Iron in Water (exp:9) - assignment - Q-A

Determination of Iron in Water
(1) Q: Discuss the environmental significance of “iron” in water.
Ans: As far as is known, human suffer no harmful effects from drinking waters containing iron and manganese. Such waters, when exposed to the air so that oxygen can enter, become turbid and highly unacceptable from the aesthetic viewpoint owing to the oxidation of iron and manganese to the Fe3+, and Mn4+ states which form colloidal precipitates. The rates of oxidation are not rapid, and thus reduced forms can persist for some time in aerated waters. This is especially true when the pH is below 6 with iron oxidation and below 9 with Manganese oxidation. The rates may be increased by the presence of certain inorganic catalysts of through the action of micro-organisms.
(2) Q: Why hydrochloric acid and potassium permanganate are added to the sample in the determination of iron?
Ans: Hydrochloric acid and potassium permanganate are added to the sample in the determination of iron because, some portion of iron may exist as iron hydroxide precipitates, it is necessary that all iron is in soluble condition. Treating the water to be tested with hydrochloric acid to dissolve ferric hydroxide does this. For determination of total iron, it should be ensured that all iron exist in ferric form Fe3+. this is most readily accomplished by using potassium permanganate, an oxidizing agent.
(3) Q: Ground water with high dissolved iron concentration often becomes after extraction (in contact with air). Explain why.
Ans: Ground water with high dissolved iron concentration often becomes turbid after extraction (in contact with air) because, such waters, when exposed to the air so that oxygen can enter, become turbid. Iron in water is frequently accompanied by heavy growths of iron bacteria. Iron is common in the earth and water-containing CO2, which seeps through iron bearing material, dissolves it to ferrous bicarbonate form Fe (HCO3) 2. The ferrous bicarbonate easily oxidized into ferric hydroxide Fe (OH) 3. Which is precipitated as rusty sediment.

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