Method of producing fluoroapatite, fluoroapatite, and adsortion apparatus

Abstract

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.

1 . A fluoroapatite which is obtained by reacting a hydroxyapatite having at least one hydroxyl group with a hydrogen fluoride having a fluorine atom, wherein the at least one hydroxyl group is substituted with the fluorine atom,
 wherein the fluoroapatite contains Ca to be eluted to an acid solution when the fluoroapatite is in contact with the acid solution, wherein a concentration of the Ca in the acid solution is 12 ppm or less.   
   
   
       2 . The fluoroapatite according to  claim 1 , wherein the fluoroapatite to be in contact with the acid solution is formed of sintered particles which are obtained by sintering dried particles of the fluoroapatite having an average particle size of 40 μm±5 μm. 
   
   
       3 . The fluoroapatite according to  claim 2 , wherein the acid solution is a buffer solution having a pH of 5 at room temperature. 
   
   
       4 . The fluoroapatite according to  claim 3 , wherein the concentration of the Ca is a concentration in 1 ml of the buffer solution. 
   
   
       5 . The fluoroapatite according to  claim 4 , wherein when a column having a filling space is prepared, the sintered particles are filled in the filling space, the buffer solution is supplied into the filling space, an eluate of 50 CV is discharged out of the filling space of the column at a flow rate of 1.0 ml/min, and then 1 ml of an eluate following the eluate of 50 CV is collected, wherein the calcium concentration in said 1 ml eluate is 12 ppm or less. 
   
   
       6 . A fluoroapatite which is obtained by reacting a hydroxyapatite having at least one hydroxyl group with a hydrogen fluoride having a fluorine atom, wherein the at least one hydroxyl group is substituted with the fluorine atom,
 wherein when the fluoroapatite is granulated to obtain dried particles having an average particle size of 40 μm±5 μm, the dried particles are sintered to obtain sintered particles, a column having a filling space is prepared, the sintered particles are filled into the filling space, a buffer solution having a pH of 5 at room temperature is prepared, the buffer solution is supplied into the filling space to obtain an eluate containing Ca, 50 CV of the eluate is discharged out of the filling space of the column at a flow rate of 1.0 ml/min, and 1 ml of the eluate is collected, a concentration of Ca contained in the eluate is 12 ppm or less.   
   
   
       7 . The fluoroapatite according to  claim 6 , wherein the Ca concentration is 10 ppm or less. 
   
   
       8 . The fluoroapatite according to  claim 7 , wherein the Ca concentration is 5 ppm or less. 
   
   
       9 . The fluoroapatite according to  claim 6 , wherein the amount of impurities in the fluoroapatite is 300 ppm or less. 
   
   
       10 . The fluoroapatite according to  claim 9 , wherein the amount of impurities in the fluoroapatite is 100 ppm or less. 
   
   
       11 . The fluoroapatite according to  claim 9 , wherein the impurity is ammonium. 
   
   
       12 . The fluoroapatite according to  claim 10 , wherein the impurity is ammonium. 
   
   
       13 . A fluoroapatite having high acid resistance and represented by a formula Ca 10 (PO 4 ) 6 (OH) 2-2x F 2x , wherein 0≦x1, which is obtained by reacting a hydroxyapatite having at least one hydroxyl group with hydrogen fluoride-containing solution, wherein when
 granulating the fluoroapatite to obtain dried particles having an average particle size of 40 μm±5 μm;   sintering the dried particles to obtain sintered particles;   filling the sintered particles into a column having a filling space;   passing a buffer solution having a pH of 5 at room temperature at a rate of 1.0 ml/min through the sintered particles in the column; and   discharging a first eluate of 50 CV,   an eluate directly following the first eluate has a Ca concentration of 12 ppm or less.   
   
   
       14 . The fluoroapatite according to  claim 13 , wherein the Ca concentration is 10 ppm or less. 
   
   
       15 . The fluoroapatite according to  claim 14 , wherein the Ca concentration is 5 ppm or less. 
   
   
       16 . The fluoroapatite according to  claim 13 , wherein the amount of impurities in the fluoroapatite is 300 ppm or less. 
   
   
       17 . The fluoroapatite according to  claim 16 , wherein the amount of impurities in the fluoroapatite is 100 ppm or less.