Waste electrical and electronic equipment (WEEE) generation is a global problem. Despite the growing awareness and deterring legislation, most of the WEEE is disposed improperly, i.e. landfilled or otherwise shipped overseas, and treated in sub-standard conditions. Informal recycling of WEEE has catastrophic effects on humans and the environment. WEEE contains considerable quantities of valuable metals such as base metals, precious metals and rare earth elements (REE). Metal recovery from WEEE is conventionally carried out by pyrometallurgical and hydrometallurgical methods.
In this PhD research, novel metal recovery technologies from WEEE are investigated. Using acidophilic and cyanide-generating bacteria, copper and gold were removed from crushed electronic waste with removal efficiencies of 98.4 and 44.0%, respectively. The leached metals in solution were recovered using sulfidic precipitation and electrowinning separation techniques. Finally, a techno-economic assessment of the technology was studied. This research addresses the knowledge gap on two metal extraction approaches, namely chemical and biological, from a secondary source of metals. The essential parameters of the selective metal recovery processes, scale-up potential, techno-economic and sustainability assessment have been studied.
1.2 Research goals and questions
1.3 Research approach and methodology
1.4 Structure of this dissertation
2 Electronic waste as a secondary source of metals, its management and recovery technologies
2.2 Global and regional WEEE generation
2.3 Waste as a secondary resource in transition to a circular economy
2.4 Improper management of WEEE
2.5 Transboundary movement of WEEE
2.6 Metals in WEEE
2.7 Metal recovery from WEEE
2.8 Physical pretreatment of WEEE
2.9 Treatment and refining of WEEE
2.10 Conclusions and perspectives
3 Biorecovery of metals from electronic waste – A review
3.2 Microbial mobilization of metals from electronic waste
3.3 Biorecovery of metals
4 Characterization of discarded printed circuit boards and a multi-criteria analysis approach for metal recovery technology selection
5 Bioleaching of copper and gold from discarded printed circuit boards
5.2 Materials and methods
6 Two-step leaching of valuable metals from discarded printed circuit boards, process kinetics, and optimization using response surface methodology
6.2 Materials and methods
6.4 Leaching of copper in oxidative medium
6.5 Leaching of gold in ammoniacal thiosulfate medium
7 Selective recovery of copper from the leachate solution by sulfide precipitation and electrowinning
7.2 Materials and methods
8 Techno-economic assessment and environmental sustainability analysis of a newly developed metal recovery technology
8.3 Sustainability assessment of the newly developed technology
8.4 Techno-economic assessment of the processes
9 General discussion and conclusions
9.2 Motivation for metal recovery from WEEE
9.3 Electronic waste as a secondary source of metals
9.4 Metal extraction from the discarded PCB
9.5 Recovery: electrowinning versus sulfidic precipitation
9.6 Techno-economic assessment and environmental sustainability analysis of an emerging technology at an early stage of development
9.7 Strategies for the development of a sustainable technology to recover metals from electronic waste
9.8 Overall conclusions
IHE Delft PhD programme leads to a deepening of a field of specialisation. PhD fellows do scientific research, often with conclusions that directly influence their region. At IHE Delft, PhD researchers from around the world participate in problem-focused and solution-oriented research on development issues, resulting in an inspiring research environment. PhD fellows work together with other researchers from many countries dealing with topics related to water and the environment.
PhD research is often carried out in the ‘sandwich’ model. Preparation and final reporting – the first and last portion of the programme – are carried out in Delft, while actual research is done in the fellow’s home country, under co-supervision of a local institute. Regular contacts with the promotor are maintained through visits and long-distance communication. This enables researchers to employ solutions directly to problems in their geographical region.
IHE Delft PhD degrees are awarded jointly with a university. The degrees are highly valued and fully recognised in all parts of the world.