Water Nuggets Practice Exam

What precipitates are known to foul a cation exchange resin?

1. Iron and Manganese

2. Sulfates

3. Chlorate and Borate

4. Sodium Chloride and Potassium Chloride

The correct answer is: Iron and Manganese

Cation exchange resins are designed to remove positively charged ions from water, replacing them with hydrogen ions or other cations. However, certain precipitates can foul or coat the resin, inhibiting its effectiveness. Iron and manganese are known to form insoluble precipitates, especially when there is a change in pH or when the concentration of these metals exceeds certain thresholds. These metals commonly come from natural sources, such as groundwater or industrial processes, and can precipitate out of solution, forming solid deposits. When these solid forms build up on the cation exchange resin, it can significantly reduce the exchange capacity of the resin and impair its ability to treat water effectively. Understanding the behavior of iron and manganese in water treatment is crucial, as their precipitation can lead to operational issues, requiring additional processes to manage or remove the foulants before the cation exchange resin can function optimally again.