Laboratory tests on arsenic leaching from excavated shale rock by elevated temperatures

Abstract

This manuscript focuses on the leaching of geogenic arsenic (As) from shale rock at different temperatures. In Japan, the utilisation of geogenic contaminated soils and rocks for construction such as in embankment is much encouraged. Therefore, when applying thermally active geo-systems such as thermal energy storage and ground-source heat pump, which are associated with ground temperature changes, we need to know its impact on the leaching behaviour of such contaminated geomaterials. In this study, the leaching of chemicals from an excavated shale rock containing geogenic As was assessed using a shaking and non-shaking batch test. In those experiments, different temperatures up to 40 ºC and contact times ranging from 6–360 h were employed. Overall, it was found out that more As was leached with elevated temperatures and its concentration was notably higher under the non-shaking condition. Further, under the non-shaking condition, its concentration was highest at 40 ºC with contact time of 360 h, whereby ca. 0.06 mg/L As was leached, which is 6 times the permissible limit of 0.01 mg/L in Japan.