Pre-treatment of Anion & Cation Exchange Resins

Pre-treatment of Anion & Cation Exchange Resins

New ion exchange resins often contain solvents, unreacted monomers and low polymers, and may have adsorbed metal ions such as iron, copper and aluminium. When the resin contacts acid or other solutions, these soluble impurities pass into the liquid and pollute the effluent in the initial period. New resin must therefore be pre-treated in the ion exchange equipment before use.

1. Pre-treatment of cation resins

First, using saturated brine in a volume of about three times the resin volume, soak the resin in the brine for 18–20 hours; then drain the brine and rinse with clean water until the effluent is no longer yellow.

Next, soak in 2%–4% NaOH solution (same volume) for 2–4 hours (or perform a small-capacity rinse), drain the alkali and rinse the resin until the effluent is nearly neutral.

Finally soak in 5% HCl solution (same volume) for 4–8 hours, drain the acid and rinse with clean water to neutral.

2. Pre-treatment of anion resins

The first step is the same as for cation resins. Then soak in 5% HCl for 4–8 hours, drain the acid and wash with water to neutral; finally soak in 2%–4% NaOH solution for 4–8 hours, drain the alkali and wash with clean water to neutral.