Enrichment of Konya Inlice epitermal gold ores

Au, used as the chemical symbol for the metallic element gold, comes from the Latin word Aurum, which means 'shining dawn'. In the periodic table, element gold, a transition metal, is tucked properly between mercury (Hg) and platinum (Pt). Gold is also one of the rare and the most precious elements found in the earth's crust with an average thickness of 35 km. Two in ten million of the earth's crust are gold; for this reason, people's desire to have a gold has never diminished throughout history; on the contrary, having a gold has been considered as the symbol of power and wealth. Besides the ability to be one of the rare elements in the earth's crust, gold is the best-known conductor in nature. It also does not react with water and oxygen; that is, it does not oxidize. Because of this feature, it is widely used in the electronics, healthcare and space industries. The fact that gold has an easily malleable feature gives it an extraordinary advantage over shaping. Therefore, gold is the indispensable metal of the jewelry and the jewelry industry. Throughout history, the most important feature of gold, besides being a symbol of power, beauty and magnificence, is the most reliable investment tool throughout the ages. It has become an actor of the economy since it started to be used as money. With the increasing world trade volume and interstate commerce after the Industrial Revolution, gold has become an important element in world history by increasing the role in money and trade (finance) policies of states. Nowadays, the upward trend in gold prices has increased the efforts to recover this metal all over the world. Gold can be obtained as the main product from its own ores by enriching as it can be recovered as a by-product from sulfur colored metal ores. A large part of the gold, which is recovered as a by-product from other metal ores, is obtained from the copper ores. A little gold is also produced in the process of extracting silver and lead. Moreover, about 25-30% of world gold production is provided from technological scrap, and old ornaments and scrap coins. In studies done, while 85% of world gold production is based on the principle of dissolution of gold because of the direct cyanidation process, depending on the mineralization, the rest of the gold is recovered by physical or/and physicochemical methods. In recent years, along with increasing environmental awareness both in the world and in our country, in order to reduce environmental hazards and obtain qualified pre-concentrate, physical and physicochemical methods have been preferred. Along with the limited number of laboratory-scale studies done by physical and physicochemical methods on gold and silver ores in different regions of Turkey, the plant application which gold is obtained by physicochemical methods in our country is limited to Tüprag-Efemçukuru gold enrichment plant with flotation. When approached from this aspect, obtaining pre-concentration of the gold from gold mineralization in the different regions of Turkey by gravitational and flotation methods or by a combination of these methods, and the facility-based application of this are thought to be important both economically and environmentally. Within the scope of this thesis, the first one of the enrichment methods applied to the epithermal gold ore belonging to the Konya-Inlice region, ground to a small size, is enriched with Falcon Concentrator, which is an enrichment method with gravity. During these experiments, the effects of parameters such as centrifugal force, the effect of bowl type and the pulp solid ratio of feed have been investigated. Conventional flotation technique was applied as the second enrichment method. In these enrichment experiments, appropriate particle size, flotation time, amount of reactive and amount of depressant and the effect of pH have been examined. It has also been investigated that under which conditions, rough concentrate produced in optimum conditions obtained as a result of systematic experiments will be subjected to cleaning process. Chemical and mineralogical examination of the ore to be used in experimental work has been carried out before the enrichment experiments have been done within the scope of the thesis. The ore samples were divided into 2 groups according to the color and were named as the oxidized group and the sulphurous group formed by blending 3 kinds of gray different samples, very close to each other as average grade. According to the chemical analysis result, there are 2.38 ppm Au in the yellow colored oxidized run-of-mine sample and 1.39 ppm Au in the gray colored sulphurous run-of-mine sample. In the mineralogical studies, while the minerals forming the oxidized sample were quartz, barite, a small amount of pyrite and ilmenite, the minerals forming the sulphurous sample were identified as pyrite, galena, barite and native silver. With all oxidized and sulphurous samples ground under 53 microns in size from the epithermal bearing gold ore in the Konya Inlice region, physical enrichment experiments have primarily been carried out with the Falcon Concentrator at 15 % solid in the pulp constantly, at an average feed rate of 6 lt/min, using smooth bowl and by subjecting to 100 G, 200 G and 300 G gravitational force. In the Falcon enrichment experiments conducted with the smooth bowl, while 2.46 ppm Au concentrate was obtained with 43% efficiency in experiments with sulfurous sample at 200 G, 1.85 ppm concentrate Au was acquired with the efficiency of 21% in experiments with oxidized sample at 300 G. As a result of the Falcon experiments with the bowl including special fluidized grooves or riffles, while 4.79 ppm Au concentrate was obtained with 7% efficiency in experiments with sulfurous sample at 300 G, 2.70 ppm concentrate Au was acquired with the efficiency of 2% in experiments with oxidized sample at 300 G. In conventional flotation experiments in which the effect of the reagent amount was examined, the optimum concentrate grade as 4.21 ppm Au and efficiency as 73% were obtained in the experiment in which 240 g/t Aerophine 3418A and 240 g/t Aero 208 were used as collectors. When the results were compared in the flotation experiments in which the effect of the depressant amount was investigated, the highest gold recovery efficiency was acquired with 88% efficiency (2.39 ppm Au) in the experiment using 1500 g/t silicate depressant (Na2SiO3) while the highest grade was obtained with 4.21 ppm Au (73% gold recovery efficiency) in the experiment in which 2000 g/t Na2SiO3 was used. xxv Considering that the best efficiency in gold enrichment experiments is achieved by the collector combination of 3418A and Aero 208 and that the optimum grade and efficiency have been obtained at pH 4.5 in previous experimental studies done with these collectors, the effect of pH on the recovery of gold has been investigated by carrying out flotation experiments for Konya Inlice gold ore both at natural pH (6.6-6.9) and at pH 4-4.5. When looking at the grade and recovery efficiencies, similar to other literature studies, better results were obtained with 4.21 ppm Au and 73 % efficiency. Based on the results of the rough flotation, to obtain a higher grade of final concentrate, its effect on the gold recovery and the gold grade were examined by performing the four-stage cleaning flotation with and without collectors in the conditions (1500 g/t Na2SiO3, 240 g/t 3418 A, 240 g/t Aero 208 and at pH 4-4.5) where the best efficiency is obtained from the rough flotation. While in cleaning experiments with collectors added, the grade and efficiency was increasing as a result of 4 stages, in experiments without addition, it decided that it would be better for the cleaning cycle to remain in 2 steps in practice due to the decline in values after 2nd step. As a result of the two-stage cleaning experiments carried out without collector addition, the gold content in the final concentrate increased to 5.23 ppm and while the efficiency was calculated as 21.61 %; in case of distribution of middlings, the concentrate efficiency theoretically increased to 65.66%. In consequence of the four-stage cleaning experiments with 25 g/t Aerophine 3418A and 25 g/t Aero 208 collectors added at each stage, the gold content in the final concentrate increased to 8.37 ppm and while the efficiency was calculated as 36.37 %; in the event of distribution of middlings, the concentrate efficiency increased to 78.10% in theory. When all works done were evaluated, the best result for the overall sulphurous sample ground to below 74 microns was obtained with conventional flotation in which 4-stage collector-assisted cleaning process was carried out after using 240 g/t Aerophine 3418A, 240 g/t Aero 208 collectors and 1500 g/ton Na2SiO3 depressant. While the final preconcentrate was obtained with 8.37 ppm Au content and the efficiency of 36.37 %, by distributing the middlings, the concentrate efficiency rose to 78.10 % theoretically. In order to be able to separate the obtained preconcentrate from the sulfur content; by this means, for the purpose of being able to increase the gold recovery efficiency and the grade, pressure oxidation can be carried out in autoclave under high pressure and temperature after the material has been subjected to a size reduction process again. The loaded solution can be eluted from the active carbon under pressure or organic (alcohol additive) elution methods and the final solution having rich gold content can be obtained after oxidized ore enriched with agitation leaching and carbon-in-pulp process, respectively. Finally, doré bar can be produced from the gold solution subjected to electrolysis (electrowinning) and smelting processes, and then doré bar can be converted to pure gold with refining process.