Ion-exchange Solid-phase Research Articles

A performance comparison of photo-fenton decolorization of methylene blue by using bentonite/iron composites prepared by liquid phase and solid phase ion exchange method

Nowadays, there is a wide range of pollutants present, which requires the treatment of wastewater. The photo-Fenton method has been recognized as valuable in this area. In this study, iron/bentonite composites were created using both liquid phase and solid phase iron exchange techniques, and they were utilized as a photocatalyst for the degradation of methylene blue through photo-Fenton process. Various factors affecting the photocatalytic decolorization were investigated, including the initial concentration of the dye, weight of the catalyst, pH of the solution, and concentration of hydrogen peroxide. The decolorization efficiency of the iron/bentonite composites prepared using the solid phase and liquid phase ion exchange approaches was found to be 99% and 95%, respectively. Based on the data, it can be concluded that the performance of both catalysts was almost equally influenced by the initial dye concentration, catalyst weight, solution pH, and hydrogen peroxide concentration. Moreover, the solid phase ion exchange method demonstrated greater reusability compared to the liquid phase ion exchange method. Consequently, it can be stated that the solid phase ion exchange approach is a suitable and straightforward alternative to the conventional liquid phase ion exchange method for producing a photo-Fenton catalyst.

Phosphorus-doped MoS2 with sulfur vacancy defects for enhanced electrochemical water splitting

MoS2 is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability. However, the poor conductivity and low activity limit its catalytic performance; furthermore, MoS2 is unable to satisfy the requirements of most industrial applications. In this study, to obtain a P-doped MoS2 catalyst with S vacancy defects, P is inserted into the MoS2 matrix via a solid phase ion exchange at room temperature. The optimal P-doping amount is 11.4 wt%, and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with the corresponding overpotentials of 93 and 316 mV at 10 mA cm−2 in an alkaline solution; these values surpass the overpotentials of most previously reported MoS2-based materials. Theoretical calculations and results demonstrate that the synergistic effect of the doped P, which forms active centers in the basal plane of MoS2, and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst. Density functional theory calculations demonstrate that P optimizes the free energy of the MoS2 matrix for hydrogen adsorption, thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS2. The enhanced catalytic activity of P-doped MoS2 for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier. This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in large-scale applications.

Acidity tuning of HZSM-5 zeolite by neutralization titration for coke inhibition in supercritical catalytic cracking of n-dodecane

Reducing the acid density and strength of HZSM-5 zeolite are typical strategies to inhibit coke deposition during catalytic cracking reactions. Herein, direct titration of HZSM-5/H2O suspension using dilute NaOH aqueous solution at room temperature was introduced to neutralize excessive Brønsted acid sites of HZSM-5 zeolite (Si/Al = 25). SEM, XRD, N2 adsorption and n-propylamine temperature-programmed decomposition confirmed that simultaneous acid strength weakening and acid density reducing were achieved without obvious influence on crystalline or textural property. The evolution of the surface charge during the titration process tracked by Zeta-potential measurement reveals that the mechanism of such neutralization is: liquid phase neutralization between H+ and OH− & solid phase ion exchange between Na+ and H+. Supercritical catalytic cracking of n-dodecane over a series of partial neutralized HZSM-5 catalysts showed that moderate neutralization can enhance the conversion of n-dodecane by alleviating both the coke amount and harmfulness per unit mass of coke.

Применение метода твердофазного ионного обмена для насыщения наноионитов лекарственными средствами в отсутствие фонового электролита

В настоящее время актуальной является проблема разработки систем целевой доставки лекар-ственных средств с использованием наноразмерных носителей. В этой связи большой интерес прояв-ляется к полимерным материалам в силу их физических свойств, большой емкости по переносу ле-карств, биосовместимости и низкой токсичности. Наноразмерные иониты (НИО), полученные в виде устойчивых гидрозолей (катионных – НИК и анионных – НИА) по своим характеристикам имеют по-тенциал для использования в качестве доставщиков ионных форм лекарственных средствЦелью данной работы является описание способа получения чистых лекарственных форм на базе наноионитов методом твердофазного ионного обмена, который возможен только в случае, если одной фазой является макроионит, а другой – наноионит той же полярности.Способ проиллюстрирован на примере получения НИА в форме аниона ди-N-метилглюками-новой соли гадопентата (торговое название «Магневист») – контрастного агента при МРТ диагностике. Получение препарата целевой доставки актуально из-за потенциальной токсичности соединений гадо-линия.Было проведено независимое изучение твердофазного ионного обмена для систем с мак-роионитами. Эксперимент заключался в переносе определенного иона с одной анионообменной ко-лонки (1) в (Вr-) форме на другую, такую же, но в ОН-форме (2), методом пропускания наногидрозоля НИА известной концентрации через систему последовательно соединенных колонок. Контроль сте-пени переноса бромида осуществлялся путем измерения концентрации Вr-, смываемого с колонки 2 раствором натриевой щелочи после разъединения колонок. Бромид определяли хроматографически. Сведя баланс количества эквивалентов пропущенного НИА и смытого бромида, установили, что твер-дофазный ионный обмен прошел в полном объеме. Бромид полностью перенесен с колонки 1 на ко-лонку 2.Получив доказательство эффективности способа твердофазного ионного обмена, применили этот подход для получения частиц наногидрозоля НИА, нагруженных анионом [Gd-ДТПА]2-. Исполь-зовали макроанионит и НИА в солевых формах, так как комплекс гадолиния устойчив в нейтральных и слабокислых средах. Контроль полноты перевода АВ-17(Сl-) в форму [Gd-ДТПА]2– проводили мето-дом одновременного ионохроматографического определения обоих анионов в пробах, отбираемых на выходе из колонки. Далее переносили комплекс гадолиния в наногидрозоль (Вr-), пропуская НИА через колонку с макроанионитом в форме [Gd-ДТПА]2-. Таким образом, в процессе твердофазного ионного обмена насытили гидрозоль НИА анионом [Gd-ДТПА]2-, вытесняя бромид в фазу макро анионита. По-лученный методом твердофазного ионного обмена гидрозоль в форме [Gd-ДТПА]2- передан на испы-тание в РНИМУ им. Н.И. Пирогова.Благодаря возможностям твердофазного ионного обмена можно легко и быстро переводить наноиониты в ионную форму лекарственного средства, насыщать полистирольные наночастицы, не те-ряя при этом дорогостоящие компоненты в окружающем растворе. Отсутствие посторонних химиче-ских примесей в полученном препарате имеет первостепенное значение при его медицинском приме-нении, так как при этом сводятся к минимуму нежелательные побочные эффекты.

Влияние термообработки на формирование активных центров меди, полученных путем взаимодействия хлорида меди с H-морденитом

The heat treatment effect on the formation of catalytically active copper centers obtained by solid-phase ion exchange between copper chloride and zeolite H-Mordenite was studied using X-ray absorption spectroscopy in the near edge (XANES) and extended (EXAFS) regions beyonds the copper K-edge. The spectra were measured in reaction conditions, at temperatures ranging from room temperature to 400°C. The analysis of the spectra performed by direct calculations of Cu K-XANES and Cu K-EXAFS fitting with account for anharmonic corrections showed that up to 200 ° C ion exchange does not occurs and copper remains in the state of CuCl. The heating above 200 ° C result in implantation of copper atom in zeolite framework.

Nano Ion Exchangers as Modifiers of Chromatographic Phases and Sources of Analytical Signal

A method is developed for preparing of nanosized ion exchangers (nano ion exchangers, NIEX) as water-stable sols of a given ionic form of two types: nano cation exchangersand nano anion exchangers. According to their physicochemical properties, nano ion exchangers are simultaneously dissolved hypercharged ions and microscopic solid ion exchangers capable of solid-phase ion exchange. In chromatographic and other methods of analysis, can serve as modifiers of stationary and mobile phases, providing a high capacity of the first one and special buffer properties of the second one. Some results of using for the creation of polymodal phases for ion chromatography, as a modifier in capillary electrophoresis, and in a luminescence method for the determination of heavy metals (using copper as an example) in aqueous solutions are presented.

Determination of Amino Acids in Corn Seed by Gas Chromatography–Mass Spectrometry

A gas chromatography–mass spectrometry method was developed for the determination of free amino acids from corn inbred lines flour. Amino acids were extracted using 6% trichloroacetic acid. The extracts were purified using an ion-exchange solid phase, derivatized as trifluoroacetic butyl esters, and analyzed. The 15N-methionine was used as the internal standard. The method was repeatable for most of the amino acids (coefficient of variation was in the order of 20%), and good accuracy and limits of detection were obtained. Among the free amino acids determined, the highest concentrations were obtained for aspartic acid, proline, gamma-aminobutyric acid, lysine, alanine, glutamic acid, and histidine. The study established the variation of the free amino acids within the inbred lines.

Microscale analysis of amino acids using gas chromatography–mass spectrometry after methyl chloroformate derivatization

To conduct studies of stable isotope incorporation and dilution in growing plants, a rapid microscale method for determination of amino acid profiles from minute amounts of plant samples was developed. The method involves solid-phase ion exchange followed by derivatization and analysis by gas chromatography–mass spectrometry (GC–MS). The procedure allowed the eluent to be derivatized directly with methyl chloroformate without sample lyophilization or other evaporation procedures. Sample extraction and derivatization required only ca. 30 min and quantification of the 19 amino acids eluted from the cation exchange solid-phase extraction step from a single cotyledon (0.4 mg fresh weight) or three etiolated 7-day-old Arabidopsis seedlings (0.1 mg fresh weight) was easily accomplished in the selected ion monitoring mode. This method was especially useful for monitoring mass isotopic distribution of amino acids as illustrated by Arabidopsis seedlings that had been labeled with deuterium oxide and 15N salts. Sample preparation was facile, rapid, economical, and the method is easily modified for integration into robotic systems for analysis with large numbers of samples.

Kinetics of H+/Na+ solid-phase ion exchange on iron(III) hydrogen sulfate

The kinetics of solid-phase reaction between iron(III) hydrogen sulfate and sodium chloride was studied by thermal analysis followed by analysis of leaving gases. The exchange kinetics are described by the soft cylinder model. The hydrogen and sodium ion interdiffusion coefficients were determined for various temperatures, as well as the activation energy of interdiffusion. Sodium ion diffusion through the product layer is the rate-controlling stage of the reaction.

HEPATOPROLIFERIN A GROWTH FACTOR FROM HEPATOCYTES REVEALED THE STATUS OF A COMPLETE HEPATOMITOGEN

P667 Quiescent hepatocytes in liver regeneration need to be primed by factors such as TNF-α and IL-6. To reach competence, by entering into the cell cycle’s G1-phase, they also require the complete mitogens HGF, TGF-α and EGF. The latter together with the co-mitogen norephinephrin (NE) augment proliferation. For the hepatocytes to progress fully into DNA synthesis the replication of hepatocytes also require potentiating factors such as insulin. Termination of liver regeneration needs TGF-β and activin. Liver regeneration is controlled by two kinds of factors, viz. priming or initiating- (IFs) and progressing or potentiating factors (PFs). The IFs are thought to be paracrinal and organ specific, while the PFs are mainly endocrinal and originate from the blood or other organs. The PFs lack organ specificity. Rat hepatoproliferin (HPF) was purified to SDS-PAGE homogeneity into two active species of 14 and 18.5 kDa. In an AA sequencing attempt the two species were found to be molecular diverse containing only a few amino acids. Through several manipulations it became clear that HPF aggregate to larger molecular sizes (big-HPF). By using de-aggregating conditions HPF was purified to homogeneity as small-HPF with a mol size of 1.03 kDa. With solid-phase ion-exchange, we established that small-HPF was an ionic molecular complex; containing three catecholamines and one disulphonated disaccharide. The two ionic-species had exceptionally high affinity for each other and a large tendency to aggregate to 14, 30 and 62 kDa. The structure of the amine was elucidated by HPLC and EC detection; while that of the disaccharide by (i) DEAE-HPLC with ABEE derivatization and (ii) RP-HPLC with OPA derivatization. Radioactive tracing aided in elucidating some of the sub-structures. Separate the ionic-species had no bio-activity, but after recombination activity was restored. Aim: The aim of this study was to assess the mitogenic status of HPF in human cells. Methods: HPF which stimulates rat hepatocyte on its own was assessed for its ability to stimulate the human hepatoma cell line (PLC/PRF-5) towards replication. The ability of HPF, whether acting on its own as a complete mitogen, was determined by investigating its sole ability to stimulate the incorporation of 3H-TdR into DNA of PLC/PRF-5. The co-mitogenic potential of HPF was also determined by assessing its ability to augment DNA synthesis through combining it with TNF-α, TGF-α or EGF respectively. Results: The hepatoma cell line’s response to the latter growth factors (GFs) when used alone showed the same kind of response for all, namely a bi-phasic bell-shaped dose-dependent response i.e. stimulation at low levels and inhibition at higher levels. However, HPF showed only a linear dose-response at the levels used for GFs (i.e. 1.0 - 15 ng/5 x 105 cells). The hepatoma cells unexpectedly did not respond to HGF at any level tested (0.5 – 6 ng/5 x 105 cells), although it is 10 x more potent than the other complete mitogens. Also the inhibition of cell proliferation by TGF-β started only at 15 ng/5 x 105 cells. Conclusion: Since HPF was able to stimulate DNA synthesis on its own, we conclude that HPF was a complete mitogen for human hepatoma cells. HPF did not act as a co-mitogen since it did not cause an augmentation when combined with the said GFs but showed instead an additive effect on DNA synthesis when used with some of these complete mitogens.

Effect of preparation of a CsX zeolite catalyst on the oxidative conversion of methane

The catalytic performance considering methane dimerization, thermal behaviour and basicity of CsX catalysts prepared by different methods have been studied. Conventional ion exchange, solid phase ion exchange and impregnation are utilized as methods for preparation of the CsX zeolite catalysts investigated. Different relationships between the catalytic, thermal and basic properties depending on the mode of preparation have been found. Both impregnated and solid phase ion exchanged samples create suitable basicity for higher C 2-selectivity and C 2-yield of these samples, as compared to the ion exchanged.

Rapid Purification of Tubulin from Tissue and Tissue Culture Cells Using Solid-Phase Ion Exchange

Tubulin can be purified from tissue or tissue culture cell starting material in less than 6 h using a combination of a solid-phase ion exchanger and one cycle of temperature-dependent polymerization and depolymerization. The use of a solid-phase ion exchanger (MemSep DEAE) greatly reduces the time required for the ion exchange step compared to conventional exchangers. The use of sodium glutamate to elute tubulin from the exchanger stabilizes the protein and facilitates the final polymerization step of the purification. The procedure can be performed successfully with less than 100 mg of tissue culture cell protein as starting material. The final material is >90% pure and active as judged by sodium dodecyl sulfate-gels and by binding of the bicyclic colchicine analog 2-methoxy-5-(2′,3′,4′-trimethoxyphenyl)-tropone.

Gas chromatographic-mass spectrometric determination of isotopic enrichment of 6- 15NH 2 in adenine nucleotides

A gas chromatographic-mass spectrometric method for the determination of isotopic abundance in [6- 15NH 2]adenine nucleotides is described. The method involves formation of the di-t-butyldimethylsilyl (TBDMS) derivative of adenine following isolation of the nucleotide fraction with solid-phase ion-exchange chromatography and subsequent acid hydrolysis of nucleotides to free base. Mass spectra for both adenine-diTBDMS and [6- 15NH 2]adenine-diTBDMS were obtained to identify those ions containing the 6-NH 2 moiety. The base peak ( m z 306) was formed by loss of C 4H 9 (57) and constitutes approximately one-third of the total ion current. Using selected ion monitoring of the m z 306/ m/z 307 ratio, levels of isotopic abundance of 1.0–50.0 mol% excess could be measured reproducibly with the injection of 10–20 pmol of the adenine-diTBDMS derivative obtained from isolated rat hepatocytes. Confirmation that measured isotopic abundance was referable to labeling of the 6- 15NH 2 group was obtained by oxidation of adenine to hypoxanthine and determination of enrichment in the hypoxanthine-diTBDMS derivative. The method was used to study the formation of [6- 15NH 2]adenine nucleotides during the incubation of isolated rat hepatocytes with [ 15N]alanine. A level of approximately 6.0 mol% excess was observed at 60 min incubation.