At Sellafield, iron hydroxide precipitation is used as an effluent treatment strategy, in a particular part of the plant. What is the primary purpose that this treatment is employed on site?

To remove multivalent heavy metal ions, such as trace actinides.

To remove soluble fuel cladding metals, such as magnesium.

To remove monovalent ions, such as caesium.

To remove uranium and plutonium complexes.