HF Treatment / Fluoride Removal
  |
High fluoride levels in wastewater can be problematic for industries using hydrofluoric acid as a cleaning agent or etchant, such as the semiconductor, solar cell or metals manufacturing industries, or as a reactant or catalyst in the plastics, pharmaceutical, petroleum refining and refrigeration industries. Fluoride concentrations from these industries may range from 100 to more than 10,000 ppm in rinse waters, but discharge limits are often below 20 ppm. On site treatment is essential to economically support manufacturing facilities. For industrial applications, a Calcium Hydroxide solution (also called Milk of Lime) is frequently used to force the precipitation of fluorides as Calcium Fluoride, according to the following chemical reaction. Ca(OH)2 + 2HF = CaF2 + 2H2O Calcium Hydroxide solution has low solubility and is corrosive, which complicates its handling and increases operating expenses, especially since it must be significantly overdosed to work effectively. Employing a combination of Calcium Hydroxide and Calcium Chloride will often provide a more economical and effective system. If there are heavy metals also present in the wastewater, such as Copper, Zinc and Chrome, then treatment with the MetFloc™ family of chemicals may be the simplest and most economical life cycle cost solution. Once the Calcium Fluoride has precipitated out of solution and treated with an appropriate coagulant, such as an anionic polymer solution, the waste water can be effectively filtered to remove the fluorides from the waste water. The resulting filter cake is safe to handle and remove for off site disposal. Wastech designs fluoride removal systems that are tailored to the specific needs of industrial facility operators. The key features of Wastech fluoride removal systems are:
|