Which chemical is commonly used to eliminate iron from water?

Potassium permanganate is a strong oxidizing agent that is commonly used to treat water containing iron. It reacts with soluble ferrous iron (Fe²⁺) to convert it into insoluble ferric iron (Fe³⁺) through an oxidation reaction. The ferric iron then precipitates out of the solution, allowing it to be removed from the water during the filtration process. This is particularly effective in water treatment processes where the removal of iron is necessary to prevent staining and to improve water quality.

The other options focus on different applications. Chlorine is primarily used for disinfection and oxidation of organic materials rather than specifically targeting iron removal. Alum is often used as a coagulant to aid in the removal of suspended solids but does not address iron removal directly. Sodium hydroxide is used to adjust pH levels and may precipitate iron, but it is not as effective as potassium permanganate in directly removing iron with the desired effectiveness in typical water treatment scenarios. Thus, potassium permanganate stands out as the most effective chemical for eliminating iron from water.