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Cut‐off Net Acid Generation pH in Predicting Acid‐Forming Potential in Mine Spoils
Author(s) -
Liao B.,
Huang L. N.,
Ye Z. H.,
Lan C. Y.,
Shu W. S.
Publication year - 2007
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0420
Subject(s) - chemistry , environmental science
Acidification of mine wastes can lead to a series of environmental problems, such as acid drainage, heavy metal mobilization, and ecosystem degradation. Prediction of acid‐forming potential is one of the key steps in management of sulfide‐bearing mine wastes. In this paper, the acid‐forming potential of 180 mine waste samples collected from 17 mine sites in China were studied using a net acid generation (NAG) method. The samples contained different contents of total sulfur (ranging from 0.6 to 200 g kg −1 ), pyritic sulfur (ranging from 0 to 100 g kg −1 ), and acid neutralization capacity (ANC, ranging from −41 to 274 kg H 2 SO 4 t −1 ). Samples with high acid‐forming potential are generally due to their high sulfur content or low acid neutralization capacity. After the samples were oxidized by H 2 O 2 , the amounts of acid generation and the final NAG pH were measured. Results indicated that the final NAG pH gave a well‐defined demarcation between acid‐forming and non‐acid‐forming materials. Samples with final NAG pH ≥ 5 could be classified as non‐acid‐forming materials, while those with NAG pH ≤ 2.5 could be classified as moderate to strong acid‐forming materials. Materials with NAG pH > 2.5, but < 5, had low risk of being acid‐forming. The confirmation of cut‐off NAG pH will be used as a rapid and cost‐effective operational monitoring tool for the in‐pit prediction of acid‐forming potential of mine wastes and classification of waste types.