Characterisation of Antimony-bearing Scorodite for Remediation of Toxic Mine Waste

Since the dawn of civilization, humankind has been extracting metals and minerals for the production of goods, energy and buildings. These activities have created great wealth, but they have also produced huge quantities of solid and liquid waste, known collectively as 'mine waste'. It has been estimated that the quantity of solid mine waste generated throughout the world matches that of Earth materials moved by fundamental global geological processes, at approximately several thousand million tonnes per year. Mine wastes contain toxic antimony (Sb) in concentrations that pose serious hazards to ecosystems, health and livelihoods. Humans can develop problems such as DNA damage and lung cancer from ingestion or inhalation of Sb-bearing particles. The risks posed by exposure to Sb can be mitigated by the formation of insoluble minerals that take up the Sb so it has low bioaccessibility. One such mineral is scorodite, hydrated iron arsenate oxide (FeAsO4.2H20). No one has evaluated the potential for scorodite to take up Sb, even though Sb and As (arsenic) have similar chemical properties, and they have been shown to substitute for one another in other minerals. We have discovered an Sb-rich scorodite in decomposed mine tailings from Bolivia, but the full potential of scorodite to take up Sb has not been investigated. Therefore, this study is aimed at answering the questions 'How efficient is scorodite at taking up Sb compared to As?', What are the chemical and mineralogical properties of Sb-rich scorodites?', and 'What are the predicted bioaccessibilities of Sb-bearing scorodites?' By answering these questions, we will be able to design schemes for remediating Sb-contaminated mine wastes using Sb-bearing scorodites, and thus improve the lives of 10s to 100s of thousands of people worldwide.

The beneficiaries of the research are:

(1) The scientific community interested in the causes and impacts of mine wastes. This community will benefit from the novel data provided by the study, in that Sb-bearing scorodite might be increasing recognised as a store of Sb in mine waste environments, in that minerals are re-emphasised as having major remedial potential in mining-affected environments; and in that new challenges and research in mine wastes will be initiated. The scientific community will be informed of the results by publication in high-impact journals in the fields of earth and environmental sciences. The results will also be presented at national and international conferences (e.g., Mineralogical Society, Goldschmidt, Tailings and Mine Waste).

(2) Industry, and governmental and non-governmental organisations working on remediating and managing ARD/AMD-affected areas, including:
(i) The Environment Agency
(ii) The Coal Authority
(iii) NGOs such as WWF and the Catholic Agency for Overseas Development (CAFOD)
(iv) Mining companies.
These organisations will benefit from having a sound scientific understanding of the nature and importance of scorodite, and the potential bioaccessibility of Sb in this mineral. These new data will support the future design of management and remediation schemes, and also impact on new mine development and environmental protection. For example, if our work proves that scorodite is highly efficient at sequestering Sb and reducing its bioaccessibility, then schemes can be designed to promote the formation of this mineral. Key colleagues in (2) will be informed of the results by invitations to research laboratories. The results will be made available to all members of (2) through a dedicated project website, other live presentations and articles in the popular scientific media.