Abstract

A toxic waste “slag” generated in a lead (Pb) recovery plant was characterized and its local “slag” dispersion was monitored. The major constituents of the “slag”, in increasing weight percent, were CaO (1.5), PbO (3.4), SiO₂ (5.2), Na₂O (17.8), SO₃ (27.5) and Fe₂O₃ (40.7). The “slag” was alkaline with a pH of 10 and an electrical conductivity of 606 dS m^-1. Tests for Pb leaching indicated that, in a moderately acid environment, as much as 8 mg Pb L^-1 may be washed out of the “slag”; there are amounts that are well above the limits set by Mexican legislation. The highest concentration of Pb in soil surrounding the recycling plant (447 mg Pb kg^-1) was found 50 m southwest of the recovery plant. Due to its high Pb level and easy dispersion into the environment, the health of human settlements in the area could be at risk.

Key words: Toxic waste, alkaline material, Pb leaching.