Extraction of Precious Metals from Electronic Waste
17th, July 2019, Thrusday, 4:00pm, ChE Seminar hall
Electronic waste (e-waste) is the fastest growing waste stream with an annual growth rate of 3-5%1. The study by United Nations University reported that electronic waste (e-waste) is expected to grow to 52.2 Mt by 2021 as compared to 44.7 Mt in 20162. E-waste contains various toxic substances and therefore unregulated accumulation may lead to a serious threat to human health and the environment. However, e-waste with their high content of base and precious metals is regarded as a potential secondary resource of metals while plastic present can also be converted into valuable products. Metals and plastic are the major components of e-waste with a share of 61% and 21% respectively3. Therefore, this study aims at the development of sustainable technology for e-waste management by conversion of e-waste plastic into valuable product followed by separation of different metals for further reuse. The Waste Printed Circuit Board (WPCB) of the desktop computer has been used in this study. The integrated process can be divided into four parts viz. (1) pyrolysis of WPCB, (2) separation of metal fraction, (3) metal leaching and (4) individual metal recovery. The adopted methodology involves the shredding of WPCB followed by the pyrolysis of WPCB. The effect of different process parameters such as temperature and time on the pyrolysis of WPCB has been investigated. The temperature and time were varied from 200 to 600 °C and 10 to 60 min respectively. Solid (metal-carbonaceous material mixture) and gases were obtained as the product after the pyrolysis of WPCB. The pyrolysis at 400 °C for 20 min found to be optimum for metal recovery. The metal fraction has been separated from the metal-carbonaceous material mixture and efficiency of metal fraction separation is around 90%. This metal fraction can be directly used by metal industries for the formation of different alloys or/and recovery of individual metal. Efforts have also been made in this study for the recovery of Cu and Ni using H2SO4-CuSO4-NaCl system from the metal fraction. The effect of time was studied on the recovery of Cu and Ni by varying time from 1 to 5 h. Around 100% recovery of Cu and Ni was achieved within 4 h and other reaction conditions used were: 0.5 M H2SO4, 7.5 g/L Cu, 46.6 g/L Cl-, 1/20 (g/mL) solid to liquid ratio, 70°C temperature, and 700 rpm stirring speed. The said process provides a viable solution for the sound management of e-waste and metal recovery.