Toxicity characterization of metals from various waste printed circuit boards

Toxicity characterization (TC) of printed circuit board (PCB) of various obsolete electrical and electronic equipment (EEE) was performed. The end-of-life EEE considered in the study include personal computer (PC), laptop, washing machine (WM), television (TV) and air conditioner (AC). The standardized procedures i.e. EP, TCLP, ASTM Method D-3987 and SPLP were employed for toxicity characterization of PCBs in terms of metal leachability against their total metallic contents. Further, the standard SPLP was modified (MSPLP) to imitate Indian acid rain conditions to comparatively assess metal leachability. Except Se, there was statistically significant (P < 0.05) difference in metal contents of PCBs from different sources with Cu (maximum: 231133 ± 3889 mg/kg in laptop) and Pb (maximum: 73900 ± 22100 mg/kg in laptop) being the predominant metallic species. The TC test conditions showed statistically significant (P < 0.05) difference in metal leachability from respective EEE. Results indicated that Pb (maximum: 226.74 ± 3.11 mg/l in TCLP for laptop) and Ni (maximum: 0.942 ± 0.053 mg/l in SPLP for AC) in leachates exceeded the threshold toxicity limit. The general sequence of metal leachability, from most labile to least labile, from waste PCBs was: Pb > Cu > Zn > Al > Ni > Cd > Se > As > Ba. Except Pb, Cu and Zn, the ASTM procedure at neutral pH showed insignificant metal leachability. Standard SPLP and the MSPLP showed similar effect of Indian and western acid rain conditions on metal leachability. Greater leachability of Pb and Ni simultaneously indicated possible risk to the environment upon e-waste disposal.