METHOD FOR SYNERGISTIC STABILIZATION/SOLIDIFICATION OF RED MUD AND PHOSPHOGYPSUM

Abstract

The present invention discloses a method for synergistic stabilization/solidification of red mud and phosphogypsum. The method includes: grinding and mixing red mud and phosphogypsum, adding deionized water, uniformly stirring the mixture to prepare slurry, adjusting a pH value of the slurry to 7.5-8.5, adding a conditioner and conducting stirring, adding a stabilizer and an anti-permeability agent, uniformly stirring the mixture to obtain a gel product, and conducting solidification for 12-24 h to solidify the red mud and phosphogypsum, to obtain a red mud-phosphogypsum solidified material. In the present invention, the neutralization reaction between acidic ions in phosphogypsum and basic ions in red mud is adopted to reduce a pH value of the red mud and a transfer capability of pollutants in waste residues; synergistic solidification processing is conducted on two types of solid wastes: red mud produced in the aluminum smelting industry and phosphogypsum produced in the phosphorus chemical industry.

Claims

1. A method for synergistic stabilization/solidification of red mud and phosphogypsum, comprising the following specific steps: grinding and mixing red mud and phosphogypsum, adding deionized water, uniformly stirring the mixture to prepare slurry, adjusting a pH value of the slurry to 7.5-8.5, adding a conditioner and conducting stirring, adding a stabilizer and an anti-permeability agent, uniformly stirring the mixture, and conducting solidification for 12-24 h, to obtain a red mud-phosphogypsum solidified material.

2. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein particle sizes of both the red mud and phosphogypsum are less than or equal to 10 mm.

3. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

4. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein the red mud and phosphogypsum are mixed according to a mass ratio of 1:3-1:7.

5. The method for synergistic stabilization/solidification. of red mud and phosphogypsum according to claim 1, wherein the conditioner is prepared by the following steps: drying a natural aluminosilicate mineral or an industrial aluminum-silicon material, conducting calcination at 500-900 C. for 2 h cooling, and grinding an obtained product into fine powder with a specific surface area of 350-450 m.sup.2/Kg; and mixing the fine powder with a NaOH solution with a concentration of 3-5 mol/L according to a mass ratio of (2.5-3):1, and allowing reaction at 20-120 C. for 1-2 h.

6. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein an addition amount of the conditioner is 9%-11% of a total mass of the red mud and phosphogypsum.

7. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein the stabilizer is one of sodium polyacrylate, calcium lignin sulfonate, and polyacrylamide or a mixture of several of sodium polyacrylate, calcium lignin sulfonate, and polyacrylamide at any ratio.

8. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein an addition amount of the stabilizer is 2%-4% of a total mass of the red mud and phosphogypsum.

9. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein the anti-permeability agent is triethanolamine or diatomite.

10. The method for synergistic stabilization/solidification of red mud and phosphogypsum according to claim 1, wherein an addition amount of the anti-permeability agent is 0.5%-1.5% of a total mass of the red mud and phosphogypsum.

Description

DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to specific embodiments.

Embodiment 1

[0024] A method for synergistic stabilization/solidification of red mud and phosphogypsum is provided, including the following specific steps:

[0025] (1) Grind red mud and phosphogypsum, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified. material and reduce the sizes of solid materials of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

[0026] (2) Mix the red mud and phosphogypsum in step (1) at a mass ratio of 1:4, add deionized water, uniformly stir the mixture to prepare slurry, adjust a pH value of the shiny mixture to 8 with dilute sulfuric acid; and add a conditioner accounting for 9% of a total mass of the red mud and phosphogypsum, where the conditioner is a gel material, which is a type of aluminosilicate bonding material prepared by the following steps: drying a natural aluminosilicate mineral fly ash as a raw material for 1 h in an electrothermal constant temperature blast drying oven, conducting calcination in a muffle furnace at 500 C. for 2 h, cooling, and grinding an obtained product into fine powder with a specific surface area of 350 m.sup.2/Kg; and mixing the fine powder with a NaOH solution with a concentration of 5 mol/L according to a mass ratio of 2.5:1, and conducting the dehydration-condensation reaction of the fine powder for 2 h under the excitation of the NaOH solution.

[0027] (3) Add, to the slurry in step (2), polyacrylamide accounting for 3% of the total mass of the red mud and phosphogypsum as a stabilizer and triethanolamine accounting for 1% of the total mass of the red mud and phosphogypsum as an anti-permeability agent, uniformly mix the mixture, and conduct solidification at room temperature for 20 h, to obtain a red mud-phosphogypsum solidified material.

[0028] It can be learned through measurement that a concentration of water-soluble fluoride in the solidified material is 8.75 mg/L, and a solidification rate can reach 93%. The water-soluble fluoride is measured in accordance with the environmental standard of the People's Republic of China: solid waste-extraction procedure for leaching toxicity-sulfuric acid & nitric acid method (HJ/T299-2007). A concentration of water-soluble fluorine in unsolidified. phosphogypsum is 125 mg/L, and exceeds 100 mg/m.sup.2 specified in the State Standard of the People's Republic of China: Identification standards for hazardous wastes-Identification for extraction toxicity (GB5085.3-2007), the same below.

Embodiment 2

[0029] A method for synergistic stabilization/solidification of red mud and phosphogypsum is provided, including the following specific steps:

[0030] (1) Grind red mud and phosphogypsum, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified material and reduce sizes of solid materials of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

[0031] (2) Mix the red mud and phosphogypsum in step (1) at a mass ratio of 1:7, add deionized water, uniformly stir the mixture to prepare slurry, adjust a pH value of the slurry mixture to 7 with dilute sulfuric acid; and add a conditioner accounting for 10% of a total mass of the red mud and phosphogypsum, where the conditioner is a gel material, which is a type of aluminosilicate bonding material prepared by the following steps: drying a natural aluminosilicate mineral kaolin as a raw material for 1I h in an electrothermal constant temperature blast drying oven, conducting calcination in a muffle furnace at 900 C. for 2 h, cooling, and grinding an obtained product into fine powder with a specific surface area of 400 m.sup.2 Kg; and mixing the fine powder with a NaOH solution with a concentration of 3 mol/L according to a mass ratio of 2.5:1, and conducting dehydration-condensation reaction of the fine powder for 1 h under the excitation of the NaOH solution.

[0032] (3) Add, to the slurry in step (2), calcium lignin sulfonate accounting for 4% of the total mass of the red mud and phosphogypsum as a stabilizer and diatomite accounting for 0.5% of the total mass of the red mud and phosphogypsum as an anti-permeability agent, uniformly mix the mixture, and conduct solidification at morn temperature for 12 h, to obtain a red mud-phosphogypsum solidified material. It can be learned through measurement that, a concentration of water-soluble fluoride in the solidified material is 12.5 mg/L, and a solidification rate can reach 90%.

Embodiment 3

[0033] A method for synergistic stabilization/solidification of red mud and phosphogypsum is provided, including the following specific steps:

[0034] (1) Grind red mud and phosphogypsum, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified material and reduce sizes of solid materials in a mixture of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

[0035] (2) Mix the red mud and phosphogypsum in step (1) at a mass ratio of 1:5, add &ionized water, uniformly stir the mixture to prepare slurry, adjust a pH value of the shiny mixture to 7.5 with dilute sulfuric acid; and add a conditioner accounting for 11% of a total mass of the red mud and phosphogypsum, where the conditioner is a gel material, which is a type of aluminosilicate bonding material prepared by the following steps: drying a natural aluminosilicate mineral: iron industry slag as a raw material for 1 h in an electrothermal constant temperature blast drying oven, conducting calcination in a muffle furnace at 800 C. for 2 h, cooling, and grinding an obtained product into fine powder with a specific surface area of 450 m.sup.2/Kg; and mixing the fine powder with a NaOH solution with a concentration of 4 mol/L according to a mass ratio of 2.8:1, and conducting dehydration-condensation reaction of the fine powder for 1.5 h under the excitation of the NaOH solution.

[0036] (3) Add, to the slurry in step (2), polyacrylamide accounting for 3% of the total mass of the red mud and phosphogypsum as a stabilizer and triethanolamine accounting for 1% of the total mass of the red mud and phosphogypsum as an anti-permeability agent, uniformly mix the mixture, and conduct solidification at room temperature for 20 h, to obtain a red mud-phosphogypsum solidified material. It can be learned through measurement that a concentration of water-soluble fluoride in the solidified. material is 2.5 mg/L, and a solidification rate can reach 98%.

[0037] Embodiment 4

[0038] A method for synergistic stabilization/solidification of red mud and phosphogypsum is provided, including the following specific steps:

[0039] (1) Grind red mud and phosphogypsum, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified material and reduce sizes of solid materials in a mixture of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

[0040] (2) Mix the red mud and phosphogypsum in step (1) at a mass ratio of 1:6, add deionized water, uniformly stir the mixture to prepare slurry, adjust a pH value of the slurry mixture to 7.5 with dilute sulfuric acid; and add a conditioner accounting for 10% of a total mass of the red mud and phosphogypsum, where the conditioner is a gel material, which is a type of aluminosilicate bonding material prepared by the following steps: drying a natural aluminosilicate mineral: kaolin as a raw material for 1 h in an electrothermal constant temperature blast drying oven, conducting calcination in a muffle furnace at 700 C. for 2 h, cooling, and grinding an obtained product into fine powder with a specific surface area of 350 m.sup.2/Kg; and mixing the fine powder with a NaOH solution with a concentration of 4 mol/L according to a mass ratio of 2.5:1, and conducting dehydration-condensation reaction of the fine powder for 2 h under the excitation of the NaOH solution.

[0041] (3) Add, to the slurry in step (2), sodium polyacrylate accounting for 3.5% of the total mass of the red mud and phosphogypsum as a stabilizer and triethanolamine accounting for 1.2% of the total mass of the red mud and phosphogypsum as an anti-permeability agent, uniformly mix the mixture, and conduct solidification at room temperature for 24 h, to obtain a red mud-phosphogypsum solidified material. It can be learned through measurement that a concentration of water-soluble fluoride in the solidified material is 6.25 mg/L, and a solidification rate can reach 95%.

[0042] Embodiment 5

[0043] A method for synergistic stabilization/solidification of red mud and phosphogypsum is provided, including the following specific steps:

[0044] (1) Grind red mud and phosphogypsum, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified material and reduce sizes of solid materials in a mixture of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid.

[0045] (2) Mix the red mud and phosphogypsum in step (1) at a mass ratio of 1:3, add deionized water, uniformly stir the mixture to prepare slurry, adjust a pH value of the shiny mixture to 8.5 with a dilute sodium hydroxide solution; and add a conditioner accounting for 9% of a total mass of the red mud and phosphogypsum, where the conditioner is a gel material, which is a type of aluminosilicate bonding material prepared by the following steps: drying an industrial aluminum-silicon material: aluminum-silicon thermal insulation fire clay as a raw material for 1 h in an electrothermal constant temperature blast drying oven, conducting calcination in a muffle furnace at 800 C. for 2 h, cooling, and grinding an obtained product into fine powder with a specific surface area of 400 m.sup.2/Kg; and mixing the fine powder with a NaOH solution with a concentration of 5 mol/L according to a mass ratio of 3:1, and conducting dehydration-condensation reaction of the fine powder for 1 h under the excitation of the NaOH solution.

[0046] (3) Add, to the slurry in step (2), a mixture, accounting for 3.5% of the total mass of the red mud and phosphogypsum as a stabilizer, of sodium polyacrylate and polyacrylamide at a mass ratio of 1:2 and triethanolamine accounting for 1.5% of the total mass of the red mud and phosphogypsum as an anti-permeability agent, uniformly mix the mixture, and conduct solidification at room temperature for 24 h, to obtain a red mud-phosphogypsum solidified material. It can be learned through measurement that a concentration of water-soluble fluoride in the solidified material is 11.25 mg/L, and a solidification rate can reach 91%.

Comparative Example

[0047] Red mud and phosphogypsum are grinded, where the grinding operation is conducted to increase a surface area of solid particles contained in a red mud-phosphogypsum solidified material and reduce sizes of solid materials in a mixture of the red mud and phosphogypsum, to make particle sizes of solid particles of the red mud and phosphogypsum less than or equal to 10 mm; the red mud is Bayer red mud, and the phosphogypsum is an industrial residue produced during the preparation of phosphoric acid. The red mud and phosphogypsum were mixed at a mass ratio of 1:7, and uniformly stirred; water was added to prepare slurry; and the slurry is molded and solidified for 20 h, to obtain a red mud-phosphogypsum solidified material It can be learned through measurement that a concentration of water-soluble fluoride in the solidified material is 80 mg/L, and a solidification rate is 36%.

[0048] It can be learned through comparing Embodiments 1 to 5 with Comparative Example in this specification that, the solidified material prepared after directly mixing the red mud and phosphogypsum has high-content water-soluble fluorine and a low solidification rate. Moreover, the long-time stockpiling of the solidified material will easily result in environmental pollution. Therefore, Embodiments 1-5 are superior to Comparative Example.