The Separation of Carbonaceous Matter from Refractory Gold Ore Using Multi-Stage Flotation: A Case Study

As a pre-treatment method of refractory gold ore, carbonaceous matter (C-matter) flotation was investigated with multi-stage flotation by rougher, scavenger, and cleaner stages. Different dosages of kerosene and MIBC (4-Methyl-2-pentanol) were applied and the optimum dosage was selected by testing in each flotation stage. With the combination of each stage, four circuit designs were suggested, which were a single-stage rougher flotation (R), rougher-scavenger flotation (R+S), rougher-scavenger-scavenger cleaner flotation (R+S+SC), and rougher-rougher cleaner-scavenger-scavenger cleaner flotations (R+S+RC+SC). The results indicated that the scavenger flotation increased C-matter recovery but reduced C-matter grade compared with single-stage rougher flotation. Cleaning of the scavenger flotation concentrate improved C-matter grade significantly, but reduced recovery slightly. Cleaning of the rougher flotation concentrate achieved overall improved selectivity in flotation. A combination of rougher-scavenger flotation followed by cleaning of both concentrates (R+S+RC+SC) resulted in 73% C-matter recovery and a combined cleaner concentrate grade of 4%; the final tailings C-matter grade was 0.9%, where the C-matter remaining in the tailings was locked, and fine grained. The results demonstrate the need for the multi-stage flotation of C-matter from refractory gold ore to achieve selective separation and suggested the potential of C-matter flotation as the pre-treatment for efficient gold production.

Characterization of polymetallic ore and flotation concentrate from the Mária Mine (Rožňava, Špis-Gemer Ore Mts., Eastern Slovakia)

The contribution deal with the study on composition of tetrahedrite-bearing siderite ore from Maria Mine nearby Rožnava and of tetrahedrite concentrate prepared from this ore by froth flotation. The Rožnava ors field consists of two main vein systems, namely Mária and Strieborná (Argenteous/Silvery) ones, respectively. The both vein systems are situated in the Early Paleozoic Gelnica Group of the Gemeric Superunit, in Bystrý Potok Formation (Upper Silurian) and in the Drnava Formation (Early Devonian). The filling of vein systems is formed mainly by siderite, quartz, tetrahedrite, pyrite, arsenopyrite, chalcopyrite, ankerite, albite, pyrrhotite, marcasite, less tourmaline, sericite, chlorite, apatite, magnetite, etc. The rock surroundings is represented by quartzy metapsammite, sericitic-quartzite and sericitic-graphitic phyllites (Jakubiak, 2008, Blišt’an, 2009, Varga, 2013, Mikus, 2018). Thus, metal ore as a feed to froth flotation and obtained concentrate were subjected to grain size analysis. The grain size fractions were assayed using GA, AAS, MS-ICP and CHNS. Mineral composition of samples was studied using XRD. So, polymetal ore contains 18.99 % SiO2, 37.01 % FeO, 1.84 % MnO, 7.36 % C, 2.36 % Cu, 1.70 % Sb, 0.15 % As, 2.32 % S, 770 ppm Ag and 216 ppm Hg. Tetrahedrite concentrate containing 25.59 % Cu, 19.68 % Sb, 1.19 % As, 20.08 % S, 0.57 % Ag, 1.20 % Hg, 1 % SiO2, 16.16 % FeO, 0.48 % MnO and 2.17 % C at a mass yield of 4 % was prepared. XRD study showed that siderite occurs as a dominant mineral in metal ore. Quartz, tetrahedrite and sericite are presented as accompanying minerals. Accessories are represented by chlorite, probably clinochlore. As to flotation concentrate, tetrahedrite is dominant mineral, which accompanied by siderite. Accessories can be represented by chalcopyrite, arsenopyrite, sericite, pyrite, quartz and chlorite.

Research into thickening processes of concentrates of gold-bearing ores

The aim was to improve the thickening of an ultra-fine flotation concentrate by efficient flocculants when processing refractory sulphide gold-bearing ores from South Urals deposits. The chemical ore composition was studied using gravimetric, atomic absorption, chemical, X-ray fluorescent, assay test and electron microprobe analytical methods. Particle size analysis of the ultra-fine flotation concentrate under study was performed using a Malvern Hydro Mastersizer 2000MU analyser (Malvern Panalytical Ltd, UK). In thickening experiments, samples with the same composition after the ultra-fine grinding process were used. The gold content in the ore was determined (22.8 g/t) based on analytical studies on the material composition of samples. At least 92% of the final grain size class is -20 microns. Laboratory tests performed on eight samples containing polyacrylamide-based flocculants revealed an optimal A44 flocculant (produced in China). The flocculant meets the requirements for minimum flow rate, deposition rate and L:S ratio. The specific performance of the JX20 radial thickener (JPMFex Corp. Ltd., China) was calculated. The optimal flocculant flow rate is 200 g/t per 1 t of thickened material, leading to thickening 50 t of pulp per 1 m2 of thickener per day. The A44 flocculant is recommended for pilot testing. Thus, developing, testing and implementing fundamentally new reagents and improving existing technologies of processing gold-containing ores and concentrates are necessary to intensify the ore dewatering processes after ultra-fine grinding.

Insights into Selection of the Auxiliary Collector and Its Applicability Analysis for Improving Molybdenite Flotation

In this study, two auxiliary collectors (methyl naphthalene and naphthalene) of molybdenite and the traditional collector (kerosene) were mixed for molybdenite flotation, respectively. According to the selection and analysis of the auxiliary collector, it was found that the surface energy (γC= 4.50 mJ/m2) of the polycyclic aromatic hydrocarbons is very close to that (γS= 42.55 mJ/m2) of the molybdenite {100} surface. Therefore, it can be physically adsorbed onto the molybdenite {100} surface according to the principle of similar compatibility. Batch flotation was conducted on actual ore with the mixed collector, compared with kerosene alone. Batch flotation results showed that the mixed collector at a mass ratio of 95:5 of main collector to auxiliary collector at pH 11.0 improved molybdenite flotation, that is, the Mo recovery was increased by 3–4%. The practical application feasibility of the auxiliary collector was analyzed by the filtration speed of the flotation concentrate and the crystal resolution characteristics of the auxiliary collector. The results show that solid naphthalene (Nap) is easy to crystallize at low temperature and adhere to the surface of the flotation concentrate, resulting in a decrease of filtration velocity, while liquid methylnaphthalene (MNap) does not crystallize at low temperature. These results imply that the mixed collector Kerosene/MNap can generate a superior synergistic effect and achieve better collecting capacity than kerosene alone, resulting in the increase of flotation recovery by 3–4 percentage points. Moreover, the addition of MNap has little negative impact on the subsequent treatment of the product.

Selective Pre-leaching of Tellurium From Telluride-Type Gold Concentrate

With a telluride-type gold ore flotation concentrate as the research object, the Na2S + NaOH collaborative leaching process was applied to selectively separate tellurium before the cyanide leaching of gold and silver. The effects of process parameters including the type of leaching agent, the amount of leaching agent, liquid-solid ratio, leaching temperature, and leaching time on the leaching rate of tellurium were investigated. The results showed that the tellurium leaching rate could reach 78.14% under the optimum conditions of −0.038 mm (95%) grinding fineness, 80 g/L Na2S concentration, 30 g/L NaOH concentration, 4:1 liquid-solid ratio, 80°C leaching temperature and 3 h′s leaching time. The kinetic analysis showed that the leaching process of tellurium from telluride-type gold concentrate was a mixed type of chemical reaction control and diffusion control. The grain parameter in the leaching process was 0.26263 and the apparent activation energy E = 17.12 kJ/mol. Tellurium could be pre-leached from the telluride-type gold flotation concentrate through the Na2S + NaOH alkaline leaching process to achieve the effective separation of tellurium from noble metals, which, when eliminating the adverse effects of telluride on the leaching of gold and silver, provides new ideas for the extraction of rare element tellurium.