Method for controlling the properties of biogenic silica

Abstract

Porous amorphous silica can be obtained from siliceous plant matter containing non-siliceous inorganic substances. The siliceous plant matter is soaked in an aqueous solution which includes a chelating agent. The chelating agent is present in an amount which helps to extract at least some of the non-siliceous inorganic matter. The aqueous solution is then separated from the siliceous plant matter. Beneficial properties are imparted to the siliceous plant matter by controlling the amount of at least one preselected non-siliceous inorganic substance in the siliceous plant matter. At the end of the process, the siliceous plant matter is heat treated in the presence of oxygen at a temperature to produce the resulting amorphous silica having the beneficial properties.

1 - 25 . (canceled) 
     
     
         26 . A process for production of porous amorphous silica from siliceous plant matter containing non-siliceous inorganic matter, the process comprising the steps of:
 a) manipulating the amount of at least one preselected non-siliceous inorganic substance in said siliceous plant matter by controlling the amount of the chelating agent, or by introducing mineral acids into said siliceous plant matter, or by mixing the desired amount of preselected non-siliceous inorganic matter into the siliceous plant matter, such that the amount of the preselected non-siliceous inorganic substance remaining in the plant matter is established at a preselected amount of from 20 ppm to 25,000 ppm, said preselected amount of the at least one preselected non-siliceous inorganic substance selected to control the surface area of the porous amorphous silica obtained after heat treatment within the range of 10 m 2 /g and 450 m 2 /g, the preselected non-siliceous inorganic substance including elements or compounds of alkali metals, alkali earth metals, aluminum, boron, iron, manganese, titanium, and/or phosphorus; and   b) heat treating said siliceous plant matter in the presence of oxygen at a temperature in the range of 200° C. to 1,000° C. wherein the resulting silica is comprised of silica of porous amorphous form.   
     
     
         27 . The process of  claim 26 , wherein the manipulating of the amount of the at least one preselected non-siliceous inorganic substance in said siliceous plant matter is by controlling the amount of the chelating agent. 
     
     
         28 . The process of  claim 27 , wherein the chelating agent is selected from the group consisting of citric acid, acetic acid, ethylenediamine, ethylenediaminetetracetic acid, di mercapto succinic acid, trimethylaminetricarboxylic acid, alphalipoic acid, and diethylenetriaminepentaacetic acid. 
     
     
         29 . The process of  claim 28 , wherein the amount of chelating agent is from 0.001 kg per kg of plant matter to 1 kg per kg of plant matter. 
     
     
         30 . The process of  claim 29 , wherein the chelating agent is citric acid and the amount of citric acid is from 0.01 kg per kg of plant matter to 0.1 kg per kg of plant matter. 
     
     
         31 . The process of  claim 26 , wherein the manipulating of the amount of the at least one preselected non-siliceous inorganic substances in said siliceous plant matter is by introducing mineral acids into said siliceous plant matter. 
     
     
         32 . The process of  claim 31 , wherein said at least one mineral acid is selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and perchloric acid. 
     
     
         33 . The process of  claim 26 , wherein the manipulating of the amount of the at least one preselected non-siliceous inorganic substances in the siliceous plant matter is by mixing the desired amount of preselected non-siliceous inorganic matter into the siliceous plant matter. 
     
     
         34 . The process of  claim 26 , wherein the surface area of said amorphous silica is controlled in a specified narrow band within the range of 10 m 2 /g and 450 m 2 /g by controlling the amount of said preselected non-siliceous inorganic matter in the siliceous plant matter and/or the heat treatment temperature. 
     
     
         35 . The process of  claim 26 , wherein the pore volume of said amorphous silica is controlled in a specified narrow band within the range of 0.50 cc/g and 0.05 cc/g by controlling the amount of said preselected non-siliceous inorganic matter in the siliceous plant matter and/or the heat treatment temperature. 
     
     
         36 . The process of  claim 26 , wherein the pore diameter of said amorphous silica is controlled in a specified narrow band within the range of 10 Angstroms and 200 Angstroms by controlling the amount of said preselected non-siliceous inorganic matter in the siliceous plant matter and/or the heat treatment temperature. 
     
     
         37 . The process of  claim 26 , wherein the amount of wherein the amount of non-siliceous inorganic substances in the in the siliceous plant matter, is controlled in a range within the range of 300 ppm and 15,000 ppm. 
     
     
         38 . The process of  claim 26 , wherein the content of non-siliceous inorganic substances in the heat treated silica is controlled in a range within the range of 10 ppm and 1,000 ppm by post washing the silica with at least one of water, mineral acids, chelants, and pH adjustment chemicals. 
     
     
         39 . The process of  claim 38 , wherein the content of non-siliceous inorganic substances in the heat treated silica is controlled in a range within the range of 100 ppm and 500 ppm by post washing the silica with at least one of water, mineral acids, chelants, and pH adjustment chemicals 
     
     
         40 . The process of  claim 26 , wherein said heat treatment temperature is in the range of 200° C. to 1,000° C. 
     
     
         41 . The process of  claim 26 , wherein said preselected non-siliceous inorganic matter in the siliceous plant matter is comprised of at least one of lithium, sodium, potassium, magnesium, calcium, aluminum, boron, iron, manganese, titanium or phosphorus. 
     
     
         42 . The process of  claim 26 , wherein the content of said preselected non-siliceous inorganic matter in said siliceous plant matter is chemically controlled. 
     
     
         43 . The process of  claim 26 , wherein the content of preselected non-siliceous inorganic matter and heat treating temperature are controlled to prevent formation of crystalline structures in said amorphous silica.