Removal of Arsenic from Drinking and Process Water

Abstract

A method of removing arsenic and heavy metals from water using metal salt hydroxide-gels is provided. The arsenic present in water is adsorbed onto the hydroxide-gels which can effectively be filtered through a diatomaceous earth (DE) filtration bed. The combination of DE mixed hydroxide-gels is also effective in removing arsenic from water and heavy metals from water.

1 . A method of removing arsenic from arsenic-containing water comprising: contacting said water with a precipitating composition comprising a metal salt hydroxide-gel. 
   
   
       2 . The method of  claim 1 , further comprising separating said water from said precipitating composition. 
   
   
       3 . The method of  claim 2 , wherein said separating is performed using a filter. 
   
   
       4 . The method of  claim 3 , wherein said filter is a diatomaceous earth filter bed coated with a metal salt hydroxide-gel. 
   
   
       5 . The method of  claim 1 , wherein said metal salt hydroxide-gel is formed prior to contacting said water with said precipitating composition. 
   
   
       6 . The method of  claim 1 , wherein the pH of the precipitating composition and arsenic-containing water is adjusted to form a metal salt hydroxide-gel after contacting the precipitating composition and said water. 
   
   
       7 . The method of  claim 3 , wherein said filter is selected from the group consisting of: diatomaceous earth, cellulose, and perlite. 
   
   
       8 . A method of removing heavy metals from heavy metal-containing solution comprising: contacting said solution with a metal salt hydroxide-gel; and passing said solution through a filter. 
   
   
       9 . The method of  claim 8 , wherein said metal salt hydroxide-gel comprises lanthanum and iron. 
   
   
       10 . The method of  claim 8 , wherein said filter is a diatomaceous earth filter bed. 
   
   
       11 . The method of  claim 8 , wherein said filter is a diatomaceous earth filter bed coated with a metal salt hydroxide-gel. 
   
   
       12 . A composition for removing arsenic or heavy metal from arsenic- or heavy metal-containing water comprising: diatomaceous earth, a lanthanum salt and an iron salt. 
   
   
       13 . The composition of  claim 12 , wherein said lanthanum salt and iron salt are chlorides. 
   
   
       14 . The composition of  claim 12 , wherein said metal is arsenic. 
   
   
       15 . The composition of  claim 12 , wherein said metal is a heavy metal. 
   
   
       16 . A method of using the composition of  claim 12 , comprising mixing the precipitating composition with arsenic- or heavy metal-containing water and adjusting the pH so that a metal salt hydroxide-gel is formed. 
   
   
       17 . A method of making a diatomaceous earth-coated hydroxide-gel comprising: contacting a precipitating composition with diatomaceous earth; and adjusting the pH to form a diatomaceous earth-coated hydroxide-gel. 
   
   
       18 . A method of making a diatomaceous earth-coated hydroxide-gel comprising: contacting metal salts with diatomaceous earth, forming a composition; and aging the composition. 
   
   
       19 . The method of  claim 18 , further comprising separating the solid composition from the liquid. 
   
   
       20 . The method of  claim 18 , further comprising contacting arsenic-containing water with the composition; and adjusting the pH of the resulting composition to form a diatomaceous-coated gel.