4. Conclusions
Arsenic and Hg can be determined in acetic acid extracts of solid waste residues by combining chemical vapor generation with atomic spectrometric techniques. Using NaBH4 as reducing agent for measur- ing As and Hg by AAS and SnCl2 as reducing agent for measuring Hg by AFS, the obtained detection limits are well below the concentration limits of the Norms for classification of waste residue concerning the toxicity of the elements. The efficient vapor generation of arsine re- quired the previous reduction of As(V) to As(III), using KI. The addition of KMnO4 to convert all organo-mercury compounds to Hg2+ previous- ly to the cold vapor generation was required for both detection tech- niques. The proposed methods are accurate and precise and can be used in routine, requiring simple instrumentation. This procedure might well be extended to other solid waste after TLCP.
The analysis of the extracts of two solid waste residues, a retorted shale and a spent catalyst, demonstrate that these two residues are non-toxic concerning As and Hg.