MINERALS & METALLURGICAL PROCESSING Vol. 30 No. 3 • August 2013 151 Fungal leaching of metals from electronic scrap Sadia Ilyas and Jae-chun Lee* Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea *Corresponding author email address: jclee@kigam.re.kr Abstract The present study was carried out to develop an economically feasible and environmentally friendly technique to extract metals such as Al, Fe, Cu, Zn and Ni from electronic scrap by employing Penicillium chrysogenum strain KBS3. Studies were carried out in various leaching modes, including one-step leaching with combined growth and leaching phases (Mode 1), two-step leaching with alternative growth and leaching phases (Mode 2), spent medium leaching with separated growth and leaching phases (Mode 3), leaching with fresh growth medium without fungal culture (Mode 4), leaching with deionized water (Mode 5) and leaching with commercial organic acids (Mode 6). The main lixiviants produced in leaching Mode 1 were citric, tartaric, oxalic and gluconic acids in concentrations of 12, 2.5, 1.8 and 152 mM, whereas in leaching Mode 2, the concentrations were 15, 0.5, 1.0 and 1,162 mM, respectively. In leaching Mode 3, 63 mM citric acid, 23 mM tartaric acid and 29 mM oxalic acid was observed. At 5% pulp density, both leaching Modes 1 and 2 showed similar metal extraction yields from the electronic scrap at 35º C. Approximately 96% Al, 98% Zn, 48% Cu, 25% Fe, 66% Pb and 73% Ni were extracted in leaching Mode 1 in 14 days. In leaching Mode 3, 85% Al, 81% Zn, 97% Cu, 22% Fe, 50% Pb and 63% Ni were extracted in 14 days. The extraction yield of Cu was much lower in leaching Modes 1 and 2 (48- 50%) than in leaching Mode 3 (97%), as well as in leaching Mode 6 (98%) with organic acids, including citric, tartaric, oxalic and gluconic acids. Paper number MMP-12-084. Original manuscript submitted November 2012. Revised manuscript accepted for publication January 2013. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to February 28, 2014. Copyright 2013, Society for Mining, Metallurgy, and Exploration, Inc. Introduction Technical innovations in electrical and electronic equipment with new functionalities and designs stimu- late consumer purchasing and lead a rapid increase in the production of waste materials. Terazono et al. (2006) have reviewed the data on electronic waste generation in different parts of the world. Studies by Bertram et al. (2002) have also affrmed that waste electrical and electronic components are the fastest growing waste category, which emphasizes the need for effcient recycling strategies. The recycling of electronic waste is an important subject, not only from the perspective of waste treatment, but also from the perspective of the recovery of valuable materials. However, the recycling of electronic scrap is still limited, due to the heterogeneity of the materials present in the products (Veit et al., 2005). Bioleaching-based processes offer a number of advantages over conventional pyro or hydrometal- lurgical methods (Lee et al. 2007; Lee and Pandey, 2012). These advantages include simple, inexpensive (in some cases) and ecofriendly approaches and the generation of less active leach residue relative to other metallurgical processes. Although biohydrometallurgical pro- cesses have been successfully applied to the leaching of metals from ores (Olson et al., 2003; Rawlings, 2002), data pertaining to the application of these processes for the extraction of elec- tronic scrap are still scarce. Recently, a few studies have been undertaken for the extraction of metals from electronic scrap/ printed circuit boards (Brandl et al., 2001; Faramarzi et al., 2004; Ilyas et al., 2007; Ilyas et al., 2010). These studies were conducted with mesophilic chemolithotrophic bacteria (Aci- dithiobacillus ferooxidans and Acidithiobacillus thiooxidans), cyanogenic bacteria (Chromobacterium violaceum) or moderate thermophilic bacteria (Sulfobacillus thermosulfdooxidans). However, compared to bacterial leaching, fungal leaching has several advantages, including (i) the ability to grow at a higher pH, thus making it more suitable for the bioleaching of alkaline solid waste; (ii) a generally faster leaching process with a shorter lag phase and (iii) the chelation of excreted metabolites (e.g., organic acids) with metal ions, thus reduc- ing toxicity to the biomass (Burgstaller and Schinner, 1993; Aung and Ting, 2005). The specifc objectives of this work are as follows: • Collection, isolation and enrichment of a fungal strain. Key words: Penicillium chrysogenum, Bioleaching, Electronic scrap, Organic acids Minerals & Metallurgical Processing, 2013, Vol. 30, No. 3, pp. 151-156. An official publication of the Society for Mining, Metallurgy, and Exploration, Inc.