Gold bioleaching of electronic scrap material by cyanogenic bacteria and its enhancement with biooxidation

GOLD BIOLEACHING OF ELECTRONIC SCRAP MATERIAL BY CYANOGENIC BACTERIA AND ITS ENHANCEMENT WITH BIOOXIDATION PHAM VAN ANH (B. Eng. (Hons.), HUT) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2009 ACKNOWLEDGEMENTS This thesis would not have been possible without help and support from many people. First of all, I would like to express my gratitude to my supervisor, Associate Professor Ting Yen Peng, for his guidance, encouragement and support from the initial until the completion. I wish to thank the National University of Singapore for financial support so that I can pursuit this research, to thank Cimelia Resource Recovery Pte Ltd for providing ESM as material for this study. Many thanks to lab officers, Mr Sukianto, Ms Li Xiang, and particularly Ms Sylvia Wan for their assistance during the last two years. I would like to thank all my lab mates, Vu Phuong Thanh, Ng Wenfa, Adriyan Harimawan, and Shailendra Mishra for suggestion, advice and help whenever I need during my course. Without your willingness and support, this thesis can not be submitted. Last but not least, thank to my friends and my family for support and always being by my side. i TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii SUMMARY vi NOMENCLATURE viii LIST OF TABLES ix LIST OF FIGURES xii CHAPTER 1: INTRODUCTION 1 CHAPTER 2: LITERATURE REVIEW 4 2.1 Electronic Scrap Material (ESM) as a secondary gold ore 4 2.1.1 Economic value of gold 4 2.1.2 Gold in electronic devices 6 2.1.3 Electronic Scrap Material 7 2.2 Metallurgical recovery of metals from ESM 2.2.1 Definitions and classification 9 9 2.2.2 Process of gold recovery from ESM 11 2.2.3 Bioleaching in practice 12 2.3 Cyanogenic microorganisms and cyanide producing mechanism 13 2.3.1 General introduction 13 2.3.2 Chromobacterium violaceum 14 2.3.3 Pseudomonas fluorescens 15 2.4 Applying cyanogenic microorganisms in gold bioleaching 16 2.4.1 Potentials in bioleaching precious metals 16 2.4.2 Gold bioleaching by C. violaceum and P. fluorescens 17 2.5 Factors influence gold bioleaching efficiency 18 2.5.1 Growth conditions 18 2.5.1.1 Oxygen 18 2.5.1.2 pH 19 2.5.1.3 Temperature 19 ii 2.5.1.4 Glycine 2.5.2 ESM 20 21 2.5.2.1 Characteristics of ESM 21 2.5.2.2 Effects of ESM on microbial growth 22 2.6 Bio-oxidation of ESM before bioleaching gold 23 2.6.1 Bio-oxidation gold ores 23 2.6.2 Bio-oxidation ESM 25 CHAPTER 3: MATERIALS AND METHODS 28 3.1 Materials 28 3.1.1 Electronic Scrap Material (ESM) 28 3.1.2 Bacteria 28 3.2 Experimental methods 3.2.1 Analysis methods 28 29 3.2.1.1 Particle size distribution 29 3.2.1.2 Specific Surface Area 29 3.2.1.3 Acid digestion 29 3.2.1.4 Inductively Coupled Plasma Optical Emission Spectrometer 30 (ICP-OES) 3.2.1.5 Scanning Electron Microscopy/Energy Dispersive using X-Ray 32 (SEM/EDX) 3.2.1.6 Toxicity Characteristic Leaching Procedure (TCLP) 32 3.2.1.7 pH measurement 34 3.2.1.8 Optical Density 34 3.2.1.9 Free Cyanide Concentration Analysis 34 3.2.2 Bacterial culture 36 3.2.3 Bioleaching experiments 37 3.2.3.1 Shake flask bioleaching 37 3.2.3.2 Bioleaching in bioreactor 38 3.2.4 Bio-oxidation experiments 40 3.2.5 Chemical leaching 40 iii CHAPTER 4: RESULTS AND DISCUSSION 42 4.1 Characterization of ESM 42 4.1.1 Particle size distribution 42 4.1.2 Specific surface area 42 4.1.3 ESM elemental composition 43 4.1.4 Toxicity Characteristic Leaching Procedure tests 45 4.2 Pretreatment ESM 4.2.1 Chemical leaching 46 46 4.2.1.1 Acid leaching 47 4.2.1.2 Ferric leaching 47 4.2.2 Bio-oxidation by Acidobacillus ferrooxidans 4.3 Culture Chromobacterium violaceum and Pseudomonas fluorescens in fresh 51 54 medium in flasks 4.4 Bioleaching non-biooxidized ESM 4.4.1 One-step bioleaching 59 59 4.4.1.1 pH profiles 59 4.4.1.2 Free cyanide concentration 63 4.4.1.3 Gold leaching profiles 68 4.4.1.4 Copper leaching profiles 73 4.4.2 Two-step bioleaching 78 4.4.2.1 pH profiles 78 4.4.2.2 Free cyanide concentration 82 4.4.2.3 Gold leaching profiles 86 4.4.2.4 Copper leaching profiles 91 4.4.3 Comparison of Chromobacterium violaceum and Pseudomonas 94 fluorescens, one-step and two-step in bioleaching non-biooxidized ESM 4.5 Bioleaching biooxidized ESM 4.5.1 pH profiles 97 98 4.5.2 Free cyanide concentration 102 4.5.3 Gold leaching profiles 105 4.5.4 Copper leaching profiles 109 iv 4.5.5 Comparison of bioleaching non-biooxidized ESM and biooxidized ESM 113 by Chromobacterium violaceum and Pseudomonas fluorescens 4.6 Bioleaching ESM by Pseudomonas fluorescens in bioreactor 115 4.6.1 Growth in fresh medium 115 4.6.2 Bioleaching ESM 116 4.6.3 Effects of aeration to gold leaching efficiency 119 4.6.4 Comparison of bioleaching in flasks and bioreactor 121 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS 122 5.1 Conclusions 122 5.2 Recommendations 124 REFERENCES 126 APPENDICES 133 v SUMMARY Bioleaching has been used for many years to recovery metals such as copper and zinc from low-grade ores or low-grade mineral resources. Electronic scrap materials, with its significant gold content, is recognized as a new emerging and fast-growing waste stream and could be considered as a ‘secondary ore’ for gold due to its high concentration. The bioleaching mechanisms responsible for the metal recovery in mining operations may be also applied in the bio-mining of precious metals from such wastes. This project focused on the bioleaching of gold from ESM by cyanogenic bacteria and its enhancement by biooxidation. The ESM used in this project were fine particles, of size [...]... Literature Review CHAPTER 2: LITERATURE REVIEW 2.1 Electronic Scrap Material (ESM) as a secondary gold ore 2.1.1 Economic value of gold Sources of gold Gold is found in nature in two major types of deposits: gold- quartz lodes and fossil placers Contribution of other deposits is very small Gold usually exists in the form of native gold and electrum (alloy of gold and silver) It also occurs in some others minerals... Investigation of bioleaching gold from ESM by C violaceum and P fluorescens in a range of pulp density 0.5-8%w/v; - Biooxidation ESM by At ferrooxidans in comparison with chemical leaching; - Determination of the effects of biooxidation on bioleaching gold from ESM by C violaceum and P fluorescens in a range of pulp density 0.5-8%w/v; and - Evaluation of the potential in the use of a bioreactor in bioleaching. .. Review 2.1.3 Electronic Scrap Material Definition When electronic products are discarded, they become electronic waste (e-waste) These wastes are also called electronic scrap, or electronic scrap material (ESM) ESM can be defined as a mixture of various metals, particularly copper, aluminum, and steel, attached to, covered with, or mixed with various types of plastics and ceramics (Hoffman, 1992) Its metal... on applying biooxidation before bioleaching This approach is new and novel in gold bioleaching Thus, effects of biooxidation by Acidithiobacillus ferrooxidans prior to the bioleaching gold by C violaceum and P fluorescens were determined Biooxidation should help to remove the mineral matrix, release gold and reduce unnecessary cyanide consumed in the complexation with metals other than gold Moreover,... absence of ESM 57 Figure 4.6 (a) Growth of P fluorescens in shake flask in absence of ESM 58 Figure 4.6 (b) pH profile and cyanide production of P fluorescens in shake flask in absence of ESM 58 Figure 4.7 (a) pH profile in one-step bioleaching with 0.5% pulp density 60 Figure 4.7 (b) pH profile in one-step bioleaching with 1% pulp density 61 Figure 4.7 (c) pH profile in one-step bioleaching with 2%... the gold price in the last decade Market value of gold as well as other metals varies with availability and demand (Gasparrini, 1993) Thus, increasing demand and decreasing availability (as discussed above) will lead to higher and higher price of gold in the near future 5 Literature Review Figure 2.1 Market price of gold in the last decade (http://www.goldprice.org /gold- price-history.html#10_year _gold_ price)... Cyanide profile in one-step bioleaching with 2% pulp density 67 Figure 4.9 (d) Cyanide profile in one-step bioleaching with 4% pulp density 67 Figure 4.9 (e) Cyanide profile in one-step bioleaching with 8% pulp density 68 Figure 4.10 (a) Gold leaching in one-step bioleaching with 0.5% pulp density 70 Figure 4.10 (b) Gold leaching in one-step bioleaching with 1% pulp density 71 Figure 4.10 (c) Gold leaching... reports on bioleaching precious metals by cyanogenic microorganisms: silver from silver containing jewelry waste, platinum from spent platinum containing automobile catalytic converter, gold from ESM, by P plecoglossicida, (Faramarzi and Brandl, 2006; Brandl et al., 2008); and gold by C violaceum and P fluorescens which will be listed in next sections) 2.4.2 Gold bioleaching by C violaceum and P fluorescens... are few studies on bioleaching gold by P fluorescens from electronic scrap (Brandl et al., 2008) In a study on bioleaching by C violaceum and P fluorescens, the former was found to be more efficient than the latter in leaching nickel from nickel powder (Faramarzi et al., 2004) Gold recovery by the two bacteria varies, depending on the type of materials (even different with same material from different... addition of glycine, etc.) Gold leaching by C violaceum is highly variable depending on ore type and its gold content (Lawson et al., 1999) For example, after seven days bioleaching, C violaceum ATCC 12472 could dissolve 83% of gold from gold coated glass slides, reaching concentration of nearly 40 mg/l, but only 28% gold from gold concentrate ore with concentration of 0.25 mg/l in the same paper of Campbell ... major types of deposits: gold- quartz lodes and fossil placers Contribution of other deposits is very small Gold usually exists in the form of native gold and electrum (alloy of gold and silver)... applied in the bio-mining of precious metals from such wastes This project focused on the bioleaching of gold from ESM by cyanogenic bacteria and its enhancement by biooxidation The ESM used... REVIEW 2.1 Electronic Scrap Material (ESM) as a secondary gold ore 2.1.1 Economic value of gold 2.1.2 Gold in electronic devices 2.1.3 Electronic Scrap Material 2.2 Metallurgical recovery of metals