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Recovery of valuable materials from electronic waste

Kastanaki Eleni

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Summary

As the e-waste generation increases continuously, the estimation of future quantities and the key metals contained in them is of primary importance to policy makers, producers and manufacturers, so as to promote actions and legislations related to their sustainable management. In order to cope with the increasing demand for supply resources, the recycling of discarded devices can ensure the way to sustainability. To assess the feasibility of urban mining, three questions must be answered: What quantities of key metals will potentially be available in discarded devices in the future? What will the economic revenue of recycling be and for which metals is the process financially viable? How can we improve the recycling efficiency of the various key metals? This thesis focuses on estimating future quantities of 4 e-waste categories: laptops and mobile phones due to their rapid-increasing waste stream, lithium-ion batteries from electric vehicles, and photovoltaic waste as emerging e-waste. Among the four e-waste categories, PV waste is also chosen to experimentally recover Ag, which can offer significant economic revenue.This thesis accomplishes a detailed estimation of future End-of-Life (EoL) tablet/laptops amounts in Greece by considering various parameters and clarifying their effect on the estimated e-waste amounts. The content of precious metals (PMs) and critical raw materials (CRMs) in these obsolete e-wastes both for average and dynamic changing parameters is estimated, which revealed the great potential recovery of PMs and CRMs. Moreover, the waste mobile phone generation and their embedded key metals (CRMs and PMs) in Greece until 2035 (2010-2035), differentiating between feature phones and smartphones are estimated. The quantities of precious and critical raw materials in obsolete smart and feature phones in Greece until 2035 are calculated and it is revealed that effective recycling of obsolete phones (1995-2020) can cover the demand for key metals for new smartphones in Greece for more than a decade.Considering the rapid promotion of electric vehicles (EV) in the European Union (EU), a new e-waste category is emerging, the lithium-ion batteries (LIBs). The generation of future electric vehicles (EV) battery waste in the EU-27 countries is estimated. LIBs require proper management through circular economy business models. These include Remanufacturing, Reuse and Recycling of LIBs to extend their life before valuable materials are recovered. Material and substance flow analysis with a 3-parameter Weibull distribution function are employed to quantify all battery waste flows and their embedded materials. The available LIBs for remanufacturing and the capacity of Second Life LIBs are calculated. The recovered metals Li, Co, Ni and Cu in the waste LIB are calculated considering the recycling efficiencies of the 2020 EU Battery Directive.Furthermore, the estimation of future photovoltaic (PV) waste amounts in EU-27 countries considering the targets set by each country in the national energy and climate plans (NECP) for the implementation of solar photovoltaic systems is accomplished. The thesis addresses the questions “when will large amounts of panel waste be generated in the EU countries and what will their composition be?” Also, a timescale for starting an economically viable recycling industry for PV panel waste in EU based on the annual PV waste generated in each country is estimated.Finally, a novel hydrothermal technique for the recycling of c-Si PV waste panels with a focus on Ag recovery is developed. In the past, research on panel waste recycling has focused on Si, glass and Al recovery, but more recent studies also aim at Ag leaching and recovery, due to the high value of Ag. This thesis investigates Ag and Al leaching from waste monocrystalline and polycrystalline silicon photovoltaic (PV) panels, focusing on both cells and ribbons, by hydrothermal process using mild HNO3 solutions. Under the range of tested parameters, treatment time was the most important factor, followed by HNO3 normality and S/L ratio, while process temperature (100-140 oC) was not statistically significant. Al leaching was satisfactory under the hydrothermal conditions. Under the optimal hydrothermal conditions Ag can be efficiently leached (100%).

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