Method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron

Abstract

The present invention discloses a method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron. The method includes: dissolving red mud in water, introducing excessive SO.sub.2, introducing O.sub.2 for aeration, and refluxing part of alkaline leachate after filtering; when pH of a red mud mixture decreases to below 3, washing and filtering the red mud mixture, adding NaOH to acidic leachate to adjust its pH to a strongly alkaline level, aging and filtering the leachate, treating filter residue to recover Fe.sub.2O.sub.3, and refluxing part of alkaline leachate after filtering to the red mud mixture; and adjusting pH of the remaining alkaline leachate after filtering to a weakly acidic level, and conducting filtering to recover aluminum.

Claims

1. A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron, comprising the following steps: S1: grinding red mud and dissolving the red mud in slurry liquid, wherein the slurry liquid is water and/or alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry; introducing SO.sub.2 and O.sub.2 for aeration oxidation to obtain a red mud mixture; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and S2: adjusting pH of the acidic leachate obtained by filtering to a strongly alkaline level to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕-½ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to a weakly acidic level, and conducting filtering to separate and recover Al(OH).sub.3.

2. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (1), the red mud is ground into a particle size of 100-200 meshes.

3. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein a liquid-solid ratio of the red mud slurry is 7:1.

4. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (1), SO.sub.2 is introduced by allowing the SO.sub.2 gas to be in reverse contact with the red mud slurry for absorption.

5. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (1), the introduction amount of the SO.sub.2 gas is 1-12 L per m.sup.3 of the red mud slurry.

6. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (1), an introduction volume ratio of the O.sub.2 gas to the SO.sub.2 gas is 1:(1-5).

7. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein washing needs to be conducted 3-8 times after filtering.

8. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (1), pH of the red mud mixture needs to be below 3.

9. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (2), pH of the alkaline leachate needs to be above 13.

10. The method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron according to claim 1, wherein in step (2), the weak acidity means that pH needs to be above 4.7.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The FIGURE is a flowchart of a process according to the present invention.

DETAILED DESCRIPTION

(2) The present invention is further described below with reference to embodiments and accompanying drawings without limiting the present invention in any way. Any transformation or replacement made based on the teachings of the present invention shall fall within the protection scope of the present invention.

Embodiment 1

(3) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(4) S1: grinding red mud to 100 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 0.4 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture, where the introduction amount of the SO.sub.2 gas is 12 L per m.sup.3 of red mud slurry, an introduction volume ratio of O.sub.2 gas to the SO.sub.2 gas is 1:1, and pH of the red mud slurry reaches below 3; and filtering the red mud mixture, and conducting washing three times to obtain dealkalized red mud and acidic leachate; and

(5) S2: adjusting pH of the acidic leachate obtained by filtering to 13 to obtain alkaline leachate; filtering the alkaline leachate, and conducting washing three times to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 2

(6) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(7) S1: grinding red mud to 200 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 1 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture, where the introduction amount of the SO.sub.2 gas is 1 L per m.sup.3 of red mud slurry, an introduction volume ratio of O.sub.2 gas to the SO.sub.2 gas is 1:5, and pH of the red mud slurry reaches below 3; and filtering the red mud mixture, and conducting washing eight times to obtain dealkalized red mud and acidic leachate; and

(8) S2: adjusting pH of the acidic leachate obtained by filtering to above 13 to obtain alkaline leachate; filtering the alkaline leachate, and conducting washing six times to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 3

(9) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(10) S1: grinding red mud to 120 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 1.5 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture, where the introduction amount of the SO.sub.2 gas is 4 L per m.sup.3 of red mud slurry, an introduction volume ratio of 02 gas to the SO.sub.2 gas is 1:2, and pH of the red mud slurry reaches below 3; and filtering the red mud mixture, and conducting washing four times to obtain dealkalized red mud and acidic leachate; and

(11) S2: adjusting pH of the acidic leachate obtained by filtering to 13.5 to obtain alkaline leachate; filtering the alkaline leachate, and conducting washing five times to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 4

(12) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(13) S1: grinding red mud to 150 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water; conducting uniform stirring to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 2 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture, where the introduction amount of the SO.sub.2 gas is 8 L per m.sup.3 of red mud slurry, an introduction volume ratio of O.sub.2 gas to the SO.sub.2 gas is 1:3, and pH of the red mud slurry reaches below 3; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and

(14) S2: adjusting pH of the acidic leachate obtained by filtering to 13.2 to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 5

(15) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(16) S1: grinding red mud to 180 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 3 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and

(17) S2: adjusting pH of the acidic leachate obtained by filtering to above 13 to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅕ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 6

(18) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(19) S1: grinding red mud to 200 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and/or alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 3 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and

(20) S2: adjusting pH of the acidic leachate obtained by filtering to above 13 to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ¼ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 7

(21) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(22) S1: grinding red mud to 100 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 3 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and

(23) S2: adjusting pH of the acidic leachate obtained by filtering to 13 to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ⅓ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 8

(24) A method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron is provided, including the following steps:

(25) S1: grinding red mud to 200 meshes, and dissolving the red mud in slurry liquid, where the slurry liquid is water and alkaline leachate obtained after filtering; uniformly stirring the mixture to obtain red mud slurry, where a liquid-solid ratio is 7:1; preparing SO.sub.2 flue gas of a certain concentration in a buffer bottle by an air compressor with exhaust gas produced by calcination of pyrite in a rotary calcining kiln; introducing sulfur-containing flue gas into the red mud slurry at a blast rate of 3 m.sup.3/h in a form of reverse contact for mixing; conducting aeration oxidation to obtain a red mud mixture; and filtering the red mud mixture to obtain dealkalized red mud and acidic leachate; and

(26) S2: adjusting pH of the acidic leachate obtained by filtering to 13 to obtain alkaline leachate; filtering the alkaline leachate to obtain alkaline leachate after filtering and filter residue; drying and sintering the filter residue, washing an obtained product with water, and conducting drying to recover Fe.sub.2O.sub.3; returning ½ of the alkaline leachate after filtering to step (1) as the slurry liquid; and adjusting pH of the remaining alkaline leachate after filtering to 4.7, and conducting filtering to separate and recover Al(OH).sub.3.

Embodiment 9

(27) A desulfurization rate, Fe and Al recovery rates, and components of dealkalized red mud were tested.

(28) The test was conducted according to the method in Embodiment 8, and the control test was constructed according to the methods in Embodiments 1 to 7. Desulfurization rates of flue gas, Fe and Al recovery rates, and components of dealkalized red mud were tested. The results were shown in Table 1 and Table 2.

(29) TABLE-US-00001 TABLE 1 A relationship between a blast rate and a desulfurization rate when a reflux rate is 1/5 Blast rate (m.sup.3/h) 0.4 1 1.5 2 3 Desulfurization rate 97.45% 97.05% 96.87% 96.55% 96.10%

(30) TABLE-US-00002 TABLE 2 A relationship between a reflux rate and a desulfurization rate when a blast rate is 3 m.sup.3/h Reflux rate 1/5 1/4 1/3 1/2 Desulfurization rate 96.10% 96.54% 97.03% 97.55%

(31) Through test, in Embodiments 1 to 8, an average recovery rate of Fe.sub.2O.sub.3 reached 89.79%, and an average recovery rate of Al(OH).sub.3 reached 79.30%. 100 g of dealkalized red mud was subject to secondary grinding, washed with deionized water repeatedly until the washing solution is neutral, and then dried thoroughly. A sample of the dried dealkalized red mud was acquired, and the content of Na.sub.2O and K.sub.2O of the sample was determined by a method for chemical analysis of bauxite in GBT3257.9-1999: a flame atomic absorption spectrophotometric method. The result showed that in the dealkalized red mud, the average content of Na.sub.2O was 0.87% (wt) and the average content of K.sub.2O was 0.39% (wt). In this way, Fe and Al in red mud are recovered and utilized, and the efficient desulfurization of flue gas and dealkalization of red mud are implemented. Therefore, the method is a new method and process that can implement comprehensive treatment and turn waste into treasure.