Inventory of pollution suffered by ion exchange resin operation

Ion exchange resin is widely used in Water Treatment Systems, but its performance is easily affected by a variety of pollutants, resulting in reduced exchange capacity and deterioration of effluent water quality.

1. Organic pollution
Humic acid, flocculent organic matter and high molecular carboxylic acid (molecular weight 500-5000) in natural water bodies are the main pollutants. Such substances carry negative charges and preferentially adsorb on the surface of anionic resins, occupying active groups or causing degradation of alkaline groups.

Experimental data show that when the chemical oxygen demand (COD) of raw water exceeds 15 mg/L, the working exchange capacity of anionic resins can drop by 40%-50%.

2. Grease pollution
Oil substances form a hydrophobic film on the surface of the resin and block the microporous structure. Studies have shown that when the oil content in water is greater than 0.5 mg/L, the blockage rate of resin micropores increases to 60%, resulting in a 35% decrease in ion diffusion rate.

3. Suspended matter pollution
Suspended particles (such as silt and colloidal clay) block the liquid membrane exchange channel on the resin surface by physical encapsulation. Cationic resins are more susceptible due to their larger pore size.

4. Colloidal silica contamination
Colloidal silica (particle size <0.1μm) is negatively charged and easily adsorbed on the surface of anionic resins and polymerized into a silicate deposition layer. When the colloidal silica concentration in the raw water is >3mg/L, the attenuation rate of the anionic resin exchange capacity is accelerated by 50%.

5. High-valent metal ion contamination
High-valent ions such as Al³+ and Fe³+ combine with the sulfonic acid group (-SO₃⁻) of the cationic resin to form an irreversible complex. Laboratory simulations show that when the Fe³+ concentration is >0.3mg/L, the effective exchange sites of the resin are reduced by 25%.

6. Regeneration agent impurity contamination
Industrial-grade NaOH often contains impurities such as Fe³+ (200-500ppm) and NaCl (3%-5%). Statistics show that when a low-purity regeneration agent (purity <96%) is used, the risk of anionic resin contamination increases by 4 times.

7. Other pollution factors
The metabolites of microorganisms (such as sulfate-reducing bacteria) can block the resin pores. When the total number of bacteria is greater than 10⁴ CFU/mL, the resin pressure difference increases by 15%-20%. In addition, nitrogen-containing organic matter (such as amino acids) reacts with the resin group to form a complex, leading to irreversible pollution.