Toxicity of and metals in coal combustion ash leachate

Abstract

Land disposal of coal combustion ash can have a potential impact on the ecosystem due to the leaching of metals with increasing acidity of precipitation. The objective of this research was to study the effect of pH on the concentration of metals leached from coal combustion ash and to measure the toxicity of the leachates. Bottom coal combustion ash was leached with hydrochloric acid (HCl) or acetic acid (CH 3COOH) at pH4, 5, 6 or 7. The toxicity of the aqueous leachates and concentrations of the metals (arsenic, cadmium, chromium, copper, iron, lead, nickel, silver and zinc) therein were measured using Microtox ® ( Vibrio fischeri—EC 50%) and atomic absorption spectrophotometry, respectively. Toxicity and metal concentrations of the leachates were highest when ash was leached with HCl at pH 4. Toxicity and metal concentrations of ash leached with CH 3COOH were significantly lower compared with ash leached with HCl. High correlation ( r) was observed between the toxicity and the metal concentrations in both the acid leachates.