Ferrolite / Manganese Greensand

What is Ferrolite?

Ferrolite is a filtration media (filter media) used to remove iron (Fe) and manganese (Mn) from groundwater or well water.
It originated in Japan and was developed by Tohken Co., Ltd. (products: Ferrolite MC and Ferrolite GC).

Ferrolite works by catalytic oxidation - which accelerates the oxidation reaction between dissolved iron / manganese with oxygen or chlorine so that it turns into a solid form (precipitate) that can be filtered.

How Ferrolite Works

1. Raw water (usually well water) often contains Fe²⁺ and Mn²⁺, which are iron and manganese in dissolved form that cannot be filtered directly.

2. As water flows through the Ferrolite layer, a catalytic oxidation reaction occurs:

   Fe2+→Fe3+→Fe(OH)3↓Fe^{2+} \rightarrow Fe^{3+} \rightarrow Fe(OH)_3 \downarrowFe2+→Fe3+→Fe(OH)3↓ Mn2+→Mn4+→MnO2↓Mn^{2+} \rightarrow Mn^{4+} \rightarrow MnO_2 \downarrowMn2+→Mn4+→MnO2↓

   These Fe(OH)₃ and MnO₂ precipitates are captured in the media.

3. The result: water comes out of the filter with very low levels of iron and manganese.

Ferrolite type

Advantages of Ferrolite

• ✅ No need for heavy chemical regeneration, just regularbackwash with water.

• ✅ High durability, can last several years without replacement.

• ✅ High filtration capacity, suitable for industry and household.

• ✅ Effectively removes Fe and Mn at the same time, even in high levels.

• ✅ Does not add taste or odor to water (different from greensand which contains permanganate).

Limitations or Notes

• Need sufficient dissolved oxygen (DO) content in water for the oxidation process to run well.

• If Fe/Mn levels are too high, aeration or light chlorination before entering the Ferrolite filter is recommended.

• If backwashing is infrequent, the media may become clogged with iron deposits.

Brief Comparison with Other Media

What is Manganese Greensand

Manganese greensand is a filter media made from glauconite sand (green natural zeolite) coated with manganese oxide (MnO₂).
This manganese layer provides strong oxidizing ability, so it can convert iron (Fe²⁺) and manganese (Mn²⁺) dissolved in water into a solid precipitate (Fe³⁺, Mn⁴⁺) that is easily filtered.

How Manganese Greensand Works

There are two main mechanisms depending on how it is used:

1. Regenerative mode (using potassium permanganate, KMnO₄)

• After the manganese layer on the media is depleted (reduced), the media is regenerated with KMnO₄ solution (purple).

• The main reaction:

  Fe2++MnO2→Fe(OH)3↓+Mn2+Fe^{2+} + MnO_2 \rightarrow Fe(OH)_3 \downarrow + Mn^{2+}Fe2++MnO2→Fe(OH)3↓+Mn2+}

  Then regenerated again:

  Mn2++KMnO4→MnO2+K+++other productsMn^{2+}+KMnO_4 \rightarrow MnO_2+K^+++other productsMn2+++KMnO4→MnO2+K+++other products

• So, the media can be used repeatedly without being replaced, just regenerated periodically.

2. Non-regenerative mode (direct oxidation)

• Used with chlorine or aeration in front of the filter.

• Chlorine acts as an oxidizer that helps activate the MnO₂ layer.

Main Uses

Manganese greensand is used to remove:

• Iron (Fe²⁺)

• Manganese (Mn²⁺)

• Hydrogen sulfide (H₂S) → the cause of rotten egg odor in water.

Simple Filtration Process

1. Raw water → (optional) light aeration/chlorination

2. Enter the tube containing manganese greensand media

3. Oxidation reaction → iron/manganese precipitates out

4. Sediment retained in media

5. Media is backwashed to remove impurities

Pros

• Effective for Fe, Mn, and H₂S at once

• Can be used in water with high iron content

• Media can be regenerated, does not have to be replaced frequently

• Long proven and widely used around the world

Disadvantages

• Requires regeneration chemicals (KMnO₄) → needs regular maintenance

• Water pH must be > 6.8 for the oxidation reaction to work properly

• If regeneration is delayed, the manganese layer degrades and filtration fails

• Durability may decrease when frequently exposed to excess chlorine or muddy water

Comparison with Ferrolite

Conclusion

Manganese Greensand is a classic and effective filter media for reducing Fe, Mn, and H₂S by utilizing chemical oxidation reactions by the MnO₂ layer.
However, it requires periodic regeneration with KMnO₄ to remain active, unlike media such as Ferrolite or Birm which work catalytically without regeneration chemicals.