Leaching behaviour of selected trace elements in chemically weathered alkaline fly ash

• Published in: The Science of the total environment 1988-10, Vol.76 (2), p.229-246
• Main Authors: Warren, C.James, Dudas, Marvin J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Other industrial wastes. Sewage sludge; Pollution; Wastes
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/0048-9697(88)90110-6

In a laboratory study alkaline fly ash was leached in a series of lysimeters with dilute H 2SO 4. The weathered residues retrieved after leaching were analyzed for major constituents by atomic absorption spectrophotometry and trace elements by instrumental neutron activation analysis. The characteristics of the weathered residues ranged from highly leached acidified material, from which many constituent elements had been mobilized, to minimally leached alkaline material containing accumulations of newly formed secondary minerals. The leaching behavior of constituent trace elements was related to the chemical environment of the leachates and partitioning among two previously identified major phases within parent ash particles and with newly formed secondary minerals. Elements such as Rb, Cs, Pb, Ta, Ti, and Hf were enriched in the highly leached portion of the residue sequence, suggesting association with the resistant internal Si-rich glass matrix of ash particles. Between 50 and 80% of the total Mn, Sb, Th, Cr, Zn, Co, Sc, and rare earth elements was also retained in the highly leached ash residues. About 50% of the total Sr, V, and U, and more than 80% of the total As and B was dissolved from the ash under acidic conditions. With the exception of B, all elements that were mobilized from the acidified ash residues were also attenuated in the alkaline residues in association with one or more of the newly formed secondary minerals.