Can You Remove Fluoride By Boiling Water?

Why Boiling Won't Remove Fluoride from Water

Trying to remove fluoride from water by boiling it? Boiling water concentrates the fluoride, although the steam that escapes contains much lower amounts of the ion.
Trying to remove fluoride from water by boiling it? Boiling water concentrates the fluoride, although the steam that escapes contains much lower amounts of the ion. Dorling Kindersley / Getty Images

Some people want fluoride in their drinking water, while others seek to remove it. One of the most common questions I get relating to fluoride removal is whether or not you can boil fluoride out of your water. The answer is no. If you boil water or leave it on a hot plate for an extended period of time, the fluoride will become more concentrated, remaining in the water as a fluorine salt.

The reason is because you're not trying to boil out elemental fluorine, which is F2, but fluoride, F-, which is the ion.

The boiling point of the fluoride compound (which is 19.5°C for HF and 1,695°C NaF) doesn't apply because you're not dealing with the intact compound. Trying to boil out fluoride is like trying to boil out sodium or chloride from dissolved salt in water!

Boiling to Distill Water to Remove Fluoride

However, you can boil water to remove fluoride if you capture the water that is evaporated and then condense it (distill it). The water you collect will contain much less fluoride than your starting water. As an example, when you boil a pot of water on the stove, the fluoride concentration in the water in the pot increases. The water that escapes as steam contains much less fluoride.

Methods That Remove Fluoride from Water

There are effective methods to remove fluoride from water or lower its concentration, including:

  • Distillation - boiling the water, collecting the vapor, and chilling the vapor until it forms liquid water
  • Reverse Osmosis - forcing water through a semipermeable membrane, leaving the fluoride and other ions on one side of the membrane, with higher purity water on the other side.
  • Activated Alumina - running water across activated alumina (aluminum oxide), which captures the fluoride so the water has a lower ion concentration.

    Methods That Do Not Remove Fluoride

    These methods do not remove fluoride from water:

    • As mentioned, normal boiling does not remove fluoride. It increases its concentration.
    • Most water filters don't touch fluoride (Brita, Pur, etc.).
    • Freezing water doesn't remove fluoride. However, fluoride lowers the freezing point of water (freezing point depression). It's reasonable that ice from fluoridated water will be higher purity than the source water, providing some liquid remains. Similarly, icebergs are fresh water rather than salt water. The fluoride ion concentration is low, so using freezing to purify water is impractical. If you freeze a tray of fluoridated water into ice, the ice will have the same fluoride concentration as the water.

    Fluoride concentration is increased after exposure to nonstick cookware. Teflon is a fluorine compound, which leaches slightly into water and foods.