WaterSolutions Weak Base Anion Exchange Resins

Weak base anion resin is used as a single resin to obtain partially deionized water without removal of CO₂ and SiO₂. For complete demineralization, the combination of weak base and strong base anion is an excellent choice for larger plants, as it provides optimum operation costs. The weak base has very high regeneration efficiency and provides additional capacity to the system. The weak and strong anion combination is well suited to treat waters with low alkalinity or degassed feed, when the Free Mineral Acid (FMA: Cl, NO₃,  SO₄) is typically > 60% of the total anions. DOWEX™ MARATHON™ WBA resin is the resin of choice for general demineralization.

Weak base anions are particularly effective in handling natural organics, which are usually high molecular weight, weakly acidic compounds that affect both weak base and strong base anion resins. In a weak base - strong base anion configuration, some of the organics will pass through the weak to the strong base. The design should therefore account for SBA organic loading at the end of the cycle, as the resin will require additional NaOH to desorb the organics. There are important differences in loading capacity or reversibility to organics between different anion types. For more information on organic tolerance of resins, see the resin selection guide.

For treating resins contaminated with silica or organics, see silica removal (20KB PDF) and brine cleaning of anion resins for organic contamination (26KB PDF).

The weak and strong anion resins can either be designed in two separate vessels or for counter-flow regeneration in one vessel with or without a separation nozzle plate. For separated anions, DOWEX MARATHON WBA and DOWEX MARATHON A resins are recommeded. DOWEX MARATHON WBA and DOWEX MARATHON A LB resins are designed to be used together as a layered bed in a single column without a nozzle plate. For plants with UPCORE™ systems, the suggested resins are DOWEX UPCORE Mono WB-500 resin and DOWEX UPCORE Mono A-500 resin or DOWEX UPCORE Mono A-625 resin.