SELEN-IXTM: ION EXCHANGE AND ELECTROCHEMISTRY AT WORK TO COST EFFECTIVELY REMOVE SELENIUM FROM MINE IMPACTED WATERS TO ULTRA-LOW CONCENTRATIONS
Farzad Mohammadi, Patrick Littlejohn and David Kratochvil
BioteQ Environmental Technologies, Vancouver, Canada
ABSTRACT
With more rigorous regulations being enacted in the mining industry, a need exists for cost effective and environmentally compliant technologies to remove selenium from mine impacted waters to ultra-low concentrations. Existing selenium treatment methods
have high life cycle costs, introduce risks of acute fish toxicity, and produce biological waste residues that may represent future liabilities. Furthermore, achieving selenium discharge limits of less than 3 ppb is a challenge for existing technologies. Selen-IX™ is a technology developed by BioteQ that selectively removes selenium from mine impacted waters to less than 1 ppb. The technology is purely physico-chemical and takes advantage of the basic principles of ion exchange and electrochemistry. Unlike conventional electrocoagulation that removes suspended solids and breaks emulsions
or oxidizes heavy metals, the electrochemical process employed by Selen-IX
TM relies on creating conditions where iron acts as a highly effective reducing reagent transforming selenium from a dissolved species into elemental selenium bound in a solid phase. The iron-selenium by-product of Selen-IX™ is purely inorganic,
non-hazardous, and chemically stable (Figure 1). Due to their high iron content, the solids produced by Selen-IX™ are of interest to the steel making industry as a low cost feedstock. This offtake potential can not only reduce the life cycle cost of selenium removal by reducing disposal costs but more importantly, eliminate the risk of future environmental liabilities.
In this paper, the basics of Selen-IX
TM technology are presented along with results of successful piloting on streams from coal and copper-gold deposits.
Figure - XRD spectra of iron-selenium solids produced during pilot campaign
KEYWORDS
Selenium, cost effective treatment, mine impacted waters, ion exchange, electrochemistry, iron