Investigation the calcite hydrophobisation of different grain sizes

This paper presents the investigations of possibility of calcite hydrophobisation. Two samples of calcite of different size classes from the site 'Dobar kamen', Arandjelovac, Serbia, were used in the experimental work. Modifying the surface of calcite was carried out by stearic acid with 'dry' method. Concentrations of stearic acid in the modifying method were as follows: 0.3, 0.5, 0.8, 0.9, 1, 2, 2.5, 3 and 4%. The results showed that a complete hydrophobicity (I0=99.9%) of calcite sample with the medium diameter (d50) 10.87 μm was achieved at concentration of stearic acid of 0.8%, while for the sample with the mean grain diameter (d50) of 29.14 μm, it was achieved at concentration of stearic acid of 3%. These results were confirmed by the microscopic analysis

Definition the technology method of apatite flotation concentration from the phosphate deposit 'Lisina'

This paper presents the importance of phosphate in the world, and the problems that arise in the process of preparing the low-grade phosphate ore for obtaining the phosphate concentrate using the flotation concentration. The apatite concentrates are obtained using the selective flotation from the silicate and oxide minerals while defining the process of selective flotation of apatite from carbonate deposits is the major problem worldwide. The experimental part of this paper presents the results of laboratory flotation tests of phosphate ore from the surface part of the location 'Panjevica' of the deposit 'Lisina'. The results have enabled definition of the flotation process in continuous conditions of work

The process of obtaining quartz sand size fraction -0.4 + 0.05 mm for use in water glass production

The paper presents the process of quartz sand processing from the „Bijela Stijena“-Skočić deposit in the plant „Kesogradnja d.o.o.“ at Kozluk near Zvornik, Republic of Srpska. Bearing in mind the fact that this quartz sand is used for water glass production in the company „Birač“ - Zvornik or „Alumina“ Zvornik, it was necessary to meet the quality requirements prescribed by that industrial production. Thus, the required size was -0.4+0.05 mm and the Fe2O3 content was maximum of 0.04%. Based on the laboratory tests, a technological scheme for the quartz raw material valorization was conceived in the separation of the company „Kesogradnja d.o.o.“. The obtained results showed that quartz sand for water glass size fraction -0.4+0.05 mm could be obtained in the plant. Also, by introducing a magnetic concentration after washing and grading, the Fe2O3 content was reduced from 0.131% as it is in the initial sample to 0.038% which meets the required conditions from the water glass producers

Reactions of calcite in water in the presence of stearic acid

In the suspension of water and calcite, with pH 10.14, on the border of calcite / water was formed a double electric layer. Its structure, or hydrophilic properties of minerals, depended on the concentration of potential determination ions, Ca2+ i 2 CO3 , pH of the environment, and the adsorption of water molecules and ions (and molecules), formed in a suspension of calcite as a result of its solubility in alkaline media. The structure of such a way formed electrical double layer, influenced on interaction of minerals with stearic acid as a surface of active substance. In the presence of stearic acid, the pH value of slurry decreased to 8.72 due to the dissociation of stearic acid in alkaline medium and reaction of neutralization. As the result of dissociation, in the suspension, besides the un-dissociated acid molecules, there were also stearine ions CH3(CH2)16COO-, (St-), which have reacted with the surface of minerals, transforming it from hydrophilic to hydrophobic

Application of lime in the polyvinyl chloride industry

This paper presents the importance of limestone in a variety of industries with a special focus on the use of limestone as filler in the industry of polyvinyl chloride (PVC). Of Out of all fillers, used in the industry of PVC processing, calcium carbonate type of fillers are 80%. Fillers are used in order to improve various mechanical properties of polymer such as tensile and breaking properties, density, bending strength, hardness, thermal stability, viscosity and more. Latest trends of industrial development and demands of the processing industry for high quality carbonate fillers influenced the implementation process of surface modification limestone and calcite, which is the main constituent of fine micronized limestone in order to enhance its performance

Surface adsorption of stearic acid by natural calcite

In order to obtain hydrophobic material, the surface of natural limestone with the high content of calcite (>95%), was treated with 0.5, 1, 1.5, 2, 3 and 4% of stearic acid. Two methods were used for modification: the solution method and the dry coating. The obtained products were characterized using the thermal analysis (DT/TG), X-ray powder diffraction analysis (XRPD), scanning electron microscopy (SEM) and by the evaluation of floating test. Results of floating test showed that when the solution method was applied, the hydrophobicity arrived at above 99% when the amount of stearic acid was 1.5%, while with the dry coating the same hydrophobicity was achieved with 3% of stearic acid. From the position of the principal exothermic peak (> 310 °C) at DTA curves, for calcites modified with dry coating and with the solution method, it can be concluded that with both modification processes, the same active sites exist at the calcite surface onto which stearic acid may be chemisorbed. However, the position and the intensity of the other exothermic peaks, indicate the differences in bonding of stearic acid at the calcite surface during the solution method and the dry coating

PVC mixtures’ mechanical properties with the addition of modified calcite as filler

In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system

Adsorption of T-2 toxin by natural mineral adsorbents

The contamination of animal feed with mycotoxins represents a worldwide problem leading to economic losses in animal production. According to the Food and Agriculture Organization (FAO), 25% of the world's cereal grain production is contaminated with mycotoxins. The most common mycotoxins found in grains are the aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone and the ergopeptine alkaloids. Trichothecenes, constitute the largest group of Fusarium mycotoxins. Among others, T-2 toxin is the most acute toxic trichothecene. In this paper, adsorption of T-2 toxin by natural mineral adsorbents zeolite-clinop-tilolite and smectite minerals - bentonite and hectorite, at pH 3 was investigated. The highest adsorption index was achieved for hectorite (95%), while clinoptilolite and bentonite showed low adsorption index for T-2 toxin, 8% and 13%, respectively. Results of T-2 toxin adsorption on hectorite, at different amount of solid phase in suspension, and at pH 3, 7 and 9, showed that toxin adsorption indexes increased with increase of adsorbent concentration in suspension, at all investigated pH values. No significant differences in T-2 toxin adsorption by hectorite, at pH 3, 7 and 9 were observed