A new experimental procedure to obtain titania powders as anatase phase by a sol-gel process

Titania powders were synthesized by a sol-gel process using titanium tetrabutoxide as precursor. The syntheses were performed in water or in solutions of dimethylformamide (dmf) or dimethylsulfoxide (dmso). It is demonstrated, by X-ray diffraction patterns of the synthesized powders, that the samples obtained in dmf or dmso solutions are crystalline (anatase phase) with some minor amount of brookite phase, whereas the sample synthesized in water is amorphous. The anatase phase can be obtained independently of any previous or further treatment of the synthesized powder, such as hydrothermal or heat treatment, providing a new, simple, quick and inexpensive route to synthesize anatase powders. From the peak broadening of the anatase (101) diffraction, the crystallite sizes were calculated as 6 nm.

The chemistry involved in the steam treatment of lignocellulosic materials

Pretreatment of lignocellulosic materials is essential for bioconversion because of the various physical and chemical barriers that greatly inhibit their susceptibility to bioprocesses such as hydrolysis and fermentation. The aim of this article is to review some of the most important pretreatment methods developed to date to enhance the conversion of lignocellulosics. Steam explosion, which precludes the treatment of biomass with high-pressure steam under optimal conditions, is presented as the pretreatment method of choice and its mode of action on lignocellulosics is discussed. The optimal pretreatment conditions for a given plant biomass are defined as those in which the best substrate for hydrolysis is obtained with the least amount of soluble sugars lost to side reactions such as dehydration. Therefore, pretreatment optimization results from a compromise between two opposite trends because hemicellulose recovery in acid hydrolysates can only be maximized at lower pretreatment severities, whereas the development of substrate accessibility requires more drastic pretreatment conditions in which sugar losses are inevitable. To account for this heterogeneity, the importance of several process-oriented parameters is discussed in detail, such as the pretreatment temperature, residence time into the steam reactor, use of an acid catalyst, susceptibility of the pretreated biomass to bioconversion, and process design.

Uso de frascos de polipropileno descartáveis no pré-tratamento de amostras de água para determinação de chumbo, cobre e mercúrio por voltametria de onda quadrada

In this work a simple and versatile procedure is described for treating water samples using small polypropylene (PP) vials (4 mL) for determining heavy metals by square wave voltammetry (SWV). This procedure involves treatment with nitric acid (0.2 mol L-1) and boiling in a water-bath (~ 100 ºC). This process is completed after one hour and allows the pretreatment of several samples simultaneously. The accuracy was estimated using addition/recovery studies and certified water sample analysis, yielding an agreement near to 100%.

Evaluation of sample processing methods for the polar contaminant analysis of sewage sludge using liquid chromatography - mass spectrometry (LC/MS)

Monitoring of sewage sludge has proved the presence of many polar anthropogenic pollutants since LC/MS techniques came into routine use. While advanced techniques may improve characterizations, flawed sample processing procedures, however, may disturb or disguise the presence and fate of many target compounds present in this type of complex matrix before analytical process starts. Freeze-drying or oven-drying, in combination with centrifugation or filtration as sample processing techniques were performed followed by visual pattern recognition of target compounds for assessment of pretreatment processes. The results shown that oven-drying affected the sludge characterization, while freeze-drying led to less analytical misinterpretations.

Caracterización de la biomasa inactiva de Aspergillus niger O-5 como sorbente de Pb (II)

The inactive biomass of fungus Aspergillus niger O-5 obtained in Cuba was characterized as sorbent of Pb2+ by several structural analysis and others techniques. In addition, the biomass was studied for the separation / preconcentration of Pb2+ from aqueous solution. The maximum biosorption capacity was obtained for the contact time of 30 min and pH 5. The kinetic of sorption process occurred according to the model of Ho. The Freundlich or Langmuir models suitably described the experimental adsorption isotherms. The biomass can be used as sorbent for Pb2+ with a maximum capacity of 4.7 - 6.2 mg g-1. The pretreatment with NaOH solution improved its sorption capacity.

Produção de gás de síntese por plasma térmico via pirólise de metano e dióxido de carbono

In this work the production of synthesis gas from a mixture of methane (CH4) and carbon dioxide (CO2) by thermal plasma was studied. The best relation found for the gas mixture [CO2]/[CH4] was 1.3. Under the excess of CH4 in the gas mixture soot was formed and also benzene, indene and naphthalene were identified. The disulfides compounds in the gas mixture were degraded causing no interference in the synthesis gas production, suggesting no needs of pretreatment step for sulfurorganic compounds removal in the process

Biochemical properties of Bacillus sp. ITP-001 lipase immobilized with a sol gel process

This work presents biochemical characterization of a lipase from a new strain of Bacillus sp. ITP-001, immobilized using a sol gel process (IB). The results from the biochemical characterization of IB showed increased activity for hydrolysis, with 526.63 U g-1 at pH 5.0 and 80 ºC, and thermal stability at 37 ºC. Enzymatic activity was stimulated by ions such as EDTA, Fe+3, Mn+2, Zn+2, and Ca+2, and in various organic solvents. Kinetic parameters obtained for the IB were Km = 14.62 mM, and Vmax = 0.102 mM min-1 g-1. The results of biochemical characterization revealed the improved catalytic properties of IB.

Use of sorghum straw (Sorghum bicolor) for second generation ethanol production: pretreatment and enzymatic hydrolysis

Agronomic biomass yields of forage sorghum BRS 655 presented similar results to other energy crops, producing 9 to 12.6 tons/ha (dry mass) of sorghum straw. The objective of this study was to evaluate the lignocellulosic part of this cultivar in terms of its potential in the different unit processes in the production of cellulosic ethanol, measuring the effects of pretreatment and enzymatic hydrolysis. Three types of pre-treatments for two reaction times were conducted to evaluate the characteristics of the pulp for subsequent saccharification. The pulp pretreated by alkali, and by acid followed by delignification, attained hydrolysis rates of over 90%.

Determination of sulfate in the wet-process of phosphoric acid by reverse flow injection

An improved method based on reverse flow injection is proposed for determining sulfate concentration in the wet-process of phosphoric acid (WPA). The effect of reagent composition, flow rate, temperature, acid concentration, length of the reaction coil, and linear response range on the flow system is discussed in detail. Optimal conditions are established for determining sulfate in the WPA samples. Baseline drift is avoided by a periodic washing step with EDTA in an alkaline medium. A linear response is observed within a range of 20 - 360 mg L-1, given by the equation A = 0.0020C (mg L-1) + 0.0300, R² = 0.9991. The detection limit of the proposed method for sulfate analysis is 3 mg L-1, and the relative standard deviation (n = 12) of sulfate absorbance peak is less than 1.60%. This method has a rate of up to 29 samples per hour, and the results compare well with those obtained with gravimetric method.

The Li+, Na+ and K+ ion exchange reaction process on the surface of mixed oxide SiO2/TiO2/Sb2O5 surface prepared by the sol-gel processing method

The porous mixed oxide SiO2/TiO2/Sb2O5 obtained by the sol-gel processing method presented a good ion exchange property and a high exchange capacity towards the Li+, Na+ and K+ ions. In the H+/M+ ion exchange process, the H+ / Na+ could be described as presenting an ideal character. The ion exchange equilibria of Li+ and K+ were quantitatively described with the help of the model of fixed tetradentate centers. The results of simulation evidence that for the H+ / Li+ exchange the usual situation takes place: the affinity of the material to the Li+ ions is decreased with increasing the degree of ion exchange. On the contrary, for K+ the effects of positive cooperativity, that facilitate the H+ / K+ exchange, were revealed.

Simultaneous determination of Cd and Pb in antibiotics used in sugar-cane fermentation process by GFAAS

A method has been developed for the simultaneous determination of Cd and Pb in antibiotics used in sugar-cane fermentation by GFAAS. The integrated platform of transversely heated graphite atomizer was treated with tungsten to form a coating of tungsten carbide. Six samples of commercial solid antibiotics were analyzed by injecting 20 µL of digested samples into the pretreated graphite platform with co-injection of 5 µL of 1000 mg L-1 Pd as chemical modifier. Samples were mineralized in a closed-vessel microwave-assisted acid-digestion system using nitric acid plus hydrogen peroxide. The pyrolysis and atomization temperatures of the heating program of the atomizer were selected as 600°C and 2200°C, respectively. The calculated characteristic mass for Cd and Pb was 1.6 pg and 42 pg, respectively. Limits of detection (LOD) based on integrated absorbance were 0.02 µg L-1 Cd and 0.7 µg L-1 Pb and the relative standard deviations (n = 10) for Cd and Pb were 5.7% and 8.0%, respectively. The recoveries of Cd and Pb added to the digested samples varied from 91% to 125% (Cd) and 80% to 112% (Pb).

Photo-Fenton process for treating biological laboratory wastewater containing formaldehyde

Laboratories consume great amounts of hazardous chemicals substances and consequently generate wastewater containing them, for example formaldehyde. This substance is widely utilized to preserve biological samples generating many liters of this residue every year. The present work proposes the use of the photo-Fenton process to treat formaldehyde wastewater using sunlight irradiation. Some aspects were investigated such as the iron source, sample and hydrogen peroxide concentration and also the use of stirred systems. The use of ferrioxalate (0.5 mmol L-1) improved the efficiency of the process in relation to the use of iron nitrate, while at least 1.0 mol L-1 H2O2 is necessary to treat the sample of the 500 mg C L-1. Under these conditions, every formaldehyde detectable was degradeted and 89% of the dissolved organic carbon was removed in two hours of exposure to sunlight. These results are satisfaction considerate for São Paulo State Environmental Agency.

The notion of process in nonstandard theory and in Whiteheadian metaphysics

In this article I intend to show that certain aspects of A.N. Whitehead's philosophy of organism and especially his epochal theory of time, as mainly exposed in his well-known work Process and Reality, can serve in clarify the underlying assumptions that shape nonstandard mathematical theories as such and also as metatheories of quantum mechanics. Concerning the latter issue, I point to an already significant research on nonstandard versions of quantum mechanics; two of these approaches are chosen to be critically presented in relation to the scope of this work. The main point of the paper is that, insofar as we can refer a nonstandard mathematical entity to a kind of axiomatical formalization essentially 'codifying' an underlying mental process indescribable as such by analytic means, we can possibly apply certain principles of Whitehead's metaphysical scheme focused on the key notion of process which is generally conceived as the becoming of actual entities. This is done in the sense of a unifying approach to provide an interpretation of nonstandard mathematical theories as such and also, in their metatheoretical status, as a formalization of the empirical-experimental context of quantum mechanics.

The effect of wood supply and bleaching process on pulp brightness stability

One hundred different 5.5-year-old Eucalyptus grandis x Eucalyptus urophylla wood clones were cooked to kappa number 15-17.5 and the resulting kraft pulps oxygen-delignified to kappa 9.5-11.5 under fixed conditions, except for chemical charges. Thirteen samples showing large variations in effective alkali requirement, pulp yield and O-stage efficiency and selectivity were selected for brightness reversion studies. These samples were bleached to 90-91% ISO by DEDD and DEDP sequences and their brightness stability and chemical characteristics determined. Heat reversion of the eucalyptus kraft pulps was strongly influenced by the wood supply, with brightness loss varying in the range of 2.1-3.6 and 0.8-1.7 %ISO for ODEDD and ODEDP bleached pulps, respectively. Pulps bleached by the ODEDP sequence showed reversion values 1.3-1.9 % ISO lower than those bleached by the ODEDD sequence. Pulp carbonyl content decreased by 35-40% during the final peroxide bleaching stage. Carbonyl and carboxyl groups correlated positively with brightness reversion, as did permanganate number and acid soluble lignin. Pulp final viscosity and metal and DCM extractives contents showed no significant correlation with brightness reversion. Pulping, oxygen delignification and ECF bleaching performances also showed no correlation with brightness reversion.

Application of simulated annealing in simulation and optimization of drying process of Zea mays malt

Kinetic simulation and drying process optimization of corn malt by Simulated Annealing (SA) for estimation of temperature and time parameters in order to preserve maximum amylase activity in the obtained product are presented here. Germinated corn seeds were dried at 54-76 °C in a convective dryer, with occasional measurement of moisture content and enzymatic activity. The experimental data obtained were submitted to modeling. Simulation and optimization of the drying process were made by using the SA method, a randomized improvement algorithm, analogous to the simulated annealing process. Results showed that seeds were best dried between 3h and 5h. Among the models used in this work, the kinetic model of water diffusion into corn seeds showed the best fitting. Drying temperature and time showed a square influence on the enzymatic activity. Optimization through SA showed the best condition at 54 ºC and between 5.6h and 6.4h of drying. Values of specific activity in the corn malt were found between 5.26±0.06 SKB/mg and 15.69±0,10% of remaining moisture.