Professor Vladimir Zaitsev

D.Sc., PhD, Corr. member of Acad. of Sci. of Ukraine

2008

1. Bifunctionalized Mesoporous Silicas for Cr(VI) Reduction and Concomitant Cr(III) Immobilization
   NATALIYA SHEVCHENKO, VLADIMIR ZAITSEV, AND ALAIN WALCARIUS
   Environ. Sci. Technol. 2008, 42, 6922–6928
   Surfactant-templated thiol-functionalized mesoporous silica adsorbents have been prepared by cocondensation of mercaptopropyltrimethoxysilane and tetraethoxysilane in the presence of cetyltrimethylammonium bromide, which were thenpartially oxidized to get bifunctionalized materials containing both thiol and sulfonic acid moieties (MCM-41-SH/SO3H). The resulting organic-inorganic hybrid was applied to the uptake of chromium species according to a reduction-sorption mechanism involving reduction of Cr(VI) by thiol groups and immobilization of Cr(III) onto sulfonic acid moieties. These processeswerestronglyaffectedbypH,andtheoptimalconditions for effective chromium sequestration resulted from a compromise between pH values low enough to ensure quantitative reduction of Cr(VI) and not too low to enable Cr(III) binding to sulfonate groups, which was best achieved at pH 2-3. The effect of the solid-to-solution ratio and the relative amounts of -SH and -SO3H groups was also discussed. Even if Cr(VI) reduction by thiol groups resulted in the formation of sulfonic acid moieties, their contentwasnot highenoughto ensure quantitative Cr(III) immobilization, which was only attained with materials containing already some sulfonic acid groups prior to contacting Cr(VI) solutions. Redox speciation of sulfur and chromium species was analyzed by X-ray photoelectron spectroscopy (XPS)andusedto support theproposedmechanism.
2. Organosilica composite for preconcentration of phenolic compounds from aqueous solutions
   Zaitsev, V.N., Khalaf, V.A., Zaitseva, G.N.
   (2008) Analytical and Bioanalytical Chemistry, 391 (4) pp.1335-1342.
   A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO2) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol) (TX). Under static conditions phenol was quantitatively extracted onto TX-SiO2 in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO2 for phenol is 2.4 mg g-1 with distribution coefficients up to 3.4 × 104 mL g-1; corresponding data for 1-naphthol are 1.5 mg g-1 and 3 × 103 mL g-1. The distribution coefficient does not change significantly for solution volumes of 0.025-0.5 L and adsorbent mass less than 0.03 g; 1-90 μg analyte can be easily eluted by 1-3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A540) and phenol concentration (C) in water was found according to the equation A540 = (6 ± 1) × 10-2 + (0.9 ± 0.1)C (μmol L-1) with a detection range from 1 × 10-8 mol L-1 (0.9 μL g-1) to 2 × 10-7 mol L-1 (19 μL g-1), a limit of quantification of 1 μL g-1 (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical analysis. The detection limit of 1-naphthol with this method is 6 μL g-1 while the quantification limit is 20 μL g-1. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08-3.2 mL g-1.
3. Recovery of iodide ions from geothermal water with silica with grafted alkylammonium groups
   Trokhimenko, O.M., Anan'eva, V.V., Zaitsev, V.N., Gerda, V.I., Golub, A.A.
   (2008) Russian Journal of Applied Chemistry, 81 (3), pp. 403-406.
   Effect of a number of factors (time of contact and mass ratio of phases, acidity and temperature of the medium, concentrations of macrocomponents of geothermal water) on the sorption recovery of iodide ions with 3-(octadecyldimethylammonio)propylsilica and 3-(trimethylammonio)propylsilica from aqueous solutions was studied. Sorption isotherms were discussed. The possibility of using 3-(octadecyldimethylammonio)-propylsilica for recovery of iodide ions from highly mineralized geothermal water was analyzed.
4. Quantitative physicochemical analysis of equilibria on chemically modified silica surfaces.
   Y.V. Kholin, V.N. Zaitsev  
   Pure Appl. Chem., Vol. 80, No. 7, pp. 1561–1592, 2008. doi:10.1351/pac200880071561
   Quantitative physico-chemical analysis (QPCA) allows to determine the stoichiometric compositions and physicochemical parameters of species in equilibrium systems proceeding from the composition-property dependencies. The paper discusses modifications to the routine QPCA procedures required to characterize properties of reagents fixed on surfaces of silica-organic hybrid materials. The cooperative effects and the energetic heterogeneity of fixed reagents are especially important in this context. It follows that the main peculiarities of silica surfaces chemically modified by aliphatic amines are a) the pronounced energetic heterogeneity of reagents caused by the non-random surface topography, b) the decrease of the bacisity of amines induced by their interactions with residual surface silanols, and c) the expressed sensibility of reactions in the near-surface layer to the state of its hydration. The interaction of grafted organic bases with metal ions results in the preferred formation of bis metal-ligand complexes. Stability constants of complexes are decreased as a consequence of fixation and depend on not only donor but also acceptor ability of a solvent. Also, the denticity of polydentate ligands may decrease as a result of grafting. The changes of protolytic and complexing properties in the case of grafting of weak acids and phosphorus containing complexons are due to their interactions with another surface groups and the influence of hydration effects in the near-surface layer.
5. ВОЛЬТАМПЕРОМЕТРИЧЕСКИЕ ХАРАКТЕРИСТИКИ УГЛЕСИТАЛЛОВОГО ЭЛЕКТРОДА, МОДИФИЦИРОВАННОГО КОМПОЗИТНЫМ ПОКРЫТИЕМ НА ОСНОВЕ ОКСИДА СИЛИЦИЯ И ОРГАНИЧЕСКИХ ПОЛИЭЛЕКТРОЛИТОВ
   О. Ю. Наджафова, Т. С. Рожанчук, В. Н. Зайцев, В. В. Шевченко
   Укр.хим.журн., 2008, т.72, №1, с. 59-64.
   Исследованы вольтамперометрические (ВА) характеристики углеситаллового электрода (УЭ), модифицированного композитным покрытием на основе оксида силиция и органических полиэлектролитов (УЭ SiO2 – ПЭ) – полидиметилдиаллиламмоний хлорида (ПДМДА), а также катионоактивного олигоуретансемикарбазида разветвленного строения (ОУТС). Покрытие синтезировано по золь – гель технологии в присутствии неионогенных поверхностно- активных веществ (НПАВ). Наилучшими токопроводящими и массообменными свойствами обладает композитное покрытие, полученное в присутствии 0,15 моль/л НПАВ Tween 20 при объемном соотношении SiO2:ПДМДА:ОУТС=1:1:0,125. Модифицированный электрод активно сорбирует азо- краситель люмогаллион (ЛГ). Показана возможность дальнейшего использования УЭ SiO2 – ПЭ – ЛГ для ВА определения Mo (VI) в отсутствие Hg (II) без электрохимического накопления. Градуировочный график линеен в диапазоне концентраций Мо (VI) 2÷100 мкмоль/л.
6. Методи концентрування та визначення фенольних сполук (Огляд)
   В. М. Зайцев, В. А. Халаф, Г. М.
   Зайцева Методы и объекты химического анализа, 2008, т. 3, № 1, С. 4–21
   Розглянуто основні методи концентрування, розділення і детектування моно- та поліядерних фенольних сполук, а також їх хлор-, алкіл- та нітропохідних. Критично оцінено переваги та недоліки застосування існуючих твердофазних екстрагентів на основі карбону, полімерів і хімічно модифікованих кремнеземів при визначенні фенольних сполук у воді, ґрунті, біологічних рідинах та фармацевтичних препаратах.
   V.N. Zaitsev, V.A. Khalaf, G.N. Zaitseva.
   Methods of pre-concentration and determination of phenolic compounds (Review).
   Modern approaches used for pre-concentration, separation and detection of mono- and polynuclear phenolic compounds and their chloro-, alkyl- and nitroderivatives were overviewed. Main attention was given to determination of phenolic compounds in water, soil, biological liquids and pharmaceuticals after their preconcentration on carbon, organic polymers and on organo-mineral composite materials.
7. КОНДУКТОМЕТРИЧЕСКОЕ ОПРЕДЕЛЕНИЕ КОНЦЕНТРАЦИИ КИСЛОТНЫХ ЦЕНТРОВ НА ФУНКЦИОНАЛИЗИРОВАНЫХ МАТЕРИАЛАХ
   В.Н. Зайцев, Н.Г. Кобылинская, Л.С. Костенко, В.И. Герда
   Журн. аналит. химии, 2008, т. 63, №8, с.852-859.
   На примере органокремнеземов с иммобилизированными кислотными группами различного типа проведен сравнительный анализ методов кондуктометрического и рН-метрического титрований для определения концентрации кислотных групп. Показано, что метод кондуктометрии является перспективным для оценки энергетической неоднородности привитого слоя и содержания функциональных групп на поверхности органокремнеземов. Установлено, что метод рН-метрии применим, главным образом, для определения концентрации групп сильнокислотных органокремнеземов, а кондуктометрического титрования - для всех типов изученных материалов.
   Zaitsev, V.N., Kobylinskaya, N.G., Kostenko, L.S., Gerda, V.I.
   Conductometric determination of the concentration of acid centers on functionalized materials.
   Journal of Analytical Chemistry Volume 63, Issue 8, August 2008, Pages 779-786
   The potentialities of conductometric titration were investigated for the study of protolytically active groups using organosilicas with immobilized acid groups of different types as an example. The methods of conductometric and pH-metric titration were compared in determining the concentrations of these groups. It was found that pH metry was mainly applicable to the determination of strongly acid groups of organosilicas, whereas conductometric titration can be applied to the determination of all types of test materials. It was shown that conductometry is a promising method for estimating the energetic heterogeneity of the immobilized layer and the concentration of functional groups on the surface of organosilicas.
8. Sorption extraction coupled with atomic absorption spectrometry (SE-AAS) using silica modified with ethylendiamintriacetic acid for determination of Cu(II), Pb(II) and Cd(II) in Kiev artesian water.
   Pylypiuk N. M., Shevchenko N. V., Valkarius A., Zaitsev V. M.
   Вісник Харківського національного університету. 2008. № 820. Хімія. Вип. 16(39), с.91-97
   Kharkov University Bulletin. 2008. № 820. Chemical Series. Issue 16(39).
   Application of silica with covalently bonded groups of ethylendiamintriacetic acid (SG-ED3A) was offered as a solid-phase extracting agent for Cu(II), Pb(II) and Cd(II) dynamic pre-concentration in SE-AAS analysis of artesian water. Working in optimum conditions (using pH 5 for sorption extraction and 1% thiourea in 0.1 M HCl as an eluent solution) leads to 100-fold concentration of the ions and total recovery not less than 88% and 78% for Cu(II) and Pb(II) respectively. In such conditions SG-ED3A is of nonexpendable use. Studying the adsorption isotherm and the dependence of desorption rate versus pH revealed the adsorption of metal ions from the solution by forming ML and ML2 complexes with ED3A groups. The proposed method was approved by studying contents of Cu(II), Pb(II) and Cd(II) in artesian waters of Kiev 10 deep wells. It was fixed that concentrations of copper and lead were 150-300 and 10 times lower than their maximal exposure limits (MEL) correspondingly. In every sample, cadmium content was found to be lower then its MEL and limit of detection (LOD) of the proposed method.
9. Анионообменные свойства 3-(триметиламмоний)-пропилкремнезема В.Е. Самусева, В.Н. Зайцев, Трохименко О.М. Известия вузов. Химия и химическая технология.- 2008.- Т. 51, № 7.- С. 18-20.
10. Кремнезем з ковалентно закріпленими групами пропілтіоетиламіну як адсорбент для концентрування іонів золота (ІІІ) та паладію (ІІ) з хлоридних розчинів
    Зайцев В.М., Конопліцька О.П., Зайцева Г.М.
    Методы и объекты химического анализа, 2008, т. 3, № 2, С. 178-184.
    Вивчено оптимальні умови сорбції іонів золота (ІІІ) та паладію (ІІ) на кремнеземі з ковалентно закріпленими групами пропілтіоетиламіну (SiO2-SN). Показано, що зазначені іони в інтервалі рН 1,5–3 на 95±5% вилучаються SiO2-SN з хлоридних (СCl ≤ 0,1 M) розчинів вторинної переробки електронної сировини. Граничне значення кількісного вилучення металів на SiO2-SN становить 132 мг/г та 20 мг/г для золота та паладію відповідно. З фази адсорбенту метали можуть бути кількісно елюйовані 2–4 мл 10% розчину тіосечовини. Запропоновано сорбційно-атомно-абсорбційну методику визначення Au (III) та Pd (II) з технічних розчинів переробки електронних приладів (мікросхем, транзисторів) та спеціальних фармпрепаратів (Тауредон).
    V.M. Zaitsev, O.P.Konoplitska, G.M. Zaitseva.
    Silica with covalently immobilized groups of propylthioethyleamine as adsorbent for pre-concentration aurum (III) and palladium (II) ions from chlorhydric solutions – Optimal adsorption conditions of aurum (III) and palladium (II) ions by silica with immobilized propylthioethyleamine (SiO2-SN) were studied. It was demonstrated that mentioned ions can be selectively adsorbed on SiO2-SN at the pH range 1,5–3 with the recovery 95±5% from the chloride (СCl ≤ 0,1 M) solutions of repeated processing of electronic raw material. Boundary value of quantitative recovery of metal ions by SiO2-SN reached 132 mg·g-1 and 20 mg·g-1 for aurum and palladium ions respectively. The adsorbed metal ions can be quantitatively desorbed with 2–4 ml 10% solution of thiourea.Adsorption-atomic-absorbance method for determination of Au (III) and Pd (II) from technical solutions of processing of electronic devices (microcircuits, transistors) and special pharmaceuticals (Tauredon) was proposed.
11. Сорбційна здатність кремнеземів з прищепленими комплексоутворюючими групами до іонів Zn(II), Hg(II), Fe(III), Cu(II), Cd(II) та Pb(II)
    Рева Т., Зайцев В., Трохименко О.
    Методы и объекты химического анализа, 2008, т. 3, № 2, С. 202-207.
    T. Reva,V. Zaitsev, O.Trokhymenko.
    Adsorption properties of silicas with covalently attached complexing groups towards Zn(ІІ), Hg(ІІ), Fe(ІІІ), Cu(ІІ), Cd(ІІ) and Pb(ІІ) ions – Quantitative characteristics of silica-based adsorbents having covalently attached complexing groups in adsorption processes for some heavy metal ions have been studied.
    Ключові слова: кремнезем · прищеплені комплексоутворюючі групи · сорбція · концентрування Keywords: silica · attached complexing groups · sorption · concentration

Head of the laboratory of chemistry for organo-mineral materials Department of analytical chemistry Taras Shevchenko National University of Kyiv 60 Vladimirskaya Str., Kiev Ukraine 01601
tel: +380-97-0980693, e-mail: vnzaitsev@gmail.com, http://anchem.knu.ua/ua/main_ukr.html
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