Dragan T. Stojiljković

Adsorption Kinetics of Reactive Dyes on Ash from Town Heating Plant

Abstract In order to investigate the mechanism of adsorption of reactive dyes from the textile industry on ash from heating plant produced by brown coal combustion, some characteristic sorption constants are determined using Langergren adsorption equations for pseudo-fi rst and pseudo-second order. Combined kinetic models of pseudo-first order and pseudo-second order can provide a simple but satisfactory explanation of the adsorption process for a reactive dye. According to the characteristic diagrams and results of adsorption kinetic parameters of reactive dyes on ashes, for the applied amounts of the adsorbents and different initial dye concentrations, it can be concluded that the rate of sorption is fully functionally described by second order adsorption model. According to the results, the rate constant of pseudo-second order decreases with increasing initial dye concentration and increases with increasing amount of adsorbent – ash.

The influence of montmorillonite modification on the properties of composite material based on poly(methacrylic acid)

In this work a new class of functional composites was prepared based on the organically modificated montmorillonite and methacrylic acid. In the first step, the native montmorillonite was mixed with poly(ethylenimine) monomer to promote the intercalation process. In the second step, the methacrylic acid and initiator (potassium persulfate) were added and polymerization was carried out at 80°C for 2 hours. Characterization of the obtained composite material was performed by Fourier transform infrared spectroscopy. The change in interlamellar spacing of montmorillonite after polymer composite preparation was determined by X-ray diffraction. In prepared composite samples the existence of two crystalline phases was estimated by X-ray measurements. In the first, the poly(methacrylic acid) chains are intercalated within the montmorillonite layers, and in the second, they are dispersed in the polymer matrix. The influence of montmorillonite on the thermal properties of the obtained composites was measured using the combined thermogravimetry and differential scanning calorimetry method. The porosity of the prepared samples was determined by isotherm adsorption and the desorption of nitrogen (Brunauer–Emmett–Teller method). It was assessed that a certain amount of polymer is deposited on the montmorillonite and thus covering of the micropores and partially covering of the mesopores was achieved.

Predicting the behavior of nonwoven geotextile materials made of polyester and polypropylene fibers

Predicting the behavior of geotextiles made of polyesters and polypropylene fibers is described by differential equations derived from mechanical models. Thereby, we describe the behavior of geotextiles up to the elastic limit. The elastic limit represents the permissible load which the geotextile material may be subjected to during exploitation, and without distorting its structure. The elastic limit is defined by analyzing the stress–strain curve of analyzed geotextiles. Nonwoven geotextile materials of polyester and polypropylene fibers with surface mass of 150, 200, 250, 300 and 500 g/m2 were used as experimental material.

Scaling potential of geothermal water from the well A-2 at Vranjska Banja: Serbia

Geochemical and physicochemical characteristics of geothermal water from A-2 well are investigated in order to estimate its tendency towards the formation of scale in the pipe installation. Based on the geochemiocal analysis of major elements and groups, as well as triangular plots, this geothermal water can be classified as NaAlk·SO4 type. The ternary diagram classifies it as steamheated-peripheral water. A-2 has a good utilization capacity of 1 L s-1 at the water temperature of 84 °C. Regarding this, SI values are determined as the measure of tendency to form deposits. A positive SI value of calcite (0.14) and aragonite (0.03) at the temperature of 84 °C suggests a very low tendency to form scale, as well as the possible occurrence of a minor proportion of carbonate minerals. XRD mineralogical and SEM analyses of the scale have confirmed its calcite composition. SI values for the temperature of 25 °C indicate the safe silicate minerals deposition due to the positive temperature coefficient. The obtained SI values indicate that the A-2 geothermal water in Vranjska Banja is suitable for use in piping installations because it shows poorly pronounced tendency to form deposits.