Processes and compositions for water treatment

• US 20040040912A1
• Filed: 09/17/2003
• Published: 03/04/2004
• Est. Priority Date: 10/27/2000
• Status: Active Grant

• Current Assignee: Nauveau Technology Investments
• Original Assignee: Nauveau Technology Investments
• Inventors: McConchie, David M., Davies-McConchie, Fiona Gaye, Clark, Malcolm William
• Granted Patent: US 7,077,963 B2
• Time in Patent Office: Days
• US Class Current: 210/724
• CPC Class Codes: C02F 1/281 using inorganic sorbents
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/5236 using inorganic agents
• CPC Class Codes: C02F 1/5245 using basic salts, e.g. of aluminium and iron
• CPC Class Codes: C02F 1/5254 using magnesium compounds and phosphoric acid for removing ammonia
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2101/14 Fluorine or fluorine-containing compounds
• CPC Class Codes: C02F 2101/20 Heavy metals or heavy metal compounds
• CPC Class Codes: C02F 2103/10 from quarries or from mining activities
• CPC Class Codes: C02F 2209/06 pH
• CPC Class Codes: Y10S 210/904 -CN containing
• CPC Class Codes: Y10S 210/912 Heavy metal

Abstract

The invention provides compositions comprising bauxite refinery residues that have been reacted with sufficient calcium and magnesium ions that they have a reaction pH of less than 10.5, and one or more water treating additives. The invention also provides processes for treatment of water containing dissolved inorganic substances involving stepwise treatment of the water in which the reacted bauxite refinery residues are added after the addition of a pH-raising additive. The invention also provides processes for treatment of water containing dissolved inorganic substances in which the reacted bauxite refinery residues are added stepwise, with one or more water treating additives also being added in at least one of the steps. The invention also provides a process for the neutralisation of bauxite refinery residue by reacting it with a base amount and a treating amount of calcium ions and a base amount and a treating amount of magnesium ions for a time sufficient to produce an at least partially-neutralised residue exhibiting a reaction pH of less than 10.5.

Claims

5. A process for treating water containing dissolved inorganic substances, comprising the steps of

(i) adding a first amount of neutralised bauxite refinery residue to said water in an amount sufficient to decrease the concentration of at least one inorganic substance in said water;

and

(ii) adding a second amount of neutralised bauxite refinery residue to said water in an amount sufficient to decrease the concentration of at least one of said inorganic substances to below a predetermined level;

wherein in at least one of step (i) and step (ii), said neutralised bauxite refinery residue is added to said water together with one or more water treating additives; and

wherein said neutralised bauxite refinery residue is red mud that has been treated with seawater, saline ground water or other water containing sufficient calcium and magnesium ions to react with substantially all of the hydroxide, carbonate, fluoride and oxalate ions present in the red mud, and for a time sufficient for the red mud to exhibit a reaction pH of less than 10.5, in a standard soil test when 1 part by weight of the neutralised red mud is mixed with 5 parts by weight of distilled or deionised water.

6. A process according to claim 5 further comprising at least one subsequent addition of neutralized bauxite refinery residue, with or without added water treating additives, in an amount sufficient to decrease the concentration of at least one other inorganic substance to below a predetermined level.

7. A process according to claim 5 further including the step of separating or allowing to settle at least part of any insoluble material suspended in the water after step (i) and before step (ii).

8. A process according to claim 5, comprising the steps of

(i) adding a first amount of neutralised red mud to said water in an amount sufficient to decrease the concentration of at least one of said inorganic substances in said water;

(ii) adding a second amount of neutralised red mud to said water in an amount sufficient to decrease the concentration of at least one of said inorganic substances in said water; and

(iii) adding a third amount of neutralised red mud to said water in an amount sufficient to decrease the concentration of at least one of said inorganic substances to below a predetermined level;

wherein in at least one of steps (i), (ii) and (iii), said neutralised red mud is added to said water together with one or more water treating additives; and

wherein said neutralised bauxite refinery residue is red mud that has been treated with seawater, saline ground water or other water containing sufficient calcium and magnesium ions to react with substantially all of the hydroxide, carbonate, fluoride and oxalate ions present in the red mud, and for a time sufficient for the red mud to exhibit a reaction pH of less than 10.5, in a standard soil test when 1 part by weight of the neutralised red mud is mixed with 5 parts by weight of distilled or deionised water.

9. A process according to claim 8, further including the step of

(i)(a) separating or allowing to settle at least part of any insoluble material suspended in the water after step (i).

10. A process according to claim 8, further including the step of

(ii)(a) separating or allowing to settle at least part of any insoluble material suspended in the water after step (ii).

11. A process according to claim 8, further including the steps of

(i)(a) separating or allowing to settle at least part of any insoluble material suspended in the water after step (i) and

(ii)(a) separating or allowing to settle at least part of any insoluble material suspended in the water after step (ii).

12. A process according to any one of claims 5-11, wherein said water treating additive is selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal oxides, calcium hypochlorite, sodium hypochlorite, sodium alum, ferrous sulfate, aluminium sulfate, soluble phosphates, phosphoric acid, hydrotalcite, zeolites, olivines, pyroxenes, barium chloride, silicic acid and salts thereof, meta silicic acid and salts thereof, and magadiite.

13. A process according to claim 12, wherein said water treating additive is selected from the group consisting of sodium hydroxide, sodium carbonate, calcium hydroxide, calcium carbonate, magnesium oxide, calcium hypochlorite, sodium hypochlorite, sodium alum ferrous sulfate, aluminium sulfate, ammonium phosphate, phosphoric acid, hydrotalcite, zeolites, olivines, pyroxenes, barium chloride, silicic acid and salts thereof, meta silicic acid and salts thereof, and magadiite.

14. A composition comprising a mixture of neutralised bauxite refinery residue and a water treating additive;

wherein said neutralised bauxite refinery residue is red mud that has been treated with seawater, saline ground water or other water containing sufficient calcium and magnesium ions to react with substantially all of the hydroxide, carbonate, fluoride and oxalate ions present in the red mud, and for a time sufficient for the red mud to exhibit a reaction pH of less than 10.5, in a standard soil test when 1 part by weight of the neutralised red mud is mixed with 5 parts by weight of distilled or deionised water.

1. A process for treating acidic water containing dissolved inorganic substances, comprising the steps of

(i) adding a pH-raising additive in an amount sufficient to increase the pH of the water to a predetermined value;

and

(ii) adding neutralised bauxite refinery residue to the water in an amount sufficient to decrease the concentration of at least one of said inorganic substances in said water to below a predetermined level;

wherein said neutralised bauxite refinery residue is red mud that has been treated with seawater, saline ground water or other water containing sufficient calcium and magnesium ions to react with substantially all of the hydroxide, carbonate, fluoride and oxalate ions present in the red mud, and for a time sufficient for the red mud to exhibit a reaction pH of less than 10.5, in a standard soil test when 1 part by weight of the neutralised red mud is mixed with 5 parts by weight of distilled or deionised water.

2. A process according to claim 1, wherein after step (i) said water contains water-insoluble substance suspended therein, further including the step of separating or allowing to settle at least part of the water-insoluble substance before step (ii).

3. A process according to claim 1, wherein said pH raising additive is selected from the group consisting of calcium hydroxide, sodium carbonate, sodium hydroxide, potassium hydroxide, sodium bicarbonate, calcium carbonate and magnesium oxide.

4. A process according to claim 1, wherein said neutralised bauxite refinery residue is added together with one or more water treating additives.

15. A composition according to claim 14 which is a mixture of neutralised bauxite refinery residue and one or more substances selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal oxides, calcium hypochlorite, sodium alum, ferrous sulfate, aluminium sulfate, soluble phosphates, phosphoric acid, hydrotalcite, zeolites, olivines, pyroxenes, barium chloride, silicic acid and salts thereof, meta silicic acid and salts thereof, and magadiite.

23. A process according to claim 1 wherein said neutralised bauxite refinery residue is a neutralised red mud according to claim 22.

16. A process for neutralising red mud, comprising mixing red mud with an aqueous treating solution containing a base amount and a treating amount of calcium ions and a base amount and a treating amount of magnesium ions, for a time sufficient to produce an at least partially neutralised red mud and a spent aqueous solution, wherein:

said at least partially neutralised red mud has a reaction pH, when one part by weight is mixed with 5 parts by weight of deionised or distilled water, of less than 10.5;

said base amounts of calcium and magnesium ions are 8 millimoles and 12 millimoles, respectively, per litre of the total volume of said treating solution and said red mud;

said treating amount of calcium ions is at least 25 millimoles per mole of total alkalinity of the red mud expressed as calcium carbonate equivalent alkalinity; and

said treating amount of magnesium ions is at least 400 millimoles per mole of total alkalinity of the red mud expressed as calcium carbonate equivalent alkalinity, provided that said aqueous treating solution is other than seawater.

17. A process according to claim 16 wherein said treating amount of calcium ions is from 25 to 50 millimoles per mole of total alkalinity of the red mud expressed as calcium carbonate equivalent alkalinity.

18. A process according to claim 16 or claim 17 wherein said treating amount of magnesium ions is from 400 to 600 millimoles per mole of total alkalinity of the red mud expressed as calcium carbonate equivalent alkalinity.

19. A process according to claim 16 wherein said treating amount of magnesium ions and said treating amount of calcium ions are in a molar ratio in the range of 12 to 20.

20. A process according claim 16 wherein said reaction pH is in the range of from 8.4 to 8.8.

21. A process according to claim 16 wherein said aqueous treating solution is a bittern brine.

22. A neutralised red mud when prepared by the process of any one of claims 16 to 21.

24. A process according to claim 5 wherein said neutralised bauxite refinery residue in at least one of step (i) and step (ii) is a neutralised red mud according to claim 22.

23-1. A composition according to claim 14 wherein said neutralised bauxite refinery residue is a neutralised red mud according to claim 22.