Which type of filter is designed to remove iron and manganese through adsorption and oxidation?

• A. Activated carbon filter
• B. Manganese greensand filter
• C. Reverse osmosis system
• D. Bag filter

Answer: (B)

The manganese greensand filter is specifically designed to remove iron and manganese from water through a process that involves both adsorption and oxidation. This type of filter utilizes a special type of greensand that is treated with potassium permanganate, which facilitates the oxidation of soluble manganese (Mn²⁺) and iron (Fe²⁺) ions, converting them into insoluble particles (MnO₂ and Fe(OH)₃) that can be easily filtered out.

The greensand media provides a surface for the oxidation reaction to occur, and as water passes through the filter, the oxidized particles adhere to the surface, effectively removing them from the water. This method is particularly effective because it not only captures the metals through filtration but also ensures that higher concentrations can be treated owing to the oxidizing capability of the media.

In contrast, activated carbon filters primarily remove organic compounds and chlorine through adsorption but are not specifically designed for iron and manganese removal. Reverse osmosis systems are effective for a broad range of contaminants, but typically do not target iron and manganese specifically, often requiring pre-treatment for these elements. Bag filters are generally used for larger particulates and will not effectively address dissolved metals like iron and manganese that need oxidation and a specific adsorption process to be