To address iron problems when using resin exchange, which pre-treatment step is recommended?

To address iron problems when using resin exchange, which pre-treatment step is recommended?

• A. Remove iron before resin
• B. Add polyphosphates
• C. Add reducing agent
• D. Increase pH

Answer: (A)

Iron in water can foul ion exchange resin by forming insoluble iron hydroxide that coats the resin beads, blocking exchange sites and reducing capacity. The best way to prevent this is to remove the iron before it reaches the resin, so the bed operates cleanly and efficiently. This pre-treatment is typically done by oxidizing the iron (to convert Fe2+ to Fe3+) and then filtering, or by another filtration step that removes iron prior to contact with the resin. Increasing pH tends to precipitate iron and can worsen fouling rather than prevent it. Reducing agents may keep iron in a soluble form that still poses problems inside the bed, and polyphosphates are not a reliable solution for protecting resin in this context. Removing iron beforehand directly guards the resin performance and longevity.

Iron in water can foul ion exchange resin by forming insoluble iron hydroxide that coats the resin beads, blocking exchange sites and reducing capacity. The best way to prevent this is to remove the iron before it reaches the resin, so the bed operates cleanly and efficiently. This pre-treatment is typically done by oxidizing the iron (to convert Fe2+ to Fe3+) and then filtering, or by another filtration step that removes iron prior to contact with the resin. Increasing pH tends to precipitate iron and can worsen fouling rather than prevent it. Reducing agents may keep iron in a soluble form that still poses problems inside the bed, and polyphosphates are not a reliable solution for protecting resin in this context. Removing iron beforehand directly guards the resin performance and longevity.