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Review of Chromium Speciation Research. Research Project: Assessing the Impact of Chromium in the Environment Assessing the Impact of Chromium in the.

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Presentation on theme: "Review of Chromium Speciation Research. Research Project: Assessing the Impact of Chromium in the Environment Assessing the Impact of Chromium in the."— Presentation transcript:

1 Review of Chromium Speciation Research

2 Research Project: Assessing the Impact of Chromium in the Environment Assessing the Impact of Chromium in the Environment Funding provided by the Florida Department of Environmental Protection RCRA Program

3 Chromium Exists as Several Chemical Species Most common oxidation states: 0, +3, +6 0: Elemental Chromium (Cr) +3: Trivalent Chromium Species: Cr +3, Cr 2 O 3 +6: Hexavalent Chromium Species: CrO 4 2-, Cr 2 O 7 -

4 Chromium Speciation Important! The characteristics and properties of trivalent chromium and hexavalent chromium are greatly different. Cr(VI) is much more toxic and mobile than Cr(III)

5 pH Cr 2 O 3 CrO 4 2- Cr 2 O 7 - Cr 3+ Eh (volts) Chromium Eh-pH Diagram

6 Fate of Chromium in CCA- Treatment Process –CrAsO 4 –Cu(OH)CrAsO 4 –CuCrO 4 –Cr(OH) 3 –Cr 6+ /wood complexes –Cr 3+ /wood complexes –Cu 2+ /wood complexes CrO 3 CuO As 2 O 5 Treating SolutionTreated Wood Cr +6 Cr +3

7 Research Objective Examine the fate and behavior of hexavalent chromium in various environmental media impacted by CCA

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9 0.0 mg Cr +6 /l0.3 mg Cr +6 /l0.6 mg Cr +6 /l

10 Alkaline Digestion SW-846 Method 3060A

11 IC System Detector Integrator Analytical Column Guard Column LC Pump

12 Experiment 1 Examination of the fate of hexavalent chromium in soils spiked with CCA solution Cr(VI)/Cr(total) concentrations were measured over time Leachable Cr(VI) and Cr(III) concentrations measured over time (SPLP)

13 Soil Types

14 Reduction in Total Cr+6 with Time

15 Experiment 2 How Much CrVI is in CCA-Treated Wood

16 Results Alkaline digestions on CCA-treated wood samples show Cr +6 concentrations in the range 7 to 250 mg/kg (less 3% of all Chromium) SPLP leachates have no detectable Cr +6 concentrations

17 Experiment 3 Under what leaching conditions would Cr +6 form?

18 Chromium Leachability as a Function of Time (weathered wood sample)

19 TCLP & SPLP MSW Landfill Leachate Alkaline Leachate

20 Experiment 4 Will Cr +6 be formed in simulated alkaline leachate? Scenario: saturated concrete

21 Chromium Leaching in Concrete Leachate

22 Experiment 5 Is Cr +6 formed during combustion of CCA-treated wood?

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