Abstarct: In this thesis, the dissolution (leaching) process in the Zarshouran Gold Plant was investigated. The main objective was to identify the factors influencing gold recovery and to propose strategies for optimizing operational conditions. For this purpose, a series of laboratory-scale leaching experiments were designed and conducted in which variables such as temperature, pH, sodium cyanide concentration, solid percentage, and leaching time were examined. The results indicated that each parameter had a specific level of influence on the overall recovery rate. The average recovery was approximately 50%, and the highest recorded recovery, 55.65%, was obtained under the following experimental conditions: temperature of 25 °C, pH = 11, cyanide concentration of 300 ppm, solid percentage of 28%, and agitation time of 18 hours. This value was 14.8% higher than the plant’s operational conditions (25 °C, pH = 10, 500 ppm cyanide, 36% solids, and 20 hours of agitation), indicating a 14.8% improvement in process efficiency. baxsed on the analysis of the results and at the request of the industrial unit, several supplementary experiments were carried out. These included increasing cyanide concentration to assess its effect on recovery, using ammonia to evaluate its influence on enhancing reaction kinetics, conducting several adsorption tests on activated carbon, and performing a test for removing copper ions from the pulp—considered one of the most significant interfering ions in gold leaching due to cyanide consumption and blockage of activated carbon pores that should otherwise adsorb gold. The reagent used for this purpose was sodium sulfide (Na₂S). The experiments involving increased cyanide concentration did not show any considerable improvement in gold recovery. The ammonia tests indicated that extending leaching time beyond twenty hours had no effect on increasing recovery. Activated carbon adsorption experiments also demonstrated that carbon contact time beyond twelve hours did not improve adsorption. In the copper-removal experiment, sodium sulfide was able to increase the copper content in the solid phase from 130 ppm to 559 ppm without precipitation in the solution, indicating that copper ions present in the pulp were successfully precipitated and prevented from entering the leaching stage.