IronIronWQT 134

Aquatic Chemistry II

Standard Methods 20th ed #3500 Iron (#110)

Applied Water and Spent water Manual Chapter 38

Lecture 6

WQT 134Aquatic Chemistry II

Standard Methods 20th ed #3500 Iron (#110)

Applied Water and Spent water Manual Chapter 38

Lecture 6

Week 6 Objectives Week 6 Objectives

1. Understand the role and function of Iron in water treatment.

2. Understand how to measure Iron (SM #3500, #110)

3. Comprehend iron concentrations in nature.

1. Understand the role and function of Iron in water treatment.

2. Understand how to measure Iron (SM #3500, #110)

3. Comprehend iron concentrations in nature.

Reading assignment: American Public Health Association (APHA), American Water Works Association (AWWA) & Water Environment Federation (WEF). 1999.   Standard Methods for the Examination of Water and Wastewater, 20th edition Jackson. 1993. Applied Water and Spentwater Manual.

Reading assignment: American Public Health Association (APHA), American Water Works Association (AWWA) & Water Environment Federation (WEF). 1999.   Standard Methods for the Examination of Water and Wastewater, 20th edition Jackson. 1993. Applied Water and Spentwater Manual.

Iron #3500, #110Iron #3500, #110

Total Iron: The amount of ferrous (Fe+2) and ferric iron (Fe+3) in a sample. Determined using a colorimeter. Total Iron: The amount of ferrous (Fe+2) and ferric iron (Fe+3) in a sample. Determined using a colorimeter.

Digestion Process

Digestion Process

Color Development

Color Development

Measure 50 ml of your sample into 125 ml erlenmeyer flaskMeasure 50 ml of your sample into 125 ml erlenmeyer flask

Add 2 ml concentrated HCl (use pipette)Add 2 ml hydroxylamine hydrochloride solutionAdd a few glass beads and boil Cool to room temperature and pour 38 ml into 100 ml volumetric flask

Add 2 ml concentrated HCl (use pipette)Add 2 ml hydroxylamine hydrochloride solutionAdd a few glass beads and boil Cool to room temperature and pour 38 ml into 100 ml volumetric flask

Add 10 ml ammonium acetate bufferAdd 2 ml phenanthroline solutionDilute to mark with water

Add 10 ml ammonium acetate bufferAdd 2 ml phenanthroline solutionDilute to mark with water

Iron #3500, #110Iron #3500, #110Beer’s Law : (physical chemistry) The law which states that the absorption of light by a solution changes exponentially with the concentration, all else remaining the same.

Beer’s Law : (physical chemistry) The law which states that the absorption of light by a solution changes exponentially with the concentration, all else remaining the same.

Iron #3500, #110Iron #3500, #110Factoids• Iron (Fe) is the first element in Group VIII of the periodic table

• atomic number of 26, atomic weight of 55.85

• Common valences of 2 and 3; solubility of ferrous ion (Fe2+) is controlled by the carbonate concentration.

• Average Fe in the earth’s crust is 6.22%

• Soils Fe ranges from 0.5 to 4.3%

• Streams averages ~0.7 mg/L

• Groundwater averages 0.1 to 10 mg/L. Iron

• Minerals hematite, magnetite, taconite, and pyrite.

Factoids• Iron (Fe) is the first element in Group VIII of the periodic table

• atomic number of 26, atomic weight of 55.85

• Common valences of 2 and 3; solubility of ferrous ion (Fe2+) is controlled by the carbonate concentration.

• Average Fe in the earth’s crust is 6.22%

• Soils Fe ranges from 0.5 to 4.3%

• Streams averages ~0.7 mg/L

• Groundwater averages 0.1 to 10 mg/L. Iron

• Minerals hematite, magnetite, taconite, and pyrite.

Iron #3500, #110Iron #3500, #110

Factoids• Ferrous ion (Fe2+) is soluble form in nature

• On exposure to air or addition of oxidants, ferrous iron is oxidized to the ferric state (Fe3+) and may hydrolyze to form red, insoluble hydrated ferric oxide

Factoids• Ferrous ion (Fe2+) is soluble form in nature

• On exposure to air or addition of oxidants, ferrous iron is oxidized to the ferric state (Fe3+) and may hydrolyze to form red, insoluble hydrated ferric oxide

Pipe Corrosion/Fe staining/Fe in GWPipe Corrosion/Fe staining/Fe in GW

~20,000 gpd~20,000 gpd

Iron #3500, #110Iron #3500, #110Day 1Day 1 Day 2Day 2 Day 4Day 4 Day 16Day 16

flo

w d

irec

tio

nfl

ow

dir

ecti

on

Iron #3500, #110Iron #3500, #110 BC Column Final Pore Water

Flo

w D

ire

ctio

n

orangeorangedarkdark

Fe(II)Fe(II)aqaqFe(II)Fe(II)aqaq

highhigh

magnetitemagnetitemagnetitemagnetite

sideritesideritesideritesideritemediummedium

inhibitorsinhibitors green rustgreen rustgreen rustgreen rust

lowlow

goethitegoethitegoethitegoethite

Zachara et al., (2001) proposed that dissolved Zachara et al., (2001) proposed that dissolved Fe(II) concentrations control secondary solid Fe(II) concentrations control secondary solid phase products of Fe oxide reduction.phase products of Fe oxide reduction.

Zachara et al., (2001) proposed that dissolved Zachara et al., (2001) proposed that dissolved Fe(II) concentrations control secondary solid Fe(II) concentrations control secondary solid phase products of Fe oxide reduction.phase products of Fe oxide reduction.

Fe (mg L-1)

0 5 10 15 20 25

1

2

3

4

5

6

7

Iron #3500, #110Iron #3500, #110

Iron #3500, #110Iron #3500, #110

What is Iron?• Iron occurs in the minerals hematite(Fe2O3), magnetite (Fe3O4), ferrihydrite (FeOOH), aresenopyrite (FeAsS), siderite (FeCO3), aluminosilicates, and pyrite (FeS). It is widely used in steel, alloys, as well as for environmental remediation of nitrates and arsenic.

Why do we care?•Iron in residual waters after treatment can cause laundry and fixture staining, corrosion, rust, odor and aesthetic taste problems and iron bacterial blooms in drinking water.

What is Iron?• Iron occurs in the minerals hematite(Fe2O3), magnetite (Fe3O4), ferrihydrite (FeOOH), aresenopyrite (FeAsS), siderite (FeCO3), aluminosilicates, and pyrite (FeS). It is widely used in steel, alloys, as well as for environmental remediation of nitrates and arsenic.

Why do we care?•Iron in residual waters after treatment can cause laundry and fixture staining, corrosion, rust, odor and aesthetic taste problems and iron bacterial blooms in drinking water.

Iron #3500, #110Iron #3500, #110How is it done?1. Iron is brought into solution, reduced to the ferrous state

by boiling with acid and hydroxylamine, and treated with 1,10-phenanthroline at pH 3.2 to 3.3. Three molecules of phenanthroline chelate each atom of ferrous iron to form an orange-red complex.

2. The colored solution obeys Beer’s law; its intensity is independent of pH from 3 to 9. Thus, sample is run at 510 nm on a colorimeter

3. A set of standards is run along with unknown sample and a blank to determine Fe concentration.

4. Plot absorbance or percent transmission (on the vertical or y-axis) vs. iron concentration (on the x or horizontal axis) in mg/l as a linear graph.

5. Determine unknown Fe concentration

How is it done?1. Iron is brought into solution, reduced to the ferrous state

by boiling with acid and hydroxylamine, and treated with 1,10-phenanthroline at pH 3.2 to 3.3. Three molecules of phenanthroline chelate each atom of ferrous iron to form an orange-red complex.

2. The colored solution obeys Beer’s law; its intensity is independent of pH from 3 to 9. Thus, sample is run at 510 nm on a colorimeter

3. A set of standards is run along with unknown sample and a blank to determine Fe concentration.

4. Plot absorbance or percent transmission (on the vertical or y-axis) vs. iron concentration (on the x or horizontal axis) in mg/l as a linear graph.

5. Determine unknown Fe concentration

Iron #3500, #110Iron #3500, #110

What are advantages of the procedure?

•Accuracy of dissolved or total concentrations of iron as low as 10 μg/L can be determined with a spectrophotometer using cells with a 5 cm or longer light path.

•No pretreatment necessary for well or potable water samples

What are advantages of the procedure?

•Accuracy of dissolved or total concentrations of iron as low as 10 μg/L can be determined with a spectrophotometer using cells with a 5 cm or longer light path.

•No pretreatment necessary for well or potable water samples

Iron #3500, #110Iron #3500, #110What are disadvantages of the procedure?

•Preliminary treatment is a must for waste or organic rich stream water

•Cyanide, nitrite, and phosphates (polyphosphates more so than orthophosphate), chromium, zinc in concentrations exceeding 10 times that of iron, cobalt and copper in excess of 5 mg/L, and nickel in excess of 2 mg/L.

•Bismuth, cadmium, mercury, molybdate, and silver precipitate phenanthroline.

•Color or organic matter may necessitate digestion before use of the extraction procedure.

What are disadvantages of the procedure?

•Preliminary treatment is a must for waste or organic rich stream water

•Cyanide, nitrite, and phosphates (polyphosphates more so than orthophosphate), chromium, zinc in concentrations exceeding 10 times that of iron, cobalt and copper in excess of 5 mg/L, and nickel in excess of 2 mg/L.

•Bismuth, cadmium, mercury, molybdate, and silver precipitate phenanthroline.

•Color or organic matter may necessitate digestion before use of the extraction procedure.

Iron #3500, #110Iron #3500, #110

What are typical values in nature?

•The United Nations Food and Agriculture Organization recommended level for irrigation waters is 5 mg/L.

•The U.S. EPA secondary drinking H2O MCL is 0.3 mg/L.

What are typical values in nature?

•The United Nations Food and Agriculture Organization recommended level for irrigation waters is 5 mg/L.

•The U.S. EPA secondary drinking H2O MCL is 0.3 mg/L.

Iron #3500, #110Iron #3500, #110

What are the units and conversions?

•Fe in mg/l

What are the units and conversions?

•Fe in mg/l

Calculations and Formulas?

mg/L as Fe = mg/l as read from standard curve

mg/L as Fe = (curve value)(dilution factor)

Calculations and Formulas?

mg/L as Fe = mg/l as read from standard curve

mg/L as Fe = (curve value)(dilution factor)

Iron #3500, #110Iron #3500, #110Example Problem?Example Problem?

If 25 ml of sample has been diluted to 100 ml, and then 50 ml of this solution was used for analysis, the dilution factor to multiply times the curve value (which is in terms of concentration- would be 4.0) Suppose the diluted sample produced an absorbance equivalent to 0.145 mg/L then the actual concentration would be:

mg/l as Fe = (0.145)(4)= 0.580 mg/l as Fe

If 25 ml of sample has been diluted to 100 ml, and then 50 ml of this solution was used for analysis, the dilution factor to multiply times the curve value (which is in terms of concentration- would be 4.0) Suppose the diluted sample produced an absorbance equivalent to 0.145 mg/L then the actual concentration would be:

mg/l as Fe = (0.145)(4)= 0.580 mg/l as Fe

Iron #3500, #110Iron #3500, #110

Tips and Suggestions?

1. If It says Fume Hood….. Keep it in the Fume Hood!!2.36 N Sulfuric acid will burn on contact, wear gloves!!!3.Let spectrophotometer warm up a bit to 510 nm4.Run all samples in succession5.Take your time and try to learn/play with making a

graph in Excel; its a great tool to have.

Tips and Suggestions?

1. If It says Fume Hood….. Keep it in the Fume Hood!!2.36 N Sulfuric acid will burn on contact, wear gloves!!!3.Let spectrophotometer warm up a bit to 510 nm4.Run all samples in succession5.Take your time and try to learn/play with making a

graph in Excel; its a great tool to have.

Water containing high iron is objectionable in a public water

supply because:

Water containing high iron is objectionable in a public water

supply because:

a. e

xces

s iro

n will

sca

..

b. e

xces

s iro

n will

sta

..

c. e

xces

s iro

n cau

se...

d. i

ron

conte

nt has

no...

25% 25%25%25%

a. excess iron will scale pipes

b. excess iron will stain plumbing fixtures

c. excess iron causes “baby blue” syndrome

d. iron content has no effect on the water supply

a. excess iron will scale pipes

b. excess iron will stain plumbing fixtures

c. excess iron causes “baby blue” syndrome

d. iron content has no effect on the water supply

Red water may be caused by iron concentrations above:

Red water may be caused by iron concentrations above:

a. 0

.01

mg/L

b. 0

.03

mg/L

c. 0

.1 m

g/L

d. 0

.3 m

g/L

25% 25%25%25%

a. 0.01 mg/L

b. 0.03 mg/L

c. 0.1 mg/L

d. 0.3 mg/L

a. 0.01 mg/L

b. 0.03 mg/L

c. 0.1 mg/L

d. 0.3 mg/L

Dissolved iron in excessive amounts results in consumer

complaints about:

Dissolved iron in excessive amounts results in consumer

complaints about:

a. h

ardnes

s

b. c

orrosi

on

c. s

mel

l

d. t

urbid

ity

25% 25%25%25%

a. hardness

b. corrosion

c. smell

d. turbidity

a. hardness

b. corrosion

c. smell

d. turbidity

Which of the following chemicals will most likely keep

iron in suspension?

Which of the following chemicals will most likely keep

iron in suspension?

a. c

hlorin

e

b. l

ime

c. p

olyphos

phate

d. p

otass

ium

per

ma.

..

25% 25%25%25%

a. chlorine

b. lime

c. polyphosphate

d. potassium permanganate

a. chlorine

b. lime

c. polyphosphate

d. potassium permanganate

Before iron, manganese, and hydrogen sulfide can be

removed by filtration they must first be converted to:

Before iron, manganese, and hydrogen sulfide can be

removed by filtration they must first be converted to:

Inso

luble

pre

c...

Gas

es th

rough

...

An o

dor fr

ee s

...

Gas

es th

rough

...

25% 25%25%25%

a. Insoluble precipitates through oxidation

b. Gases through flash mixing

c. An odor free state through settling

d. Gases through adequate detention time

a. Insoluble precipitates through oxidation

b. Gases through flash mixing

c. An odor free state through settling

d. Gases through adequate detention time

Unlike most surface waters, ground waters may need to

have these materials removed

Unlike most surface waters, ground waters may need to

have these materials removed

Iron a

nd m

anga.

..

Coppe

r and

man

...

Iron a

nd co

ppe.

..

Softe

ning a

gen...

25% 25%25%25%

1. Iron and manganese

2. Copper and manganese

3. Iron and copper

4. Softening agents

1. Iron and manganese

2. Copper and manganese

3. Iron and copper

4. Softening agents

Iron and manganese may be removed from source waters by oxidation. The following chemicals are often used to precipitate iron. Check all

that apply

Iron and manganese may be removed from source waters by oxidation. The following chemicals are often used to precipitate iron. Check all

that apply

Chlo

rine

Pota

ssiu

m p

erm

...

Alu

m

Sodiu

m h

ydro

xi...

1 a

nd 2

onl

y

20% 20% 20%20%20%

1. Chlorine

2. Potassium permanganate

3. Alum

4. Sodium hydroxide

5. 1 and 2 only

1. Chlorine

2. Potassium permanganate

3. Alum

4. Sodium hydroxide

5. 1 and 2 only