The role of the 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid reagent in determining the thorium ion (IV)

The aim is to develop a method for the amperometric determination of thorium (IV) ion with 2,7-dinitroso-1,8-dihydroxynaphthalene-3,6-disulfoxyl reagent. Methods of amperometric determination of thorium by solution of 2,7-dinitrozo-1,8-dihydroxynaphthalene-3,6-disulfonic acid on different acid-base properties of background electrolytes and buffer mixtures are considered. The half-wave potential of new reagent was found by logarithmic analysis equal 0.72 V at pH 2.82, which once again indicates on the irreversibility of the process of electrooxidation of the studied organic reagent in used acid-base medias. The conditions for amperometric titration of thorium are optimized, and the influence of outside accompanying metals on the shape of curves and the results of its determination are investigated.

Determining Stability Constants of Complexes Between Ester Betulin Derivatives and β-Cyclodextrin by Affinity Capillary Electrophoresis

Inclusion complexes of ester betulin derivatives (pentacyclic lupane triterpenoids) with β-cyclodextrin (β-CD) were studied by affinity capillary electrophoresis. Stability constants were calculated from dependencies of viscosity-corrected effective electrophoretic mobilities on β-CD concentration (0-10 mM) in background electrolytes using nonlinear regression fitting. Logarithms of stability constants at 25 °C for 1:1 and 1:2 β-CD complexes of betulin 3,28-diphthalate, betulin 3,28-disuccinate and betulin 3,28-disulfate (95 % confidence interval) are 4.25 (4.16-4.32) and 7.27 (6.73-7.50), 4.38 (4.26-4.48) and 7.58 (6.90-7.84), 4.04 (4.00-4.08) and 5.91 (4.60-6.20), respectively

Effect of Ionic Strength and Coexisting Ions on the Biosorption of Divalent Nickel by the Acorn Shell of the Oak Quercus crassipes Humb. & Bonpl.

This study investigated the effect of ionic strength and background electrolytes on the biosorption of Ni2+ from aqueous solutions by the acorn shell of Quercus crassipes Humb. & Bonpl. (QCS). A NaCl ionic strength of 0.2 mM was established to have no effect on the Ni2+ biosorption and the biosorption capacity of the heavy metal decreased as the ionic strength increased from 2 to 2000 mM. The background electrolytes (KCl, NaNO3, Na2SO4, CaCl2, MgSO4, and MgCl2) had no adverse effects on the biosorption of Ni2+ at a concentration of 0.2 mM. However, at background electrolyte concentrations of 2 and 20 mM, divalent cations (Ca2+ and Mg2+) had greater negative effects on the biosorption of Ni2+ compared to the monovalent cations (Na+ and K+). Additionally, the SO42− and Cl− anions affected the biosorption of Ni2+. The fractional power, Elovich, and pseudo-second order models represented the kinetic processes of the biosorption of Ni2+ adequately. The results show that QCS can be a promising and low-cost biosorbent for removing Ni2+ ions from aqueous solutions containing various types of impurities with different concentrations.

EFFECT OF SURFACTANTS ON THE REDUCTION OF LEAD(II) IONS ON LEAD ELECTRODE

The effect high molecular weight water-soluble surfactants with different functional groups have on the electroreduction of lead(II) ions on a lead electrode in various electrolytes is studied. A copolymer of methacryloylaminophenol with acrylic acid, a leather waste hydrolyzate, and a copolymer of monoethanolamine with vinyl ether acetate are used as surfactants. The electrolytes that are used are 1 M KCl, KBr, KNO3, HCOONa, NH2SO3H, 0.5 M Na2SO4, and 0.35 M Na3C6H5O7 .2H2O. It is shown that in 1.0 M KCl or KBr solutions, there is no inhibition of the electroreduction of lead(II) ions by the adsorption layers of surfactants. It is found that the inhibitory effect of polymers on the electroreduction of lead(II) ions in different background electrolytes increases in the order KCl > KBr > Na3C6H5O7.2H2O > Na2SO4 > KNO3 > HCOONa > NH2SO3H. Key words: lead ions, electroreduction, surfactants, electrolyte, lead electrode, exchange current.

Electrodeposition process of perrhenate ions from KNO3 and Na2SO4 background electrolytes in the presence of citric acid

Processes involved in the electrodeposition of perrhenate ions were studied from two different potassium nitrate and sodium sulfate background electrolytes in the presence of citric acid on graphite electrode by cyclic voltammetry method. Anodic and cathodic potentials of deposited film were determined. After electrolysis process, morphology and content of obtained deposited layers were investigated by SEM and X-Ray methods. The coated film from sodium sulfate background electrolyte was not uniform and Re content was 60.83-65.5%, in case of potassium nitrate electrolyte, the deposited film was more densely located, and Re content was 80.94-82.52%. In the presence of nickel sulfate and citric acid, an alloy was formed with content of Re 80.94-82.52%, 14.10-11.83% of Ni, 4.96-5.66% of impurities, which were confirmed by X-Ray method. The current density decreased with addition of citric acid into sodium sulfate background electrolyte and in cathodic area, the reduction potential of perrhenate ions remained the same, but oxidation potentials changed from 0.25 to 0.35 V and from 0.5 to 0.6 V. The influence of citric acid on potentials of the processes of reduction and oxidation of perrhenate ions from potassium nitrate gave following results: reduction peaks shifted from -0.35 to -0.55 V, and multi peaks of oxidation appeared which were not noticeable without citric acid. It was shown that citric acid has inhibitory effect on reduction and oxidation of perrhenate ions. It is shown that the electrochemical reduction of perrhenate ions leads to the formation of rhenium dioxide in different forms.