Increasing the recoverability of diamonds in the process of x-ray luminescent separation using phosphor-containing compositions
Authors:   Institute of Comprehensive Exploitation of Mineral Resources Russian Academy of Sciences, Chanturia Valentin , Morozov Valery ,   National University of Science and Technology «MISiS», Dvoichenkova Galina ,   Institute of Comprehensive Exploitation of Mineral Resources Russian Academy of Sciences, Chanturia Elena ,   National University of Science and Technology «MISiS»
Published: November 2022

Introduction. A promising way to solve the problem of reducing the losses of weakly and abnormally luminescent diamonds in the process of X-ray luminescent separation is to modify their spectral characteristics with special compositions of phosphors. The phosphor-containing compositions used include inorganic and organic phosphors that provide the necessary change in the kinetic characteristics of the diamond X-ray luminescence signal. The purpose of the work. Investigation of the mechanism of the process and selection of compositions of phosphorcontaining compositions that provide the required modification of spectral characteristics and increase the extraction of weakly and abnormally luminescent diamonds in the process of X-ray-luminescent separation. Methodology results. Studies of the mechanism of formation of the X-ray luminescence signal from diamond-phosphor complexes were carried out by determining the degree of coating of the surface of diamonds with phosphors by the visiometric method and the amplitude of the luminescence signal with varying concentrations of phosphor in the emulsion. The effectiveness of the selected compositions of the phosphor-containing composition was evaluated by determining and comparative analysis of the acquired spectral and kinetic characteristics of the diamond-phosphor complexes using the Polyus–M separator. The evaluation of the effectiveness of the selected formulations was determined by the results of a test on industrial X-ray luminescent separators. Research results. The mechanism of formation of the X-ray luminescence signal from a diamond with a phosphorcontaining composition fixed on its surface is determined. It is shown that the total signal is the sum of the diamond and phosphor signals attenuated by screening and scattering of luminescent radiation by 5-15% for the diamond signal and 20-40% for the phosphor signal. The use of inorganic phosphors based on zinc sulfide, or a mixture of phosphor based on zinc orthosilicate and anthracene in compositions is justified, providing an increase in the intensity of the X-ray luminescence signal of a weakly luminescent diamond by 2.5 times, and preserving the shape of the X-ray luminescence signal of natural diamonds. It is proposed to use catalytic cracking as a collector of a diesel fraction compound and heavy gas oil, which ensures effective fixation of the phosphor on the surface of diamonds. The composition of the composition (FL-530, anthracene, diesel fraction, THCC) is proposed, which provides the required modification of spectral characteristics and detection of low-luminous diamonds. Resume. The results of the tests carried out on diamonds of various sizes have established the possibility of increasing the extraction of diamonds by 5-15% due to the detection of diamond crystals with weak or abnormal luminescence. At the same time, the required selectivity of the process with respect to kimberlite minerals is maintained. Conclusions. The results of the research are recommended for practical implementation in X-ray luminescent separation schemes at ALROSA processing plants to reduce losses of weakly and abnormally luminescent diamonds and will also be used in further studies of the possibility of increasing the selectivity of separation of diamonds and rock minerals during kimberlite enrichment.