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

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

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

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

Background 5MeBT  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

Background Freundlich Isotherm  Adsorption modeled by the equation: q = K F c 1/n  In linear form: log q = log K F + 1/n log c

Research Approach Adsorption of 5MeBT onto GAC  Experiments conducted at varying temperature, pH, concentrations, and GAC type:

Research Approach Adsorption of 5MeBT onto GAC  Experiments were conducted in triplicate at concentrations in the range of ppm 5MeBT –Each experiment included 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

Research Approach Sample Analysis  Analyses were accomplished using high performance liquid chromatography (HPLC) –fitted with a UV detector ( = 254 nm) Aromatic compounds absorb UV light

Results- GAC Effect

Results- Temperature Effects for pH = 3

Results- pH Effects at 15  C

Results- Discussion pK a = 2.0 pK a =8.8 GAC Effects - pH = 7.2 and 8.5 pH Effects Temperature Effects -Below pK a, temperature is less important

Isotherm Results Summary ExperimentpHTempCarbonK F Value 115Calgon Calgon Calgon Calgon Calgon Calgon Norit Calgon59.09

Metals

Research Objective Metals Hydrophilic SideHydrophobic Side

Immobilization of Metals to GAC using Benzotriazole

Research Approach Metals

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

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)

Results - Metals

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…

Questions?