Defluorination with hydrochloric acid
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The by-product hydrochloric acid produced in the fluorine chemical manufacturing process contains impurities of fluorine; in this fluorine-containing hydrochloric acid, fluorine exists in the form of dilute hydrofluoric acid and forms an azeotrope with hydrochloric acid. It is difficult to separate it effectively using methods such as distillation, adsorption, or extraction. The only method for removing high concentrations of fluorine from hydrochloric acid is precipitation. The precipitation method is mainly divided into chemical complexation and flocculation precipitation, that is, adding compounds to form water-insoluble fluorine-containing precipitates, or utilizing the chemical property of compounds to form layers through complexation reactions with fluoride ions. Many processes employ the addition of Ca compounds for defluorination, but this not only reduces the concentration of hydrochloric acid but also sometimes fails to achieve the desired removal rate of fluoride ions. Let’s discuss the options available for hydrochloric acid-based defluorination processes, as well as the advantages and disadvantages of different defluorinating agents.
There is a current approach that involves adding calcium hydroxide directly for neutralization, thereby producing calcium fluoride precipitate and calcium chloride solution; calcium fluoride can be used as fluorite, while calcium chloride can serve as a desiccant.
There is now a device called a short-path distillation kettle that you can give it a try
Let’s see if special resins for defluorination can be used
I’m wondering if anyone knowledgeable has the actual gas-liquid equilibrium data for the HF-HCl-H2O ternary system, so as to determine whether it is possible for HF and HCl to separate within this ternary system
If you have a method for removing fluoride using boiling water, please contact me. We have developed fluoride-removing agents tailored for wastewater from various industries. Phone number: 18462051858
It is ideal to use incompatible complexation reactions for defluorination. It is under testing, and the results are very noticeable!
You can try using nanoscale magnesium salts to remove fluoride
1. If the fluoride ion concentration is below 500 ppm, calcium chloride is added to remove fluoride; after the reaction, calcium fluoride precipitate and hydrochloric acid are formed； The final fluoride ion concentration in hydrochloric acid is approximately 20 ppm. 2. If the fluoride ion concentration is greater than 5000 ppm, concentrated sulfuric acid is added; hydrogen fluoride gas and hydrogen chloride gas are released, and the hydrogen fluoride liquid is obtained through condensation ； Hydrogen chloride is absorbed with pure water to obtain high-purity hydrochloric acid. Concentrating dilute sulfuric acid yields 93% sulfuric acid, which is reused. Wastewater is sent to the wastewater treatment plant (in the wastewater: sulfuric acid less than 1%, hydrofluoric acid less than 10 ppm).
This post was last edited by shiqin778 on 2021-9-26 at 16:15; defluorination can be achieved through distillation.