Recovery of gold from gold mining tailings in Port Sudan by cyanidization process

In this thesis study, it was tried to determine the gold recovery conditions by cyanidation method from the tailing resulting from gold production by mercury amalgamation method from the gold mines in the Sudan-Port Sudan region. According to the mineralogical and chemical analyzes performed on the studied residue sample, the main components of the sample were determined to be 77.10% SiO2, 8.08% Al2O3, 5.76% Fe2O3, 1.67% CaO and 0.97% K2O. The tailings sample also has a grade of 16.86 g/ton Au. Mixing leaching, percolation leaching and Vat leaching methods were used in the studies. Adsorption studies on activated carbon with the Carbon in Pulp (CIP) method, modeling of the prediction of the leaching process using the data obtained from mixing leaching studies with the Artificial Neural Networks (Kroeker, Wasylishen, & Hanna) method, and feasibility studies for a possible small-scale cyanidation plant were carried out. In agitation leaching studies; The effects of stirring speed, pH, NaCN concentration, solid/liquid ratio and temperature on gold dissolution were examined. Experiments were carried out in a hot water bath that could be adjusted to various temperatures. As the stirring speed increased in the range of 0-600 rpm, the Au dissolution rate also increased. As the pH increased in the range of 10-10.30, the Au dissolution rate increased. As the NaCN concentration increased in the concentration range of 0.05-0.5 g/L, the Au dissolution rate also increased. Temperature studies were carried out in the range of 25-85 °C, and as the temperature increased, the Au dissolution rate also increased. Studies on the effect of solid/liquid ratio were carried out at 20%-50% solid/liquid ratio. As the solid/liquid ratio increases, the Au dissolution efficiency naturally decreases. In the studies, 87.91% Au dissolution efficiency was achieved as a result of a 120-minute leaching process at 25 °C, 0.5 g/L NaCN concentration, pH 10.30, and solid/liquid ratio of 40%. For percolation leaching studies, the tailing sample was agglomerated using cement due to the dewatering problem experienced in the agitation leaching experiments. In the agglomeration studies, the best strength results in aqueous environment were achieved at 7/100 and 9/100 cement/tailing sample (w/w) ratios. In the studies, optimum conditions such as NaCN concentration and pH solid/liquid ratio obtained from agitation leaching experiments were used and it carried out at 25 °C. Flow rates of 0.5, 1.0, 1.5 and 2.0 L/min were used as solution flow rates. According to the results obtained, it was determined that the solution flow rate had no effect on the Au dissolution rate. As a result of the studies, approximately 85% Au dissolution efficiency was achieved at all flow rates studied after a 120-minute leaching process. In Vat leaching studies, agglomerates made with cement were used, as in percolation leaching studies. In the studies, optimum conditions such as NaCN concentration, pH and solid/liquid ratio obtained from agitation leaching experiments were used and were carried out at 25 °C. Studies were carried out by moving the chamber containing the sample up and down at intervals of 2, 3 and 5 minutes. Approximately 83% Au dissolution efficiency was achieved as a result of a 120-minute leaching process performed with 3-minute intervals. CIP studies were carried out for 120 minutes under appropriate leaching conditions obtained from agitation leaching. As a result of the studies, approximately 94% of the dissolved gold and approximately 98% of the dissolved copper were adsorbed to activated carbon. ANN studies; it was carried out using obtained from agitation leaching experiments data gainst time, pH, NaCN concentration, solid/liquid ratio and temperature. The 72 Au dissolution efficiency data obtained after each experiment for 75, 90 and 120 minutes were estimated by training the data obtained for other periods. As a result of the training of 72 pieces of data, the average error of the new data obtained compared to the real data was found to be 1.66. That is, the prediction results are on average ± 1.66 points away from the actual data. Feasibility studies were carried out to establish a small cyanidation plant with a capacity of 270 Ounces/month. The results obtained from Vat leaching experiments were taken as basis for feasibility studies. As a result of the studies, it is predicted that the facility will be able to turn a profit after approximately 1 month.