Method for the separation of metal ions that are divalent or higher from strong acids or highly acidic media

Abstract

The present invention relates to a method of purifying strong acids or strongly acidic media to remove di- and higher valent metal ions, which can be used within the context of the production of high-purity silica. The invention further relates to the use of special ion exchangers for carrying out the method according to the invention and the resultant high-purity silicas.

1 . A method of producing high-purity silica, the method comprising: adding a silicate solution with a viscosity from 0.1 to 10000 poise to a preparation with a pH of less than 2.0 containing an acidifying agent, with the proviso that during the adding the pH is always less than 2.0 and at least one phosphonate ion exchanger is brought in contact, for the purpose of ion exchange, with at least one acid medium that is formed within the process. 
     
     
         2 . The method according to  claim 1 , wherein at least one phosphonate ion exchanger is brought in contact with a liquid phase of a precipitate suspension that formed during adding the silicate solution. 
     
     
         3 . The method according to  claim 1 , further comprising separating the silica from a precipitate suspension that formed as a result of adding the silicate solution and is treated at least once with an acidic washing medium, whose pH is less than 2.0, with the proviso that at least one phosphonate ion exchanger is brought in contact with the acidic washing medium. 
     
     
         4 . The method according to  claim 1 , further comprising separating the silica is separated from a precipitate suspension that formed as a result of adding the silicate solution and is treated at least once with an acidic washing medium, whose pH is less than 2.0, with the proviso that at least one phosphonate ion exchanger is brought in contact both with the acidic washing medium, and with a liquid phase of the precipitate suspension. 
     
     
         5 . The method according to  claim 1 , wherein at least one acid medium, which is brought in contact with at least one phosphonate ion exchanger, is circulated by pump or is moved in order to improve ion exchange. 
     
     
         6 . The method according to  claim 1 , wherein the acidifying agent contained in the preparation comprises sulphuric acid. 
     
     
         7 . The method according to  claim 1 , wherein the ion exchange with the phosphonate ion exchanger takes place in parallel with the production of the high-purity silica or within the timeframe of the production process. 
     
     
         8 . The method according to  claim 1 , wherein the production of the high-purity silica is a continuous or a discontinuous process. 
     
     
         9 . The method according to  claim 1 , wherein the phosphonate ion exchanger undergoes regeneration in parallel with the production of the high-purity silica or within the timeframe of the production process. 
     
     
         10 . The method according to  claim 1 , wherein the phosphonate ion exchanger undergoes regeneration. 
     
     
         11 . The method according to  claim 9 , wherein an alkaline solution used for regeneration comprises tartrate, citrate, oxalate or EDTA ions. 
     
     
         12 . The method according to  claim 1 , wherein the at least one acid medium is purified through the use of an acid retardation process. 
     
     
         13 . Use of an aminomethylphosphonic acid- or aminomethylphosphonate-functionalized phosphonate ion exchanger for a method according to  claim 1 . 
     
     
         14 . The use of a phosphonate ion exchanger for a method according to  claim 1 , wherein the exchanger is functionalized with structural units of the formula R—NR′CH 2 P(O)(OH) 2  and wherein R′ represents any residue except hydrogen, which is identical to or different from R. 
     
     
         15 . The use of a phosphonate ion exchanger for a method according to  claim 1 , wherein the exchanger is functionalized with structural units of the formula R—NHCH 2 P(O)(OH) 2  and wherein R represents any residue. 
     
     
         16 . The use of a phosphonate ion exchanger for a method according to  claim 1 , wherein the exchanger is functionalized with structural units of the formula RR′C[PO(OH) 2 ] 2  and wherein R′ represents any residue, which is identical to or different from R. 
     
     
         17 . The use of a phosphonate ion exchanger for a method according to  claim 1 , wherein as well as the normal structural units of formula R—P(O)(OH) 2  the exchanger additionally contains sulphonic acid or sulphonate groups. 
     
     
         18 . The use of a phosphonate ion exchanger according to  claim 1 , wherein the functional phosphonic acid groups are in a form at least partially loaded with alkali metal ions or in neutralized form. 
     
     
         19 . Silica, produced by a method according to  claim 1 , wherein the content of zirconium, tin or a combination thereof, is below 0.1 ppm. 
     
     
         20 . The silica according to  claim 19 , wherein the content of zirconium, tin or a combination thereof, is below 0.05 ppm. 
     
     
         21 . The method according to  claim 10 , wherein an alkaline solution used for regeneration comprises tartrate, citrate, oxalate or EDTA ions.