Which material is manganese greensand, and which is the coating?

• A. Sand coated with aluminum dioxide
• B. Glauconite sand coated with manganese dioxide
• C. Quartz sand coated with potassium permanganate
• D. Granular activated carbon coated with chlorine

Answer: (B)

Manganese greensand is primarily made from glauconite, a mineral that is rich in iron and can naturally remove iron and manganese from water. The significant characteristic of greensand is its manganese oxide coating, which allows it to effectively oxidize and precipitate dissolved iron and manganese, facilitating their removal in water treatment processes.

By selecting glauconite sand that is coated with manganese dioxide, it becomes particularly effective in filtration applications. The manganese dioxide coating enhances the greensand's capability to oxidize and remove these metals through an adsorption process, making option B the correct answer.

Other materials listed do not accurately reflect the composition or function of manganese greensand, as they either involve different types of sand or coatings that do not possess the same treatment properties.