STUDY ON THE EFFECT OF CYANIDATION’S VARIABLES ON GOLD, SILVER, AND COPPER EXTRACTION OF TOGURACHI’S WASTE ORE PT. NUSA HALMAHERA MINERALS AND REDUCTION OF DISSOLVED COPPER BY SART PROCESS

• Main Author: FAUZAN (NIM : 12513035), FACHRI
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/27043
• Institution: Institut Teknologi Bandung

There are several gold recovery methods from the cyanidation leaching solution, <br /> <br /> one of which is the precipitation process using zinc powder (i.e. Merrill-Crowe <br /> <br /> Process). The ability of zinc to precipitate metals that are more noble than zinc can <br /> <br /> cause problems when the treated ore has a high base metal (especially copper) <br /> <br /> content. High levels of copper in the ore would increase cyanide consumption in <br /> <br /> which approximately 2.3 kg of NaCN is consumed for every 1 kg of leached copper. <br /> <br /> The co-dissolution of copper would subsequently increase zinc powder <br /> <br /> consumption on the Merrill-Crowe process and reducepurity of dore bullion <br /> <br /> products. There are several processes that can be used to reduce the concentration <br /> <br /> of dissolved copper which can simultaneously regenerate cyanide in the cyanidation <br /> <br /> leach solution, one of which is the SART (Sulphidization - AcidificationRecycling-Thickening) <br /> <br /> process. In this study, a series of cyanidation tests were <br /> <br /> conducted to study the effect of cyanidation’s variables on extraction of gold, silver, <br /> <br /> and copper in the cyanidation process of Togurachi’s waste ore PT. Nusa <br /> <br /> Halmahera Minerals that have high copper content and the effectiveness of SART <br /> <br /> process to decrease the concentration of dissolved copper in cyanidation leach <br /> <br /> solution was evaluated. <br /> <br /> The experiment started with the sample preparation of Togurachi’s waste ore PT. <br /> <br /> NHM for cyanidation leaching experiment using pulverized bottle roll test method <br /> <br /> under variations of ore size fraction (D80) at 30 &#956;m, 50 &#956;m and 70 &#956;m, free cyanide <br /> <br /> concentration at 500 ppm, 1000 ppm and 2000 ppm, dissolved oxygen <br /> <br /> concentration at 15 ppm, 20 ppm, and 25 ppm, and cyanidation pH values of 10.5, <br /> <br /> 11, and 11.5. The pregnant leach solution was then used for SART experiments in <br /> <br /> a closed reactor with variations of dissolved copper concentration at 40 g/L and 200 <br /> <br /> g/L, pH variations of precipitation process at 4.5, 5, and 5.5, variations of <br /> <br /> precipitation time at 10 minute, 20 minute, 40 minute, and 60 minutes, and <br /> <br /> variations of dosage of Na2S at 1x, 1.25x, 1.5x, 2x, and 2.5x stoichiometry. <br /> <br /> The experimental results show that the best conditions of cyanidation leaching <br /> <br /> process recommended for treating Togurachi waste ore in PT. NHM is at ore size <br /> <br /> fraction (D80) of 30 &#956;m with free cyanide concentration of 500 ppm, dissolved <br /> <br /> oxygen concentration of 15 ppm, and a leaching pH value of 10.5 that resulted in <br /> <br /> gold, silver, and copper extraction of 93.53%, 94.66%, and 49.14%, respectively. <br /> <br /> The highest percentage of copper precipitation of 88.64 % and 97.62%, respectively <br /> <br /> was obtained by SART process at pH 4.5 for 10 minute using Na2S dosages of 2.5x <br /> <br /> stoichiometry for a low grade copper solution (40 g/L) and 1.5x stoichiometry for <br /> <br /> high grade copper solution (200 g/L) with regeneration of free cyanide of 94.22% <br /> <br /> and 80.01%, respectively.