Tech Manual Excerpt Water Chemistry and Pretreatment Calcium Fluoride Scale Prevention Calcium Fluoride Fluoride levels in the feedwater of as low as 0.1 mg/L can create a scaling potential if Scale Prevention the calcium concentration is high. The calculation of the scaling potential is analogous to the procedure described in Calcium Sulfate Scale Prevention (Form No. 45-D01553-en) for CaSO4. Calculation 1. Calculate the ionic strength of the concentrate stream (Ic) following the procedure described in Scaling Calculations (Form No. 45-D01551-en): Eq. 1 2. Calculate the ion product (IPc) for CaF2 in the concentrate stream: Eq. 2 where: m 2+ 2+ ( Ca )f = M Ca in feed, mol/L m – – ( F )f = M F in feed, mol/L 3. Compare IPc for CaF2 with the solubility product (Ksp) of CaF2 at the ionic strength of the concentrate stream, Figure 2 /11/. If IPc ≥ Ksp, CaF2 scaling can occur, and adjustment is required. Adjustments for CaF2 Scale Control The adjustments discussed in Calcium Sulfate Scale Prevention (Form No. 45-D01553-en) for CaSO4 scale control apply as well for CaF2 scale control. Page 1 of 3 Form No. 45-D01556-en, Rev. 4 April 2020 Figure 1: Ksp for SrSO4 versus ionic strength /10/ Page 2 of 3 Form No. 45-D01556-en, Rev. 4 April 2020 Figure 2: Ksp for CaF2 versus ionic strength /11/ Excerpt from FilmTec™ Reverse Osmosis Membranes Technical Manual (Form No. 45-D01504-en), Chapter 2, "Water Chemistry and Pretreatment." 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 3 of 3 Form No. 45-D01556-en, Rev. 4 April 2020.