Um sistema microcontrolado para o monitoramento on-line, in situ e remoto de pH, condutividade e temperatura de águas

A portable microcontrolled system is proposed to monitor conductivity, temperature and pH in on-line, in situ and remote way from a water reservoir faraway 200 m. The system comprises two modules: one for data reception (located in laboratory) and another for data acquisition/transmission (located near water reservoir). It uses a microcontroller and a transceiver to remote data transmission/reception by radio frequency. Variations of water parameters were simultaneously monitored without interruption during a period of ten hours with a relative error about 4.0 %. The developed system showed simple, stable, accurate, robust and low-cost to determine parameters of water in field.

Alvejamento químico de caulins Brasileiros: efeito do potencial eletroquímico da polpa e do ajuste do pH

Samples of Kaolin from different regions in Brazil were characterized by XRD, SEM and chemical analysis. A chemical bleaching study with pH adjustment was accomplished with the fractions below 37 μm, after classification by screening. The main objective was to evaluate the conditions of chemical bleaching that most increase the brightness of these kaolin's samples. Increases between 2.63 and 2.98% in the brightness (ISO) were observed after the chemical bleaching. We could say that the reduction of Fe3+ to Fe2+ during the chemical bleaching promoted an increase in the brightness, based on the Pourbaix Diagrams.

Descoloração e degradação do azo corante Vermelho GRLX-220 por ozonização

The discoloration and degradation of the textile dye RED GRLX-220 using the electrochemically generated ozone was investigated. Total discoloration was rapidly achieved in both acid and basic conditions. A pseudo-first order kinetics was observed for discoloration, influenced by pH and ozonation time. A considerable degree of mineralization (60%) was obtained after 30 min of ozonation in alkaline medium. The feasibility of organic matter oxidation during the ozonation process increased in both acidic and alkaline media. The toxicity decreased after the ozonation process, suggesting that the byproducts are less toxic than the parental compound.

Zn-edta degradation by catechol-driven fenton reaction

Zn-EDTA degradabilty by catechol-driven Fenton reaction was studied. Response surface methodology central composite design was employed to maximize this complex degradation. Theoretical speciation calculations were in good agreement with the experimental results. Fenton and Fenton type treatments are typically thought to be applicable only in the highly acidic range, representing a major operational constraint. Interestingly, at optimized concentrations, this CAT-driven Fenton reaction at pH 5.5 achieved 100% Zn-EDTA degradation; 60% COD and 17% TOC removals, using tiny amounts of CAT (50 µM), Fe(III) (445 µM) and H2O2 (20 mM) with no evident ferric sludge.

Influência do pH nas propriedades físico-químicas, térmicas e mecânicas de filmes de poli(vinil álcool)/poli(ácido acrílico)/aciclovir

Drug-loaded films represent an alternative method for the treatment of skin lesions caused by Herpes simplex, since they facilitate delivery of the drug directly at the site of lesion. The objective of this work was to prepare PVA/PAA films containing AC at pH 2.0 and 4.0. The results show that the pH of the film preparations influences the polymer¾drug interaction kinetic order and the degree of swelling. The mechanism of release of AC from the films obtained at pH 4.0 was anomalous, whereas for the films prepared at pH 2.0 the release followed zero-order kinetics.

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.

Processing of spent NiW/Al2O3 catalysts

Spent oxidized (500 ºC, 5 h) commercial NiW/Al2O3 catalysts were processed using two different routes: a) fusion with NaOH (650 ºC, 1 h), the roasted mass was leached in water; b) leaching with HCl or H2SO4 (70 ºC, 1-3 h). HCl was the best leachant. In both routes, soluble tungsten was extracted at pH 1 with Alamine 336 (10 vol.% in kerosene) and stripped with 2 mol L-1 NH4OH (25 ºC, one stage, aqueous/organic ratio = 1 v/v). Tungsten was isolated as ammonium paratungstate at very high yield (> 97.5%). The elements were better separated using the acidic route.

Preparative separation of C19-diterpenoid alkaloids from Aconitum carmichaelii Debx by pH‑zone-refining counter-current chromatography

The technique of pH-zone-refining counter-current chromatography was successfully applied to preparatively separate three C19-diterpenoid alkaloids from the crude extracts of Aconitum carmichaelii for the first time using a two-phase solvent system of petroleum ether-ethyl acetate-methanol-water (5:5:1:9, v/v/v/v). Mesaconitine (I), hypaconitine (II), and deoxyaconitine (III) were obtained from 2.5 g of the crude alkaloids in a one-step separation; the yields were 4.16%, 16.96%, and 5.05%, respectively. The purities of compounds I, II, and III were 93.0%, 95%, and 96%, respectively, as determined by HPLC. The chemical structures of the three compounds were identified by electrospray ionization mass spectrometry (ESI-MS) and NMR.

Adsorção de alfa-lactalbumina do soro de leite em hidroxiapatita: efeito do pH e da temperatura e análise termodinâmica

The nutritional and functional benefits offered by whey protein α-lactalbumin justify the great interest in its manufacture in large quantities at a high purity level. Hydroxyapatite is a calcium phosphate material able to adsorb proteins and can be synthesized at low production cost. Therefore, this work evaluated the adsorption of α-lactalbumin on hydroxyapatite using solid-liquid phase equilibrium data reported as adsorption isotherms. Van't Hoff's thermodynamics analysis showed that the adsorption process is entropically driven.

Final chlorine dioxide stage at near-neutral pH for bleaching eucalypt pulp

It is well known that pH is an important parameter for controlling the eucalyptus pulp bleaching when using the final chlorine dioxide stage, since it affects the effectiveness of the process. Recommendations found in the literature for operating are in the 3.5 to 4.0 range. However, in this paper it was shown that final chlorine dioxide has better performance, with significant brightness gain while also preserving pulp quality, when it is operated at near neutral pH. This result can be explained by the generation of sodium bicarbonate in situ upon adding carbon dioxide at this stage.

ASYMMETRIC SULFOXIDATION OF ALBENDAZOLE TO RICOBENDAZOLE BY FUNGI: EFFECT OF pH

Albendazole (ABZ) is an anthelmintic drug used for the treatment of infectious diseases in veterinary and human medicine. This drug is a prochiral drug that after administration, is rapidly oxidized in the pharmacologically active sulfoxide metabolite, which is also known as ricobendazole (ABZSOX). ABZSOX has a stereogenic center and possibly two enantiomers, (+)-ABZSOX and (-)-ABZSOX. In the present work, we investigate the pH effect on the asymmetric stereoselective sulfoxidation of ABZ into ABZSOX by employing the fungi Nigrospora sphaerica, Papulaspora immera Hotson, and Mucor rouxii. The results show a possibility of obtaining the pure enantiomers of the ricobendazole drug using fungi as biocatalytic agents. The three fungi showed a high degree of enantioselectivity expressed by enantiomeric excess. In addition, M. rouxii can be used as an alternative to obtain the (+)-ABZSOX enantiomer (ee 89.8%).

DIRECT INFUSION ESI-MS APPLIED IN THE DETECTION OF BYPRODUCTS DUE TO REDUCTIVE DEGRADATION OF ACETAMIPRID BY ZERO-VALENT IRON

This study investigated the reductive degradation of acetamiprid (5 mg L-1) in aqueous medium (at pH 2.0) induced by zero-valent iron (50 mg). The process was monitored using high-performance liquid chromatography (HPLC) to determine the degradation rate as a function of reaction time, and direct infusion electrospray ionization mass spectrometry (DI-ESI-MS) to search for (and potentially characterize) any possible byproducts formed during degradation. The results obtained via HPLC showed that after 60 min, the degradation of the substrate reached nearly 100% in an acidic medium, whereas the mineralization rate (as determined by total organic carbon measurements) was as low as 3%. Data obtained by DI-ESI-MS showed that byproducts were formed mainly by insertions of hydrogen atoms into the nitrile, imine, and pyridine ring moieties, in addition to the observation of chlorine substitution by hydrogen replacement (hydrodechlorination) reactions.

FAST GC-FID METHOD FOR MONITORING ACIDIC AND BASIC CATALYTIC TRANSESTERIFICATION REACTIONS IN VEGETABLE OILS TO METHYL ESTER BIODIESEL PREPARATION

A fast gas chromatography with a flame ionisation detector (GC-FID) method for the simultaneous analysis of methyl palmitate (C16:0), stearate (C18:0), oleate (C18:1), linoleate (C18:2) and linolenate (C18:3) in biodiesel samples was proposed. The analysis was conducted in a customised ionic-liquid stationary-phase capillary, SLB-IL 111, with a length of 14 m, an internal diameter of 0.10 mm, a film thickness of 0.08 µm and operated isothermally at 160 °C using hydrogen as the carrier gas at a rate of 50 cm s-1 in run time about 3 min. Once methyl myristate (C14:0) is present lower than 0.5% m/m in real samples it was used as an internal standard. The method was successful applied to monitoring basic and acidic catalysis transesterification reactions of vegetable oils such as soybean, canola, corn, sunflower and those used in frying process.