EXPERIMENT OF TOTAL IRON DETERMINATION & TOTAL MANGANESE

DETERMINATION

Introduction

The determination of total iron can be done by Phenanthronine method. While the total

manganese determination required Persulfate method. Iron (Fe) in  ground  waters  is  normally

present  in  the ferrous  (Fe++)  state  which  is  easily  oxidized  to  ferric  (Fe+++)  on the

exposure  to  air. Manganese (Mn) is less commonly found in groundwater than iron, rarely

found alone in a water source, and generally found with dissolved iron.

Oxidation of dissolved iron particles in water changes the iron to white, then yellow and finally

to red-brown solid particles that settle out of the water. Iron that does not form particles large

enough to settle out and that remains suspended and then leaves the water with a red tint.

Manganese usually is dissolved in water, although some shallow wells contain colloidal

manganese (black tint). These sediments are responsible for the staining properties of water

containing high concentrations of iron and manganese. These precipitates or sediments may be

severe enough to plug water pipes.

Objective

a) To determine the total iron concentration in the sample provided by using Phenanthroline

Method

b) To determine the total manganese concentration in the sample provided using Persulfate

Method

Method

Total Iron Determination

1. 50ml sample was placed into 125mL flask

2. 20ml of concentrated HCl, 1 Hydoroxylamine and a few of glass beads were added

3. Heat to boil until the volume reduced to 15~20ml. Then cool at room temperature.

4. Transfer to 50mlvolumetrik flask

5. 10ml Ammonium acetate buffer,4ml phenanthroline solution were added. Then, mixed

them well.

6. Dilute to mark with distilled water and mix well

7. Let 10-15minit for maximum color development

8. Measure absorbency at 510nm

Total Manganese Determination

1. 100ml sample was placed into 250 ml flask

2. 5ml special reagent and 1 drop H₂O₂ were added

3. Boiling until the concentrated reduced to 90ml

4. 1g of Ammonium Persulfate was added

5. Boil and prolonged boiled for 1 minute. Then, cool it immediately

6. Dilute to 100ml with distilled water and mix well

7. Absorbency was measured at 525nm.

Result

Total Iron at 510nm

(mg/L)

Total Manganese at 525 nm

(mg/L)

0.19 0.02

Discussion & Conclusion

Iron  in  ground  waters  is  normally  present  in  the ferrous  (Fe++)  state  which is

easily oxidized  to  ferric  (Fe+++)  one exposure  to  air. Iron  can  enter  a  water  system  by

leaching  natural deposits   from   iron-bearing   industrial   wastes,   effluents   from   pickling

operations, or  acidic  mine  drainage.

According to Environmental protection Agency (EPA), iron and manganese is secondary

pollutant. They are both classified under the Secondary Maximum Contaminant Level (SMCL)

standards. The SMCL for iron in drinking water is 0.3 milligrams per liter (mg/l), sometimes

expressed as 0.3 parts per million (ppm), and 0.05 mg/l (ppm) for manganese. Water with less

than these concentrations should not have an unpleasant taste, odor, appearance or side effect

caused by a secondary contaminant.

In this experiment, Iron and Manganese were measured by Spectroquant Nova 300 using

wavelength of 510nm for Iron and 525 nm wavelengths for Manganese. Total iron that has been

measured is 0.19 mg/L which is not exceed the standard of Secondary Maximum Contaminant

Level. Same goes to manganese which is measured by 0.02 mg/L of total determination

compared to SMCL standard which is 0.05 mg/L.

Question

1) What is the environmental significance of iron and manganese in water supplies?

- They cause reddish-brown (Iron) or black stains (Manganese) on clothes or household

fixtures. According to Environmental Protection Agency (EPA), iron and manganese are

considered secondary contaminants. Secondary standards apply to substances in water

that cause offensive taste, odor, color, corrosion, foaming, or staining but have no direct

affect on health.

-Besides, Iron and manganese deposits will build up in pipelines, pressure tanks, water

heaters and water softeners. This situation reduces the available quantity and pressure of

the water supply. Iron and manganese accumulations become an economic problem when

water supply or water softening equipment must be replaced. There also are associated

increases in energy costs from pumping water through constricted pipes or heating water

with heating rods coated with iron or manganese mineral deposits.

2) Discuss briefly how iron and manganese get into underground water supplies?

-Iron and manganese are common metallic elements found in the earth's crust. Water

percolating through soil and rock can dissolve minerals containing iron and manganese

and hold them in water supplies.

3) In what form must iron exist in order to be measured by the Phenanthroline method

and how is iron converted to this form?

-It is exist in form of ferric (3+) which is Iron (III). Iron (III) converted to this form by

the reaction of Iron (II) with the air.

4) In what oxidation state must the manganese be for calorimetric measurement?

-Mn (II)