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

The treatment of technological wastewater through a neutralization process is essential for adjusting the chemical properties of the water. This method aims to ensure that the wastewater meets established discharge limits, thereby protecting aquatic ecosystems and improving water quality in local waterways. Effectively managing process wastewater from large industrial facilities, such as copper rolling mills, presents a significant challenge that requires attention. In this paper, we present experimental testing of the neutralization process for technological wastewater from copper rolling mills, conducted at laboratory levels. Experimental research has shown that the neutralization process involves adding 10% Ca(OH)2 until a pH of 8.5 is achieved. The duration of the neutralization process is 30 minutes. During this time, a flocculant called Settafloc AP-17 is added at a concentration of 0.033%, specifically 6 ml per liter. This method effectively meets the water quality standards outlined in the Regulation on Limit Values of Pollutant Emissions into Water and the deadlines for compliance.

Researches in this paper included characterization of bismuth telluride single crystal doped with selenium. In order to study the effect of Se doping on the thermoelectric properties of Bi2Te2.7Se0.3 single crystal, an ingot was prepared by Bridgman method. The Bi2Te2.7Se0.3 single crystal in 11 mm × 80 mm size was grown.
The obtained empirical formula does not deviate from the given compound formula. Bulk sample was characterized by Seebeck coefficient (S) as а function of temperature in the range of 40 – 320°C by а homemade impedance meter.

Researches in this paper included synthesis and characterization of bismuth telluride single crystal doped with arsenic, obtained using Bridgman method. Compounds based on bismuth telluride are very important materials for thermoelectric refrigerators and devices for electricity production. For the monocrystal characterization, SEM – EDS, Hall and Van der Pauw method were used. The results presented in paper show the synthesis of monocrystal ingot, BiTeSe doped with arsenic. An analysis of energy dispersive spectrometry (EDS) was used to determine the chemical composition of the samples studied, as well as checking and confirming the homogeneity of the samples. Measurements of X-ray diffraction (XRD) showed that the resulting crystalline ingot represent a single crystal and confirm the compound of Bi2Te3 type. Mobility, concentration, resistivity/conductivity, of majority of charge bearers and Hall coefficient of single crystal, were determined using a Hall Effect measurement system based on the Van der Pauw method. For the sample of BiTeSe doped with arsenic Hall effect was measured at room temperature with an applied magnetic field strength of 0.37 T at different current intensities. Further characterization of the BiTeSe sample doped with arsenic was not performed, because the expected improvement in the mobility of this sample in comparison with the theoretical value of the n type Bi2Te3, was not obtained.