Biomimetic study of the Ca2+-Mg2+ and K+-Li+ antagonism on biologically active sites: new methodology to study potential dependent ion exchange

2009 ◽  
Vol 22 (1) ◽  
pp. 10-20 ◽  
Author(s):  
Beata Paczosa-Bator ◽  
Milena Stepien ◽  
Magdalena Maj-Zurawska ◽  
Andrzej Lewenstam
Keyword(s):  
Ion Exchange ◽  
Active Sites ◽  
Biologically Active

scholarly journals Ultrasound-Assisted Preparation of Mo/ZSM-5 Zeolite Catalyst for Non-Oxidative Methane Dehydroaromatization

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 313
Author(s):  
Heidy Ramirez-Mendoza ◽  
Mafalda Valdez Lancinha Pereira ◽  
Tom Van Gerven ◽  
Cécile Lutz ◽  
Ignacio Julian
Keyword(s):  
Catalytic Activity ◽  
Ion Exchange ◽  
Active Sites ◽  
Chemical Properties ◽  
Successful Implementation ◽  
Metal Dispersion ◽  
Zeolite Framework ◽  
Dispersed Catalysts ◽  
Methane Dehydroaromatization ◽  
Ultrasound Assisted

The activity and selectivity of Mo/ZSM-5, benchmarking catalyst for the non-oxidative dehydroaromatization of methane, strongly depend on the cluster size, spatial distribution, and chemical environment of the Mo-based active sites. This study discloses the use of an ultrasound-assisted ion-exchange (US-IE) technique as an alternative Mo/ZSM-5 synthesis procedure in order to promote metal dispersion along the zeolite framework. For this purpose, a plate transducer (91.8 kHz) is employed to transmit the ultrasonic irradiation (US) into the ion-exchange reactor. The physico-chemical properties and catalytic activity of samples prepared under the said irradiation procedure and traditional impregnation (IWI) method are critically evaluated. Characterization results suggest that US neither affects the crystalline structure nor the particle size of the parent zeolite. However, US-IE promotes molybdenum species dispersion, avoids clustering at the external fresh zeolite surface and enhances molybdate species anchoring to the zeolite framework with respect to IWI. Despite the improved metal dispersion, the catalytic activity between catalysts synthesized by US-IE and IWI is comparable. This suggests that the sole initial dispersion enhancement does not suffice to boost the catalyst productivity and further actions such ZSM-5 support and catalyst pre-conditioning are required. Nevertheless, the successful implementation of US-IE and the resulting metal dispersion enhancement pave the way toward the application of this technique to the synthesis of other dispersed catalysts and materials of interest.

scholarly journals ADSORBATIVE SEPARATION OF DOXYCYCLINE FROM AQUEOUS SOLUTION WITH N,N-DIETHYL N-METHYL CHITOSAN, GUM AND POLYACRYLIC ACID BASED HYDROGELS

2021 ◽  
Vol 11 (07) ◽  
pp. 44-53
Author(s):  
Mirvari Hasanova Mirvari Hasanova
Keyword(s):  
Aqueous Solution ◽  
Ion Exchange ◽  
Zeta Potential ◽  
Polyacrylic Acid ◽  
Inorganic Materials ◽  
Biologically Active ◽  
Cross Linking ◽  
Separation And Purification ◽  
Inorganic Substances ◽  
The Cross

The separation and purification of antibiotics with sorption by ion-exchange materials, as well as their delivery in biological processes by immobilization, are now widely used in biotechnology. There are many scientific studies in the literature on the sorption of antibiotics by polymer-based sorbents and inorganic materials, as well as the study of thermodynamics and kinetics of the process. In the literature, the acquisition of biologically active systems from the sorption of antibiotics by ion-exchange fibers based on various polymers and inorganic substances was carried out. However, the synthesis of selective gels for the effective separation of doxycycline and its delivery in different pH mediums by sorption with biodegradable, biocompatible polysaccharide-containing composites is one of the topical issues. Gel was synthesized from the cross-linking of N,N-diethyl N-methyl derivative of a natural polyaminosaccharide of chitosan by glutaric aldehyde. Also, pH-sensitive hydrogels that can swollen in water were synthesized from the cross-linking of a graft copolymer of cherry source gummiarabic with N-vinylpyrrolidone, as well as synthetic polymer polyacrylic acid with N,N-methylene-bis-acrylamide. The structure of the gels were identified by FTIR and NMR spectroscopy, and the sorption of doxycycline antibiotic from an aqueous solution was investigated. According to the values of zeta potential, the protonation of functional groups in the main macromolecule in an acidic medium leads to a value of zeta potential of 40÷80 mV on the surface of chitosan-based gel and others. Although the chemical structure is different, the isoelectric point is set around pH=6÷8 for all three hydrogels. The dependences of the sorption process on the amount of gels, antibiotic concentration, temperature, and pH medium were studied. The experimental data were analyzed using two adsorption models, Langmuir and Freundlich, with the later system providing the best fit. Doxycycline is adsorbed on the surface of chitosan, gummiarabic and polyacrylic acid based hydrogel composite through by physical interactions. Also, the results of thermodynamic parameters ΔG40 kJ/mol show that the nature of the adsorption process is physical, and spontaneous, too. Keywords: Chitosan, Gummiarabic-arabinogalactane, polyacrylic acid, hydrogel, sorption isoterms, doxycycline, thermodynamica.

scholarly journals Modified ion exchange jackfruit seeds resin for removal of selected trace heavy metal ions from aqueous solution

2021 ◽  
Vol 2 (2) ◽  
pp. 84-92
Author(s):  
S N Ndung’u ◽  
E W Nthiga ◽  
R N Wanjau
Keyword(s):  
Heavy Metal ◽  
Ion Exchange ◽  
Metal Ions ◽  
Heavy Metal Ions ◽  
Active Sites ◽  
Ion Exchange Resin ◽  
Standard Entropy ◽  
Environmentally Sustainable ◽  
Heavy Metal Ions Removal ◽  
Metal Ions Removal

Water is essential for every life processes. However, its quality is deteriorating every day due to the recent industrial advancements. Anthropogenic processes such as industrialization, mining and agricultural activities have led to alarming discharge of heavy metal ions to the aquatic bodies. This possess a greater threat to human, animal and the entire ecosystem wellbeing. Accumulation of heavy metal ions in drinking water beyond permissible limits is detrimental to human health. Therefore, their removal is paramount. Conventional remediation techniques have been employed but have remained expensive and not universally appropriate. This has therefore spurred research interests in the use of adsorption techniques from locally available materials as an environmentally sustainable alternative. Jackfruit seeds are discarded as wastes of a Jackfruit and can be utilized as an ion exchange resin in heavy metal ions removal from wastewater. The present study involved application of previously prepared raw and modified Jackfruit seed resins to study thermodynamics of copper (II), lead (II) and cadmium (II) ions adsorption from synthetic water. FTIR results showed presence of functional groups in raw and modified resins as important sites for studying thermodynamics of adsorption of copper (II), lead (II) and cadmium (II) ions. Thermodynamic data showed that standard Gibb’s free energy () values for all metals were negative indicating that adsorption process was feasible and favourable. Standard enthalpy change (), standard entropy () and activation energy () were positive (> 40 kJ mol-1) and in the order lead (II) > copper (II) > cadmium (II). This confirmed adsorption of copper (II), lead (II) and cadmium (II) ions onto both raw and modified resins was predominated by chemical interactions between the metal ions and the resin active sites. This was confirmed by very low values of sticking probability (S*). The findings indicated that ion exchange Jackfruit seeds resin is promising for heavy metal ions removal from wastewater in an optimized temperature controlled system.

Identification of active sites and reaction mechanism on low-temperature SCR activity over Cu-SSZ-13 catalysts prepared by different methods

2016 ◽  
Vol 6 (16) ◽  
pp. 6294-6304 ◽  
Author(s):  
Tao Zhang ◽  
Feng Qiu ◽  
Huazhen Chang ◽  
Xiang Li ◽  
Junhua Li
Keyword(s):  
Aqueous Solution ◽  
Reaction Mechanism ◽  
Low Temperature ◽  
Ion Exchange ◽  
Active Sites ◽  
One Pot ◽  
One Pot Synthesis ◽  
Low Temperature Scr

Cu-SSZ-13 catalysts with similar Si/Al and Cu/Al ratios were prepared by aqueous solution ion-exchange (Cu-SSZ-13-I) and one-pot synthesis (Cu-SSZ-13-O) methods.

scholarly journals Properties of Iron-Modified-by-Silver Supported on Mordenite as Catalysts for NOx Reduction

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1156 ◽  
Author(s):  
Perla Sánchez-López ◽  
Yulia Kotolevich ◽  
Evgeny Khramov ◽  
Ramesh Kumar Chowdari ◽  
Miguel Angel Estrada ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Bimetallic Catalysts ◽  
Active Sites ◽  
Nox Reduction ◽  
The State ◽  
Edge Structure ◽  
X Ray ◽  
Disordered Phase ◽  
Activity Test ◽  
X Ray Absorption

A series of mono and bimetallic catalysts based on a Fe-Ag mixture deposited on mordenite was prepared by ion-exchange and evaluated in the catalytic activity test of the de-NOx reaction in the presence of CO/C3H6. The activity results showed that the most active samples were the Fe-containing ones, and at high temperatures, a co-promoter effect of Ag on the activity of Fe catalysts was also observed. The influence of the order of cation deposition on catalysts formation and their physicochemical properties was studied by FTIR (Fourier Transform Infrared Spectroscopy) of adsorbed NO, XANES (X-ray Absorption Near-Edge Structure), and EXAFS (Extended X-ray Absorption Fine Structure) and discussed in terms of the state of iron. Results of Fe K-edge XANES oscillations showed that, in FeMOR catalysts, iron was present in a disordered state as Fe3+ and Fe2+. In FeAgMOR, the prevailing species was Fe3+, while in the AgFeMOR catalyst, the state of iron was intermediate or mixed between FeMOR and FeAgMOR. The Fe K-edge EXAFS results were characteristic of a disordered phase, the first coordination sphere being asymmetric with two different Fe-O distances. In FeAgMOR and AgFeMOR, coordination of Fe-O was similar to Fe2O3 with a few amount of Fe2+ species. We may conclude that, in the bimetallic FeAgMOR and AgFeMOR samples, a certain amount of tetrahedral Al3+ ions in the mordenite framework is replaced by Fe3+ ions, confirming the previous reports that these species are active sites for the de-NOx reaction. Based on the thermodynamic analysis and experimental data, also, it was confirmed that the order of deposition of the components influenced the mechanism of active sites’ formation during the two steps ion-exchange synthesis.

Obtaining Biologically Active Polypropylene Fibrous Materials

2020 ◽  
Vol 992 ◽  
pp. 764-769
Author(s):  
Sergey Bordunov ◽  
Olga Galtseva ◽  
Inna Plotnikova
Keyword(s):  
Ion Exchange ◽  
Biologically Active ◽  
Polymer Fibers ◽  
Polypropylene Fibers ◽  
Fibrous Materials ◽  
Centrifugal Forces ◽  
Polypropylene Melt ◽  
Die Forming

The paper presents the results of the development of the technology of centrifugal-die forming of biologically active fibrous materials. The modification of biologically active polypropylene fibers was carried out directly at the process of their production in the field of centrifugal forces of rotating reactor during their molding from polypropylene melt. The properties of the obtained ion-exchange and biologically active polymer fibers are studied. It is shown that obtained and modified by the centrifugal-die method polypropylene fibers can be used as biologically active fibers.

scholarly journals Analysis of alkaloids from different chemical groups by different liquid chromatography methods

2012 ◽  
Vol 10 (3) ◽  
pp. 802-835 ◽  
Author(s):  
Anna Petruczynik
Keyword(s):  
Liquid Chromatography ◽  
Ion Exchange ◽  
Chromatographic Separation ◽  
Mobile Phase ◽  
Stationary Phases ◽  
Biologically Active ◽  
System Efficiency ◽  
Bonded Stationary Phases ◽  
Silica Alumina ◽  
Chemical Groups

AbstractAlkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids — basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds. In this article we present an overview on the separation of selected alkaloids from different chemical groups by liquid chromatography thus indicating the range of useful methods now available for alkaloid analysis. Different selectivity, system efficiency and peaks shape may be achieved in different LC methods separations by use of alternative stationary phases: silica, alumina, chemically bonded stationary phases, cation exchange phases, or by varying nonaqueous or aqueous mobile phase (containing different modifier, different buffers at different pH, ion-pairing or silanol blocker reagents). Developments in TLC (NP and RP systems), HPLC (NP, RP, HILIC, ion-exchange) are presented and the advantages of each method for alkaloids analysis are discussed.

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