CO2 is difficult for both RO and EDI to remove since it has no charge or is weakly ionized. It is important to remove CO2 in the electrodeionization pretreatment because CO2 lowers EDI product water quality, competes with silica for removal, and may lead to scaling of EDI. Here are 3 ways to remove CO2 effectively in a pure water system:
Corosex absorbant media, prior to the RO
Benefits: Passive and chemical-freeDisadvantage: increases scaling potential
Raise pH before the RO to 8.3 (or before 2nd pass RO)Benefit: Makes RO highly effectiveDisadvantage: Uses chemicals (NaOH)
Use GTM (Liqui-Cel®) after the RO
Benefit: Highly effective and chemical-free
Since electrodeionization concentrate scaling is caused by the combination of 3 things: 1) Ca/Mg hardness ions, 2) CO2, and 3) high pH, scaling is prevented by removing CO2. Electropure™ EDI 'Thin Concentrate' design also lowers the pH of the concentrate, which minimizes scaling.