Process for treating aqueous chemical waste sludges and compositions produced thereby

Abstract

Waste sludges containing small amounts of certain types of reactive materials are treated by adding to such sludges materials capable of producing aluminum ions, lime and/or sulfate bearing compounds to produce a composition having a sufficient concentration of sulfate ions, aluminum ions and equivalents thereof, and calcium ions and equivalents thereof. Fly ash is preferred source of aluminum ions for this purpose. Over a period of time such compositions harden by the formation of calcium sulfo-aluminate hydrates. Hardening of the sludge facilitates its disposition and may permit the reclamation of the land now occupied by large settling ponds for such sludge. Still further, the solidification of such settling ponds may provide permanent land fill which permits immediate use of the land without the necessity for removal of the sludge. Aggregate materials may also be incorporated in the solidified waste.

What is claimed is: 
     
       1. The method of treating .Iadd.an .Iaddend.aqueous chemical waste .[.sludges.]. .Iadd.sludge including a sulfate compound .Iaddend.comprising adding to said .[.sludges.]. .Iadd.sludge .Iaddend.sufficient lime, .[.aluminum-containing material.]. .Iadd.fly ash .Iaddend.and water soluble sulfate compound to produce a composition having available sulfate ions, a second type of available ion selected from the group consisting of aluminum and ferric ions, the concentration of which is expressed in Al 2  O 3  equivalents, and a third type of available ions selected from the group consisting of calcium and magnesium, the concentration of which is expressed in CaO equivalents, wherein the composition, including available ions in said added lime, .[.aluminum-containing material.]. .Iadd.fly ash .Iaddend.and water soluble sulfate compounds includes at least 0.5 weight percent .[.--SO 4  .]. .Iadd.(--SO 4 ) -2 , .Iaddend.at least 0.2 weight percent Al 2  O 3  and equivalents thereof, and at least 0.5 weight percent CaO and equivalents thereof, .Iadd.the fly ash being present in said composition in an amount of at least 20% by weight of the amount of sludge in said composition, said composition being cementitiously hardenable through chemical reactions the products of which include calcium sulfo-aluminate hydrate or calcium alumino-sulfate hydrate, and allowing said composition to harden by chemical reaction to develop penetration resistance therein under atmospheric conditions. .Iaddend. .[. 
     
     
       2.  A method, as recited in claim 1, wherein said aluminum ion yielding material is fly ash..]. 
     
     
       3. A method, as recited in claim 1, wherein the weight ratios of available ions in said composition are in the range (Al +3  and Ca +2  include Al +3  and Ca +2  equivalents, respectively): Al +3  :Ca +2  from 1:10 to 1:2   Al +3  :(SO 4 ) -2  from 1:2 to 1:10   Ca +2  :(SO 4 ) -2  from 1:2 to 2:1   
     
     
       4. A method, as recited in claim 1, wherein said water soluble sulfate is calcium sulfate anhydrite, calcium sulfate hemihydrate, or calcium sulfate dihydrate. 
     
     
       5. A method, as recited in claim 1, wherein said sludge is the waste product of an acid making plant, said method consisting of adding lime and fly ash to obtain a composition as recited in claim 1. 
     
     
       6. A method, as recited in claim 1, wherein said sludge is the pickle liquor waste product of a steel plant, said method consisting of adding lime and fly ash to obtain a composition as recited in claim 1. 
     
     
       7. A composition comprising the reaction product of an aqueous chemical waste sludge .Iadd.including a sulfate compound .Iaddend.and selected additive materials said additive materials being selected so that the total composition of said additive materials and said sludge includes .Iadd.fly ash in a proportion of at least 20% of said sludge, .Iaddend.available sulfate ions, a second type of available ion selected from the group consisting of aluminum and ferric ions, the concentration of which is expressed in Al 2  O 3  equivalents, and a third type of available ions selected from the group consisting of calcium and magnesium, the concentration of which is expressed in CaO equivalents, wherein the composition includes at least 0.5 weight percent .[.--SO 4  .]. .Iadd.(--SO 4 ) -2 , .Iaddend.at least 0.2 weight percent Al 2  O 3  and equivalents thereof, and at least 0.5 weight percent CaO and equivalents thereof, wherein the weight ratios of available ions in said composition are in the range (Al +3  and Ca +2  includes Al +3  and Ca +2  equivalents, respectively): Al +3  :Ca +2  from 1:10 to tol: 2   Al +3  :(SO 4 ) -2  from 1:2 to 1:10   Ca +2  :(SO 4 ) -2  from 1:2 to 2:1, .Iadd. said composition, prior to reaction, being cementitiously hardenable through chemical reactions the products of which include calcium sulfo-aluminate hydrate or calcium alumino-sulfate hydrate, and allowing said composition to harden by chemical reaction to develop penetration resistance therein under atmospheric conditions. .Iaddend. .[.8. A composition, as recited in claim 7, wherein said aluminum ions yielding     
     
     
        material is fly ash..]. 9. A composition as recited in claim 7, wherein 
     
     
        said sludge is the waste product of an acid making plant. 10. A composition as recited in claim 7, wherein said sludge is the pickle 
     
     
        liquor waste product of a steel plant. 11. The method of making a cementitious composition comprising adding .[.the.]. .Iadd.to an .Iaddend.aqueous chemical waste .[.sludges.]. .Iadd.sludge including a sulfate compound, .Iaddend.sufficient lime, .[.aluminum-containing materials.]. .Iadd.fly ash .Iaddend.and water soluble sulfate compound to produce a composition having available sulfate ions, a second type of available ions selected from the group consisting of aluminum and iron ions, the concentration of which is expressed in Al 2  O 3  equivalents, and a third type of available ions selected from the group consisting of calcium and magnesium, the concentration of which is expressed in CaO equivalents, wherein the composition includes at least 0.5 weight percent .[.--SO 4  .]. .Iadd.(SO 4 ) -2  .Iaddend. at least 0.2 weight percent Al 2  O 3  and equivalents thereof, and at least 0.5 weight percent CaO and equivalents thereof, .Iadd.the fly ash being present in said composition in an amount of at least 20% by weight of the amount of sludge in said composition, said composition being cementitiously hardenable through chemical reactions the products of which include calcium sulfo-aluminate hydrate or calcium alumino-sulfate hydrate, and allowing said composition to harden by chemical reaction to develop penetration resistance therein under atmospheric conditions. .Iaddend. .[.12. A method, as recited in claim 11, wherein said aluminum 
     
     
        ion yielding material is fly ash..]. 13. A method, as recited in claim 11, wherein the weight ratios of available ions in said composition are in the range (Al +3  and Ca +2  include Al +2  and Ca +2  equivalents respectively): Al +3  :Ca +2  from 1:10 to 1:2   Al +3  :(SO 4 ) -2  from 1:2 to 1:10   
     
     
       Ca +2  :(SO 4 ) -2  from 1:2 to 2:1 14. A method, as recited in claim 11, wherein said water soluble sulfate is calcium sulfate anhydrite, 
     
     
        calcium sulfate hemihydrate, or calcium sulfate dihydrate. 15. A method, as recited in claim 11, wherein said sludge is the waste product of an acid making plant, said method consisting of adding lime and fly ash to 
     
     
        obtain a composition as recited in claim 11. 16. A method, as recited in claim 11, wherein said sludge is the pickle liquor waste product of a steel plant, said method consisting of adding lime and fly ash to obtain a composition as recited in claim 11. .Iadd. 17. A method, as recited in claim 11, wherein said composition is damp and compactible. .Iaddend..Iadd. 18. A method, as recited in claim 11, wherein said composition is pourable. .Iaddend..Iadd. 19. A method, as recited in claim 11, wherein the ratio of calcium and magnesium ions in said composition to sulfate ions in said composition is in the range of from 2:1 to 1:2. .Iaddend..Iadd. 20. A method, as recited in claim 1, wherein said composition includes from 0.5 to 4 parts fly ash per part sludge (by weight). .Iaddend..Iadd. 21. A composition, a recited in claim 7, wherein, prior to reaction, said composition includes from 0.5 to 4 parts fly ash per part sludge (by weight). .Iaddend..Iadd. 22. A method, as recited in claim 11, wherein said composition includes from 0.5 to 4 parts fly ash per part sludge (by weight). .Iaddend.