An optimal technological scheme for flotation concentration of gold-copper-arsenic ores of the Taror deposit (Republic of Tajikistan)

This article investigates the effect of material size on the efficiency of flotation concentration of gold-copperarsenic ores of the Taror deposit (Republic of Tajikistan) and studies the dependence of gold recovery on the duration of the process with the purpose of developing an alternative technological scheme for processing this ore type. According to X-ray phase analysis, Taror ore samples consist of rock-forming minerals by 92%. Ore mineralization is represented by sulphide minerals, mainly arsenopyrite, chalcopyrite and pyrite, in the total amount of 8%. Ore-forming elements include iron, sulphur, arsenic and copper with the mass fraction of 6.02%, 3.26%, 1.52% and 0.82%, respectively. Gold and silver are contained in the ore in the amount of 7.35 g/t and 20.28 g/t, respectively. The oxidation state of the ore calculated by iron comprises 51.3%. According to this indicator, this ore type can be distinguished as mixed, close to the primary type. According to the conducted chemical phase analysis of gold, this ore type belongs to the category of refractory ores. Flotation concentration experiments showed that grinding the original ore to a size of 95%–71 microns increases the recovery of gold in the concentrate by 10%, compared to grinding to a particle size of 80%–71 microns. The effect of the flotation process duration on gold recovery was also studied. To achieve the maximum gold recovery in the flotation concentrate, the duration of the main flotation and control flotation should be taken equal to 14 and 12 minutes, respectively. As a result of the experiments, a relatively simple technological solution was proposed for flotation concentration of the Taror ore, which includes the main, control and cleaning stages of flotation.

FLOTATION REAGENTS FOR FINELY DISSEMINATED GOLD EXTRACTION FROM UNENRICHED ORES AND TECHNOGENIC PRODUCTS

At the present stage of development of the mineral resource base of precious metals, the wider involvement of refractory ores and technogenic products in the mineral processing is playing a very important role. It is due to these types of mineral resources the main Russian and foreign companies plan to get the increase in the production of gold and other precious metals. Refractory ores are characterized by low content and uneven distribution of valuable components, emulsion dissemination of gold, complex material composition, flotation active silicate and carbonaceous rock components. The main technologies for their processing include combined schemes that provide intensive preliminary preparation of ore, fine and ultrafine grinding. Creation of effective reagents for flotation of fine classes of noble metals, selective depression of gold-free sulfides, like pyrite, pyrrhotite, arsenopyrite, and rock minerals is one of the recognized innovative solutions for intensifying the enrichment process of this type of raw material. The studies performed at IPKON RAS in the framework of the scientific school of Academician V.A. Chanturiya helped to develop and substantiate the novel selective reagents-collectors of dithiocarbamate type (DEDTCm, OPDTC, DBDTC, MDTC) and herbal modifiers that possess complexing properties in relation to noble metals and provide an increase in the recovery of valuable components of gold by 5-7%. A set of analytical methods - scanning electron (LEO 1420VP, Carl Zeiss) and laser microscopy (KEYNCE VK-9700, Shimadzu), X-ray fluorescence spectroscopy (ARL ADVANT’X), ICP –MS (Agilent 725 ICP-OES, Agilent Technologies), X-ray diffractometry (DRON-2.0, XRD 7000, Shimadzu), potentiometry, titrimetric analysis, methods of mathematical statistics helped to study the adsorption layer of the reagents on natural minerals and model sulfides with micro- and nanosized gold. Using an original technique for quantitative assessment of the reagent coating by image analysis (SLM), the surface area of the mineral occupied by the reagent was calculated. A method for selective flotation of gold-containing sulfides using OPDTC and oak bark extract has been developed and tested in the separation of the collective gold-arsenic concentrate of the Olympiada deposit. It showed the possibility of obtaining a gold-pyrite concentrate with an arsenic content of less than 2%. The prospect of using plant modifiers for gold recovery during flotation of complex ores has been substantiated.

Adsorption Characteristics of Combined Sulfhydryl Collector on Chalcopyrite and Arsenopyrite in Flotation of Complex Gold Ores

The paper presents the results of experimental study of the adsorption properties of the combined sulfhydril collecting reagent –a mixed solution of sodium diethyl-dithiocarbamate (DEDTC) and oxypropyl diethyl-dithiocarbamate ester (OPDTC) towardschalcopyrite and arsenopyrite with a view to its application as a selective collector of Au-containing sulfide minerals in flotationof complex refractory ores. Combined diethyl-dithiocarbamate solution (DEDTCc) incorporated a fixed content of anionic andnon-ionic components (DEDTC:OPDTC = 1:1) and occurred variable hydrophobic effect on the surface of the basic gold-bearingsulfide minerals – chalcopyrite and arsenopyrite.The mechanism of adsorption of the components of combined collector on the surface of chalcopyrite and arsenopyrite was identifiedto form characteristic molecular shape of adsorbed collector convex neoplasms and sinter chemically adsorbed film of thereactant, which is firmly anchored on the surface. The newly formed phase of the adsorbed reagent did not dissolve in water at asubsequent washing. In this case, the phase of nonionic ester OPDTC was partially removed by water and the residual adsorbeddroplets changed their shape and became flatter. By X-ray microanalysis C and O bands relating to the structure of the combinedDEDTCc were identified on the surface of arsenopyrite and chalcopyrite. The original technic for analyzing the liner dimension ofsurface images with an application of scanning laser microscopy and the software of the Analyzer was developed and the authorssucceeded to provide a quantitative evaluation of the adsorption of DEDTCc on the surface of chalcopyrite and arsenopyrite.

Prerequisites for Processing a Foam Product in the Process of Bacterial Oxidation of Gold-Bearing Concentrates in a Separate Cycle

The recovery of gold from refractory ores and concentrates is a significant problem in the modern gold processing industry. The use of bacterial oxidation technology at the Navoi Mining and Metallurgical Combine (Uzbekistan) made it possible to increase the share of recoverable gold during the processing of refractory ores from the Kokpatas and Daugyztau deposits. However, during the operation of the biological installation, a problem arose of abundant foaming in bacterial oxidation reactors. This article is devoted to the issue of foaming during biooxidation and its negative impact on the oxidation process. Methods of combating foaming and the choice of the optimal solution, providing for the processing of bio-oxidation foam in a separate cycle, have been analyzed.

Development of Technologies to Reduce Environmental Risk in Extracting Gold from Refractory Ores

The task of the countries of the Eurasian Economic Union is to look for effective technologies to recover gold from refractory ores while reducing the environmental hazard of the operations. In order to solve this problem, the Jin Xing reactant (a salt complex) was developed in the Kyrgyz Republic in the course of studying alternative highly effective agents for gold recovery from gold-bearing ores of different genesis. Joint studies of the Full Gold Mining Company, the Institute of Comprehensive Exploitation of Mineral Resources of the Russian Academy of Sciences and the Tae Jin Xing Science and Environmental Technology Company justified the application efficiency of the developed Jin Xing reactant. The paper presents the results of testing the new agent at a real mining operation.

Color and Casta in the Andean Silver Industry

Amalgamation technologies allowed refiners throughout colonial Latin America to profitably extract silver from a wider variety of metals, including even the most refractory ores. These expanded processing capabilities meant that mineral classification and sorting became even more important, as metallurgists had to identify which silver metals to treat with traditional methods and which ones to refine by amalgamation. The vocabularies used to classify metals provide critical evidence of Indigenous contributions to silver refining in the seventeenth century. By tracing the incorporation and removal of Andean color and spatial vocabularies, this chapter shows how scientific writers and translators replaced Indigenous classifications of matter with a racialized language of metallic “castas” that included “pacos,” “mulatos,” and “negrillos.” The chapter concludes by suggesting how a reading of color signatures in khipus might shed light on Andean miners’ experiences in ways that traditional historiographic methods have not yet allowed.