Using of nuclear methods at extraction of manganese, molybdenum and some other rare elements from technological products

Full text: Instrumental neutron activation (INAA) and X-ray fluorescence (XRF) analysis have been used at production of Mn enriched concentrate from ore of the 'DAUTASH' deposit suitable for melting of ferromanganese, and at extraction of Mo, Au, Ag and some other rare metals from molybdenic tails. The production of Mn enriched concentrate includes the following stages: 1) Crushing, grinding and dispersion of the initial ore on the fractions; 2) Processing by nitric acid for removal CaCO3; ) Reduction of the ore by various substances - coal, natural gas and sulfurous anhydride; 4) Transfer of the reduced Mn in a solution and its separation from dead rock by filtration; 5) Sedimentation of Mn(OH)2 or MnCO3; 6) Calcination of the precipitate at a temperature 600-700 deg. C with obtaining of MnO2 concentrate. Control of the Mn and other accompanying elements contents is necessary at each stage. The contents of Mn and other basic components (Ca, So, Fe) in various fractions were determined by INAA, which has shown that there is no segregation of the basic components. The analysis of the MnO2 concentrate by XRF has shown, that the Mn content is (61.4±0.9) %. Using of XRF as a testing method in technological processes requires the standards, which should be close to analyzed products not only by composition, but also by granularity in case of powders. To prepare a standard for each product is very difficultly, so it is necessary to know preliminary its chemical composition and physical state. Therefore, we took the technological products from different stages of the technological process and analyzed by an independent method, for example, INAA, the results of which do not depend on chemical and physical state of a sample. This method is the most available because of presence of a nuclear reactor at the Institute of Nuclear Physics located near to the manufacture. These samples further were used as standards for XRF analysis of various products. The 109Cd source was taken for excitation of the MnKα lines; Si (Li) detector with the InSpector spectrometer was used for registration of characteristic lines. At calcination or nitrate modes of processing of the Mo concentrates, so-called tails of leaching are formed. The weight of tails in relation to that of an initial concentrate changes from 5 % up to 15 %, and, accordingly, the Mo content will be from 5 % to 15 %. Tails are stored and considered as man-caused deposits from which Mo and other rare elements are taken out then. The contents of all extracted elements in this technological process were determined by INAA. Samples of 100-200 mg were irradiated at the neutron flux density of 5.7·1013 cm-2c-1 for 5 hours. HPGe detector and γ-spectrometer with the software were used for measurement and treatment of spectra. It was found that the tails contain (9.6 ± 0.3) 10-3 % Au, (2.1 ±0.2)10-3 % Ag. ∼ 1.5 ·10-'2 -10-3 % La, Ce and other elements (W, Re, As, Sb etc.) at a level of 10-2 % - 10-3 %. The Mo content in the tails was from 5 % up to 7 %. The study is supported by STCU grant Uzb-126