No abstract

The electrical conductivity of low-temperature electrolytes based on Na3AlF6 was measured by means of a tube-type cell. AC-techniques with a sine wave signal in the high frequency range were applied. Basic binary melts NaF-AlF3 were studied at different molar cryolite ratios MR = (2.0–1.2) in the temperature range from the temperature of primary crystallization to 100°C overheat. The influence of the additions of 2 wt% of Al2O3, 5 wt% of CaF2 or 2 wt% of MgF2 was investigated at the same conditions, as well. The temperature and concentration dependencies of the conductivity in the studied systems were determined.

Innovations of aluminum electrolysis process are focused on the inert electrodes and the new types of electrolytes with lower temperature of primary crystallization. The main component in new types of molten systems can be a potassium cryolite. Advantages of these electrolytes are low possible working temperature (above 660 • C) and sufficient solubility of an electrochemical active compound (alumina) at these temperatures. The electrical conductivity is one of the most important properties of the electrolytes. Electrochemical impedance spectroscopy was used as a suitable measurement method for determination of the electrical conductivity. Potassium cryolite-based mixtures with the different molar ratios (molar ratio of KF and AlF 3 ) and with various additives were studied as a function of the temperature. The molar ratio of binary melt KF-AlF 3 varied from 1.2 to 1.5 with the step of 0.1. The temperature dependence (from 655 • C to 850 • C) and the influence of the addition of Al 2 O 3 , CaF 2 , MgF 2 and LiF on the electrical conductivity were obtained. The electrical conductivity was measured by tube-type cell with stationary electrodes; AC-techniques with a sine wave signal in the high frequency range were applied. Temperature and concentration dependencies of conductivity in the studied systems were described by non-linear regression equation.

Green algae Cladophora aegagropila, present in cooling water of thermal power plants, causes many problems and complications, especially during summer. However, algae and its metabolites are rarely eliminated by common removal methods. In this work, the elimination efficiency of electrochemically prepared potassium ferrate(VI) on algae from cooling water was investigated. The influence of experimental parameters, such as Fe(VI) dosage, application time, pH of the system, temperature and hydrodynamics of the solution on removal efficiency, was optimized. This study demonstrates that algae C. aegagropila can be effectively removed from cooling water by ferrate. Application of ferrate(VI) at the optimized dosage and under the suitable conditions (temperature, pH) leads to 100% removal of green algae Cladophora from the system. Environmentally friendly reduction products (Fe(III)) and coagulation properties favour the application of ferrate for the treatment of water contaminated with studied microorganisms compared to other methods such as chlorination and use of permanganate, where harmful products are produced.

No abstract