DISSOLUTION OF METALLIC PLATINUM AS WATER-SOLUBLE SPECIES BY NATURALLY-OCCURRING COMPLEXING AGENTS

Platinum is released into the environment as a result of surface abras ion from automobile catalysts during operation. Previous investigation s showed that this finely dispersed metallic platinum is dissolved in organic matrices, e.g. a humic soil to a significantly high degree, re sulting in possibly bioavailable Pt species. In this work several natu ral complexing agents (adenosine, ADP ATP L-His, humic acid fraction, L-Met, pyrophosphate, and triphosphate) were treated with metallic pla tinum (as Pt black and as a Pt(0) containing tunnel dust) for 3-60 d. Some of the compounds used dissolved Pt(0) to a recognizable degree, w hereas others were in the range of the aqueous blanks. Comparison of P t black with a natural dust sample showed that L-methionine had in bot h cases the greatest effect after 60 d. Generally more Pt(0) vias diss olved in the dust sample (finer dispersion and smaller particle size) than in the Pt-black used. By carrying our: the experiment under natur al conditions instead of in pure oxygen-, the amounts of dissolved pla tinum are about one order of magnitude lower.