Controlled synthesis of multifunctional coatings by micro-arc oxidation method

The article is devoted to the development of the methodology for the controlled synthesis of protective coatings by the micro-arc oxidation method in order to improve the efficiency of this technology and the quality of the obtained oxide layers. Methodology includes a mathematical model of a galvanic cell based on an equivalent electrical circuit, as well as a model of the interconnections between the technological parameters of the micro-arc oxidation (MAO) process and the properties of the obtained oxide layers based on graph theory. The indicated dependences are formalized using methods of regression and correlation analysis of experimental data. A technique for the controlled synthesis of MAO coatings using the obtained regression equations is proposed. The structure and functioning algorithm of an intelligent automated system for the controlled synthesis of MAO coatings are developed. A prototype of this system was used to obtain experimental dependences of reaction parameters on the influence parameters of the micro-arc oxidation process.

Strengthened Oxygen Oxidation of Ferrous Ions by A Homemade Venturi Jet Microbubble Generator towards Iron Removal in Hydrometallurgy

Iron normally exists in the form of ferrous ion (Fe2+) in primary ore deposits of valuable metals. To remove iron from hydrometallurgical leaching solution or suspension by precipitation, ferrous ion should be oxidized to ferric ion (Fe3+) first. Due to the low oxidation rate of Fe2+ by the traditional oxygen oxidation method, industry has to use more agitating barrels, steam, and compressed gas, as well as a larger workshop area, which dramatically increases the equipment investment and operation costs. In this study, a strengthened oxygen oxidation method for Fe2+ using a homemade venturi jet microbubble generator is proposed. Microbubbles of air, oxygen, or oxygen-enriched air can be formed in the leaching solution or suspension, which can greatly improve the dissolved oxygen content in the solution and increase the gas-liquid contact area, thereby accelerating the oxygen oxidation rate of Fe2+ to Fe3+ and realizing the rapid iron removal of the leaching solution or suspension. By measuring the residual concentration of Fe2+ in the solution after oxidation reaction, it was found that the pump power, solution temperature, pH, concentration of Cu2+, and solution flow rate had great effects on the oxidation performance of the produced microbubble. By analyzing the images of the microbubbles and measuring the dissolved oxygen content in the solution, it is confirmed that the accelerated oxidation reaction rate of Fe2+ using the new proposed method was mainly due to the increase of the dissolved oxygen amount in the solution. Moreover, this method can significantly increase the purification depth of iron ion, expand production capacity, and decrease energy consumption.

Selective Leaching of Molybdenum from Bulk Concentrate by Electro-Oxidation

This paper proposes selective leaching of molybdenum from Mo/Cu complex bulk concentrates in a 5 M NaCl solution using the electro-oxidation method. Here, the effects of several factors such as pH, pulp density, current density, and temperatures were investigated. A higher leaching yield of Mo increased with increasing pH from 5 to 9 and decreased with increasing pulp density from 1 to 10%. A rise in current density did not help enhance Mo, and the elevating temperature did not always result in a higher leaching yield. Application of ultrasonic led to higher leaching yield of Mo. Ninety-two percent of leaching yield was obtained upon leaching of Mo in 5 M NaCl at 25 °C, pulp density of 5%, and the current density of 0.292 A/g under ultrasonic irradiation with a power of 27 kW. The resultant residue mainly consisted of chalcopyrite.

Development of 3H, 14C, 41Ca, 55Fe, 63Ni radiochemical analysis methods in activated concrete samples

Development of 3H, 14C, 41Ca, 55Fe and 63Ni radiochemical analysis methods were carried out independently by two laboratories using both inactivate and activated concrete samples. Two preliminary radioanalytical procedures for the non-volatile radionuclides (41Ca, 55Fe, 63Ni) and one Thermal oxidation method for the volatile radionuclides (3H, 14C) were developed. The difficulties in the method development and analysis of results are discussed.

Oxidation of α,β-Unsaturated Ketones by Organophotocatalysis Using Rhodamine 6G Under Visible Light Irradiation: Insight into Reaction Mechanism

The oxidative transformation of α,β-unsaturated ketones was investigated under the visible light-induced photocatalytic conditions using rhodamine 6G as an organophotocatalyst. In this organocatalysis, a mild co-oxidant BrCCl3 acts not only as a quencher toward the activated photocatalyst species having reductant property but also as a brominating reagent for the intermediate radicals. This study shows that the bromine atom-transfer to intermediate radicals from BrCCl3 is a key step in the reaction mechanism of our oxidation method.