The effects of colloidal SiO2 and inhibitor on the solid deposit formation in geothermal water of low hardness

Low solubility of SiO2 and its occurrence in geothermal waters in the form of ionic, colloidal and suspended state are the main cause of the solid deposit occurrence. Certain chemical types of silica, under the influence of Fe2+, Al3+, F−, OH- ions and other micro-constituents, and due to significantly decreased solubility of SiO2, stimulate nucleation, particle growth and solid deposit formation. The aim of this paper is to inhibit the process of nucleation and solid deposit formation by adding originally designed inhibitor in the form of an emulsion, when the total concentration of the present and added colloidal SiO2 is beyond the solubility limit (120 mg/dm3). By turbidimetric, SEM, EDS and XRD analysis, the processes of solid deposit formation were investigated in Vranjska Banja (Serbia) spa geothermal water source (water hardness of 4ºdH), and theoretical and practical conclusions were made

The influence of multifunctional microalloyed ceramics microstructure on its capacity properties

Modified porous alumo-silicate ceramics, alloyed with magnesium and microalloyed with aluminum, belongs to modern multifunctional ceramic materials. Microalloying has led to important changes in dielectric and electrical properties of ceramics, such as dielectric constant and electrical resistance. These changes are conditioned by the microstructural properties of modified porous ceramics. The obtained results have shown the unity of the influence of composition, structure, morphology and application of microalloyed multifunctional alumosilicate ceramics on electrophysical properties. Microstructural investigations have shown that this type of ceramics has an amorphous-crystal structure, which causes important changes in its electrical properties and affects its activity. Therefore the ceramics can be considered as an active dielectric. A correlation between microstructural properties and structurally sensitive, i.e. electrophysical properties of microalloyed multifunctional alumo-silicate ceramics, was confirmed

Removal of cationic dye from water by activated pine cones

Adsorption of a cationic phenothyazine dye methylene blueonto activated carbon prepared from pine cones was investigated with the variation in parameters of contact time, dye concentration and pH. The kinetic data were found to follow the pseudo-second-order kinetic modelclosely. The equilibrium data were best represented by the Langmuir isotherm with maximum adsorption capacity of 233.1 mg g-1. Adsorption was favored by using a higher solution pH. Textural analysis by nitrogen adsorption was used to determine specific surface area and pore structure of the obtained carbon. Boehm titrations revealed that carboxylic groups are present in the highest degree on the carbon surface. The results indicate that the presented method for activation of pine cones could yield activated carbon with significant porosity, developed surface reactivity and considerable adsorption affinity toward cationic dye methylene blue

Leaching of chromium from chromium contaminated soil: Speciation study and geochemical modeling

Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III) and chromium(VI) were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values

The influence of multifunctional microalloyed ceramics microstructure on its capacity properties

Modified porous alumo-silicate ceramics, alloyed with magnesium and microalloyed with aluminum, belongs to modern multifunctional ceramic materials. Microalloying has led to important changes in dielectric and electrical properties of ceramics, such as dielectric constant and electrical resistance. These changes are conditioned by the microstructural properties of modified porous ceramics. The obtained results have shown the unity of the influence of composition, structure, morphology and application of microalloyed multifunctional alumosilicate ceramics on electrophysical properties. Microstructural investigations have shown that this type of ceramics has an amorphous-crystal structure, which causes important changes in its electrical properties and affects its activity. Therefore the ceramics can be considered as an active dielectric. A correlation between microstructural properties and structurally sensitive, i.e. electrophysical properties of microalloyed multifunctional alumo-silicate ceramics, was confirmed

Interaction of Mg enriched kaolinite-bentonite ceramics with arsenic aqueous solutions

Mg-enriched kaolinite–bentonite ceramics prepared in this work exhibited very porous and non-uniform structures, with grain sizes ranging from 1 to 20 μm. During the interaction of this ceramics with aqueous solutions of Na2HAsO4·7H2O, it was observed that the concentrations of Na, K, Ca and Mg in the ceramics and arsenic concentration in the solution decrease. These changes of metals concentrations in the ceramics and arsenic concentrations in water solutions appear to be on the account of arsenic deposition into the ceramics surface. The interaction of the ceramic samples prepared at 600 °C and 800 °C with used arsenic aqueous solutions reduced their arsenic concentration about 70–90%

Change of water redox potential, pH and rH in contact with magnesium enriched kaolinite–bentonite ceramics

It was established that the addition of Mg to the mixtures of kaolinite and bentonite can provide clay compositions which, after sintering at high temperatures, produce very porous ceramics with microcrystalline and amorphous regions of stoichiometric and nonstoichiometric oxides and highly developed metallized surfaces (in this case mainly with magnesium surplus). The ceramics surface exhibited high electrochemical and chemical activity when placed in contact with water. This leads to pH, EROX and rH changes of the treated waters, which can be controlled (magnesium aluminium silicate ceramics reduces or oxidises waters). In fact, with careful planning and appropriate selection of active components of the aluminium silicate ceramics it is possible to build in tailor made electric capacity, electrochemical activity and consequently program their effects on the structure and the content of the waters it interacts with

Application of Minkowski layer for intergranular fractal surfaces of multiphase active microalloyed and alloyed aluminium-silicate ceramics

Microalloyed and alloyed aluminium-silicate ceramics represents multiphase and multifunctional solid-solid system. The microstructure of aluminium-silicate ceramics matrix is arranged with favorable relationship between crystallinity and amorphousness. Numbered physical processes and interactions take place in very complex intergranular and interphase areas, making new boundaries and regions with fractal nature. Fractal nature of grains contours, macro, mezzo and micro pores and nanostructure phases at grain boundaries make this ceramics an active dielectric material. The synergistic effect of additives, dislocations and impurities leads to dislocations movement at grain boundaries and fragmentation of existing grains in a large number of micrograins with distinct fractal nature. Hence, permanent change of micromorphology occurs in intergranular area. Fractal analysis of intergranular microstructure has included application of Minkowski layer, correlated with fractal dimension. It represents convex layer of grains contour roughness and irregularity, determined in accordance with grain contours fractality. The introduction of fractal microstructure analysis allows better interpretation of many physical and physico-chemical processes, bearing in mind that Minkowski layer defines grains contact probability. (C) 2015 Elsevier B.V. All rights reserved

The role of NaCl in chlorine roasting of MoS2

This work presents the results obtained on the role of NaCl in chlorine roasting of MoS2. The process was performed in an oxygen atmosphere in the temperature range from 350 to 500 degrees C. The chlorine roasting of MoS2 in the mixture with NaCl was analysed and the products and change in the NaCl surface topography occurring during the processing were detected by x-ray diffractometry and Scanning Electron Microscopy (SEM), respectively. At a temperature below 400 degrees C chemical activity of NaCl resulted in a change of NaCl surface topography. However, only MoO3 was detected. At a temperature above 400 degrees C Na2Mo2O7, Na2SO4 and MoO3 were detected, as well as the melt around NaCl particles. Evaporation and condensation on cold wall of reaction tube of some compounds containing molybdenum and chlorine were also detected. Such phenomena will not occur if oxidation takes place without NaCl or MoS2/NaCl mixture is annealed in an inert atmosphere. This indicates that all detected phenomena were caused by NaCl reactions with products of oxidation of MoS2 and chlorine roasting of MoS2 occurred in the melt.Advanced Materials and Processes, 2nd Yugoslav Conference on Advanced Materials (YUGOMAT II), Sep 15-19, 1997, Herceg Novi, Yugoslavi