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?