Sulfidization of silver-polymetallic ores of «Goltsovoe» deposit for decreasing loss of silver in mill tailings

Abstract

The results of laboratory studies of flotation concentration of silver-polymetallic ores of the Goltsovoe deposit at the Omsukchansk concentrator are presented. The results of sieve analysis of mill tailings of the experimental sample of MTP N 101 (N 7577-i) are described. They indicate that a large amount of silver (123 g/t) is lost in the size class – 0.040 mm (yield 50.25 %). According to the results of mineralogical analysis, it is established that the major losses of noble metal are associated with its fine impregnation in oxides, sulfides and silicate rocks. The main silver-bearing minerals are acanthite, polybasite and kustelite (class – 0.040 mm). Experimental studies were carried out in two stages. The purpose of the first stage is to determine the influence of grinding fineness in flotation feed (for a finished class content of 0.074 mm in the range of 60-95 %) for silver recovery at different amounts of butyl potassium xanthate (50, 150, 300 g/t). The purpose of the second stage is to evaluate the effectiveness of sulfidization at different consumption of sodium sulfide Na2S·9H2O (50, 150, 200, 450, 750 g/t – 1 % aqueous solution) under the conditions of the optimal reagent mode established in the first stage of the study. The results of experiments to determine the optimum grinding fineness and studies on the enrichment of silver-polymetallic ore with the use of sodium sulfide as a sulfidizer are presented. The efficiency of the sulfidization process is estimated. The following experimental dependencies of silver recovery are established: on the degree of grinding and consumption of butyl potassium xanthate; on variations of grinding fineness and the consumption of sodium sulphide (with a consumption of butyl xanthate 150 g/t); and on grinding fineness at optimum consumption of sodium sulfide 150 g/t and butyl potassium xanthate 300 g/t. A comparative evaluation of dependence of silver recovery index from the degree of grinding fineness before and after introduction of sodium sulphide (collecting agent consumption of 150 g/t) is given. The mathematical models describing the dependence of silverrecovery on technological parameters, allowing to control the process of flotation of refractory ore with a large number of primary sludges and the tendency of sludging during grinding and concentration (secondary sludges) are given. The optimal consumption of flotation reagents has been experimentally established: sodium sulfide 150 g/t, butyl potassium xanthate 300 g/t with rational grinding (the content of the finished class is 0.074 mm in the flotation feed 85-95 %). Absolute recovery of silver from the ore of the silver-polymetallic deposit «Goltsovoe» in comparison with the technological indicators of the Omsukchansk concentrator processing the material in accordance with the standard mode, increased by 14.1 % (from 70.7 to 84.8 %) with the yield 9.09 % due to intensification of recovery of silver-bearing semi-oxidized sulphides with reduced flotation activity and compensation of high absorptive capacity of fine particles. The amount of silver in the size class – 0.040 mm in the sample MTB N 101 (N 7698-i) after the use of sulfidization was 83 g/t at the yield of 72.01 %, which indicates the efficiency of the process. The losses of silver in mill tailings decreased by 40 g/t (32.52 %). This proves the possibility of processing silver-polymetallic ores of the Goltsovoye deposit without reclaimer operation.