Laboratory Evaluation of Ash materials as Acid-Disturbed Land Amendments

Abstract

Fly ash (FA) and fluidized bed ash (FBA) solutions were evaluated as amendments for acid-disturbed lands, more specifically for treating acidic and metal contaminated soil. While titrating the ash materials with different volumes of acid, pH changes were monitored as a function of time and the acid volume added. The release of metals from the ash materials as a function of pH was also monitored. An acid mine drainage (AMD) solution was equilibrated with ash materials and clay and the metal removal from the solutions evaluated. Both FA and FBA produced solutions of high initial pH. However, FBA indicated a higher buffering capacity resulting in a steeper titration curve. The system pH strongly impacted metal release from the ash materials. The leaching experiment indicated a pattern whereby the basic metals (Ca and Na) were released at higher pH and the acidic metals (Fe and Cr) at lower pH. Limestone had almost double the buffer intensity but a lower initial pH than ash materials. Comparison of ash materials with two types of clay revealed that ash materials were better alternatives for treating acidic and high metal content wastes. Albeit both ash materials were able to treat AMD, their overdose could lead to trace metal accumulation with negative consequences to the environment.