Stability of Mineral Matter in Aqueous Media of the Chernobyl Unit-4 Shelter: Thermodynamic Evaluation

1996 ◽  
Vol 465 ◽  
Author(s):  
V. A. Sinitsyn ◽  
D. A. Kulik ◽  
M. Skhodorivski ◽  
V. A. Kurepin ◽  
A. Y. Abramis ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Compositional Data ◽  
Aqueous Media ◽  
Oxidation Products ◽  
Programming Approach ◽  
Mineral Matter ◽  
Aqueous Environment ◽  
Thermodynamic Evaluation ◽  
Portland Cements ◽  
Geochemical Environment

ABSTRACTA special geochemical environment exists within the Shelter (”Sarcophagus”) erected in 1986 over the destroyed Unit-4 of Chernobyl nuclear power plant (NPP). Based upon the available in situ and compositional data, thermodynamic models of solid-aqueous interactions were developed to clarify the leaching behaviour of various materials within the Shelter. The “Selektor-A” code, based on a convex programming approach to Gibbs free energy minimization, was used for the calculations. A built-in flexible hybrid thermodynamic database for the system Na-K-Ca-Mg-Cl-S-N-H-O-Si-P-Fe-Al-Sr-Cs was extended with the critically selected and matched parameters for aqueous species and solid phases in the U-Zr-Si-O-H subsystem, secondary U-minerals, mineral phases of fully hydrated Portland cements and U-bearing zircons. Modeling results show that the “Shelter waters” can selectively leach a significant quantity of U and Si from the fuel-containing masses, while Zr, Fe, Ca, Mg and some other components are rather insoluble. Serpentinite, assemblages of fully-hydrated phases of Portland cements, and oxidation products of steel structural elements are estimated to be sufficiently stable in the aqueous environment of the Shelter. Our calculations also define some feasible pathways for secondary mineral formation from evaporation of Shelter water solutions and interactions between these waters with the mineral matter inside the Shelter.

Molecularly Imprinted Polymers for Selective Adsorption of Cholesterol from Aqueous Environment

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Francesco Puoci ◽  
Francesca Iemma ◽  
Giuseppe Cirillo ◽  
Sonia Trombino ◽  
Roberta Cassano ◽  
...  
Keyword(s):  
Molecularly Imprinted Polymers ◽  
Selective Adsorption ◽  
Aqueous Media ◽  
Aqueous Environment ◽  
Polar Solvents ◽  
Molecularly Imprinted ◽  
Imprinted Polymers ◽  
Bond Forming ◽  
Preparation And Evaluation ◽  
Templating Effect

AbstractIn this work the preparation and evaluation of molecularly imprinted polymers (MIPs) based on 2-hydroxyethylmetacrylate (HEMA) for selective recovery of cholesterol from aqueous media are reported. HEMA was used as functional monomer in order to maximize the hydrogen bond forming both in prepolymerization complex and in rebinding experiments which were performed in polar solvents; in particular, an acetonitrile:water (7:3 v/v) mixture was employed. The templating effect is clearly seen in the capacity of the synthesized polymers to bind cholesterol, and their selectivity was evaluated using two steroids quite similar to cholesterol such as progesterone and hydrocortisone which are less effectively bound by the matrices.

Efficient removal of diuretic hydrochlorothiazide from water by electro-Fenton process using BDD anode: a kinetic and degradation pathway study

2019 ◽  
Vol 16 (8) ◽  
pp. 613 ◽  
Author(s):  
Hélène Monteil ◽  
Nihal Oturan ◽  
Yoan Péchaud ◽  
Mehmet A. Oturan
Keyword(s):  
Electrochemical Oxidation ◽  
Oxidation Reaction ◽  
Oxidation Process ◽  
Aqueous Media ◽  
Degradation Pathway ◽  
Constant Current ◽  
Gas Chromatography Mass Spectrometry ◽  
Aqueous Environment ◽  
Fenton Process ◽  
Kinetic Rate Constant

Environmental contextHydrochlorothiazide, a common diuretic pharmaceutical, occurs in environmental waters because current treatment technologies are unable to eliminate it from wastewater. To remove this environmentally hazardous chemical from water, we developed an advanced electrochemical oxidation process to efficiently degrade and mineralise the compound. Wider application of the process holds the promise of general, efficient destruction of pharmaceuticals in aqueous media. AbstractThe degradation and the mineralisation of the diuretic hydrochlorothiazide were studied by an advanced electrochemical oxidation process, ‘electro-Fenton’, which generates in situ hydroxyl radicals that are able to successfully oxidise or mineralise organic pollutants. In this study, a 0.1mM (29.8mgL−1) hydrochlorothiazide solution was completely oxidatively degraded in 15min under constant current electrolysis at 500 mA. The absolute kinetic rate constant of the oxidation reaction was also determined as (4.37±0.04)×109M−1s−1. The quasi-complete mineralisation of the solution was obtained with electrolysis for 6h under the same applied current. Several oxidation reaction intermediates were identified using gas chromatography-mass spectrometry (GC-MS). The formed carboxylic acids during the mineralisation process were also studied; oxamic, oxalic, acetic and maleic acids were identified and their concentrations were monitored throughout the electrolysis. The ions released during the treatment were also considered. Based on these data and the total organic carbon (TOC) removal results, a possible mineralisation pathway was proposed. These findings enable the conclusion that the electro-Fenton process is an efficient and environmentally-friendly method to eliminate the hazardous drug hydrochlorothiazide from an aqueous environment.

A photo-oxidation of croconic acid into oxalic acid

1995 ◽  
Vol 73 (8) ◽  
pp. 1298-1304 ◽  
Author(s):  
Paul-Louis Fabre ◽  
Paule Castan ◽  
Diane Deguenon ◽  
Nicole Paillous
Keyword(s):  
Nmr Spectroscopy ◽  
Oxalic Acid ◽  
Electrochemical Oxidation ◽  
Oxidation Process ◽  
Aqueous Media ◽  
Oxidation Products ◽  
Acid Oxidation ◽  
Experimental Conditions ◽  
Photo Oxidation ◽  
C Nmr

Croconic acid, H2C5O5, is readily oxidized. This may be attested by decolorization of the solutions and by observation of oxalic acid complexes. The oxidation products are identified by 13C NMR spectroscopy as oxalic and mesoxalic acids, and experimental conditions are specified. The oxidation process requires dioxygen and photons. In parallel, the electrochemical oxidation of croconic acid is studied in aqueous media and in acetonitrile. A potential–pH diagram is drawn. Keywords: croconic acid, oxalic acid, oxidation, electrochemistry, photochemistry.

Solidification of Microbiologically Treated Ion-Exchange Resins Using Portland Cement-Based Systems

1992 ◽  
Vol 294 ◽  
Author(s):  
Ari Ipatti
Keyword(s):  
Ion Exchange ◽  
Portland Cement ◽  
Nuclear Power ◽  
Setting Time ◽  
Waste Product ◽  
Ion Exchange Resins ◽  
Portland Cements ◽  
Solidified Waste ◽  
Exchange Resins ◽  
Microbiological Treatment

ABSTRACTPretreated inactive ion exchange resins from the Loviisa nuclear power plant (NPP) were first reduced to one tenth of the original volume through microbiological treatment. During the process, the granular ion exchange resins were decomposed to result in dregs, which were solidified with two types of Portland cements. The objective of the present experiments was to investigate whether commercial cements are suitable solidification agents for this kind of waste.A total of ten mixtures were pretested for their rheological and setting properties. On the basis of the pretest results, four additional mixtures were chosen and tested for the spread value, density, air content, setting time and bleeding of the fresh waste product and for the dimensional stability and compressive strength of the hardened waste product. The cementing systems incorporated in the tests were ASTM type V Portland cement and ASTM type P Portland Composite cements. The dregs used in the tests were taken from a Pilot-Plant experiment at the Loviisa NPP and contained 2 wt-% solids.The test results were promising in showing that microbiological dregs can very easily be solidified with Portland cements to form a high-quality waste product. Thus, the microbiological treatment of spent ion exchange resins will drastically decrease the amount of solidified waste to be disposed of at the Loviisa NPP.

Traversing Phase Fields towards Nanosized Beta Tricalcium Phosphate

2013 ◽  
Vol 587 ◽  
pp. 97-100 ◽  
Author(s):  
Kārlis Gross ◽  
Juris Andersons ◽  
Martynas Misevicius ◽  
Janis Švirksts
Keyword(s):  
Tricalcium Phosphate ◽  
Alternative Pathway ◽  
Aqueous Media ◽  
Aqueous Environment ◽  
X Ray Diffraction ◽  
Apatite Phase ◽  
X Ray ◽  
Beta Tricalcium Phosphate ◽  
Phase Fields ◽  
Different Temperatures

The difficulty of beta tricalcium phosphate (β-TCP) crystallization in aqueous media opens the question whether β-TCP can be produced using an alternative pathway. Amorphous calcium phosphate (ACP) is metastable in an aqueous environment and prefers a more stable apatite phase. Others have transformed a crystallized calcium deficient hydroxyapatite (Ca-def HAp) into β-TCP, but automatic transformation from ACP to Ca-def HAp followed by transformation to β-TCP has not been addressed. This work shows the formation of Ca-def HAp after different aging times of ACP and the subsequent transition to β-TCP. An amorphous phase with a Ca/P ratio of 1.5 was synthesized, rinsed, filtered and excess fluid removed for maturation. The resulting apatite was monitored with X-ray diffraction at different temperatures. Heating at 700 °C then investigated the transition to β-TCP. It was found that Ca-def HAp formed at short aging times produced a combination of alpha and beta phases, but a longer aging time led to pure β-TCP.

Application of Zinc Sulfide Quantum Dots for Optical Sensing

2019 ◽  
Vol 806 ◽  
pp. 186-191
Author(s):  
Alexander A. Sergeev ◽  
Andrey A. Leonov ◽  
Anna N. Galkina ◽  
Sergey S. Voznesenskiy
Keyword(s):  
Quantum Dots ◽  
Zinc Sulfide ◽  
Optical Sensing ◽  
Aqueous Media ◽  
Sensory Systems ◽  
Sensory Characteristics ◽  
Sensory Response ◽  
Aqueous Environment ◽  
Environment Monitoring

The luminescent sensory systems based on manganese-doped zinc sulfide quantum dots were developed for aqueous environment monitoring. The structural, optical and sensory characteristics of quantum dots were investigated. The mechanism of ZnS:Mn2+ interaction with methane in the aqueous media, as well as factors that have a primary influence on the formation of the sensory response in the reaction with methane, were determined.

scholarly journals Iron-based magnetic molecular imprinted polymers and their application in removal and determination of di- n -pentyl phthalate in aqueous media

2017 ◽  
Vol 4 (8) ◽  
pp. 170672 ◽  
Author(s):  
Jing Li ◽  
Qingxiang Zhou ◽  
Yongyong Yuan ◽  
Yalin Wu
Keyword(s):  
Limit Of Detection ◽  
Solid Phase ◽  
Physical Adsorption ◽  
Aqueous Media ◽  
Aqueous Environment ◽  
Chromatography Method ◽  
Molecular Imprinted Polymers ◽  
Imprinted Polymers ◽  
Iron Based

Iron-based magnetic molecular imprinted polymers (Fe@SiO 2 @MIP) were synthesized for highly selective removal and recognition of di- n -pentyl phthalate (DnPP) from water. Well-defined core-shell Fe@SiO 2 nanoparticles (less than 70 nm) were decorated on MIPs reticular layers to endow DnPP-MIPs with magnetic property for the first time. Five other phthalic acid esters including dimethyl phthalate, diethyl phthalate, dipropyl phthalate, di- n -butyl phthalate and di-iso-octyl phthalate were used to investigate the adsorptive selectivity to DnPP. The designed experiments were carried out to explore the adsorption kinetics, isotherms and thermodynamics and the results demonstrated that the adsorption was a spontaneous, exothermal and physical adsorption process. The materials were proved to be excellent adsorbents in removal of DnPP with an adsorption capacity as high as 194.15 mg g −1 in optimal condition. Furthermore, a magnetic solid phase extraction with Fe@SiO 2 @MIP coupled to high-performance liquid chromatography method was successfully developed for the determination of DnPP, and the proposed method achieved a good linear range of 0.5–250 µg l −1 with a correlation coefficient ( R 2 ) of 0.999 and low limit of detection (LOD) of 0.31 µg l −1 . These materials exhibited excellent capacity in removal and highly sensitive identification of DnPP from aqueous environment samples, and opened a valuable direction for developing new adsorbents for the removal and enrichment of important pollutants.

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