Influence of the Titanium Dioxide Addition in Matrix Formulation on the Radwaste-Mortar Matrix Characteristics

1995 ◽  
Vol 412 ◽  
Author(s):  
Aleksandar D. Perić
Keyword(s):  
Titanium Dioxide ◽  
Mechanical Strength ◽  
Chemical Properties ◽  
High Water ◽  
Matrix Formulation ◽  
Leach Rate ◽  
Physico Chemical ◽  
The Matrix ◽  
Ph Range ◽  
Mortar Matrix

AbstractThe rutile form of titanium dioxide (TiO2) was added to mortar matrix preparations with the objective to improve the mechanical and physico-chemical characteristics of the radwaste-mortar matrix mixtures, in particular the leach-rate of the immobilized radionuclide. The final solidified radwaste form was made with high water-to-cement ratio (0.36) for easy leaching of the immobilized radionuclide, 37Cs. TiO2was added to the mortar formulation, replacing the appropriate amount of cement, in the amounts of 1,2,5,8 and 10 weight percents of total cement weight. In the highly basic environment of the mortar (pH ≅ 12), the titanium will form a HTiO-type membrane, which is semi-permeable and selective for the cations like Cs+ in the pH range above 5.5. Only the rutile form of TiO2was observed in the prospected radwastemortar mixture samples, using X-ray Fluorescence Spectrometry. Nevertheless, 137Cs leach-rate for the matrix formulations prepared with TiO2 was notably lower than the normally prepared (TiO2 free) samples. Furthermore, the mechanical strength of the samples prepared with TiO2 was higher than that of the TiO 2-free samples, and the correlation between the mechanical strength and TiO2 content appears to be exponential over the composition range explored here. Improvement of the physico-chemical properties of the titanium prepared formulations, is a topic of further investigations.

Influence of Aggressive Liquid Environment on the Physico-Chemical and Mechanical Characteristics of Mortar-Radwaste Mixture Form

1994 ◽  
Vol 353 ◽  
Author(s):  
Aleksandar D Perić ◽  
Ilija B Plećaš ◽  
Radojko S Pavlović
Keyword(s):  
Mechanical Strength ◽  
Mechanical Characteristics ◽  
Ph Value ◽  
Matrix Material ◽  
Liquid Environment ◽  
Leach Rate ◽  
Physico Chemical ◽  
Water To Cement Ratio ◽  
The Matrix ◽  
Leaching Experiments

AbstractMortar was used as a matrix material in an immobilization process of radioactive waste material, 137CsCl solution, where the final product had a water-to-cement ratio of 0.36. Solidified orthocylinder shaped samples, H=4.5 cm, with the exposed surface area completely open to contact leachant medium, were used in prospecting physico-chemical and mechanical characteristics of mortar-radwaste mixture forms. After curing period of 28 days in an atmosphere of defined parameters, samples were introduced to leaching in the specific leachant media. Leachants were chosen up to their aggressive influence on matrix material deterioration and decomposition: distilled water, chloride and sulphate solutions. Experiments were performed for 730 days and the 137Cs cumulative leached fraction for each leachant was calculated. Leach-rate steady-state values were obtained after approximately 290 days. The same trend in obtaining saturation value was noticed in an investigations of pH value and Ca2+ concentration in the three groups of leachants, due to a Ca2+ depletion from the matrix structure. Mortar-radwaste mixture samples were withdrawn from the leaching experiments and investigated on their mechanical strength. Mechanical strength characteristics adopted a decreasing trend for the samples treated in leachants longer than 100 days, which continued in the two years period of experimental duration.

scholarly journals Groundwater physico-chemical properties and water quality changes in shallow aquifers in arid saline wetlands, Ouargla, Algeria

2021 ◽  
Vol 11 (5) ◽  
Author(s):  
Fethi Medjani ◽  
Mohamed Djidel ◽  
Sofiane Labar ◽  
Louiza Bouchagoura ◽  
Chouaib Rezzag Bara
Keyword(s):  
Water Quality ◽  
Chemical Properties ◽  
High Water ◽  
Quality Changes ◽  
Shallow Aquifers ◽  
Shallow Water Table ◽  
Chemical Mechanisms ◽  
Desert Region ◽  
Physico Chemical ◽  
Hypersaline Water

AbstractShallow aquifers are vulnerable to natural geogenic processes as well as anthropogenic influences, and this is especially apparent in desert regions. Within arid and hyperarid climates, evaporation is a controlling hydrologic process leads to an important increase in the concentration of dissolved minerals of both surface water and groundwater. In groundwater, this increase is not only dependent on shallow water table depth, but also on the hydraulic properties of sediments present within the unsaturated zone of the aquifer itself. The main objective of this research is to investigate possible mechanisms that might influence water quality changes under seasonal conditions in shallow aquifers situated within the Saharan desert region of Algeria. In this work, we focus on observed changes in hydrogeochemical characteristics, and the possible responsible processes. Under arid conditions, high water mineralization results in hypersaline water or brine solution formation within shallow aquifers. Due to active physico-chemical mechanisms such as Na+/Ca2+ ion exchange, the successive precipitation of calcite, gypsum, mirabilite or blœdite and halite is induced. Biological processes were also observed as prevalent; evidenced by large measured variations in CO2 load concentrations. These processes contributed to an inverse relationship between CO2 and O2 concentrations within the shallow aquifers studied.

scholarly journals Influence of hydrotalcite preparation conditions on its physico-chemical properties

2019 ◽  
Vol 12 (1) ◽  
pp. 119-126
Author(s):  
Miroslava Mališová ◽  
Michal Horňáček ◽  
Pavol Hudec ◽  
Jozef Mikulec ◽  
Vladimír Jorík ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Chemical Properties ◽  
Synthesis Temperature ◽  
Optimal Synthesis ◽  
Preparation Process ◽  
Optimal Conditions ◽  
Temperature Range ◽  
Preparation Conditions ◽  
Physico Chemical ◽  
Ph Range

Abstract The aim of the research was to prepare and characterize hydrotalcite synthesized under different preparation conditions. The most common hydrotalcite preparation is the co-precipiaton method. The preparation process strongly influences the catalytic properties of hydrotalcite; therefore, optimal conditions have to be determined. During the study, seven samples of the catalyst were prepared in the pH range from 8 to 12 and the synthesis temperature range from 25 to 55 °C. Based on several catalyst properties, optimal synthesis pH 10 was found. Ideal temperature of the preparation was determined to be 35 °C, but the temperature does not have a significant effect on the catalyst properties.

scholarly journals Sterculia Gum: Chemical Structure, Composition and Physico-Chemical Properties

2019 ◽  
Vol 32 (1) ◽  
pp. 1-8
Author(s):  
N. Sharma ◽  
T. Sinderpal
Keyword(s):  
Drug Delivery ◽  
Wound Healing ◽  
Chemical Properties ◽  
High Water ◽  
Molecular Organization ◽  
Water Retention Capacity ◽  
Molecular Architecture ◽  
Retention Capacity ◽  
Gelling Agents ◽  
Physico Chemical

Physico-chemical properties are crucial characteristics of hydrocolloids as they decide the applicability of them. Rheology of system, flow behaviour and mechanical properties make hydrocolloids suitable for food industry. Modification of consistency or texture properties of functional polymers also controls their sensory characteristics, thereby they become significant essences such as thickener, gelling agents, foaming agent, texture modifier, viscosifier, emulsifier, stabilizer and binder. Industrial and pharmaceutical applications are also controlled by some suitable physico-chemical properties of hydrocolloids. The polysaccharide gum exudates constitute a architecturally distinct class of complex biomacromolecules having unique physico-chemical properties. Due to their good bio/tissue compatibility, non-toxicity, they are extensively used in the field of tissue engineering, drug delivery and wound healing. Chemical and molecular architecture of hydrocolloids in turn controls their physico-chemical and functional properties. Sterculia gum is a substituted rhamnogalacturonoglycan (pectic) type exudate gum used as suspending agent, gelling agents, emulsifier, bulk laxative, dental adhesive, drug delivery agent and wound healing agent. It exhibits high water retention capacity, high viscosity and least solubility. Solutions of sterculia gum are viscoelastic and thixotropic. Sterculia gum has been recommended as effective wound dressing material as it can form a intensely adhesive gel when dispersed in minimum ammount of water. Owing to wide applications and distinctive properties of sterculia gum, present work is an endeavor to summarize the molecular organization, chemical configuration and physico-chemical properties of sterculia gum and the factors affecting physico-chemical properties of sterculia gum.

Characterization of Solidified Radioactive Waste Due to the Incorporation of High-and Low-Density Polyethylene Granules and Titanium Dioxide in Mortar Matrices

1996 ◽  
Vol 465 ◽  
Author(s):  
Aleksandar Perić
Keyword(s):  
Titanium Dioxide ◽  
Radioactive Waste ◽  
Average Diameter ◽  
Weight Percent ◽  
Low Density Polyethylene ◽  
Accelerated Ageing ◽  
Low Density ◽  
Leach Rate ◽  
Leaching Experiments ◽  
Mortar Matrix

ABSTRACTThe rutile form of titanium dioxide (TiO2) and granules of high density polyethylene (PEHD) and low density polyethylene (PELD) were used to prepare mortar matrices for immobilization of radioactive waste materials containing ‘137Cs. PELD,PEHD and TiO2 were added to mortar matrix preparations with the objective of improving physico-chemical characteristics of the radwaste-mortar matrix mixtures, in particular the leach-rate of the immobilized radionuclide. The diameters of the PELD and PEHD used varied from 0.2 to 2.0 mm. One type of PELD and two types of PEHD were used to replace 50 weight percent of stone granules, average diameter of 2 mm, normally used in the matrix, in order to decrease the porosity and density of the mortar matrix and to avoid segregation of the stone particles at the bottom of the immobilized radioactive waste cylindrical form. TiO2 was also added to the mortar formulation, replacing 5 and 8 weight percent of the total cement weight, for each PEHD and PELD formulation. Cured samples were investigated under temperature stress conditions, where the temperature extremes were: Tmill = -20°C,Tmax= +70°C. Samples were periodically immersed in distilled water at the ambient room temperature, after each freezing and heating treatment. Results of accelerated leaching experiments for these samples and samples prepared exclusively with polyethylenes replacing 100 percents of the stone granules and TiO2, treated in nonaccelerated leaching experiments, were compared. Even using an accelerated ageing leach test that overestimates 137Cs leach rates, it can be deduced, that radionuclide leach rates from the radioactive waste mortar mixture forms were improved. Leach rates decreased from 5 percent, for the material prepared with stone aggregate, to 3.1 to 4.0 percent, for the materials prepared solely with PEHD, PELD or TiO2, and to about 3 percents for all six types of the TiO2-PEHD and TiO2-PELD mixtures tested.

scholarly journals Physico-Chemical Properties of a Hybrid Biomaterial (Pva/Chitosan) Reinforced With Conductive Fillers

2021 ◽  
Author(s):  
A. Olarte ◽  
J.N. Salgado ◽  
E. Rubio ◽  
R. Salgado ◽  
H. Hernandez ◽  
...  
Keyword(s):  
Morphological Analysis ◽  
Conductive Polymer ◽  
Chemical Properties ◽  
Nyquist Diagram ◽  
Multi Wall Carbon Nanotubes ◽  
Tension Tests ◽  
Physico Chemical ◽  
The Matrix ◽  
Conductive Fillers ◽  
Polymer Fillers

A novel hybrid material based on Polyvinyl alcohol-Chitosan (PVA-Cs) was made, reinforced with conductive polymer fillers such as polypyrrole (PPy), Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), carbon black (CB) and multi-wall carbon nanotubes (MW CNT). Our proposal is to use these fillers, which have not been studied in this context before, for obtaining composite materials, and to characterize them for the development of applications in microelectronics. FTIR analysis made evident the different func-tional groups present in the matrix and the fillers used. The use of quaternary mixtures (4 fillers) increased the contact angle, which increased the degree of hydrophobicity of the biocomposite. The Nyquist diagram of the analyzed samples showed a decrease in resistance and energy diffu-sion; the latter due to the transfer of electrons caused by the conductive polymers CB and the MWCNT. In the mechanical tension tests, Young's modulus values of 18.386 MPa were obtained, in contrast with the material matrix of PVA-Cs, which showed values of 11.628 MPa. Further-more, morphological analysis by SEM showed that the materials obtained were homogeneous, with no phase formation. The materials obtained showed higher electrical conductivity in the presence of the OH and NH2 groups, which could have possible applications in biopolymer elec-trodes.

Contribution of Soil Physical Propreties in The Assessment of Flood Risks in Tropical Areas. Case of The Mbo Plain

2021 ◽  
Author(s):  
Sylvie Noelle DJUKEM FENGUIA ◽  
David Guimolaire Nkouathio
Keyword(s):  
Chemical Properties ◽  
Infiltration Rate ◽  
High Water ◽  
Soil Samples ◽  
High Water Content ◽  
Predisposing Factor ◽  
Undisturbed Soil ◽  
Flood Risks ◽  
Physico Chemical ◽  
Permeable Soil

Abstract Flooding occurs when water is in excess and can no longer be evacuated normally. The nature of the soil has been identified as one of the major causes of flooding, hence this study aimed is to show the influence of the physico-chemical properties of the soil on the recurrence of flooding in the Mbo plain. Four soil profiles were carried out on the alluviums according to the altitudes. These profiles were described and undisturbed soil samples were taken. Then, measurements of the infiltration rate of water in the soil by the Porchet method were carried out in sixteen sites. Finally, soil samples taken by auger and core sampling were studied in the laboratory. Physico-chemical parameters such as grain size, porosity, moisture, pH, compactness and organic matter were determined. Infiltration tests carried out in situ using the Porchet method revealed a hydraulic conductivity between 10−5 and 10−7 m/s, characteristic of a semi-permeable soil. This low value of permeability results from the morpho-structural arrangement and the chemical composition of the soils of the plain. These soils are hydromorphic, which means that they are constantly flooded and temporarily waterlogged. They are more or less sandy-clay on the surface, and very clayey at depth, generally from 25 cm. The very clayey soils at the base considerably slow down infiltration and act as a real barrier layer that prevents water from infiltrating, resulting to intense runoff. These soils are very porous and compact with a fairly high water content of up to 71%. This work allows us to conclude on the role of intrinsic soil properties on the genesis of floods in lowland areas. As in many plains in Africa and in the world, the nature of the soil in the Mbo plain is a natural predisposing factor to flood risks. The methods used can be applied in areas with the same characteristics as the Mbo Plain.

scholarly journals Studies on vaccinia haemagglutinin: I. Some physico-chemical properties

1948 ◽  
Vol 46 (1) ◽  
pp. 42-48 ◽  
Author(s):  
C. M. Chu
Keyword(s):  
Chick Embryo ◽  
Chemical Properties ◽  
Rabbit Skin ◽  
Physico Chemical ◽  
Haemagglutinating Activity ◽  
Ph Range

1. Specific vaccinia haemagglutinin has been identified in vaccinia materials derived from chick embryo, rabbit skin, rabbit testis and sheep skin.2. The haemagglutinin is distinct from, and apparently unassociated with, the elementary bodies.3. Centrifugation studies indicate that the haemagglutinin activity is associated with particles of the order of 65 μ in diameter and having an approximate density value of 1·;1.4. Vaccinia haemagglutinin retains its haemagglutinating activity after boiling for 10 min. It is stable within the pH range 5·92–9·79.5. The behaviour of vaccinia haemagglutinin to various chemical procedures and an attempt at its purification are described.

scholarly journals Physico-Chemical Properties of a Hybrid Biomaterial (PVA/Chitosan) Reinforced with Conductive Fillers

2021 ◽  
Vol 11 (7) ◽  
pp. 3040
Author(s):  
A. Olarte-Paredes ◽  
J.N. Salgado-Delgado ◽  
E. Rubio-Rosas ◽  
A.M. Salgado-Delgado ◽  
H. Hernández-Cocoletzi ◽  
...  
Keyword(s):  
Morphological Analysis ◽  
Chemical Properties ◽  
Ftir Analysis ◽  
Mechanical Tension ◽  
Nyquist Diagram ◽  
Energy Diffusion ◽  
Tension Tests ◽  
Physico Chemical ◽  
The Matrix ◽  
Conductive Fillers

In this study, a novel hybrid material based on Polyvinyl Alcohol-Chitosan (PVA-Chi) was made, reinforced with conductive fillers such as the polypyrrole (PPy), Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS), carbon black (CB), and multi-wall carbon nanotube (MWCNT). In order to observe the mechanical and electrical responses of this composite material, for obtaining composite materials, and to characterize them for the development of applications in engineering, FTIR analysis made clear the different functional groups present in the matrix and the fillers used. Using quaternary mixtures (4 fillers) increased the contact angle, which increased hydrophobicity of the biocomposite. The Nyquist diagram of the analyzed samples showed a decrease in resistance and energy diffusion; the latter because of transferring electrons caused by the conductive polymers CB and the MWCNT. In the mechanical tension tests, Young’s modulus values of 18.386 MPa were obtained, in contrast with the material matrix of PVA-Chi, which showed values of 11.628 MPa. Morphological analysis by SEM showed the materials got were homogeneous. The materials got showed higher electrical conductivity in the OH’s presence and NH2 groups, which could have possible applications in biopolymer electrodes.

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