In-situ adsorptive pyrolysis of e-waste using coal and rice husk fly ash as alternative adsorbents for energy and precious metal recovery by solvent extraction

Abstract

This paper aims to use in-situ adsorptive pyrolysis combined with ultrasonication and solvent extraction for precious metal recovery from e-waste. The pyrolysis of discarded printed circuit board (PCB) and waste cable (WC) resulted in pyrolysis oil yields of 4.2–13.0 and 6.8–13.5%, respectively. Aliphatic and single-ring compounds were the major components of the pyrolysis oil. The pyrolysis char was ultrasonicated at 40 kHz for 20, 30, and 40 min at 35 °C to separate precious metals in pyrolysis char. The amounts of Au and Ag recovered by solvent extraction experiments with 2%vol HCl/2%vol HNO3, 2%vol HNO3 and 2%vol I2/2%vol H2O2 were 36.3–61.4 and 60.7–79.9%, respectively. The total energy recovery from the pyrolysis char, oil, and gas obtained from the pyrolysis of PCB was 9.0–9.2 MJ/kg. These results indicated that in-situ adsorptive pyrolysis with ultrasonication and solvent extraction could potentially facilitate e-waste conversion for energy and metal recovery processes at a lower cost.