REMOTE MONITORING OF HEAVY METALS INN IN NATURAL WATER AND EFFLUENTS Department of Chemistry, NTNU

REMOTE MONITORING OF HEAVY METALS INN IN NATURAL WATER AND EFFLUENTS

Department of Chemistry, NTNU

During the last years an increasing focus has been turned on the quality of water and environmental surveillance. This has also been founded in international agreements and conferences like The Johannesburg Summit and EU Water Framework Directive.

Motivation

Motivation

An extensive activity and interest for the safety and protection of water resources is shown in general from WFD, UN and WHO

Motivation

Additionally the importance of the water security is also shown through the large number of different world-wide organizations which focus on water quality and safety, e.g. GARNET, GESI, GEF, GREEN, GWP, Global Water, IWRN, IAEH, IAWQ, ICWQ, IGRAC, IRC, IWMI, IWRA, WEF, WFP, WQA, WRI etc.

Motivation

There is a strong linkage between the state of environment of freshwater resources in a country and its capacity for poverty eradication and development.

Motivation

Even though water is probably the most important resource and commodity we have, pollution of important water recourses is still a problem. In future it should be focus even more to protect and monitor the water quality

Making low-cost instruments with high sensitivity and reproducibility, which can operate automatically for long time of periods out in the field with little maintenance.

Challenge

Atomic Absorption Spectrometry and Atomic Emission SpectrometryInductive Couple Plasma – Mass Spectroscopy Electrochemical techniques

Ion Chromatography (with a proper detector) Neutron Activation Analysis UV/VIS Spectrometry Classical analytical methods

Methods for trace analyses

Methods for trace analyses

A great number of analytical methods are able for measuring water quality and water pollution. However, all these methods have to be used in laboratories and only a few parameters (e.g. pH, conductivity, nitrate, phosphate) can be monitored out in the field.

This fact represents a large problem in environmental monitoring in general.

Methods for trace analyses

For instance, it is not possible to detect short time pollutions and accidental spills of environmental poisons, and it often takes a long time from sampling to the answer of the analysis is finish.

Methods for trace analyses

A better way to perform environmental monitoring is to combine continuous monitoring in the filed by use of automatic equipment together with manually sampling and analyses in laboratories.

Then a more complete monitoring program can be established, which both can detect short time pollutions, but also the different methods can verify each other.

Methods for trace analyses

Through several years of research within this field, automatic equipment for continuous monitoring of heavy metals and trace metals have now been developed in our research group at NTNU. The scientific interest is large and the commercial potential is worldwide

Methods for trace analyses

Electrochemical techniques offers an interesting group of methods for remote monitoring of heavy metals.

Electrochemical techniques

Good detection limit, possible for use in natural water, moderate price, fast, and simultaneously detection of several metals

Well known and accepted theory

A problem is to find a suitable electrode materials for use in field (avoid liquid mercury)

Properties for electrode materials

High overvoltage towards HER

Wide working window

Non toxic

Slow passivitation

Possible to make nano-dimension

Resistant against fouling of biological material

Low price, easy to produce and cast

Easy to operate in field equipment

Sensor materials

Metal electrodes

Mercury, Gold, Silver, Iridium, Palladium, Platinum

Carbon substrate

Diamond (e.g. Boron doped), Glassy carbon, Graphite (heat treated electrode graphite)

Film electrodes / Meniscus

Bismuth film, Mercury film, Hg-Ag, Hg-Au…

Mixed electrodes

Alloying a metal with high hydrogen overvoltage with a metal with low hydrogen overvoltage.

A significant increase in the hydrogen overvoltage is observed for the alloyed metal, even for small additions.

Silver electrodes added bismuth

Silver electrodes contaminated with 2, 4, 6, 10, 15 % (w/w) bismuth. DPSAV in 0.05 M NH4Ac solution (pH 4,6).

Solid dental amalgam electrodes

Silver electrodes containing 2, 40, and 51 % (w/w) mercury. CV in 0.01 M HNO3 solution, scan rate 100 mV/s.

-2000

-1500

-1000

-500

0

500

-1.60 -1.40 -1.20 -1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20 0.40

2%Hg

40%Hg

51%Hg

Voltammetric apparatus for use in field

Voltammetric apparatus for use in field, small scale tests

Field Apparatus

Field Apparatus

Sampling

Avoiding contamination

Accuracy in pumping installation

Analyses

Cleaning of the electrodes and the cell system

Field instrument, advantage

Low risk for contamination or changes in the

samples due to time

Speciation studies possible in the field

Possibilities to detect short time pollution and

react immediately

Unique data for biological and / or geological

studies

Løkken

HVS

TBS

Pilot projects in Norway

Polluted river water, Løkken Verk, Norway

Løkken pyrite ore

Løkken Verk is an old mining area in middle part of Norway

Slag heap

Løkken pyrite ore, composition

Placing of the monitoring system

Raubekken, a middle large river passing through the mining area

Instrument mounted in the field.

Results

Typical voltammetric scan of water sample from the river Raubekken added NH4Cl (0.05 M) . DPASV, scan rate 20 mV/s, modulation pulse 75 mV, deposition time 30 s at – 1450 mV.

Calibration

Calibration by standard addition was performed once or twice a month.

Pb

R2 = 0.9998

0

10

20

30

0 200 400 600 800Conc (g/L)

I (

A)

Cu

R2 = 0.9516

0

10

20

30

40

50

60

0 200 400 600 800Conc (g/L)

I (

A)

Fe

R2 = 0.999

80

100

120

140

160

1000 1200 1400 1600 1800Conc (g/L)

I (

A)

Zn

R2 = 0.9969

20

30

40

50

60

500 700 900 1100 1300 1500Conc (g/L)

I (

A)

Calibration values

Average peak heights for added standards during the period

  Zn Cu FeStd.s Conc 250 mg/L 250 mg/L 220 mg/L

I (mA) 21,7 16,0 23,1

Std. Dev 1,3 1,5 1,2

Rel. Std. Dev 6,0 9,6 5,2

Cu

0.0

500.0

1000.0

1500.0

2000.0

2500.0

3000.0

14.1.04 3.2.04 23.2.04 14.3.04 3.4.04 23.4.04 13.5.04

Fe

0.0

500.0

1000.0

1500.0

2000.0

2500.0

3000.0

14.1.04 3.2.04 23.2.04 14.3.04 3.4.04 23.4.04 13.5.04

Continuous measurements from January to May 2004.One measurement every 30 minutes.

Measurements of Zn, Fe, and CuZn

0

500

1000

1500

2000

2500

3000

3500

14.1. 3.2. 23.2. 14.3. 3.4. 23.4. 13.5.Date

Co

nc

(g

/L)

0

2

4

6

8

14.1. 3.2. 23.2. 14.3. 3.4. 23.4.

Date

Tem

p (

C)

-30

-20

-10

0

10

20

4.1. 24.1. 13.2. 4.3. 24.3. 13.4. 3.5.

Date

Tem

p (

C)

A

B

High [Fe]

Low [Zn]

Comparison with ICP-MS

Comparison of voltammetric measurements against ICP-MS

Continuous analyses of zinc, iron, and copper for a time period of four months (middle of January to middle of May, 2004), in polluted river water at Løkken Verk. Sampling performed every 30 minutes, DPASV with 30 s plating time, scan rate was 20 mV/s, and modulation pulse 75 mV. NH4Cl (0.015 M) added to

the sample.

Seawater and brackish water

Costal seawater, Trondheim

Results

Voltammogram of costal seawater. DPASV, scan rate 20 mV/s, modulation pulse 75 mV, deposition time 540 s at – 1450 mV.

Zinc in seawater

Results from continuous measurements of iron in seawater. One measurement every 30 minutes.

Zn conc in costal seawater

0

5

10

15

20

25

30

35

40

45

50

14. jan. 3. feb. 23. feb. 14. mar. 3. apr. 23. apr. 13. mai.

Date

Co

nc

(g

/L)

Avg. [Zn] = 2.3 g/LAvg. [Zn] = 2.3 g/L

Iron in seawater

Results from continuous measurements of iron in seawater. One measurement every 30 minutes.

Fe

0

0.2

0.4

0.6

0.8

1

1.2

1.4

22.1. 22.1. 23.1. 23.1. 24.1. 24.1. 25.1. 25.1. 26.1.

Date

Co

nc

(g

/L)

Falconbridge, Nickel refinery

Waste Incineration Plant

Monitoring of heavy metals in purified scrubbing water at Heimdal varmesentral, Trondheim, Norway.

Waste Incineration Plant

Detection of zinc, cadmium and lead in scrubbing wastewater added NH4Cl (to 0.05M). DPASV, 120 s dep. time at -1300mV, scan rate 15 mV s-1, mod. pulse 50 mV.

Mercury in wastewater, HVS

Concentrations plotted against time

Waste Incineration Plant

Continuous monitoring of mercury in purified scrubbing water at Heimdal incineration plant Trondheim, Norway. DPASV by use of Au-Bi (4%) electrode, deposition time 300 s at 100 mV, scan rate 15 mV/s, modulation pulse 50 mV.

0

5

10

15

20

25

08-aug-03 18-aug-03 28-aug-03 07-sep-03 17-sep-03 27-sep-03 07-okt-03 17-okt-03

Date

Conc

(

g/L)

Boliden, Odda. Zinc refinery, Norway

Field instrument, maintenance

Field instrument, maintenance

Refill of supporting electrolyte solution

Polish of electrode

Cleaning cell and filter systems

Calibration

Maintenance of titanium pump

Continuous measurements have to frequently be

verified by performing manual sampling and detection

with other analytical techniques (e.g. once or twice a

months)

Collaboration with Fugro Oceanor

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Than you for your attention