Cation Exchange Resin Contamination Caused by Excessive Coagulant

Excessive coagulant can cause cation exchange resin fouling. To address suspended solids in water, coagulants are typically added during pretreatment. However, improper coagulant dosage can foul the downstream cation exchange resin.

It has been reported that when using epi-DMA (dimethylamine-epoxyhalopropane) and poly-DADMAC (diallyl dimethylamine chloride homopolymer) as coagulants, a concentration of 1 mg/L in the effluent can lead to severe fouling of the cation exchange resin. Furthermore, it has been found that coagulants with linear structures are more prone to fouling the resin and can penetrate into the resin particles. When the resin fouling is not severe, it can be revived by increasing the backwash flow rate, extending the backwash time, or introducing compressed air.

If the fouling is more severe, surfactants and dispersants can be added. Surfactants increase the hydrophilicity of the resin surface, while dispersants ensure that particles detached from the resin are dispersed into the aqueous solution. According to reports, Rohm and Haas's nonionic surfactant Triton CF-54 and dispersant Orotan 731 are effective in solving this problem. Nalco has also achieved good results by adding a revitalizing agent, a mixture of surfactants and dispersants, during the backwashing process of the contaminated resin layer. If cationic polyelectrolytes contaminate the cation exchange resin, a 4% sodium hydroxide solution can be used to dissolve the polyelectrolytes and revitalize the resin.