International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In the last few years, application of selenium has increased significantly due to its unique possibilities to acts as an antioxidant and as an anticancer reagent in human body. Due to this, selenium is one of the most important chemical elements for human health. Recently, selenium usage in microelectronics was significantly increased as semiconductors with characteristic electronic properties. The selenium is the least abundant element in earth crust, but as the application fields of selenium are widely opened, the needs of this element are larger. This opens new views in the field of improving existing and developing new technologies for extraction of selenium.
In this work, a new technology for extraction of selenium from natural resources was developed, by combining the advantages and removing the disadvantages and weaknesses of the existing technologies. The sediments near mineral water springs and used water filters with content from 0.0656 to 0.9291 % wt. of Se were used as mineral selenium resources. Also, the plants such as Astralagus bisulcatus and Stanleya pinnata with content of Se around 100 mg·kg–1 biomass were used as a plant resources. The technology presented in this work is a combination of pyrometallurgical and chemical methods in order to obtain intermediates reach with selenium, and further chemical and electrochemical extraction of selenium from these intermediates was done. The analyzes were performed using Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP-AES). The results have shown that from mineral resources can be extracted pure red technical selenium with analytical grade up to 48.3 % of Se. From the plant resources can be obtained enriched selenium intermediates with analytical grade from 1.367 to 1.604 % wt. of Se which are potential material for medicine applications.

The subject of this study is leaching process of nickel-bearing laterite ore from Ržanovo, R. Macedonia. The influence of sulfuric acid concentration (0.5, 1 and 3 M H2SO4) on the extracted Ni (%, wt.) was studied. The leaching process intensified by magnetic stirring at different temperatures (298, 323, 348 and 363 K) in the time interval of 120 min. was performed. The results were used for kinetic analysis of the leaching process. It was found that for 3 M H2SO4, the best fitting has shown the Jander and Ginstling-Braunshtein models, which point out that limiting step of the process is diffusion. Activation energy was calculated to be 42,67 kJ·mol–1 (Jander model) 40,28 kJ·mol–1 (Ginstling – Brousthein model), which confirm the diffusion controlled process.