Transcript TWO-PHASE METAL REMOVAL USING GRANULAR ACTIVATED …

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 metalcomplexing behaviors of 5-Methylbenzotriazole
(5MeBT) are necessary
Background
5MeBT
H
N
N
H3C


N
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 = KFc1/n

In linear form:
log q = log KF + 1/n log c
Research Approach
Adsorption of 5MeBT onto GAC

Experiments conducted at varying temperature,
pH, concentrations, and GAC type:
Experiment pH Temperature,C Carbon
1
2
3
4
5
6
7
8
1
1
1
3
3
3
3
5
5
15
25
5
15
25
15
15
Calgon
Calgon
Calgon
Calgon
Calgon
Calgon
Norit
Calgon
Research Approach
Adsorption 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 BritonRobinson 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
H
N
N
H3C
N
ResultsGAC Effect
Freundlich Isotherm(GAC effect)
250
200
q
150
100
50
0
-50 0
50
pH=3,Temp15C,Calgon
pH=3, Temp15C,Norit
Log.
100
Ceq
150
200
ResultsTemperature Effects for pH = 3
Freundlich Isotherm (Temp effect)
250
q
200
150
100
50
0
-50 0
100
pH=3, Temp 5C
pH=3,Temp 25C
pH=3,Temp15C
200
Ceq
300
400
ResultspH Effects at 15 C
q
Freundlich Isotherm (pH effect)
250
200
150
100
50
0
-50 0
50
pH=3, Temp 15C
pH=1, temp15C
pH=5, temp15C
100
Ceq
150
200
ResultsDiscussion
+
NH
N
N
H3C
N
H
N
H
N
pKa = 2.0
N
H3C
N
pKa =8.8H3C
•GAC Effects
- pH = 7.2 and 8.5
•pH Effects
•Temperature Effects
-Below pKa, temperature is less important
N
Isotherm Results
Summary
Experiment
1
2
pH
1
1
Temp
5
15
Carbon
Calgon
Calgon
KF Value
42.15
35.48
3
4
5
6
1
3
3
3
25
5
15
25
Calgon
Calgon
Calgon
Calgon
45.10
34.53
54.21
48.19
7
8
3
5
15
15
Norit
Calgon
39.04
59.09
Metals
Research Objective
Metals
H
N
Zn
N
electronegative
charge density
H
N
R
N
N
N
Cu
N
H
N
Cu
N
N
Zn HN
H
N
N
N
R
N
H
N
N
N
δ-
M+x
Granular
Activated
Carbon
Zn+
A
B
M
complexation reduces
negative charge density
Hydrophilic Side
Hydrophobic Side
H
N
N
N
Immobilization of Metals to GAC using
Benzotriazole
Research Approach
Metals
Research ApproachMetals 1% Granular Activated Carbon
A
500
10
20
5MeBT, ppm
Cu, ppm
pH = 1
B
500
10
20
Control
0
10
20
pH = 2
pH = 2.3
pH = 3
pH = 5
Copper added
initially
Copper added Copper added
after adsorption
initially
Research ApproachSample Analysis
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
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
% Removal
20 ppm Copper + 500 ppm 5MeBT
100
80
60
40
20
0
Scenario1
Scenario2
Control
1
2
2.3
pH
3
5
Results - Metals
% Removal
10 ppm Copper + 500 ppm 5MeBT
100
80
60
40
20
0
Scenario1
Scenario2
Control
1
2
2.3
pH
3
5
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?