Chemical characterization and local dispersion of slag generated by a lead recovery plant in Central Mexico

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), SiO 2 (5.2), Na 2 O (17.8), SO 3 (27.5) and Fe 2 O 3 (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.