Speciation and Chemical Reactions of Phosphonate Chelating Agents in Aqueous Media

2002 ◽  
pp. 59-94 ◽  
Author(s):  
A. T. Stone ◽  
M. A. Knight ◽  
B. Nowack
Keyword(s):  
Chemical Reactions ◽  
Chelating Agents ◽  
Aqueous Media

scholarly journals A Bio-logical Approach to Catalysis in the Pharmaceutical Industry

2020 ◽  
Vol 74 (5) ◽  
pp. 407-417
Author(s):  
Greg Mann ◽  
Frédéric V. Stanger
Keyword(s):  
Drug Discovery ◽  
Pharmaceutical Industry ◽  
Chemical Reactions ◽  
Chemical Process ◽  
Chemical Space ◽  
Aqueous Media ◽  
Complex Chemical ◽  
Environmentally Sustainable ◽  
Mild Conditions ◽  
Complex Chemical Reactions

Enzymes have the potential to catalyse complex chemical reactions with unprecedented selectivity, under mild conditions in aqueous media. Accordingly, there is serious interest from the pharmaceutical industry to utilize enzymes as biocatalysts to produce medicines in an environmentally sustainable and economic manner. Prominent advances in the field of biotechnology have transformed this potential into a reality. Using modern protein engineering techniques, in a matter of months it is possible to evolve an enzyme, which fits the demands of a chemical process, or even to catalyse entirely novel chemistry. Consequently, biocatalysis is routinely applied throughout the pharmaceutical industry for a variety of applications, ranging from the manufacture of large volumes of high value blockbuster drugs to expanding the chemical space available for drug discovery.

Extraction of U(VI) from aqueous media by layer double hydroxides intercalated by chelating agents

2013 ◽  
Vol 35 (3) ◽  
pp. 104-111 ◽  
Author(s):  
A. A. Kosorukov ◽  
G. N. Pshinko ◽  
L. N. Puzyrnaya ◽  
S. A. Kobets
Keyword(s):  
Chelating Agents ◽  
Aqueous Media ◽  
Layer Double Hydroxides ◽  
Double Hydroxides

Capillary electrophoresis study of iron(II) and iron(III) polyaminocarboxylate complex speciation

2011 ◽  
Vol 8 (3) ◽  
pp. 295 ◽  
Author(s):  
Jessica M. Wilson ◽  
Richard F. Carbonaro
Keyword(s):  
Capillary Electrophoresis ◽  
Chelating Agents ◽  
Aqueous Media ◽  
Background Electrolyte ◽  
Chelating Agent ◽  
Iron Cycling ◽  
Iron Species ◽  
New Methods ◽  
Peak Broadening ◽  
Oxidation By Molecular Oxygen

Environmental contextMethods for determining iron species are integral to investigations of iron cycling processes in the environment. Capillary electrophoresis is an effective tool for determining the concentrations of various iron species in solution, but the separations are highly dependent on the electrolyte composition. This study reports the use of capillary electrophoresis to separate and quantify distinct FeII and FeIII complexes with polyaminocarboxylates. AbstractThe purpose of this study was to use capillary electrophoresis to (i) separate and quantify distinct FeII and FeIII complexes with polyaminocarboxylates and (ii) develop new methods for distinguishing between FeII and FeIII in aqueous media. A 25 mM phosphate and a 50 mM 3-(N-morpholino)propanesulfonic acid (MOPS) background electrolyte (BGE), both buffered at pH 7.1, were each tested with 6 polyaminocarboxylate complexes with FeII and FeIII. Adequate separation of all FeIII-chelating agent complexes was observed with the MOPS BGE. With the phosphate BGE, sharp peaks were obtained for FeIII complexes with EDTA, HEDTA, DTPA and CDTA, however FeIII–EGTA showed excessive peak broadening, and FeIII–TMDTA showed no discernable peak. Mobilities of FeIII–EGTA, FeIII–EDTA and FeIII–HEDTA were much larger when the phosphate BGE was employed, providing evidence for ternary complex formation with phosphate during electromigration. For FeII, complexes with TMDTA and EGTA were adequately separated with either BGE, but separations of the other chelating agents resulted in their corresponding FeIII complexes due to rapid oxidation by molecular oxygen. These chelating agents may be used as preservatives and derivatising agents for the analysis of ferrous and ferric iron in environmental samples.

scholarly journals Fabrication of a metal free catalyst for chemical reactions through decoration of chitosan with ionic liquid terminated dendritic moiety

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Samahe Sadjadi ◽  
Fatemeh Koohestani ◽  
Majid M. Heravi
Keyword(s):  
Ionic Liquid ◽  
Catalytic Activity ◽  
High Activity ◽  
Functional Groups ◽  
Chemical Reactions ◽  
Knoevenagel Condensation ◽  
Aqueous Media ◽  
Metal Free ◽  
Xanthene Derivatives ◽  
Mapping Analysis

AbstractIn attempt to develop a biocompatible metal-free catalyst, a dendritic moiety was grown on chitosan through successive reactions with 2,4,6-trichloro-1,3,5-triazine and ethylenediamine. Subsequently, the terminal functional groups of the dendron were decorated with 1-methylimidazolium chloride. The catalyst was characterized with SEM, EDS, TGA, FTIR, XRD and mapping analysis. Then, the catalytic activity of the resultant composite was scrutinized for catalyzing Knoevenagel condensation and synthesis of xanthene derivatives in aqueous media under mild reaction condition. The results confirmed high activity of the catalyst, superior to ionic liquid free counterpart and bare chitosan. This observation was ascribed to the instinct catalytic activity of ionic liquid. Moreover, using control catalysts, it was confirmed that the presence of the dendritic moiety that could increase the content of ionic liquid on the backbone of the catalyst enhanced the catalytic activity.

scholarly journals Layered Double Hydroxides as Effective Adsorbents for U(VI) and Toxic Heavy Metals Removal from Aqueous Media

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
G. N. Pshinko
Keyword(s):  
Heavy Metals ◽  
Layered Double Hydroxides ◽  
Chelating Agents ◽  
Ethylenediaminetetraacetic Acid ◽  
Aqueous Media ◽  
Water Soluble ◽  
Toxic Heavy Metals ◽  
Metals Removal ◽  
The Stability ◽  
Double Hydroxides

Capacities of different synthesized Zn,Al-hydrotalcite-like adsorbents, including the initial carbonate [Zn4Al2(OH)12]·CO3·8H2O and its forms intercalated with chelating agents (ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and hexamethylenediaminetetraacetic acid (HMDTA)) and heat-treated form Zn4Al2O7, to adsorb uranium(VI) and ions of toxic heavy metals have been compared. Metal sorption capacities of hydrotalcite-like adsorbents have been shown to correlate with the stability of their complexes with the mentioned chelating agents in a solution. The synthesized layered double hydroxides (LDHs) containing chelating agents in the interlayer space are rather efficient for sorption purification of aqueous media free from U(VI) irrespective of its forms of natural abundance (including water-soluble bi- and tricarbonate forms) and from heavy metal ions. [Zn4Al2(OH)12]·EDTA·nH2O is recommended for practical application as one of the most efficient and inexpensive synthetic adsorbents designed for recovery of both cationic and particularly important anionic forms of U(VI) and other heavy metals from aqueous media. Carbonate forms of LDHs turned out to be most efficient for recovery of Cu(II) from aqueous media withpH0≥7owing to precipitation of Cu(II) basic carbonates and Cu(II) hydroxides. Chromate ions are efficiently adsorbed from water only by calcinated forms of LDHs.

Surface reactions observed by photoemission electron microscopy (PEEM)

1992 ◽  
Vol 50 (1) ◽  
pp. 286-287
Author(s):  
H.H. Rotermund
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Work Function ◽  
Chemical Reactions ◽  
Reaction Diffusion ◽  
Dynamic Processes ◽  
Clean Surface ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

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