Natural resources are limited and uncontrolled exploitation can have negative effects on the environment. It is necessary to find approach of their sustainable use. Sustainable development is the framework for defining strategies of continuous state and social progress, without harm to the environment and natural resources essential for human activities in the future. Model that regulates sustainable use considers strategies and legal regulations for exploitation of natural resources and energy. Goal is to ensure the sustainable use of natural resources at national and global level. Sustainable use of natural resources is directly related to environmental protection. Also, the preservation of the working and living environment is related to the degree of economic development and the level of education of the population about the importance of a healthy environment and the way of its preservation. Accelerated technological development leads to an improvement in the quality of life in all spheres of human activity, but in parallel, it creates the possibility of greater environmental degradation. Therefore, it is necessary, within the goals of the development policy of the society, to include the correct criteria that will contribute to sustainable development. Thus, we contribute to preserving the environment and balance of natural ecosystems.

The study is focused on the determination of the most effective chemical leaching process for the simultaneous demineralization/deashing and desulfurization of subbituminous coal from the Bogovina Basin. Coal was treated for 30 min, at different temperatures, using variable concentrations of hydrochloric, nitric, acetic and citric acids; hydrogen peroxide, mixture of hydrogen peroxide and nitric acid (pH 2), as well as by the stepwise leaching process (nitric acid + mixture of hydrogen peroxide and nitric acid, pH 2). The changes in mineral composition, caused by the chemical leaching, are followed using X-ray diffraction, whereas alterations of coal organic matter are tracked by Fourier-transform infrared spectroscopy and the content of fixed carbon. Inorganic acid leaching, regardless of the temperature and acid concentration, enabled the successful deashing of coal, whereas the percent of desulfurization was insufficient. The organic acid leaching was not satisfactory for both, deashing and desulfurization. Leaching by H2O2 and H2O2/HNO3 mixture (pH 2) resulted in moderate desulfurization, but the ash reduction was low. The most suitable method for the simultaneous effective ash (78 wt.%) and the sulfur (66 wt. %) removal from Bogovina coal is the two-step leaching, combining 10 vol. % HNO3 and mixture of 35 vol. % H2O2/10 vol. % HNO3 of pH 2 at 60?C.

For the development of the Lost Foam refractory coatings with controlled rheologic properties, the influence of the mechanical activation process on the cordierite-based filler?s properties change was examined. First of all, the test referred to the change of filler particles? size and shape, as well as to dispersion ability and stability of the coating suspension. Cordierite was obtained by synthesis in a solid state, out of the mass consisting of kaoline, alumina, quartz, sepiolite. For characterization purposes, the following methods were used: X-ray diffraction, differential thermal analysis, SEM and optical microscopy. Mechanical activation of filler was performed in a vibrating mill. The upper boundary of the grain size was 100% -30 x 10-6 m, the times were (min): 15; 30; 60. The new composition of Lost foam refractory coatings has been developed with a change of the coating production process, as well. These newly synthesized coatings proved to be effective in terms of a positive influence on a surface quality, structural and mechanical properties of aluminium castings. Test results may be useful to have the Lost Foam refractory coatings specified together with other process parameters used for the production of castings according to this casting method.

The number of pistons in axial piston pumps plays a significant role in determining the performance characteristics of the pump. While increasing the number of pistons can improve capacity, stability, and flow, it also requires careful consideration of design complexity and operational efficiency. The optimal number of pistons will depend on the specific requirements of the application and the trade-offs that can be effectively managed. With multiple pistons operating together, the resulting pressure profile is smoother, reducing fluctuations that can affect system performance. This is crucial in applications where stable pressure is necessary, as it can improve the reliability and efficiency of the hydraulic system. Each piston contributes to the total displacement, resulting in an increase in flow rate. However, this must be balanced against the potential for increased internal friction and the complexity that can arise from multiple moving parts. The effect of the number of pistons on vibration and operating balance is another important factor. A well-balanced multi-piston pump can minimize pulsations and vibrations, resulting in smoother operation. This is essential for applications where excessive vibrations can lead to wear or system instability. To perform fast Fourier transforms (FFTs) on the measured signals, each signal was sampled at 4096 points per revolution (cycle). With five measured signals (four pressures and one vibration), this resulted in a total of (4 + 1) × 4096 = 20,480 data points per revolution and 204,800 data points for 10 consecutive revolutions.

During mechanical activation, the energy of treated material is raised to a higher level that can lead to the chemical transformation of the activated material. This is the point that should be considered as a phenomenon of the mechanochemical transformations appearing as a result of mechanical activation. Sodium carbonate as a substance that is often subjected to mechanochemical synthesis was mechanically activated in this study. The subject was the monitoring of changes in the physico-chemical characteristics of sodium carbonate after exposure to different degrees of activation time within the range of 1-28 minutes. After activation, the samples were deposited in three environments, CO2, air, and vacuum, at room temperature, in a period of 64 days. The mass changes occurring during the treatment were measured depending on the processing environment. Increasing the mass was evident and was attributed to the chemisorption of moisture and carbon dioxide present in the air as a consequence of the sodium carbonate activation. The methods also used were calcimetric chemical analysis and X-ray structural analysis. According to obtained results, it was found that activated sodium carbonate is mass-transformed into sodium bicarbonate, whereby these changes are functionally dependent on activation time and the processing environment.