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Abstract  

The reactions of hydroxyl radical and hydrated electron intermediates of water radiolysis were studied in the radiolytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at pH values of 4, 6 and 8. The hydrated electron reactions are also suggested to contribute to the aromatic ring decomposition in addition to the highly effective hydroxyl radical reactions. The experimental results suggest also some contribution from the O2 −•/HO2 pair to the degradation. The degradation efficiency was found to be the highest at pH 8 and the lowest at pH 6.

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Abstract  

Binding constants of Eu(III)- and Am(III)-complexes with soil-derived humic acid were determined by solvent extraction at various pH and ionic strength. Based on the dependence of binding constants on pH and ionic strength, stabilities of the humate complexes in land water and seawater were estimated. Speciation calculation based on the binding constants indicated that Am(III) could combine with humic substances in natural water system.

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Abstract  

In this paper, the special sorption properties of mercury(II) on calcium-montmorillonite is shown. Mercuric hydroxide (Hg(OH)2) produced by the hydrolysis of mercuric ions is fairly soluble, solubility is 3.2 × 10−4 mol/dm3. As a result, indifferently of the usual behavior of other hydroxides, it remains in the aqueous solution. The sorption properties are determined by the fact: there is no precipitation at higher pH values. Montmorillonite contains permanent as well as pH-dependent charges, so the cation exchange on the permanent changes, in the interlayer space of montmorillonite and the sorption of neutral mercuric hydroxide molecules can be studied simultaneously. So, two interfacial processes of the same substance, namely the ion exchange of hexahydrate mercuric(II) ions and the sorption of neutral mercuric hydroxide molecules, can be studied in the same system.

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Journal of Thermal Analysis and Calorimetry
Authors: G. Barone, S. Capasso, P. Del Vecchio, C. De Sena, D. Fessas, C. Giancola, G. Graziano, and P. Tramonti

Abstract  

In a previous paper, we report a preliminary DSC study on bovine (BSA) and human (HSA) serum albumins. However, at accurate HPLC analysis the commercial proteins show three peaks: Fraction V-I, probably globulins (as declared by the producers), Fraction V-II (about 15–18% of the product) and Fraction V-III that represents pure BSA or HSA. A hypothesis is that the Fraction II is a covalent dimer, or trimer or a mixture of both, generated during the scalf-life of the commercial product. Denaturation enthalpies of the purified Fraction V-III and Fraction V-II of BSA, have been determined calorimetrically, at changing thepH, and the results of both compared with those obtained on the untreated protein. Few calorimetric experiments have been also carried on a BSA monomer derivative with sulphidril group protected. Computer program have been developed for the deconvolution of exo- and endothermic effects and for the analysis of thermal denaturation profiles.

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Abstract  

Initial plant scale trials of the nitrosation of an amino acid revealed a number of issues: _ Much lower yield compared to laboratory scale _ Considerable loss of mass balance _ Large excess of nitrosating agent required for complete reaction _ Highly reactive off-gases produced causing fires in the carbon absorber _ Reaction sensitive to agitation speed _ The by-product produces an impurity in the next process stage which has high human toxicity A kinetic and mechanistic study of the nitrosation reaction, using isothermal power compensation calorimetry and GC/mass spectrometry, has been undertaken in order to understand the above observations and to produce an improved manufacturing process - more robust, higher yielding, reduced effluent volumes and toxicity.

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Abstract  

A radiochemical solvent extraction method has been developed for the micro determination of Mo/VI/ using99Mo tracer. It involves removal of99mTc by ethyl methyl ketone /EMK/ and extraction of Mo with tri-n-butyl phosphate /TBP/ from 5M HCl. Different parameters affecting the extraction such as pH dependence, nature of solvent and interferences due to other radionuclides have been studied. The method can be used up to 2 g of Mo.

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Abstract  

A study has been made on the effect of pH upon the equilibrium adsorption capacity of triethyl phosphate, dimethyl phosphate and orthophosphate on to activated carbon cloth. It is shown that for molecular phosphates no dependence upon pH exists, whilst the adsorption of ionic phosphates exhibit a strong pH dependence. These adsorption trends may be explained in terms of pKa values, ionic strength and the surface charge of the activated carbon cloth is aqueous solution.

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Abstract  

The multitracer technique was applied to the simultaneous evaluation of the behavior of a large number of radioactive nuclides. The binding affinity of various trace elements with blood components and the pH-dependence of binding affinity of the elements with serum proteins were examined using the multitracer technique. Each element showed characteristic binding to each blood component and serum protein. The results are discussed in terms of chelating ability of metal ions and the nature of the serum proteins.

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Abstract  

The tracer packet technique is an efficient tool to evaluate simultaneously the behavior of some closely associated elements. The present study has been performed to determine the binding affinity of various toxic heavy and micronutrient elements with the proteins extracted from Erythrina variegata Linn. (Family: Leguminosae) seed by means of ‘tracer packet’ technique. Effects of buffer and pH dependence on the binding affinity of the elements of interest have also been examined.

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Abstract  

Distribution coefficients, pH dependence, isotherms, kinetics and breakthrough curves of Sr binding have been measured on several types of adsorbents (carbons modified with titanium silicate, crystalline titanium silicate, mixed titanium-manganese oxide, and synthetic zeolites A4 and P) from different water solutions. It is concluded that acid-base properties of the adsorbent is very important for Sr binding. Titanium silicate based adsorbents had reduced chemical stability in an artificial food fluid below pH 2, the mixed titanium manganese oxide below pH 6, zeolite A4 below pH 5 and zeolite P below pH 7. Consideration is given to the feasibility of the adsorbents for food decontamination.

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