Mechanism of Structural Changes in the Surface State and Physicochemical Properties of Columbite and Eudialyte upon Expo
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anism of Structural Changes in the Surface State and Physicochemical Properties of Columbite and Eudialyte upon Exposure to Low-Temperature Plasma V. A. Chanturiyaa, I. Zh. Bunina, *, M. V. Ryazantsevaa, E. L. Chanturiyaa, E. V. Koporulinaa, and N. E. Anashkinaa aMelnikov
Institute of Comprehensive Exploitation of Mineral Resources, Russian Academy of Sciences, Moscow, 111020 Russia *e-mail: [email protected] Received March 19, 2020; revised April 10, 2020; accepted May 27, 2020
Abstract—The mechanism of change in the structurally sensitive surface characteristics and physicochemical properties of rare-metal minerals (columbite and eudialyte) as a result of exposure to low-temperature atmospheric-pressure plasma is studied by means of DRIFT, analytical electron (SEM) and atomic force (AFM) microscopy, and measuring microhardness, electrokinetic potential, and angles of wetting. Results demonstrate the fundamental possibility of using low-temperature plasma to improve the efficiency of softening and altering the structural and chemical properties, surface hydrophobicity, and sorption activity of rare-metal minerals. DOI: 10.3103/S1062873820090105
INTRODUCTION The importance of improving the technology for processing ores and concentrates containing tantalum, niobium, zirconium and rare-earth elements is due to a number of factors: unstable mineral, chemical, granular compositions; the complex morphometric characteristics and structures of mineral crystals; and the presence of films of iron oxides and hydroxides on the surfaces of minerals (columbite, tantalite, zircon) that nullify their surface physicochemical and sorption properties [1, 2]. Such ores are processed according to complex integrated schemes. The technology for processing eudialyte concentrates is based on the multi-stage decomposition of minerals by acids (sulfuric, nitric, hydrochloric, hydrofluoric); leaching times of more than 3 h at temperatures of 80–140°С; and the use of catalysts. As a result of using technologies developed earlier, grains of eudialyte form on the surface during the acid dissolution of silicate gel. This reduces the efficiency of leaching and impedes the separation of liquid and solid phases during filtration, so the extraction of valuable components does not exceed 80% [3]. The results obtained in [4–8] showed it is possible in principle to use high-voltage nanosecond electromagnetic pulses [9] and the ponderomotive effect of a high-frequency electromagnetic field [10, 11] to increase the efficiency of disintegration and directional changes in the structural state of the surface and
technological properties of rare metal minerals (columbite, tantalite, zircon, and eudialyte) and collective concentrates of complex rare-metal ores [7, 8]. Low-temperature plasma is now widely used to modify the properties of materials (e.g., polymers, synthetic fibers, and textiles), minerals, and mineral suspensions [12]. In this work, we present new experimental data on the mechanism of changes in structural–chemical and mechanical (microhardne
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