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2827 2838 Holub M., Balintova M., Pavlikova P., Palascakova L. Study of sorption properties of zeolite in acidic conditions in dependence on particle size, Chemical Engineering

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Heavy metals, including copper, are a serious environmental problem today. As an essential part of acid mine drainage they cause degradation of surface and subsurface water quality, including drinking water. Significant character of acid mine drainage is low value of pH, as a result of hydrogen cations releasing into aqueous environment during the process of pyrite oxidation and high concentration of heavy metals. Sorption techniques are widely used to remove heavy metal ions from large volumes of aqueous solutions. The fact of low pH must be taken in consideration because it has a relevant impact on the behavior of the sorbent during the sorption process.In order to study the optimal parameters of the sorption process of Cu(II) from acid mine drainage (pH=3–4), two sorbents under model conditions in solutions with pH of 4 were studied. For this purpose low cost natural sorbents turf brush PEATSORB and natural zeolite were selected. Different contact time and various initial concentrations of ions were tested as variables. The properties of the tested sorbents were compared from the point of view of their efficiency and sorption capacity. The impact of sorption on the pH change in solution was also studied.

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Abstract  

Ion-exchange resins, especially chelating resins are used for pre-concentration of metal ions in trace analysis as well as for radiochemical separations following neutron activation of a variety of environmental samples. As part of a systematic study of the sorption characteristics of chelating resins, sorption of Zn(II) and Cd(II) by three chelating resins were studied for various acid conditions in nitrate and chloride media. Both Zn(II) and Cd(II) showed similar behavior. Under higher acid conditions, maximum sorption occurred in 3M HCl solutions. Under low acid conditions, the sorption increased with pH. Chelex 100 gave the highest sorption among the three resins.

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of acrylamide with potassium bromide and potassium bromate could produce 2,3-dibromopropanamide under acidic conditions, the chemical reaction process is as follows. 5 KBr + KBrO 3 + 3 H 2 SO 4 = 3 Br 2 + 3 H 2 O + 3 K 2 SO 4 The 2

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Journal of Thermal Analysis and Calorimetry
Authors: Blaž Likozar, Romana Cerc Korošec, Ida Poljanšek, Primož Ogorelec, and Peter Bukovec

. MUF resins are products which are synthesized by the step polymerization of melamine, urea and formaldehyde under alkaline or acidic conditions. Three reaction sequences must be considered, namely the formaldehyde addition to melamine or to urea

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99mTc-dimercaptosuccinic acid is one of the most widely applied radiopharmaceutical for renal scintigraphy. This complex was prepared by ligand exchange reaction from99mTc-gluconate at tracer concentration of technetium under acidic conditions. The exchange yield was determined by paper chromatography and reaction rate constants were calculated at different pH values.

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A technique has been developed for the qualitative determination of low-molecular-weight organic acids in radioactive, mixed hazardous wastes using thermospray liquid chromatography/mass spectrometry. A tank waste was analyzed, and the results indicated the presence of citric, glycolic, acetic, and nitrosoiminodiacetic acid (NIDA). Further investigation revealed NIDA was formed under acidic conditions with the reaction of iminodiacetic acid and the high nitrate/nitrite concentration present in the waste.

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Displacement-extraction of tracer concentrations of210Po in 1.0M (H, Na)NO3 solutions has been studied by using copper dithizonate–CCl4 solutions. Furthermore, based on the results of the displacement-extraction of polonium, a mixture of210Po,210Bi, and210Pb of tracer concentrations in 1.0M (H, Na)NO3 solutions could be satisfactorily separated with successive extractions by copper dithizonate–CCl4 and dithizone–CCl4 solutions in acidic conditions.

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A sensitive, selective, precise, and stability-indicating high-performance thin-layer chromatographic (HPTLC) method has been established for densitometric analysis of flurbiprofen in pharmaceutical tablets. Chloroform-acetone-xylene 5.0:2.0:1.0 ( v/v ) was used as mobile phase. Regression analysis of the calibration data revealed a good linear relationship between peak-area response and amount of flurbiprofen in the range 50–600 ng per band ( r 2 = 0.9993 ± 0.0004). The limits of detection (LOD) and quantification (LOQ) were 10 and 32 ng per band, respectively. Flurbiprofen was subjected to different stress conditions. An Arrhenius plot was constructed for degradation under acidic conditions and the activation energy was calculated.

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Journal of Flow Chemistry
Authors: Mariëlle M.E. Delville, Jasper J.F. van Gool, Ivo M. van Wijk, Jan C.M. van Hest, and Floris P.J.T. Rutjes

Abstract

Cyanohydrins are synthetically versatile chiral building blocks in organic synthesis. They can be conveniently synthesized in enantiomerically pure form via chemoenzymatic hydrogen cyanide addition onto the corresponding aldehyde using hydroxynitrile lyase. Recently, we reported that such transformations can be efficiently carried out in a continuous flow manner using microreactors. Since racemization of enantiopure cyanohydrins occurs readily under slightly basic conditions, they should be protected before the follow-up reactions, preferably under acidic conditions. In this contribution, we demonstrate that the methoxyisopropyl protection of mandelonitrile can be conveniently optimized in an automated microscale continuous flow system and subsequently scaled up under the same conditions by applying a larger flow reactor.

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