Tech Fact

Removal of CO2 in Dealkalization with Weak Acid Cation Resin

Application Carbon dioxide (CO2) in water is present as an equilibrium mixture of the dissolved − 2− Description gas CO2, the weak acid H2CO3, and the HCO3 and CO3 anions associated with bicarbonate and carbonate alkalinity. The exact equilibrium ratio of these four species depends on the pH and temperature of the water.

In a dealkalization system using a weak acid cation (WAC) resin in the H-form, the system removes alkalinity and partially softens the water. The WAC resin exchanges hydrogen for hardness ions associated with alkalinity. The resulting low pH

converts bicarbonate and carbonate alkalinity to dissolved CO2 gas, which is then removed by degasification.

Reliably and effectively removing as much CO2 as possible by degasification reduces the amount of alkalinity that could form posttreatment due to equilibrium

conversion of CO2 and protects sensitive downstream processes and equipment

from potential CO2-related .

Solution DuPont™ Ligasep™ Degasification Modules use a proprietary polymethylpentene (PMP) hollow fiber membrane that provides an efficient transfer of gases between a liquid and a gas.

The membrane does not allow water to pass through the membrane but freely allows gas to pass through. Equilibrium between the liquid and gas phase is offset when a vacuum and a strip gas is applied to one side of the membrane. This creates a driving force to move dissolved gases from the water to the gas side of the membrane.

Ligasep™ Degasification Modules offer a clean, efficient and stable process to

decarbonate water to concentrations of 5 mg/L or less of CO2 (8.35 mg/L as CaCO3) to reduce the load on downstream exchange equipment.

Key Benefits l Improves process reliability l Protects downstream equipment from CO2 corrosion l Efficient and stable way to decarbonate to concentrations of 5 ppm or less of

dissolved CO2, even for variable feedwater quality l Potentially reduces chemical consumption and operating costs (note: this will depend on system design and configuration)

l Eliminates potential cross-contamination from strip gas compared to decarbonators

Page 1 of 2 Form No. 45-D02163-en, Rev. 1 March 2020 Schematic Diagram

for illustration purposes only

DuPont Products l Ligasep™ LDM-040-HS or LDM-120-HS Degasification Modules l AmberLite™ IRC83 H, AmberLite™ HPR8300 H, or AmberLite™ HPR8400 H Resins

Have a question? Contact us at: All information set forth herein is for informational purposes only. This information is general information and may differ from that based on actual conditions. Customer is responsible for determining whether products and the information in this document are www.dupont.com/water/contact-us appropriate for Customer's use and for ensuring that Customer's workplace and disposal practices are in compliance with applicable laws and other government enactments. The product shown in this literature may not be available for sale and/or available in all geographies where DuPont is represented. The claims made may not have been approved for use in all countries. Please note that physical properties may vary depending on certain conditions and while operating conditions stated in this document are intended to lengthen product lifespan and/or improve product performance, it will ultimately depend on actual circumstances and is in no event a guarantee of achieving any specific results. DuPont assumes no obligation or liability for the information in this document. References to “DuPont” or the “Company” mean the DuPont legal entity selling the products to Customer unless otherwise expressly noted. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. No freedom from infringement of any patent or trademark owned by DuPont or others is to be inferred. DuPont™, the DuPont Oval Logo, and all trademarks and service marks denoted with ™, ℠ or ® are owned by affiliates of DuPont de Nemours Inc. unless otherwise noted. © 2020 DuPont.

Page 2 of 2 Form No. 45-D02163-en, Rev. 1 March 2020