Mobilidade de bário em solo tratado com sulfato de bário sob condição de oxidação e redução

In order to evaluate possible solubility of BaSO4 in soils under reducing conditions, column leaching assay was settled down, where the soil received three doses of BaSO4 (100, 300 and 3000 mg kg-1) at two humidities. After reaching an Eh of -200 mV rainfall of 200 mm per day-1 was simulated. The condition of reduction led to the increased levels of barium in the fractions of higher lability and the highest levels of barium in the leachate extract, which were above the potability standards. Only 0.05% of barium in the column that received the highest dose was removed by leaching.

Avaliação da porosidade de microcápsulas contendo proteína bioativa por porosimetria de mercúrio e adsorção de nitrogênio

Microcapsules containing lactoferrin were produced by spray drying using dextrin:octenylsuccinate starch, as wall materials. Porosity characteristics of spray-dried microcapsules were investigated by mercury intrusion porosimetry and nitrogen adsorption. The outer and inner structures of microcapsules were studied by Scanning Electron Microscopy and sizes were determined by Laser Diffraction. Results indicate that all microcapsules presents adsorption isotherm of type II and that micropores on the microcapsules surface will be very few or none. Our results show that microstructure, surface area and size of microcapsules are affected by dextrin: octenylsuccinate starch proportion. Pore characteristics for various microcapsules are found to be different.

Determinação da constante de dissociação (Ka) do captopril e da nimesulida: experimentos de química analítica para o curso de farmácia

This paper presents the determination of the dissociation constant (Ka) of captopril and nimesulide as contextualized experiments to teach chemical concepts to students of Pharmacy. Captopril is an antihypertensive drug, which presents high water-solubility and weak acid properties. The pKa of carboxylic acid group of captopril is 3.7. Nimesulide is a non-steroidal anti-inflammatory drug sparingly soluble in water. It is weakly acidic (pKa ≈ 6.5) because of its methanesulfonamide functional group. The pKa of captopril was determined by potentiometric titration with NaOH 2.0 x 10-2 moL L ¹. The pKa of nimesulide was determined by using spectrophotometry and photometric titration. The experimental values of pKa of both drugs are in very good agreement with those from literature

Poly(ethylene-co-methyl acrylate)/poly(caprolactone) triol blends for drug delivery systems: characterization and drug release

Poly(ethylene-co-methyl acrylate) (EMA) and poly (caprolactone) triol (PCL-T) blends, a biodegradable aliphatic polyester with low molecular weight and moderate water solubility containing diltiazem hydrochloride (DZ) were studied in terms of the thermal and morphological properties, and drug release mechanism. An increase in the PCL-T content in the EMA/PCL-T/DZ films decreased the degree of DZ crystallinity. Drug release from these films is temperature-dependent, and it is possible to modify the drug release rate by adjusting the EMA/PCL-T composition of the blends. The mechanism of drug release is governed by PCL-T melting and PCL-T leaching from EMA matrix.

Investigando cinza da casca do arroz como fase estacionária em cromatografia: uma proposta de aula experimental nos cursos de graduação

This article describes an experiment that involves the extraction and separation of the pigments of spinach extract by column chromatography using the silica obtained from rice husk ash as a stationary phase. The experimental procedure is very simple to apply in the chemistry laboratory, and allowed to illustrate some concepts of organic chemistry: structure of organic molecules, solubility, polarity, extraction, partition coefficient, adsorption and retention factor (Rf), as well as objectives and fundamentals of chromatographic methods. The experiment can be carried out in a 4 h period.

Caracterização físico-química de filmes comestíveis de amido adicionado de acerola (Malphigia emarginata D.C.)

Edibles films are an alternative to synthetic materials used for packing food products. Barbados cherry is rich in vitamin C and carotenoids. The aim of this study was to characterize and develop films by casting from cassava starch, lyophilized Barbados cherry pulp and glycerol. The films were characterized with respect to thickness, water vapor permeability (WVP), water solubility, vitamin C, carotene and mechanical properties. The interaction of pulp and glycerol reduced film thickness. An increase in pulp concentration up to 60% increased WVP but beyond this concentration reduced both WVP and solubility leading to an increased level of vitamin C and β carotene in the films.

Evaluation of chitosan microparticles containing curcumin and crosslinked with sodium tripolyphosphate produced by spray drying

The aim of this study was to encapsulate curcumin into chitosan, using sodium tripolyphosphate (TPP) as an ionic crosslinker by the spray drying method. The influence of TPP on the properties of the final product, such as solubility, morphology, loading efficiency, thermal behavior, swelling degree and release profiles, was evaluated. The microparticles had a spherical morphology (0.5-20 µm) with no apparent porosity or cracks. Results indicated the formation of a polymeric network, which ensures effective protection for curcumin. Controlled-release studies were carried out at pH 1.2 and 6.8, to observe the influence of pH on curcumin release while the mechanism was analyzed using the Korsmeyer-Peppas equation.

Remoção de íons Pb2+ de solução de bateria automotiva por caulinita modificada com óxido de manganês

Nine absorbents were prepared using a mixture of Amazonian kaolinite and MnO2 at three temperatures (600, 700 and 900 ºC) in order to retain Pb2+ ions contained in the battery solutions. The batch experiments carried out with the batteries used water for 3 h and the kinetic isotherm was fitted with the pseudo-second order Lagergren equation. Findings show that synthesized adsorbents AD4, AD5 and AD7 performed well in reducing the Pb2+ ion content from 0.36 to 0.00 mg g-1. The better performance for removing the Pb2+ ions occurred for adsorbents synthesized in the temperature range from 600 to 700 ºC.

Determinação dos parâmetros cinéticos e termodinâmicos da adsorção de L-cisteína em ouro por meio da técnica de microbalança a cristal de quartzo

This article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 s-1, Keq=(1.8 ± 0.3) x 10(4) M-1 and ΔGads = - (5.8 ± 0.2) kcal mol-1.

Absorção de bário por plantas de arroz (Oryza sativa L.) e mobilidade em solo tratado com baritina sob diferentes condições de potencial redox

Two parallel tests were carried out to evaluate barium solubility in soils treated with barite under reducing conditions: one in leaching columns and another with potted plants cultivated with rice. Soils were treated with three doses of barite and kept at two humidity levels. The reduction (-200 mV) condition promoted an increase in barium in the geochemical fraction of higher liability, higher concentrations of barium in the leached extracts, and higher absorption by rice plants. As a result of increased uptake and accumulation of barium, the plants showed stunted growth

Solution thermodynamics of methocarbamol in some ethanol + water mixtures

Apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of solution and mixing, for methocarbamol in ethanol + water mixtures, were evaluated from solubility data determined at temperatures from 293.15 K to 313.15 K and from calorimetric values of drug fusion. The drug solubility was greatest in the mixtures with 0.70 or 0.80 mass fraction of ethanol and lowest in neat water across all temperatures studied. Non-linear enthalpy-entropy compensation was found for the dissolution processes. Accordingly, solution enthalpy drives the respective processes in almost all the solvent systems analyzed.

Separation and characterization of asphaltenic subfractions

The structure of the various asphaltenic subfractions found in crude oil was evaluated. For this purpose, C5 asphaltenes were extracted from an asphaltic residue using n-pentane as the flocculant solvent. The different subfractions were isolated from the C5 asphaltenes by the difference in solubility in different solvents. These were characterized by infrared spectroscopy, nuclear magnetic resonance, X-ray fluorescence, elementary analysis and mass spectrometry. The results confirmed that the subfractions extracted with higher alkanes had greater aromaticity and molar mass. However, small solubility variations between the subfractions were attributed mainly to the variation in the concentrations of cyclical hydrocarbon compounds and metals.

Adsorção do corante Reativo Azul 19 em solução aquosa por lama vermelha tratada quimicamente com peróxido de hidrogênio

Adsorption of Reactive Blue 19 dye onto activated red mud was investigated. Red mud was treated with hydrogen peroxide (LVQ) and heated at both 400 ºC (LVQ400) and 500 ºC (LVQ500). These samples were characterized by pH, specific surface area, point of zero charge and mineralogical composition. Adsorption was found to be significantly dependent on solution pH, with acidic conditions proving to be the most favorable. The adsorption followed pseudo-second-order kinetics. The Langmuir isotherm was the most appropriate to describe the phenomenon of dye removal using LVQ, LVQ400 and LVQ500, with maximum adsorption capacity of 384.62, 357.14 and 454.54 mg g-1, respectively.

Avaliação do potencial de uso da hidroxiapatita para fertilização de solos

Plants absorb phosphorus from the soil, which has low levels of this element due to the poor solubility of these compounds in soil and high adsorption capacity of the element by soil particles. Therefore, the purpose of this study was to assess, using hydroxyapatite nanoparticles synthesized in the laboratory, the amount of phosphorus available under different conditions. The results showed that the phosphorus compound had highest solubility in hydroxyapatite sintered at 300°C in an oven for 2h and diluted to 0.05M with MilliQ water, corroborating the theory that the stronger the agglomeration of the nanoparticles, the fewer the pores and the poorer their solubility.

Contextualizando reações ácido-base de acordo com a teoria protônica de Brönsted-Lowry usando comprimidos de propranolol e nimesulida

This paper reports the use of alternative materials for teaching experimental chemistry. In this context, nimesulide and propranolol tablets were used to teach chemical concepts about acid-base reactions according to Brönsted-Lowry protonic Theory. Important topics of Organic, Analytical and Pharmaceutical Chemistry were discussed, such as purification by acid-base extraction, solubility of organic compounds in aqueous solutions, buffers, the dissociation constant (pKa), potentiometric titration and ionization of drugs in biological fluids. The purification of propranolol and nimesulide from tablets produced yields of 75% and 90%, respectively. The experimental values of pKa for both drugs were in agreement with those from the literature.