Uses
Anions such as selenite and selenate can be easily adsorbed on the positively charged surface of iron(II) hydroxide where they are subsequently reduced by Fe2+. The resulting products are poorly soluble (Se0, FeSe, or FeSe2).
Iron(II) hydroxide has also been investigated as an agent for the removal of toxic selenate and selenite ions from water systems such as wetlands. The iron(II) hydroxide reduces these ions to elemental selenium, which is insoluble in water and precipitates out.
Note: pKsp = 15.097 where p is the -log and Ksp is the Solubility Product Constant. This means it has a low tendency to dissolve, but is not entirely insoluble. An acidic solution would allow this to disassociate more because the H+ would react with the OH- in the compound.
In a basic solution iron(II) hydroxide is the electrochemically active material of the negative electrode of the nickel-iron battery.
Read more about this topic: Iron(II) Hydroxide