Estudo das propriedades e biodegradabilidade de blendas de poliéster/amido submetidas ao ataque microbiano

This work deals with the biodegradation of blends of poly(beta-hydroxybutyrate)/starch and poly(beta-hydroxybutyrate-co-hydroxyvalerate)/starch. The blends were obtained by evaporation of the solvent in the mixture of the polymers in chloroform. Tests were carried out in presence of micro-organisms which acted as biodegradation agents. The blends were consumed as carbon substrate and the production of CO2 was evaluated in the process. In addition, the polyesters' mechanical properties were reduced by the incorporation of starch in its structure. (¹H) NMR and infrared spectroscopy detected some characteristic polyester degradation groups in the polyesters' chemical structure, thus confirming the alteration suffered by it.

Singlet oxygen reactivity in water-rich solvent mixtures

The 3-methylindole (3MI) oxygenation sensitized by psoralen (PSO) has been investigated in 100%, 20% and 5% O2-saturated water/dioxane (H2O/Dx) mixtures. The lowering of the ¹O2* chemical rate when water (k chem∆3MI = 1.4 × 109 M-1 s-1) is replaced by deuterated water (k chem∆3MI = 1.9 × 108 M-1 s-1) suggests that hydrogen abstraction is involved in the rate determining step. A high dependence of the chemical rate constant on water concentration in H2O/Dx mixtures was found showing that water molecules are absolutely essential for the success of the 3MI substrate oxidation by ¹O2* in water-rich solvent mixtures.

Efficient synthesis of sulfonamide derivatives on solid supports catalyzed using solvent-free and microwave-assisted methods

In this work we report the synthesis of sulfonamide derivatives using a conventional procedure and with solid supports, such as silica gel, florisil, alumina, 4Å molecular sieves, montmorillonite KSF, and montmorillonite K10 using solvent-free and microwave-assisted methods. Our results show that solid supports have a catalytic activity in the formation of sulfonamide derivatives. We found that florisil, montmorillonite KSF, and K10 could be used as inexpensive alternative catalysts that are easily separated from the reaction media. Additionally, solvent-free and microwave-assisted methods were more efficient in reducing reaction time and in increasing yield.

Encapsulation of naproxen in nanostructured system: structural characterization and in vitro release studies

Nanoparticles were produced by solvent emulsification evaporation method with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process (73 ± 1.5%), excellent encapsulation efficiency (81.3 ± 4.2%) and spherical shape. X-rays diffraction demonstrated the loss of drug crystallinity after encapsulation; however, the profile of the diffractograms of the poly-ε-caprolactone (PCL) nanoparticles was kept. Differential scanning calorimetry thermograms, correspondingly, exhibited the loss of drug melting peak and the increasing of the melting point of the PCL nanoparticles, evidencing an interaction drug-polymer. Naproxen release was low and sustained obeying the Higuchi´s kinetic. The results show that nanoparticles are promising sustained release system to the naproxen.

Synthesis of quinoxaline 1,4-di-N-oxide derivatives on solid support using room temperature and microwave-assisted solvent-free procedures

We describe the synthesis of 12 new ethyl and methyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives on solid supports with room temperature and microwave-assisted solvent-free procedures. Results show that solid supports have good catalytic activity in the formation of quinoxaline 1,4-di-N-oxide derivatives. We found that florisil and montmorillonite KSF and K10 could be used as new, easily available, inexpensive alternatives of catalysts. Additionally, room temperature and microwave-irradiation solvent-free synthesis was more efficient than a conventional procedure (Beirut reaction), reducing reaction time and increasing yield.

Optimization of solvent mixtures for extraction from bark of Schinus terebinthifolius by a statistical mixture-design technique and development of a UV-Vis spectrophotometric method for analysis of total polyphenols in the extract

A statistical mixture-design technique was used to study the effects of different solvents and their mixtures on the yield, total polyphenol content, and antioxidant capacity of the crude extracts from the bark of Schinus terebinthifolius Raddi (Anacardiaceae). The experimental results and their response-surface models showed that ternary mixtures with equal portions of all the three solvents (water, ethanol and acetone) were better than the binary mixtures in generating crude extracts with the highest yield (22.04 ± 0.48%), total polyphenol content (29.39 ± 0.39%), and antioxidant capacity (6.38 ± 0.21). An analytical method was developed and validated for the determination of total polyphenols in the extracts. Optimal conditions for the various parameters in this analytical method, namely, the time for the chromophoric reaction to stabilize, wavelength of the absorption maxima to be monitored, the reference standard and the concentration of sodium carbonate were determined to be 5 min, 780 nm, pyrogallol, and 14.06% w v-1, respectively. UV-Vis spectrophotometric monitoring of the reaction under these conditions proved the method to be linear, specific, precise, accurate, reproducible, robust, and easy to perform.

Supersaturation-controlled crystallization

Identification of product requirements and quality, together with the management of production are key issues in chemical engineering. Quality control of crystalline products is part of the quality of many industrially manufactured products like paper, paintings, medicines and fertilizers. In most crystallization cases, quality is described with the size, polymorph, shape and purity of the crystal. The chemical composition, hydrodynamics and driving force, together with the operating temperature are in a key position when the properties of a crystalline product are controlled with the crystallization process. This study concentrates on managing the identified properties of a crystalline product with the control of a driving force. The controlling of the driving force can be based on the change of solubility or the change of concentration. Solubility can be changed with temperature, pressure and an antisolvent. The concentration of crystallizing compound, the solute can be changed with the evaporation of the solvent and with the addition of a reagent. The present study focuses on reagent addition and temperature change as methods of changing the level of the driving force. Three control structures for direct control of supersaturation are built, one for cooling crystallization and two for reactive crystallization. Closed loop feedback control structures are based on the measurement of the solute concentration with attenuated total reflection - Fourier transform infrared spectrometer. The details of the reagent feed are analyzed with experimental studies and with results of computational fluid dynamic simulations of the inert particle pulse in the premixer and inert particle injection to the mixing tank. Nucleation in conditions of controlled reactive crystallization is analyzed with Nielsen’s equation of homogeneous nucleation. The resulting control systems, based on regulation of supersaturation, can be used to produce the desired polymorph of an organic product. The polymorph composition of product crystals is controlled repeatably with the decision of a set value of supersaturation level.

Test of a microlysimeter for measurement of soil evaporation

Quantifying soil evaporation is required on studies of soil water balance and applications aiming to improve water use efficiency by crops. The performance of a microlysimeter (ML) to measure soil evaporation under irrigation and non-irrigation was evaluated. The MLs were constructed using PVC tubes, with dimensions of 100 mm inner diameter, 150 mm depth and 2.5 mm wall thickness. Four MLs were uniformly distributed on the soil surface of two weighing lysimeters conducted under bare soil, previously installed at Iapar, in Londrina, PR, Brazil. The lysimeters had 1.4 m width, 1.9 m length and 1.3 m depth and were conducted with and without irrigation. Evaporation measurements by MLs (E ML) were compared with measurements by lysimeters (E L) during four different periods in the year. Differences between E ML and E L were small either for low or high atmospheric demand and also for either irrigated or non-irrigated conditions, which indicates that the ML tested here is suitable for measurement of soil evaporation.

Jatropha seed oil content and yield under different irrigation and potassium fertilization levels

The aim of this research was to evaluate the effects of different irrigation depths and potassium dosages, of Jatropha seed oil content and yield. The experimental design used was randomized blocks, in split-plots, with four replicates. The treatments were four water depths (plots) and four potassium dosages (subplots) applied through irrigation water. The water depths were applied based on the percentage of accumulated evaporation of a Class A (ECA) tank and of rainfall, as following: L0 = without irrigation, L40, L80 and L120, representing 40, 80 and 120% of the balance, respectively. The potassium dosages were K30, K60, K90 and K120 (30, 60, 90 and 120kg ha-1 of potassium, respectively). The oil extraction of samples was done through chemical extraction by organic solvent. The seeds used in this test were from the sampling of two seed productions from 2009, second year of crop production. It was possible to observe that irrigation use increased oil yield and decreased the oil content of Jatropha seed. Potassium fertilization did not influence oil content and yield. There was a relative increase of efficiency in water use producing oil until certain water depth, and after that there was a decrease.

Soil water evaporation under densities of coverage with vegetable residue

This study was conducted at the Agronomic Institute of Paraná (IAPAR) in Londrina, State of Paraná (PR), Brazil (latitude 23º18'S, longitude 51º09'W and average altitude of 585 m). The local climate, according to the classification of Köeppen, is Cfa type, i.e., humid subtropical climate, with rain in all seasons and can occur dry seasons during the winter. It was determined soil evaporation (E) under different coverage densities with residue from the wheat crop. The treatments were installed in weighting lysimeters of 2.66 m² and 1.3 m deep, which allows to determine E by the mass difference with measuring precision of 0.1mm at one hour intervals. Treatments consisted of 0; 2.5; 5 and 10 t ha-1 of wheat crop residues, placed evenly over each lysimeter. In the first cycle (September 22nd to October 20th, 2008), the reduction of E, as compared to a bare soil, was 4; 15 and 24%, while in the second cycle (December 1st to 30th, 2008), the reduction was of 15; 22 and 25%, respectively, for the treatments of 2.5; 5 and 10 t ha-1.

Estimation of evaporation in the Banabuiú dam, in the state of Ceará, Brazil, by different combined methods, derived from the Penman equation

The state of Ceará, Brazil, has 75% of its area covered by Brazilian semiarid, with its peculiar features. In this state, the dams are constituted in water structure of strategic importance, ensuring, both in time and space, the development and supply of water to population. However, construction of reservoirs results in various impacts that should be carefully observed when deciding on their implementation. One of the impacts identified as negative is the increased evaporation, which constitutes a major component of water balance in reservoirs, especially in arid regions. Several methods for estimating evaporation have been proposed over time, many of them deriving from the Penman equation. This study evaluated six different methods for estimating evaporation in order to determine the most suitable for use in hydrological models for water balance in reservoirs in the state of Ceará. The tested methods were proposed by Penman, Kohler-Nordenson-Fox, Priestley-Taylor, deBruim-Keijman, Brutsaert-Stricker and deBruim. The methods presented good performance when tested for water balance during the dry season, and the Priestley-Taylor was the most appropriate, since the data from de simulated water balance with evaporation estimated by this method were the closest of the water balance data observed from measures of reservoir level and the elevation-volume curve provided by the Company of Management of Water Resources of the state of Ceará - COGERH.

Specific surface charging of latex, clay and mineral oxide particles in aqueous, non-aqueous and mixed solvent systems

En djupare förståelse för växelverkan mellan partiklar i suspensioner är av betydelse för utvecklingen av en mängd olika industriella produkter och processer. Till exempel kan nämnas pigmentbaserade färger och bestrykning av papper. Genom att öka kontrollbarheten kan dessa lättare optimeras för att uppnå förbättrade produktegenskaper och/eller sänkta produktionskostnader. Av stor betydelse är även en förbättrad möjlighet att minska produktens miljöpåverkan. I avhandlingen studerades jonstyrkan och jonspecificiteten inverkan i olika akvatiska suspensioner innehållande olika elektrolyter. De partiklar som avhandlingen omfattade var metalloxider, leror samt latex. Jonstyrkan studerades från låga (c <10-3M) till och med höga (c> 10-1M) elektrolytkoncentrationer. Vid koncentrationer under 0.1 M var partikelladdningen styrd av pH och jonstyrkan. Vid högre elektrolytkoncentrationer påverkade även jonspecificiteten partikelladdningen. Jonspecificiteten arrangerades i fenomenologiska serier funna i litteraturen samt med Born modellen definierad i termodynamiken. Överraskande höga absoluta zeta-potential värden erhölls vid höga elektrolytkoncentrationer vilket visar att den elektrostatiska repulsionen har betydelse även vid dessa förhållanden. Vidare studerades titanoxidsuspensioners egenskaper i akvatiska, icke-akvatiska och blandade lösningssystem under varierande koncentration av oxal- och fosfatsyra. Vid lågt vatteninnehåll studerades även suspensioner med svavelsyra. Konduktiviteten i suspensioner med lågt vatteninnehåll ökade med tillsatt oxal- eller fosforsyra vilket är en omvänd effekt jämfört med svavelsyra eller akvatiska suspensioner. Den omvända effekten skiftade gradvis tillbaka med ökad vatteninnehåll. En analys av suspensionernas adsorption i höga etanolkoncentrationer gjordes med konduktiviteten, pH och zeta-potentialen. Viskositet studerades och applicerades framgångsrikt i viskositet/ytladdningsmodeller utvecklade för akvatiska suspensioner.

Recovery of carboxylic acids from aqueous streams by extraction and back extraction

Separation of carboxylic acids from aqueous streams is an important part of their manufacturing process. The aqueous solutions are usually dilute containing less than 10 % acids. Separation by distillation is difficult as the boiling points of acids are only marginally higher than that of water. Because of this distillation is not only difficult but also expensive due to the evaporation of large amounts of water. Carboxylic acids have traditionally been precipitated as calcium salts. The yields of these processes are usually relatively low and the chemical costs high. Especially the decomposition of calcium salts with sulfuric acid produces large amounts of calcium sulfate sludge. Solvent extraction has been studied as an alternative method for recovery of carboxylic acids. Solvent extraction is based on mixing of two immiscible liquids and the transfer of the wanted components form one liquid to another due to equilibrium difference. In the case of carboxylic acids, the acids are transferred from aqueous phase to organic solvent due to physical and chemical interactions. The acids and the extractant form complexes which are soluble in the organic phase. The extraction efficiency is affected by many factors, for instance initial acid concentration, type and concentration of the extractant, pH, temperature and extraction time. In this paper, the effects of initial acid concentration, type of extractant and temperature on extraction efficiency were studied. As carboxylic acids are usually the products of the processes, they are wanted to be recovered. Hence the acids have to be removed from the organic phase after the extraction. The removal of acids from the organic phase also regenerates the extractant which can be then recycled in the process. The regeneration of the extractant was studied by back-extracting i.e. stripping the acids form the organic solution into diluent sodium hydroxide solution. In the solvent regeneration, the regenerability of different extractants and the effect of initial acid concentration and temperature were studied.

Microwave-assisted solvent extraction and analysis of shikimic acid from plant tissues

A better method for determination of shikimate in plant tissues is needed to monitor exposure of plants to the herbicide glyphosate [N-(phosphonomethyl)glycine] and to screen the plant kingdom for high levels of this valuable phytochemical precursor to the pharmaceutical oseltamivir. A simple, rapid, and efficient method using microwave-assisted extraction (MWAE) with water as the extraction solvent was developed for the determination of shikimic acid in plant tissues. High performance liquid chromatography was used for the separation of shikimic acid, and chromatographic data were acquired using photodiode array detection. This MWAE technique was successful in recovering shikimic acid from a series of fortified plant tissues at more than 90% efficiency with an interference-free chromatogram. This allowed the use of lower amounts of reagents and organic solvents, reducing the use of toxic and/or hazardous chemicals, as compared to currently used methodologies. The method was used to determine the level of endogenous shikimic acid in several species of Brachiaria and sugarcane (Saccharum officinarum) and on B. decumbens and soybean (Glycine max) after treatment with glyphosate. The method was sensitive, rapid and reliable in all cases.