Ion Exchange & Adsorption Resins Speed Up Water Reuse Process

Industrial wastewater often contains heavy metals such as copper, lead, zinc, and cadmium, which are harmful to the environment and human health and challenging to remove through biological treatment. Resins can effectively eliminate these metal ions through chemical adsorption or ion exchange.
In ion exchange, charged groups on the resin surface exchange with heavy metal ions in wastewater, binding the metal ions to the resin while releasing hydrogen or sodium ions. Chelating resins firmly adsorb metal ions by forming chemical bonds within the resin matrix:

R-H⁺ + Cu²⁺ → R-Cu²⁺ + 2H⁺

In that,

• R-H⁺: The hydrogen ion (H⁺) on the resin, which can exchange with cations in the aqueous solution
• Cu²⁺: Copper ions (Cu²⁺) in the aqueous solution

Some industrial wastewater contains refractory organic compounds (e.g., phenols, dyes), which not only degrade water quality but may also produce odors and discoloration. Adsorption resins can remove these organic substances through physical adsorption, ensuring the water is clear and meets reuse standards.

Macroporous resins remove organic pollutants through physical adsorption. Their large surface area and porous structure provide adsorption sites for organic molecules, where hydrophobic interactions between the organic compounds and the resin’s surface retain the molecules on the resin:

C_organic + R → R-C_adsorbed

In that,

• C: organic pollutants in wastewater
• R: the adsorption site on the resin.

Organic molecules adhere to the pores or surface of the resin through intermolecular forces.

Some industrial wastewater contains high levels of calcium and magnesium ions, increasing water hardness. These hardness ions can cause scaling in equipment pipelines, affecting system performance. Softening the water through resins prevents scaling and ensures normal equipment operation.

During water softening, sodium ions on the cation exchange resin surface exchange with calcium and magnesium ions in the water, removing hardness ions and softening the water:

2R-Na + Ca²⁺ → R₂Ca + 2Na⁺

In that,

• R: the resin matrix
• Na: sodium ions
• Ca: calcium ions

The resin removes hardness ions by exchanging sodium ions for calcium ions, achieving a softening effect.

Ammonia nitrogen and nitrates are common inorganic pollutants in wastewater, particularly in effluents from electronics and semiconductor industries. Removing these pollutants helps reduce the risk of water eutrophication and decreases the ecological impact of wastewater.

Cation exchange resins exchange with ammonia nitrogen ions in wastewater, binding ammonia nitrogen to the resin. Anion exchange resins remove nitrate ions through an exchange process:

Removal of Ammonia Nitrogen:

R-H + NH₄⁺ → R-NH₄ + H⁺

In that,

• R: the resin matrix
• H: the ion originally present on the cation exchange resin
• NH₄⁺: the Ammonia Nitrogen ion

In this exchange process, the resin adsorbs the target pollutant ions, purifying the water.

Removal of Nitrate Ions:

R-Cl + NO₃^- → R-NO₃ + Cl^-

In that,

• R: the resin matrix
• Cl: the ion originally present on the anion exchange resin
• NO₃^-: the nitrate ion

In this exchange process, the resin adsorbs the target pollutant ions, purifying the water.