Process –
1. Three bed volumes of 10% w/v brine solution containing 2% w/v caustic soda should be prepared.
2. A first bed volume should be introduced into the ion exchange unit at a flow rate not exceeding 2 BV’s per hour.
3. A second bed volume should then be introduced at the same flow rate, but it should be retained in the unit for as long as possible, (if possible for 12 hours). If possible some agitation of the resin should be employed periodically throughout the retention period.
4. A third bed volume of brine should be passed through the resin at a rate of 1 BV per hour and then the resin thoroughly rinsed with clean water until free from brine.
5. The resin should be subject to a double caustic regeneration cycle before being put back on line.
N.B. Brine at a temperature exceeding the normal operational temperature should be employed (NB the maximum for acrylic anion resins is 40°C, for polystyrenic anion resins is 60°C). The effluent from the process will be highly coloured and may be smelly, it will be caustic and should be disposed of appropriately.
If there were Iron containing organic complexes present in the raw feed water, after this process there will be iron on the anion resin and it is advisable to treat the anion resin with 2BV’s of 6% hydrochloric acid immediately after completing the rinsing step of the organics removal process. This is to remove the iron that may foul the resin as an oxide and catalyse the degradation of the anion exchange sites, reducing the resin capacity.
CAUTION! It is important to ensure that the materials of construction are suitably resistant to hydrochloric acid.