Arsenic release from a natural rock under near-natural oxidizing conditions

Abstract

The solubilization of arsenic (As) from an ore material (native Arsenic [As, trig.] with Lollingite [FeAs2, rh.]) was characterized in leaching tests lasting for ≤ 99 days. The experiments were performed with materials of different particle sizes (≤ 2 mm), in different waters and under test conditions relevant to As mobilization at near surface contaminated sites. The impact of dolomite [CaMg(CO3)2], metallic iron (Fe0), and pyrite (FeS2) on As release was accessed. Two different types of batch experiments were conducted with a constant amount of the base material and different types of water (deionised, mineral, spring, and tap water). For comparison parallel experiments were conducted with 0.1M EDTA, 0.1M Na2CO3 and 0.1M H2SO4. The results indicated no significant effect of carbonate addition on As solubilization. Fe0 and FeS2 addition essentially slowed the initial As solubilization. H2SO4 was the sole leaching agent significantly influencing As solubilization from the base material. The general trend assuming that the smaller the particle size the quicker the As release was not strictly verified because in samples of smaller particle sizes (d < 0.063) As was partly oxidized to more stable species.