Use of silicon-containing polymers to improve red mud flocculation in the bayer process

Abstract

The suspended solids content of a Bayer process stream is reduced by contacting the stream with silicon-containing polymers.

What is claimed is: 
     
         1 . A flocculation method comprising:
 intermixing a silicon-containing polymer flocculant with a Bayer process stream in an amount effective to thereby flocculate at least a portion of a desilication product suspended therein; and   separating at least a portion of the flocculated desilication product thus formed.   
     
     
         2 . The flocculation method of  claim 1 , wherein the silicon-containing polymer flocculant comprises a plurality of —Si(OR)3 groups, wherein R is independently selected from the group consisting of hydrogen, C 1-20  alkyl, C 1-20  alkenyl, C 6-12  aryl, C 7-20  aralkyl, a group I metal ion, a group II metal ion, and NR′ 4+;  wherein R′ is independently selected from the group consisting of hydrogen, C 1-20  alkyl, C 1-20  alkenyl, C 6-12  aryl, and C 7-20  aralkyl; and wherein R and R′ are independently unsubstituted, hydroxy-substituted, or beta hydroxy substituted. 
     
     
         3 . The flocculation method of  claim 2 , where R is selected from the group consisting of Na + , K + , and NH 4   + . 
     
     
         4 . The flocculation method of  claim 1 , wherein the silicon-containing polymer flocculant is selected from the group consisting of a silicon-containing polyethyleneimine, a vinyl triethoxysilane copolymer, a copolymer of acrylic acid and triethoxysilylpropylacrylamide, a copolymer of acrylic acid and triethoxyvinylsilane, a silicon-containing polysaccharide, a silicon-containing styrene/maleic anhydride copolymer, a silicon-containing maleic anhydride/alkyl vinyl ether copolymer, and mixtures thereof, a silicon-containing polysaccharide, a silicon-containing maleic anhydride/alkyl vinyl ether copolymer, and mixtures thereof. 
     
     
         5 . The flocculation method of  claim 1 , wherein the silicon-containing polymer flocculant is hydroxamated. 
     
     
         6 . The flocculation method of  claim 1 , wherein at least a portion of the intermixing of the silicon-containing polymer flocculant with the Bayer process stream is conducted in at least one of a washer and a settler. 
     
     
         7 . The flocculation method of  claim 1 , further comprising adding the silicon-containing polymer flocculant to the Bayer process stream in an amount in the range of from about 0.1 part per million to about 500 parts per million. 
     
     
         8 . The flocculation method of  claim 1 , wherein the Bayer process stream further comprises a suspended red mud. 
     
     
         9 . The flocculation method of  claim 8 , further comprising flocculating at least a portion of the suspended red mud. 
     
     
         10 . The flocculation method of  claim 5 , conducted in the substantial absence of flocculants other than the hydroxamated silicon-containing polymer. 
     
     
         11 . A hydroxamated water-soluble or water-dispersible silicon-containing polymer comprising a silicon-containing group attached thereto. 
     
     
         12 . The hydroxamated silicon-containing polymer of  claim 11 , wherein the silicon-containing polymer comprises at least one —Si(OR) 3  group, wherein R is independently selected from the group consisting of hydrogen, C 1-20  alkyl, C 1-20  alkenyl, C 6-12  aryl, C 7-20  arylkyl, a group I metal ion, a group II metal ion, and NR′ 4   +;  wherein R′ is independently selected from the group consisting of hydrogen, C 1-20  alkyl, C 1-20  alkenyl, C 6-12  aryl, and C 7-20  arylkyl; and wherein R and R′ are independently unsubstituted, hydroxy-substituted, or beta hydroxy substituted. 
     
     
         13 . The hydroxamated silicon-containing polymer of  claim 12 , where R is selected from the group consisting of Na + , K + , and NH 4   + . 
     
     
         14 . The hydroxamated silicon-containing polymer of  claim 12 , wherein the silicon-containing polymer contains at least about 5 weight % of the —Si(OR) 3  group. 
     
     
         15 . The hydroxamated silicon-containing polymer of  claim 11 , wherein the hydroxamated silicon-containing polymer is selected from the group consisting of a hydroxamated silicon-containing polyethyleneimine, a hydroxamated vinyl triethoxysilane copolymer, a hydroxamated copolymer of acrylic acid and triethoxysilylpropylacrylamide, a hydroxamated copolymer of acrylic acid and triethoxyvinylsilane, a hydroxamated silicon-containing polysaccharide, a hydroxamated silicon-containing styrene/maleic anhydride copolymer, a hydroxamated silicon-containing maleic anhydride/alkyl vinyl ether copolymer, and mixtures thereof. 
     
     
         16 . The hydroxamated silicon-containing polymer of  claim 15 , wherein the hydroxamated silicon-containing polymer is a hydroxamated silicon-containing maleic anhydride/alkyl vinyl ether copolymer. 
     
     
         17 . The hydroxamated silicon-containing polymer of  claim 16 , wherein the hydroxamated silicon-containing maleic anhydride/alkyl vinyl ether copolymer is a hydroxamated silicon-containing maleic anhydride/methyl vinyl ether copolymer. 
     
     
         18 . The hydroxamated silicon-containing polymer of  claim 15 , wherein the hydroxamated silicon-containing polymer is a hydroxamated silicon-containing polysaccharide. 
     
     
         19 . The hydroxamated silicon-containing polymer of  claim 18 , wherein the hydroxamated silicon-containing polysaccharide is a hydroxamated silicon-containing starch or a hydroxamated silicon-containing cellulose. 
     
     
         20 . The hydroxamated silicon-containing polymer of  claim 19 , wherein the hydroxamated silicon-containing cellulose is a hydroxamated silicon-containing hydroxyethylcellulose. 
     
     
         21 . A flocculation method comprising
 intermixing a hydroxamated silicon-containing polymer according to  claim 11  with a Bayer process stream in an amount effective to flocculate at least a portion of solids suspended therein,   wherein the suspended solids are selected from the group consisting of red mud, desilication product, and mixtures thereof.   
     
     
         22 . The flocculation method of  claim 21 , conducted in the substantial absence of flocculants other than the hydroxamated silicon-containing polymer.