Search results for "Medium"
showing 10 items of 3746 documents
Inorganic Mercury Sequestration by a Poly(ethylene imine) Dendrimer in Aqueous Solution
2015
The interaction of the G-2 poly(ethylene imine) dendrimer L, derived from ammonia as initiating core, with Hg(II) and HgCl4 2− was studied in aqueous solution by means of potentiometric (pH-metric) measurements. Speciation of these complex systems showed that L is able to form a wide variety of complexes including 1:1, 2:1, 3:1 and 3:2 metal-to-ligand species, of different protonation states, as well as the anion complexes ((H7L)HgCl4) 5+ and ((H8L)HgCl4) 6+ . The stability of the metal complexes is very high, making L an excellent sequestering agent for Hg(II), over a large pH range, and a promising ligand for the preparation of functionalized activated carbons to be employed in the remedi…
Sulphate removal over barium-modified blast-furnace-slag geopolymer
2016
Blast-furnace slag and metakaolin were geopolymerised, modified with barium or treated with a combination of these methods in order to obtain an efficient SO4(2-) sorbent for mine water treatment. Of prepared materials, barium-modified blast-furnace slag geopolymer (Ba-BFS-GP) exhibited the highest SO4(2-) maximum sorption capacity (up to 119mgg(-1)) and it compared also favourably to materials reported in the literature. Therefore, Ba-BFS-GP was selected for further studies and the factors affecting to the sorption efficiency were assessed. Several isotherms were applied to describe the experimental results of Ba-BFS-GP and the Sips model showed the best fit. Kinetic studies showed that th…
Phosphorus-Chalcogen Ring Expansion and Metal Coordination
2017
The reactivity of 4-membered (RPCh)2 rings (Ch = S, Se) that contain phosphorus in the +3 oxidation state is reported. These compounds undergo ring expansion to (RPCh)3 with the addition of a Lewis base. The 6-membered rings were found to be more stable than the 4-membered precursors, and the mechanism of their formation was investigated experimentally and by density functional theory calculations. The computational work identified two plausible mechanisms involving a phosphinidene chalcogenide intermediate, either as a free species or stabilized by a suitable base. Both the 4- and 6-membered rings were found to react with coinage metals, giving the same products: (RPCh)3 rings bound to the…
Decomposition Process of Carboxylate MOF HKUST-1 Unveiled at the Atomic Scale Level
2016
HKUST-1 is a metal-organic framework (MOF) which plays a significant role both in applicative and basic fields of research, thanks to its outstanding properties of adsorption and catalysis but also because it is a reference material for the study of many general properties of MOFs. Its metallic group comprises a pair of Cu2+ ions chelated by four carboxylate bridges, forming a structure known as paddle-wheel unit, which is the heart of the material. However, previous studies have well established that the paddle-wheel is incline to hydrolysis. In fact, the prolonged exposure of the material to moisture promotes the hydrolysis of Cu-O bonds in the paddle-wheels, so breaking the crystalline n…
From 1D coordination polymers to Metal Organic Frameworks by the use of 2-pyridyl oximes.
2020
The synthesis and characterization of coordination polymers and metal&ndash
Polymorphism and Metallic Behavior in BEDT-TTF Radical Salts with Polycyano Anions
2012
Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd2− (=C[C(CN)2]32−), two closely related radical salts: α'-(ET)4tcpd·THF (1) (THF = tetrahydrofurane) and α'-(ET)4tcpd·H2O (2) have been prepared, depending on the solvent used in the synthesis. With the mono-anion tcnoetOH− (=[(NC)2CC(OCH2CH2OH)C(CN)2]−) two polymorphs with similar physical properties but different crystal packings have been synthesized: θ-(ET)2(tcnoetOH) (3) and β''-(ET)2(tcnoetOH) (4). Finally, with the mono-anion tcnoprOH− (=[(NC)2CC(OCH2CH2CH2OH)C(CN)2]−) we have prepared a metallic…
Modelling the dependence on medium and ionic strength of molybdate acidbase properties, and its interactions with phytate
2016
The importance of molybdenum from a biological, environmental and technological point of view is very well known since many decades [15]. In particular, it is mainly present in aqueous solutions as molybdate (MoO42), which is the biologically active form, entering in the cells by active transport systems. Though molybdate is the major species in neutral to basic pH conditions, at lower pH it undergoes protonation and, chiefly, polymerization, even at millimolar concentration levels [2]. Consequently, the modelling of its speciation and acidbase properties is not very simple, as demonstrated by the nonhomogeneity of available literature data. In this light, our group has started a systematic…
Hydration process and rheological properties of cement pastes modified by orthophosphate addition
2005
Abstract The use of cement by nuclear industry for confining low radioactive waste knows a constant increase. The interest bore to this material is due to its mechanical and chemical properties. However, these properties may be modified by the nature and the amount of wastes introduced with the mixing solution especially with large amount of phosphate. Precipitation of hydroxylapatite in the cement paste at the very beginning after mixing was emphasized from a particular concentration of orthophosphate. It was also found that this phenomenon leads to an early rigidification of the cement paste. From a kinetics point of view, the evolution of hydration was both delayed and slowed down accord…
Comparisons of processing and strength properties of two adhesive systems for composite joints
2007
Abstract In the present study rheological, static and impact tests are carried out on two adhesive resins usually employed in marine applications; then single lap joint tests are conducted on composites joints evidencing the effect of the curing time of both resins on the mechanical properties of the joint. The applicability and workability conditions of the adhesive resins are determined evaluating the curing evolution by a preliminary rheological analysis; then the relation of curing properties with the mechanical performances of the resins themselves and with ones of the composite joints is estimated. Static flexural and Izod impact tests are performed on the resins at increasing time af…
Case series of fluoroscopic findings and 3D reconstruction of human spinal MRIs of the space of Okada.
2020
Objective To better understand the unexpected spread of contrast medium observed by conventional fluoroscopic X-ray images during standard neuraxial techniques used in the treatment of pain. The support of 3D reconstruction of MRI images of structures within the lumbar spine was used to better understand the space of Okada. Methods Lumbar facet joint and epidural corticosteroid injections in five patients under fluoroscopic guidance with loss of resistance to air or saline to identify the facet joints or epidural space. Next, in a retrospective study, the authors examined the retrodural space of Okada and the neighboring tissues with 3D reconstruction of spinal MRIs of seven patients withou…