization was achieved in a 20% wt NaOH solution, and the cellulosic pulp was suspended and vigorously mixed for 1, 2 and 3 h, at 50 A degrees C. The previously characterized mercerized pulps were hydrolyzed (100 A degrees C, 30% H2SO4, v/v), and the results are compared with those obtained for unmercerized pulp (described in a companion paper). The starting sample was characterized by viscometry, alpha-cellulose content, crystallinity index and scanning electron microscopy. During the reactions, aliquots were withdrawn, and the liquor was analyzed by HPLC. The residual pulps (non-hydrolyzed) were also characterized by the techniques described for the initial sample. The results revealed that pretreatment decreases the polyoses content as well as causes a decrease of up to 23% in the crystallinity and up to 21% in the average molar mass of cellulose after 3 h of mercerization. The mercerization process proved to be very important to achieve the final target. Under the same reaction conditions (30% and 100 A degrees C, 6 h), the hydrolysis of mercerized pulp generated yields of up to 50% more glucose. The results of this paper will be compared with the results of subsequent studies obtained using other acids, and enzymes, as catalysts.

Characterization of depolymerized residues from extremely low acid hydrolysis (ELA) of sugarcane bagasse cellulose: Effects of degree of polymerization, crystallinity and crystallite size on thermal decomposition

Sugarcane bagasse cellulose was subjected to the extremely low acid (ELA) hydrolysis in 0.07% H2SO4 at 190, 210 and 225 degrees C for various times. The cellulose residues from this process were characterized by TGA, XRD, GPC, FIR and SEM. A kinetic study of thermal decomposition of the residues was also carried out, using the ASTM and Kissinger methods. The thermal studies revealed that residues of cellulose hydrolyzed at 190, 210 and 225 degrees C for 80,40 and 8 min have initial decomposition temperature and activation energy for the main decomposition step similar to those of Avicel PH-101. XRD studies confirmed this finding by showing that these cellulose residues are similar to Avicel in crystallinity index and crystallite size in relation to the 110 and 200 planes. FTIR spectra revealed no significant changes in the cellulose chemical structure and analysis of SEM micrographs demonstrated that the particle size of the cellulose residues hydrolyzed at 190 and 210 degrees C were similar to that of Avicel. (C) 2011 Elsevier B.V. All rights reserved.

Preliminary Characterization of Novel Extra-cellular Lipase from Penicillium crustosum Under Solid-State Fermentation and its Potential Application for Triglycerides Hydrolysis

Current studies about lipase production involve the use of agro-industrial residues and newly isolated microorganisms aimed at increasing economic attractiveness of the process. Based on these aspects, the main objective of this work is to perform the partial characterization of enzymatic extracts produced by a newly isolated Penicillium crustosum in solid-state fermentation. Lipase extract presented optimal temperature and pH of 37 A degrees C and 9-10, respectively. The concentrated enzymatic extract showed more stability at 25 A degrees C and pH 7. The enzymes kept 100% of their enzymatic activity until 60 days of storage at 4 and -10 A degrees C. The stability under calcium salts indicated that the hydrolytic activity presented decay with the increase of calcium concentration. The specificity under several substrates indicated good enzyme activities in triglycerides from C4 to C18.

Adding value to the Brazilian sisal: acid hydrolysis of its pulp seeking production of sugars and materials

The present work is inserted into the broad context of the upgrading of lignocellulosic fibers. Sisal was chosen in the present study because more than 50% of the world's sisal is cultivated in Brazil, it has a short life cycle and its fiber has a high cellulose content. Specifically, in the present study, the subject addressed was the hydrolysis of the sisal pulp, using sulfuric acid as the catalyst. To assess the influence of parameters such as the concentration of the sulfuric acid and the temperature during this process, the pulp was hydrolyzed with various concentrations of sulfuric acid (30-50%) at 70 A degrees C and with 30% acid (v/v) at various temperatures (60-100 A degrees C). During hydrolysis, aliquots were withdrawn from the reaction media, and the solid (non-hydrolyzed pulp) was separated from the liquid (liquor) by filtering each aliquot. The sugar composition of the liquor was analyzed by HPLC, and the non-hydrolyzed pulps were characterized by viscometry (average molar mass), and X-ray diffraction (crystallinity). The results support the following conclusions: acid hydrolysis using 30% H2SO4 at 100 A degrees C can produce sisal microcrystalline cellulose and the conditions that led to the largest glucose yield and lowest decomposition rate were 50% H2SO4 at 70 A degrees C. In summary, the study of sisal pulp hydrolysis using concentrated acid showed that certain conditions are suitable for high recovery of xylose and good yield of glucose. Moreover, the unreacted cellulose can be targeted for different applications in bio-based materials. A kinetic study based on the glucose yield was performed for all reaction conditions using the kinetic model proposed by Saeman. The results showed that the model adjusted to all 30-35% H2SO4 reactions but not to greater concentrations of sulfuric acid. The present study is part of an ongoing research program, and the results reported here will be used as a comparison against the results obtained when using treated sisal pulp as the starting material.

Influence of the Sol-Gel pH Process and Compact Film on the Efficiency of TiO2-Based Dye-Sensitized Solar Cells

The influence of pH during hydrolysis of titanium(IV) isopropoxide on the morphological and electronic properties of TiO2 nanoparticles prepared by the sol-gel method is investigated and correlated to the photoelectrochemical parameters of dye-sensitized solar cells (DSCs) based on TiO2 films. Nanoparticles prepared under acid pH exhibit smaller particle size and higher surface area, which result in higher dye loadings and better short-circuit current densities than DSCs based on alkaline TiO2-processed films. On the other hand, the product of charge collection and separation quantum yields in films with TiO2 obtained by alkaline hydrolysis is c. a. 27% higher than for the acid TiO2 films. The combination of acid and alkaline TiO2 nanoparticles as mesoporous layer in DSCs results in a synergic effect with overall efficiencies up to 6.3%, which is better than the results found for devices employing one of the nanoparticles separately. These distinct nanoparticles can be also combined by using the layer-by-layer technique (LbL) to prepare compact TiO2 films applied before the mesoporous layer. DSCs employing photoanodes with 30 TiO2 bilayers have shown efficiencies up to 12% higher than the nontreated photoanode ones. These results can be conveniently used to develop optimized synthetic procedures of TiO2 nanoparticles for several dye-sensitized solar cell applications.

Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility

Abstract Background In recent years, biorefining of lignocellulosic biomass to produce multi-products such as ethanol and other biomaterials has become a dynamic research area. Pretreatment technologies that fractionate sugarcane bagasse are essential for the successful use of this feedstock in ethanol production. In this paper, we investigate modifications in the morphology and chemical composition of sugarcane bagasse submitted to a two-step treatment, using diluted acid followed by a delignification process with increasing sodium hydroxide concentrations. Detailed chemical and morphological characterization of the samples after each pretreatment condition, studied by high performance liquid chromatography, solid-state nuclear magnetic resonance, diffuse reflectance Fourier transformed infrared spectroscopy and scanning electron microscopy, is reported, together with sample crystallinity and enzymatic digestibility. Results Chemical composition analysis performed on samples obtained after different pretreatment conditions showed that up to 96% and 85% of hemicellulose and lignin fractions, respectively, were removed by this two-step method when sodium hydroxide concentrations of 1% (m/v) or higher were used. The efficient lignin removal resulted in an enhanced hydrolysis yield reaching values around 100%. Considering the cellulose loss due to the pretreatment (maximum of 30%, depending on the process), the total cellulose conversion increases significantly from 22.0% (value for the untreated bagasse) to 72.4%. The delignification process, with consequent increase in the cellulose to lignin ratio, is also clearly observed by nuclear magnetic resonance and diffuse reflectance Fourier transformed infrared spectroscopy experiments. We also demonstrated that the morphological changes contributing to this remarkable improvement occur as a consequence of lignin removal from the sample. Bagasse unstructuring is favored by the loss of cohesion between neighboring cell walls, as well as by changes in the inner cell wall structure, such as damaging, hole formation and loss of mechanical resistance, facilitating liquid and enzyme access to crystalline cellulose. Conclusions The results presented herewith show the efficiency of the proposed method for improving the enzymatic digestibility of sugarcane bagasse and provide understanding of the pretreatment action mechanism. Combining the different techniques applied in this work warranted thorough information about the undergoing morphological and chemical changes and was an efficient approach to understand the morphological effects resulting from sample delignification and its influence on the enhanced hydrolysis results.