Post on 28-Feb-2022
Immobilization of antimony (Sb) in shooting range
soil by soil amendments
Espen Mariussen
Arnljot Strømseng
Norwegian Defence Research Establishment (FFI)
- Metal accumulation in small arms shooting ranges
Helsinki 21-22. May 2013
Stop butt
Ground water surface
Bedrock
Metals
Cu
Pb Sb
Zn Surface
run-off
Leachate
Antimony in shooting ranges
• Lead bullets contain Sb as an alloy
– Used as an hardening agent
• For the years 2004-2008
– Annually input of approximately 14 metric ton of Sb
– Both in stop-but zones and heterogeneously spread
• Sb is readily mobilized from the bullets during weathering
– Elevated concentrations in run-off water (5-20 µg/L)
• Sb is a particular problem when contaminated soil is to be deposited at
waste disposal sites.
• Often categorized as hazardous waste due to the high mobility of Sb.
• Increase considerably the cost of remediation projects
Helsinki 21-22. May 2013
Stabilization of elements in soil
• Reactive sorbents added to the soil may adsorb and reduce leakage
of hazardous metals.
– Less spread into environment from stop butts
– Safer and more economical feasible waste disposal
• The sorbents should adsorb both cationic (Pb and Cu) and anionic
species (Sb).
• The goal is:
– Identify sorbents with high capacity and ability of sorption
– Identify sorbents that are economical feasible
– Identify sorbents that are easy to handle
Helsinki 21-22. May 2013
1. Hydroxyapatite (Ca5(PO4)3(OH)):
– Used as an amendment to stabilize Pb and Cu in soil
2. Finely grounded olivine (Mg2Fe2SiO4):
– Used in the field as a leakage barrier to reduce leakage of metals from
disposed shooting ranges
– Contain Fe and Mg oxides with presumed binding properties to both cations
and anions
3. Iron oxides
a) Ferric oxyhydroxide (Fe(O)OH) from Kemira®
b) Ferric oxide (Fe2O3) from Merox®
• Charged surface groups that can form complexes with both
cations and anions
4. Zero-valent iron (Fe0)
a) (Fe0)-grit (0.3-1mm) and (Fe0)-powder (< 150 µm)
• Oxidize into amorphous Fe-oxides with high sorption capacity
to both cations and anions.
Reactive sorbents tested
Experimental
• 2-4% sorbent (w/w) mixed in soil
– Tractor mixer and cement mixer
Experimental • PVC columns (~75 L) prepared with soil and connected to a vacuum pump
– 6 different soil types from stop-butt were tested
• Regularly addition of rainwater by a sprinkler system (3-5L each application)
• Collection of soil water
Helsinki 21-22. May 2013
Leakage of Sb from butt soil
-Column study with simulated precipitation
-Leakage from the reference soil
Evjemoen soil Rena soil
Sessvoll soil
Ulven soil
Treshold limit for hazardous waste
Treshold limit for non-hazardous waste
Treshold limit for inert waste
• All soils had Sb-leakage above the threshold limit for non-hazardous
waste
• Four of the soils have Sb-leakage above the threshold limit for
hazardous waste
– Waste disposal of hazardous waste involves high cost
Helsinki 21-22. May 2013
Leakage of Cu, Sb and Pb from butt soil
-Column study with simulated precipitation
-Leakage from the reference soil
Evjemoen 2 soil Steinsjøen soil
Results
• Effects of the soil amendments
Helsinki 21-22. May 2013
Hydroxyapatite as sorbent
Helsinki 21-22. May 2013
Rena soil
Ulven soil
Evjemoen soil
Sessvoll soil
Increased leakage of Sb
•Anion exchange with PO3-
•Suitable for Pb and Cu, but not in combination with Sb
Olivine as sorbent
Helsinki 21-22. May 2013
Evjemoen soil Rena soil
Sessvoll soil Ulven soil
Increased leakage of Sb
•Anion exchange with PO3- or carbonates??
•Suitable as a leakage barrier but not as soil amendment
Iron oxides as sorbent; Merox® Fe2O3
• Reduced leakage of Sb
• Three of the soils below threshold for hazardous waste
• Not adequate performance compared to hydrated iron oxides
• Non-hydrated iron oxide with higher proportion of crystalline Fe-forms may
implicate less sorption sites
Helsinki 21-22. May 2013
Evjemoen soil Rena soil
Sessvoll soil Ulven soil
Zerovalent iron as sorbent; Fe0-powder
Helsinki 21-22. May 2013
Evjemoen soil
Rena soil
Sessvoll soil Ulven soil
Zerovalent iron as sorbent; Fe0-grit
• Reduced leakage of Sb >95%
• Three of the soil types below threshold limits for inert waste
• One of the soils still above threshold limit for hazardous waste
• Crusting and compaction of the soil due to oxidation of the iron
• Zerovalent iron is a very promising product as a soil stabilizing agent
• Zerovalent iron oxidizes to rust, which consists of hydrated iron(III) oxides Fe2O3·nH2O
and iron(III) oxide-hydroxide FeO(OH)·Fe(OH)3
Helsinki 21-22. May 2013
Evjemoen 2 soil Steinsjøen soil
Iron oxide-hydroxide as sorbent; Kemira® Fe(O)OH
Helsinki 21-22. May 2013
Evjemoen 2 soil Steinsjøen soil
Reduced leakage of Sb >95%
•Well below threshold limits for inert waste
•Very promising product as a soil stabilizing agent
Iron oxides as soil stabilizing agent
• Iron oxides creates surface complexes with both anions and cations
– ( FeO−, FeOH0, FeOH2+).
• Adsorption is governed by pH and the iron oxides iso-electric point.
– At low pH, predominantly positive charge which will favour sorption of anions
(such as Sb and As)
– At high pH, predominantly negative charge which will favour sorption of cations
(such as Pb and Cu)
• High surface area of the sorbent will increase the number of sorption
sites
• Amorphous forms of the sorbent will favour sorption compared to
crystalline forms
Helsinki 21-22. May 2013
Iron and iron oxides as sorbents for Sb depend
on several factors
• Iron oxide-hydroxide (Fe2O3·nH2O or Fe(O)OH)) probably better
than the iron oxides (Fe2O3, Fe3O4).
– More sorption sites due to an amorphous state with a high surface area
– Crystalline properties of the iron oxides will reduce sorption
• pH dependency
– The surface charge properties (-FeOH-, -FeOH, FeOH2+) varies
depending on pH
• Acid conditions should favor Sb-adsorption
• Anarobic or aerobic conditions
– Aerobic conditions will increase oxidation of zerovalent iron which
probably will increase the sorption capacity.
– Zerovalent iron oxidizes to rust, which consists of hydrated iron(III)
oxides Fe2O3·nH2O and iron(III) oxide-hydroxide FeO(OH)·Fe(OH)3
Helsinki 21-22. May 2013
Thank you for your attention
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Helsinki 21-22. May 2013