Fluoroapatite Production via Hydrogen Fluoride pH Control
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Solution Overview
Problem
The existing methods for producing fluoroapatite result in particles with ammonia as an impurity, leading to inconsistent characteristics and limited acid resistance due to the difficulty in removing ammonia and the limited substitution of hydroxyl groups by fluorine atoms.
Innovation Solution
A method involving the preparation of a slurry with hydroxyapatite and a hydrogen fluoride-containing solution, where the pH is adjusted between 2.5 and 5, allowing for the substitution of hydroxyl groups with fluorine atoms, reducing impurities like ammonia, and enhancing acid resistance by recrystallization of fluoroapatite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ammonium hydrogen fluoride is used as a fluorine source to synthesize fluoroapatite, then the synthesis process is simple, but ammonia remains adsorbed in the particles as an impurity that is very difficult to remove
Solution Approach 1:
The patent extracts and removes the harmful ammonia impurity from the synthesis system by replacing ammonium hydrogen fluoride with hydrogen fluoride as the fluorine source. This substitution eliminates the introduction of ammonia into the particles, thereby improving particle purity while maintaining synthesis feasibility
Solution Approach 2:
The patent changes the chemical parameter of the fluorine source from ammonium hydrogen fluoride to hydrogen fluoride. This parameter change eliminates ammonia introduction while maintaining the fluorination capability, thereby resolving the contradiction between ease of manufacture and particle purity
2Productivity
If ammonium hydrogen fluoride is used as a fluorine source, then the synthesis can proceed, but the amount of ammonia remaining in particles varies from lot to lot making uniform characteristics difficult to obtain
Solution Approach 1:
The patent removes the source of batch variability (ammonia from ammonium hydrogen fluoride) by substituting hydrogen fluoride as the fluorine source. This elimination of the variable impurity source enables consistent batch-to-batch particle characteristics while maintaining synthesis productivity
Solution Approach 2:
The patent changes the fluorine source parameter from ammonium hydrogen fluoride to hydrogen fluoride, which eliminates the lot-to-lot variability caused by ammonia content fluctuations. This parameter change achieves both productivity and manufacturing precision
3Quantity of substance
If ammonia remains in fluoroapatite particles, then the particles can be produced, but the substitution of hydroxyl groups by fluorine atoms is inhibited limiting acid resistance improvement
Solution Approach 1:
The patent extracts and eliminates ammonia from the system by using hydrogen fluoride instead of ammonium hydrogen fluoride as the fluorine source. This removal of ammonia inhibition enables complete substitution of hydroxyl groups by fluorine atoms, thereby achieving high acid resistance while maintaining fluoroapatite production
Solution Approach 2:
The patent changes the fluorine source parameter to hydrogen fluoride, which removes the ammonia inhibition effect on hydroxyl group substitution. This parameter change enables achieving both production quantity and reliability (acid resistance)
Data Source
AI summary
A method of producing a fluoroapatite is provided. The method comprises preparing a slurry containing a hydroxyapatite which has at least one hydroxyl group, preparing a hydrogen fluoride-containing solution containing a hydrogen fluoride, mixing the hydrogen fluoride-containing solution with the slurry to obtain a mixture to thereby adjust a pH of the mixture in the range of 2.5 to 5, and reacting the hydroxyapatite with the hydrogen fluoride in the mixture in a state that the pH of the mixture is adjusted within the above range to thereby obtain the fluoroapatite by substituting the at least one hydroxyl group of the hydroxyapatite with fluorine atom of the hydrogen fluoride. The method can produce the fluoroapatite having improved acid resistance by reducing an impurity, such as ammonia, derived from a raw material to a low or very low level. Further, a fluoroapatite having high acid resistance is also provided. Furthermore, an adsorption apparatus using such a fluoroapatite is provided.