Effect of Direct and Indirect Pre-Oxidation of Gold Ore from Doup North Sulawesi using Ozone Gas on the Gold Extraction in the Cyanidation ProcessChanovanto Chrisna, Zela Tanlega Ichlas, Mohammad Zaki Mubarok and Erwin KartaatmajaE3S Web Conf., 543 (2024) 02015DOI: https://doi.org/10.1051/e3sconf/202454302015