Organic Matter Contamination of Cation Exchange Resins

Organic matter contamination of cation exchange resins has been studied, and research indicates that dissolved organic matter in water is primarily adsorbed onto the resin via van der Waals forces. The adsorbed organic matter is mainly composed of acidic groups, which constitute the majority of dissolved organic matter in water.

Reports of organic matter contamination of resins have been documented. Harries investigated organic contamination of cation exchange resins in mixed beds of condensate treatment systems. He found that the decrease in the exchange capacity of the cation exchange resin was related to low-molecular-weight polymers released by the anion exchange resin during operation. These low-molecular-weight polymers contaminated the cation exchange resin. The study measured the effect of different forms of anion exchange resin on the mass transfer coefficient of the cation exchange resin in the mixed bed. To verify whether residual nitrogen-containing low-molecular-weight polymers in the anion resin contaminated the cation exchange resin, Harries et al. used X-ray photoelectron spectroscopy to analyze new and old resins. The results showed that these low-molecular-weight polymers did indeed contaminate the cation exchange resin. For resins contaminated with organic matter, oxidizing agents such as H2O2 and Na2O2 can be used to decompose the adsorbed organic matter on the resin into water-soluble substances, which can then be removed from the resin. The effect of anion resin on the exchange capacity of cation resin after mixed bed regeneration: Cation resin | Anion resin (initial form) | Cation resin mass transfer coefficient/(10⁻⁴ m·s⁻¹) | Sodium-type cation resin | Amine-type cation resin | Single cation bed | 1.8 | 2.1 | Mixed bed (1:1) | Macroporous resin (Cl⁻) | 1.6 | 1.9 | Mixed bed (1:1) | Macroporous resin (OH⁻) | 1.5 | 1.8 | Mixed bed (1:1) | Gel-type resin (Cl⁻) | <0.1 | 1.2 Note: Mixed bed (1:1) indicates that the volume ratio of anion and cation resins in the mixed bed is 1:1. The degree of organic contamination of resin can be determined as follows: Add the contaminated resin to a test tube, with the resin volume approximately one-third of the test tube's volume. Then, add about four-fifths of the test tube's volume of 10% saline solution. Shake the test tube for 5 minutes, then pour off the saline solution. Repeat this process 3 to 4 times. After pouring off the last batch of saline solution, add about four-fifths of the test tube's volume of 10% saline solution again, keeping the resin in contact with this saline solution for 5-10 minutes, shaking the test tube continuously during this time. The degree of organic contamination of the resin can be determined by observing the color of the saline solution. Degree of Organic Contamination of Resin: Color of Saline Solution After Soaking | Degree of Contamination | Colorless | No Contamination | Pale Yellow | Slight Contamination | Amber | Moderate Contamination | Brown | Severe Contamination | Dark Brown or Black | Extremely Severe Contamination