Biotic vs. Abiotic Structured Mackinawite
Biotic
- Resulting from living things.
- Requires an environment conducive for microbial life.
Example – Sulfate Reducing Microorganisms (SRM) produce sulfide, and when in the presence of iron, may react to form ferrous sulfide (FeS).
Abiotic
- Resulting from physical or chemical factors rather than biological (not derived from living organisms) .
Example – a FeS reagent that is manufactured or formulated to a specification in a chemical reactor and delivered to a remediation site.
Biotic and Abiotic Formation - Similarities
The first iron sulfide formed biotically is a reactive ferrous sulfide (FeS) mineral with a “mackinawite” structure. This is also the main ingredient in FerroBlack®.
-
Both biotic- and abiotic-formed iron sulfides are generally effective in:
- Promoting reductive de-chlorination.
- Lowering hexavalent chromium concentrations.
- Binding with individual metal cations (especially those in the “2+” valence state).
- Pyrite does not form in well-controlled, anoxic, biotic systems, nor is it present in abiotic suspensions of FerroBlack®
Biotic and Abiotic Formation - Differences
- Biotic FeS is formed in-situ; abiotic FeS (mackinawite) is synthetically manufactured and delivered to the site.
- As biotic FeS is formed, any phosphate present (which is a required nutrient for biotic microorganisms) may react with soluble iron and form an insoluble iron-phosphate mineral complex (vivanite) and not be available to form FeS.
- Biotic respiration produces “extra-cellular materials” which are “sticky” leading to larger aggregated particle-sized mackinawite which may potentially change aquifer flow characteristics.
- Transformation from mackinawite (FeS) to greigite (Fe3S4) is generally accelerated in biotic systems compared to abiotic FeS.
- Abiotic FeS (FerroBlack®) is appropriate for multi-metal contamination, however the biotic capabilities for multi-metals treatment are less understood.
- Abiotic (FerroBlack®) can be manufactured stoichiometrically balanced, with excess Fe, or with excess S.
- In a biotic system, environmental professionals must create and maintain an environment viable for a living microorganism colonies in a dynamic chemical and physical ecosystem.
Why “roll the dice” by assuming the in-situ conditions will be optimal for biotic FeS Formation?
Simply, Redox Solutions offers abiotically synthesized mackinawite structured iron sulfide products that eliminate the unknown factors of biotic iron sulfide formation.