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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
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
N
N
HN
H3C
BackgroundFreundlich Isotherm Adsorption modeled by the equation:
q = KFc1/n
In linear form:
log q = log KF + 1/n log c
Research ApproachAdsorption of 5MeBT onto GAC
Experiment pH Temperature,C Carbon 1 1 5 Calgon 2 1 15 Calgon 3 1 25 Calgon 4 3 5 Calgon 5 3 15 Calgon 6 3 25 Calgon 7 3 15 Norit 8 5 15 Calgon
Experiments conducted at varying temperature, pH, concentrations, and GAC type:
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
Research ApproachSample Analysis
Analyses were accomplished using high performance liquid chromatography (HPLC)– fitted with a UV detector ( = 254 nm)
• Aromatic compounds absorb UV light
N
N
HN
H3C
Results-GAC Effect
Freundlich Isotherm(GAC effect)
-50
0
50
100
150
200
250
0 50 100 150 200
Ceq
q
pH=3,Temp15C,Calgon
pH=3, Temp15C,Norit
Log.(pH=3,Temp15C,Calgon)Log. (pH=3,Temp15C,Norit)
Results-Temperature Effects for pH = 3
Freundlich Isotherm (Temp effect)
-50
0
50
100
150
200
250
0 100 200 300 400
Ceq
q
pH=3, Temp 5CpH=3,Temp 25CpH=3,Temp15C
Results-pH Effects at 15 C
Freundlich Isotherm (pH effect)
-500
50100
150200250
0 50 100 150 200
Ceq
q
pH=3, Temp 15CpH=1, temp15CpH=5, temp15C
Results-Discussion
N
NH
HN
H3C
+
N
N
HN
H3CpKa = 2.0
N
N
N
H3C
-
pKa =8.8
•GAC Effects
- pH = 7.2 and 8.5
•pH Effects
•Temperature Effects
-Below pKa, temperature is less important
Isotherm ResultsSummary
Experiment pH Temp Carbon KF Value
1 1 5 Calgon 42.15
2 1 15 Calgon 35.48
3 1 25 Calgon 45.10
4 3 5 Calgon 34.53
5 3 15 Calgon 54.21
6 3 25 Calgon 48.19
7 3 15 Norit 39.04
8 5 15 Calgon 59.09
Metals
Research ObjectiveMetals
N
N
HN
N
N
HN
N
N
HN
N
N
HN
N
N
HN
N
N
HN
R
M+x
electronegativecharge density
δ-
N
N
HN
N
N
HN
N
N
HN
N
N
HN
N
N
HN
N
N
HN
RM
complexation reduces negative charge density
Zn+
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HNN
N
HN
NN
HN
NN
HN
Cu
CuZnN
N
HN
NN
HN
NN
HN
Zn
GranularActivatedCarbon
A
B
Zn+
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HNN
N
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
Cu
CuZnN
N
HN
NN
HN
NN
HN
Zn
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
NN
HN
Zn
GranularActivatedCarbon
A
B
Hydrophilic Side Hydrophobic Side
Immobilization of Metals to GAC using Benzotriazole
NH
N
N
H3C
N
N
N
Cu
HN
NN
CH3
N
N
N
Cu
CuN
NN
H3C
B
A
Research ApproachMetals
Research Approach-Metals
pH = 1
pH = 2
pH = 2.3
pH = 3
pH = 5
5MeBT, ppm10 20Cu, ppm
500
Copper added initially
50010 20
Copper added after adsorption
010 20
A B 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
20 ppm Copper + 500 ppm 5MeBT
020406080
100
1 2 2.3 3 5
pH
% R
emo
val Scenario1
Scenario2
Control
Results - Metals
10 ppm Copper + 500 ppm 5MeBT
020406080
100
1 2 2.3 3 5
pH
% R
emo
val Scenario1
Scenario2
Control
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?