Evolution of the earth pressure coefficient of carbonate sand undergoing varying rate of dissolution

In fluid-saturated granular materials, the physicochemical interaction between pore-fluids and grain minerals alters packing conditions, which in turn leads to stress change deformation and, in extreme cases, even collapse. Chemical weathering, either naturally occurring or induced by human activities, is among such natural processes. This article presents an experimental study illustrating the major effects of chemical weathering on the deformation and stress state of granular materials, emphasising particulate systems entirely made by highly soluble carbonate grains. Laboratory experiments are conducted by subjecting acidic environments to granular assemblies under oedometric condition. The reaction rate is controlled by regulating various testing parameters, such as acid concentration and pore fluid flow rate. Experiments revealed that the lateral earth pressure steadily reduces in some cases, while others exhibit non-monotonic evolution. From a macroscopic standpoint, the rate of the chemical reaction was critical to determine the emergence of either of these trends. Such findings are relevant for any particulate system in which the stress conditions are controlled by multi-physical processes proceeding at different rates, such as waste products within bioreactors, gouge materials within faults and natural deposits subjected to the injection/extraction of reactive fluids.

Tensiometry as a Simple Analytical Method for Quantification of Solubility and Release of Aroma Molecules in Aqueous Media

Dynamic tensiometry is shown to be a high-potential analytical tool in assessing physico-chemical characteristics of fragrance molecules, such as solubility limit, volatility as well as much rarely assessed interfacial activity of these amphiphilic molecules. Surface tension of aqueous solutions of selected essential oils has been measured as a function of time and fragrance concentration using maximum bubble pressure method. The effect of the temperature and saline solution on the rate of dissolution in water was assessed. Dynamic surface tension turned to be sensitive to the composition of fragrances, as demonstrated on examples of natural and synthetic mixtures. Furthermore, presented work reveals the possibility of maximum bubble pressure tensiometry method to quantify the amount of fragrance compositions in flavored salts, including the artificially aged carrier samples. Suggested here analytical approach can be used for the detection of the purity of essential oils, for the optimization of compositions and of the manufacturing processes of fragrances-containing products, as well as for the assessment of the release/evaporation of fragrances from carrier systems.

SYNTHESIS OF COCRYSTALS OF BETULIN WITH SUBERIC ACID AND STUDY OF THEIR PROPERTIES

Lupane triterpenoids, betulin and its derivatives, are attracting great interest due to their wide range of biological and pharmacological activities. However, the poor solubility of betulin and its derivatives in aqueous media significantly reduces their bioavailability. Obtaining cocrystals, that is, multicomponent crystal systems containing active pharmaceutical ingredients and non-toxic partner molecules in their structure, is used in pharmacy to change the physicochemical properties of drugs, including the rate of dissolution and solubility. In this study, cocrystals of betulin with suberic acid were obtained by liquid-assisted grinding method using organic solvents of different polarity: ethanol, acetone, ethyl acetate, chloroform, toluene, dioxane. The formation of cocrystals was confirmed by X-ray diffraction analysis, IR spectroscopy, and thermal analysis. It has been shown that cocrystals of betulin with suberic acid contain water molecules in their structure; anhydrous cocrystals can be obtained by heating a physical mixture of reagents until the acid melts. The results of experiments on the dissolution of cocrystals of betulin with suberic acid in comparison with the data for cocrystals of betulin with adipic acid showed that an increase in the length of the aliphatic acid chain leads to a decrease in the rate of betulin release into solution.

Micro-Fabric Transformations of Ball Clay in Alkaline Environment

Based on the strong evidence of case histories, this study focused on mineralogical and morphological changes of an artificial kaolinitic soil -Ball clay, when exposed to different concentrations of sodium hydroxide (0.1N, 1N, 4N, and 8N) under different curing periods (7, 28 and 100 days). Sediment volume tests are conducted on Ball clay with all combinations and results are analyzed with the help of analytical techniques. XRD and SEM studies are analyzed to understand the micro-level changes of alkali contaminated Ball clay. Mineralogical and morphological transmutations of Ball clay are investigated for 7, 28, and 100 days curing period. Results revealed new mineral formations like Sodalite under 4N and 8N concentrations of NaOH with 100 days interactions are well observed. The morphological transformation from needle shape to pellet shape is clear evidence of the rate of dissolution and precipitation of minerals under 100 days curing periods.

Formulation and evaluation of fast dissolving tablets of captopril

Oral administration is the most popular route for systemic effects due to its ease of ingestion, pain, avoidance, versatility and most importantly, patient compliance. The development of enhanced oral protein delivery technology by mouth dissolving Tablets which may release these drugs in the mouth are very promising for the delivery of high molecular weight protein and peptide. Good mouth feel property of MDDS helps to change the basic view of medication as “bitter pill”, particularly for pediatric patients. To prepare mouth dissolving tablet using SSG & CCM by using Antihypertensive as model drug. Captopril is a potent, competitive inhibitor of angiotensin-converting enzyme and it is a key component of the renin-angiotensin-aldosterone system. The ƛmax of Captopril was determined by scanning the 10µg / ml solution of drug using UV-Spectrophotometer and was found to be 271nm. The linear correlation was found to be 0.9995.The Fast dissolving tablets of captopril were prepared by direct compression method. Captopril can be successfully formulated as mouth dissolving tablets using various super disintegrate in different concentrations by direct compression method. The formulation containing 10% of crospovidone as super disintegrated was found to be outstanding than other formulations in terms of disintegration time and rate of dissolution.

Influence of the textural and structural functions of the Urals carnallite rocks on the kinetics of dissolution processes

В статье показана необходимость исследования кинетики процессов растворения карналлитовых пород Приуралья. Описана методика подготовки образцов и лабораторного изучения скорости растворения. Представлены данные о химическом составе образцов 4-х цветовых разностей карналлитовых пород, текстурно-структурных особенностей, результатов по определению скорости растворения и вещественного состава нерастворимого в воде остатка. Цель исследования заключалась в изучении скорости и процессов растворения в воде при температуре 500С в режиме вынужденной конвекции и оценке влияния текстурно-структурных особенностей карналлитовых пород. Задачами исследования являлись: определение солевого и минерального составов, изучениеструктуры и микровключений в шлифах, проведение экспериментов по кинетикерастворения. При решении поставленных задач использовались следующие методы: АЭС-спектрометрия, петрографический анализ, гидростатический метод, РКФА. Проанализирован фактический материал исследования, сделаны соответствующие выводы. Проведенными исследованиями было показано, что важными факторами, влияющими на кинетику процессов растворения, являются вещественный состав и текстурно-структурные свойства. В работе определена суммарная (массовая) скорость растворения образцов. Железооксидная пленка, оконтуривающая зерна карналлитовых пород, экранирует поверхность растворения, замедляя процесс диффузии. Наличие галита и неравномерное его содержание вызывает колебания скорости растворения изамедляет процесс растворения во времени. Микровключения газов положительно влияют на динамику процесса растворения, усиливая конвекцию и массоперенос. С увеличением гидродинамических параметров растворителя (плотности и вязкости) скорость растворения понижается. Установленные закономерности могут оказывать существенное влияние на процессы, происходящие при скважинной добыче (подземное растворение) и галургической переработке карналлитовых руд. The article shows the need to study the kinetics of the dissolution processes of carnallite rocks of the Permian deposits of the Urals. The technique of preparation of samples, laboratory study of the rate of dissolution in water is described. The data on the chemical composition of samples of 4-color differences of carnallite rocks, textural and structural features, the results of determining the rate of dissolution and the material composition of the water-insoluble residue are presented. The purpose of the study was to study the rate and processes of dissolution in water at a temperature of 500C in the forced convection mode and to assess the influence of the textural and structural features of the carnallite rocks of the Urals. The objectives of the study were: determination of salt and mineral compositions, study of textural and structural features and assessment of the effect of microinclusions on the kinetics of the dissolution process. When solving the tasks, the following methods were used: study of the textural and structural features of carnallite rocks - by the petrographic method; determination of the rate of dissolution and density of samples - by the gravimetric method; determination of the density of brines - pycnometric method; the chemical composition of the initial samples and solutions (brines) was analyzed by AES-spectrometry; the mineral composition of the water-insoluble residue - by X-ray quantitative phase analysis. The factual material of the research is analyzed, the corresponding conclusions are drawn. Studies have shown that important factors affecting the kinetics of dissolution processes are the material composition and textural-structural properties. In this work, the total (mass) rate of dissolution of samples was determined, including the vertical and horizontal components. The iron oxide film outlining the grains of carnallite rocks screens the dissolution surface, slowing down the diffusion process. The presence of halite and its uneven content causes fluctuations during dissolution, slowing down the dissolution process over time. Microinclusions of gases have a positive effect on the dynamics of the dissolution process, enhancing convection and mass transfer. With an increase in the hydrodynamic parameters of the solvent (density and viscosity), the dissolution rate decreases. The research results can be suitable for the organization of mining by underground dissolution and for the processing of carnallite rocks of the Permian deposits of the Urals by the halurgical method.

The Protection of Building Materials of Historical Monuments with Nanoparticle Suspensions

Marble and limestone have been extensively used as building materials in historical monuments. Environmental, physical, chemical and biological factors contribute to stone deterioration. The rehabilitation of stone damage and the delay of further deterioration is of utmost importance. Inorganic nanoparticles having chemical and crystallographic affinity with building materials is very important for the formation of protective coatings or overlayers. In the present work, we have tested the possibility of treating calcitic materials with suspensions of amorphous calcium carbonate (am-CaCO3, ACC) and amorphous silica (AmSiO2). Pentelic marble (PM) was selected as the test material to validate the efficiency of the nanoparticle suspension treatment towards dissolution in undersaturated solutions and slightly acidic pH (6.50). Suspensions of ACC and AnSiO2 nanoparticles were prepared by spontaneous precipitation from supersaturated solutions and by tetraethyl orthosilicate (TEOS) hydrolysis, respectively. The suspensions were quite stable (nine days for ACC and months for AmSiO2). ACC and Am SiO2 particles were deposited on the surface of powdered PM. The rates of dissolution of PM were measured in solutions undersaturated with respect to calcite at a constant pH of 6.50. For specimens treated with ACC and AmSiO2 suspensions, the measured dissolution rates were significantly lower. The extent of the rate of dissolution reduction was higher for AmSiO2 particles on PM. Moreover, application of the nanoparticles on the substrate during their precipitation was most efficient method.

RESEARCH OF THE PHYSICAL PROPERTIES OF DIESEL FUEL-HYDROGEN MIXTURES

The change in the viscosity of diesel fuel with dissolved hydrogen, the rate of dissolution of hydrogen in the diesel fuel, and the hydrogen diffusion coefficient in diesel fuel were experimentally determined. Dissolving hydrogen in liquid fuel changes its physical-chemical properties. It has been found that the viscosity and density of diesel fuel change little when it is saturated with hydrogen. The flashpoint in a closed crucible is reduced by 3–4 °C. The rate of dissolution of hydrogen in diesel fuel has been investigated. It has been found that the diffusion coefficient of hydrogen in diesel fuel depends significantly on the initial concentration of H2 in the fuel. The liquid fuel is advisable to supply with saturated hydrogen for the safety of the heat engine operation. The design of the hydrogen fuel saturation system with a special hydrogen sensor based on the MQ-8 sensor was proposed. The system of protection of the research stand from unauthorized emissions of hydrogen into the environment has been worked out. The protection ensures the shutdown of the stand equipment when the hydrogen concentration in the zone of its generation and supply to the fuel is at the level of 1%.

Structural transformations in the system lanthanum bromide – water – electrical field

We found several manifestations of severe influence of relatively week direct electrical fields on interactions of water with lanthanum bromide. The rate of dissolution of these crystals in water at the negative electrode exceeds this value at the positive electrode by several times. Pulse-like growth of solid micro-rods at the negative electrode from the solution of lanthanum bromide subjected to direct electrical field was observed. Auto-oscillations between the contents of water bound in hydrated lanthanum bromide and free water were found. These oscillations are attributed to severe difference of the electrical polarizabilities of free and bound water.