Rare earth metal compounds methods of making, and methods of using the same

Abstract

Rare earth metal compounds, particularly lanthanum, cerium, and yttrium, are formed as porous particles and are effective in binding metals, metal ions, and phosphate. A method of making the particles and a method of using the particles is disclosed. The particles may be used in the gastrointestinal tract or the bloodstream to remove phosphate or to treat hyperphosphatemia in mammals. The particles may also be used to remove metals from fluids such as water.

What is claimed:  
     
         1 . A rare earth compound selected from the group consisting of rare earth oxychloride, a rare earth anhydrous oxycarbonate, and a rare earth hydrated oxycarbonate wherein the compound has an absorption capacity of at least 45 mg. phosphate per gram of compound.  
     
     
         2 . The compound of  claim 1  wherein the rare earth is selected from the group consisting of lanthanum, cerium, and yttrium.  
     
     
         3 . The compound of  claim 1  wherein the rare earth is lanthanum.  
     
     
         4 . The compound of  claim 1  wherein the compound is a particle with a porous structure.  
     
     
         5 . The compound of  claim 4  wherein the porous structure is made by total evaporation of a rare earth salt solution followed by calcination.  
     
     
         6 . The compound of  claim 5  wherein the evaporation is conducted in a spray dryer.  
     
     
         7 . The compound of  claim 5  wherein the evaporation temperature is between about 120° and 500° C.  
     
     
         8 . The compound of  claim 5  wherein the calcination temperature is between about 400° and about 1200° C.  
     
     
         9 . The compound of  claim 1  having a size between about 1 and about 1000 μm.  
     
     
         10 . The compound of  claim 9  wherein the compound is formed from individual crystals having a size between about 20 nm and about 10 μm.  
     
     
         11 . The compound of  claim 6  wherein the product comprises of spheres or parts of spheres.  
     
     
         12 . The compound of  claim 5  wherein the rare earth salt solution comprises a solution selected from the group consisting of rare earth chloride and rare earth acetate.  
     
     
         13 . The compound of  claim 5  wherein the rare earth salt solution in neutralized with sodium carbonate, followed by washing, filtering, and drying.  
     
     
         14 . The compound of 13 wherein the neutralization process takes place at a temperature of about 80° C.  
     
     
         15 . The compound of  claim 14  wherein the drying takes place at a temperature of about 105° C.  
     
     
         16 . The compound of  claim 15  wherein the drying takes place for a period of about 2 hours.  
     
     
         17 . The compound of  claim 1  wherein the compound exhibits a low solubility in fluids selected from the group consisting of gastrointestinal tract fluid and blood serum.  
     
     
         18 . The compound of  claim 1  wherein the compound has a low bulk density.  
     
     
         19 . The compound of  claim 1  wherein the compound is selective for binding phosphate ions.  
     
     
         20 . The compound of  claim 1  wherein the compound exhibits substantially linear phosphate binding kinetics.  
     
     
         21 . A device having an inlet and an outlet comprising rare earth compound selected from the group consisting of rare earth oxychloride, a rare earth anhydrous oxycarbonate, and a rare earth hydrated oxycarbonate wherein the compound has an absorption capacity of at least 45 mg. phosphate per gram of compound and wherein the compound is disposed between the inlet and the outlet.  
     
     
         22 . A method of treating hyperphosphatemia in a mammal comprising providing an effective amount of rare earth compound selected from the group consisting of rare earth oxychloride, a rare earth anhydrous oxycarbonate, and a rare earth hydrated oxycarbonate wherein the compound has an absorption capacity of at least 45 mg. phosphate per gram of compound.  
     
     
         23 . A method of making a lanthanum compound comprising; 
 a. providing a lanthanum chloride solution;    b. mixing a sodium carbonate solution with the lanthanum chloride solution to form a precipitate selected from the group consisting of lanthanum oxychloride, lanthanum anhydrous oxycarbonate, lanthanum hydrated oxycarbonate, and mixtures thereof;    c. filtering precipitate; and,    d. drying the precipitate.    
     
     
         24 . The method of  claim 23  further comprising calcining the dried precipitate at a temperature of about 500° C. to about 600° for about 3 to 7 hours.  
     
     
         25 . A lanthanum oxycarbonate with a BET specific surface area within the range of about 10 m 2 /g to about 40 m 2 /g.  
     
     
         26 . The lanthanum oxycarbonate of  claim 25  wherein the lanthanum oxycarbonate has an absorption capacity of at least 45 mg phosphate/g lanthanum oxycarbonate.  
     
     
         27 . A TiO 2  particle coated with a lanthanum compound.  
     
     
         28 . The particle of  claim 27  wherein the lanthanum compound is selected from the group consisting of lanthanum oxychloride, lanthanum oxycarbonate, hydrated lanthanum oxycarbonate, and mixtures thereof.  
     
     
         29 . The particle of  claim 28  wherein the lanthanum compound has an absorption capacity of at least 45 mg. phosphate per gram of compound.  
     
     
         30 . A method of making a TiO 2  structure comprising: 
 a. forming a titanium chloride feed solution;    b. subjecting the feed solution to a controlled temperature evaporation process at a temperature higher than the boiling point of the solution but lower than the temperature where crystallization of the product becomes significant;    c. calcining the hydrolyzed product;    d. re-slurrying the calcined hydrolyzed product in a solution containing a lanthanum compound to form a suspension;    e. subjecting the suspension to total evaporation to form a final product; and    f. calcining the final product.    
     
     
         31 . The method of  claim 30  wherein the first calcination temperature is between about 400° C. and about 1200° C. and the calcination time is between about 2 and about 24 hours.  
     
     
         32 . The method of  claim 31  wherein the second calcination temperature is between about 650 and about 1100° C. and the calcination time is between about 2 and about 24 hours.  
     
     
         33 . The method of  claim 30  wherein the calcined hydrolyzed product comprises hollow spheres or parts of spheres.  
     
     
         34 . The method of  claim 30  wherein the final product is selected from the group consisting of lanthanum oxide, lanthanum oxychloride, lanthanum oxycarbonate, and mixtures thereof.  
     
     
         35 . The method of  claim 34  wherein the final product comprises crystals having a size in the range from about 20 nm to about 20 microns.  
     
     
         36 . A method for reducing the metal content in a fluid comprising contacting the fluid with a lanthanum compound selected from the group consisting of lanthanum oxycarbonate, La 2 CO 5 , La 2 O 2 CO 3 , and mixtures thereof, wherein the lanthanum compound has an absorption capacity of at least 45 mg. phosphate per gram of compound.