TWO-PHASE METAL REMOVAL USING GRANULAR ACTIVATED CARBON AND 5 METHYLBENZOTRIAZOLE

1. TWO-PHASE METAL REMOVAL USING GRANULAR ACTIVATED CARBON AND 5 METHYLBENZOTRIAZOLE 7 August 2002 Cheryl Horn, Muna Abu-Dalo, Mark Hernandez Presented by: Cheryl Horn

2. Presentation Outline • Problem Statement and Goal • Background • Research approach / experimental design • Results • Interpretation of results • Conclusion and acknowledgements

3. Problem Statement • 1300 miles of streams in Colorado affected by acid mine drainage (AMD) • AMD is generally characterized by high metal loadings and low pH • Removal of metals can be accomplished by precipitation • Costly • Large sludge volumes produced • No metals recovery

4. Project Goal • Methylated benzotriazoles derivatives may be useful in the removal of metals from solution • Adsorption characteristics have not been heavily researched • Better understanding of the adsorption and metal-complexing behaviors of 5-Methylbenzotriazole (5MeBT) are necessary

5. Background5MeBT • Commonly used in aircraft deicing fluids and corrosion inhibitors • Has been shown to be biodegradable under aerobic conditions • Strong sorption characteristics (hydrophobic) • Preliminary research indicates adsorption onto granular activated carbon (GAC) may be accurately predicted using a standard Freundlich isotherm

6. BackgroundFreundlich Isotherm • Adsorption modeled by the equation: q = KFc1/n • In linear form: log q = log KF + 1/n log c

7. Research ApproachAdsorption of 5MeBT onto GAC • Experiments conducted at varying temperature, pH, concentrations, and GAC type:

8. Research ApproachAdsorption of 5MeBT onto GAC • Experiments were conducted in triplicate at concentrations in the range of 100-2000 ppm 5MeBT • Each experiment included 15-50 ml microcosms and one 50 ml control • Microcosms were prepared using Briton- Robinson buffer to maintain acidic conditions • Samples were collected and analyzed over three days

9. Research ApproachSample Analysis • Analyses were accomplished using high performance liquid chromatography (HPLC) • fitted with a UV detector ( = 254 nm) • Aromatic compounds absorb UV light

10. Results-GAC Effect

11. Results-Temperature Effects for pH = 3

12. Results-pH Effects at 15 C

13. Results-Discussion pKa =8.8 pKa= 2.0 • GAC Effects • - pH = 7.2 and 8.5 • pH Effects • Temperature Effects • Below pKa, temperature is less important

14. Isotherm ResultsSummary

15. Metals

16. Research ObjectiveMetals Hydrophilic Side Hydrophobic Side

17. Immobilization of Metals to GAC using Benzotriazole

18. Research ApproachMetals

19. Research Approach-Metals 1% Granular Activated Carbon Control A B 5MeBT, ppm 500 500 0 Cu, ppm 10 20 10 20 10 20 pH = 1 pH = 2 pH = 2.3 pH = 3 pH = 5 Copper added initially Copper added after adsorption Copper added initially

20. Research Approach-Sample Analysis • 5MeBT concentrations determined using HPLC • Copper concentrations analyzed in the University of Colorado’s Geology laboratory using Inductive Coupled Plasma/Atomic Emission Spectroscopy (ICP/AES) • Results were confirmed using differential pulse polarography (DPP)

21. Results - Metals

22. Results - Metals

23. Conclusions & Acknowledgements • Adsorption of 5-MeBT onto GAC can be accurately predicted by the Freundlich model • Further research should be done • Metals other than Cu • Thanks to Muna, Mark, JoAnn, Jenny…

24. Questions?