Anaerobic batch leaching tests of shale rock grains

Arsenic leaching from shale rock grains was evaluated by the regulatory and modified batch leaching tests. The regulatory test was in according to the Japanese Leaching Test No. 46. The modified batch leaching tests were carried out using de-aired distilled water and eliminating headspace to simulate anaerobic conditions. The results show that dissolved oxygen (DO) in normal batch leaching tests is ~6.0 mg/L. DO can be reduced to ~2.0 mg/L by using deaired water and eliminating the headspace and shaking step. The results suggest that a pseudo anaerobic condition can be achieved by eliminating the headspace and shaking step and conducting the tests in the vacuum deaerator since the DO was very low (~1.1 mg/L). Under the pseudo anaerobic conditions, the arsenic leaching concentrations are lowest (~0.001 mg/L), implying that arsenic leaching might be suppressed under anaerobic conditions. Furthermore, these arsenic concentrations are below the regulatory standard (As < 0.01 mg/L), suggesting that the shale rock grains are environmentally safe for utilisation in geotechnical applications.