MUNICIPAL LANDFILL LEACHATE INORGANIC ANALYSIS FOCUSING ON DETECTING VALUABLE METALS

Pumped municipal solid waste landfill leachate samples (7 cells from a site in Nebraska, 4 cells from a site in Illinois) have been analyzed for 62 elements using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). A procedure for complete dissolution of solids in the leachate was developed. Complete dissolution aims to reduce material loss in filtration by eliminating the need for filtration, and frees materials entrapped in undissolved solids. The procedure uses centrifugation to separate solid phase matter from the raw sample to maximize the effect of acid, and uses Chloric, Nitric, Fluoric, and Boric acids with microwave digestion to achieve full dissolution. The dissolved solid fraction precipitates yttrium fluoride and some other metals due to over-solubility concentrations; the precipitate is recovered and redissolved for analysis. Platinum, (Post-) Transition, and Lanthanide group metals were positively detected in the landfill leachate. Individual metals from these groups were detected in either/both aqueous or/and solid phases: solid phase metals are usually at least one magnitude of concentration greater than liquid phase metals, unless the solid phase produced no detection of the metal where the liquid phase did. Noteworthy results are: in the solid phase; Al was quantified from 10 to 103 𝜇g/g of solid mass; Sc, Cr, Ti, and Cu were quantified in the solid phase from 1 to 50 𝜇g/g of solid mass; Zr and Eu were quantified from .5 to ~8 𝜇g/g of solid mass. In the liquid phase: Ti, Cr, Li, Cu, As, and Zr were quantified mostly between 10-2 to 10-1 𝜇g/g of liquid mass, but occasionally reach out of those bounds; Al, Sc, Pt, Co, and V were quantified mostly from 10-3 to 10-2 𝜇g/g of solid mass. Solid phase metals were positively detected with a minimum Limit of Detection (LOD) usually around 10-1 𝜇g/g of solid mass, including: In, Ge, Pb, Ru, Sb, Ta, Hf, Bi, Yb, La, Ti, Pd, Lu, Dy, and Tb. Liquid phase metals were positively detected with a minimum LOD usually around 10-5 𝜇g/g of liquid mass, including: Tm, Ge, Au, Pb, Sb, Ta, Hf, Sm, Nb, Ho, Ga, Bi, Yb, Pd, Er, and Cd.