Rare earth element (REE) and arsenic mobility in acid mine drainage (AMD) impacted soil

Abstract

The mobility of rare earth elements (REE) and arsenic (As) from acid mine drainage (AMD) impacted soil was investigated in a column leaching study. AMD impacted soils from prominent gold and coal mining regions in South Africa were eluted with a 1 µM CaCl2 solution for 14 h and samples were collected at timed intervals corresponding to liquid to solid (L/S) ratios from 0 to 10. The results showed fast initial leaching (L/S < 5) leading to the leaching of 30–98 % of the total soil REE contents and 0.02–1.8 % of total soil As contents. The results show substantial indications of REE leachability and hence recovery from mining impacted soils. This has the potential to improve cost effectiveness of the remediation process. Conversely, As was found to be highly retained in the AMD impacted soils. This offers insights into the comparative conditions of leachability in AMD impacted soils. Further investigation into the mineral structures present in various AMD impacted soil media under leaching conditions is needed to fully explain the underlying geochemical factors responsible for the elements’ release.

Keywords

• Rare earth elements
• Arsenic
• Leaching
• Critical elements
• Acid mine drainage