阅读说明：本技术 一种赤泥高效资源化利用方法 (Efficient resource utilization method for red mud ) 是由 潘爱芳 马昱昭 孙悦 马润勇 于 2021-09-27 设计创作，主要内容包括：本发明涉及一种赤泥高效资源化利用方法,该方法包括研磨、水洗、酸浸溶出、保温陈化、循环酸浸溶出、聚合等工艺步骤,可以将赤泥中绝大部分的铝、硅、铁、钙等组分进行分离提取,并分别转化为硅胶、净水剂、石膏等产品,实现了赤泥的全量资源化利用。本发明提供的方法,可适用于各种类型的赤泥,同时具有工艺流程简单、工艺参数可控性好、经济效益好、无二次废弃物产生、容易实现工业化等优点,为赤泥的大规模减量化利用开辟了一个新途径。(The invention relates to a high-efficiency resource utilization method of red mud, which comprises the process steps of grinding, washing, acid leaching and dissolving out, heat preservation and aging, circulating acid leaching and dissolving out, polymerization and the like, and can separate and extract most of components such as aluminum, silicon, iron, calcium and the like in the red mud and respectively convert the components into products such as silica gel, a water purifying agent, gypsum and the like, thereby realizing the full resource utilization of the red mud. The method provided by the invention is applicable to various types of red mud, has the advantages of simple process flow, good controllability of process parameters, good economic benefit, no secondary waste, easy realization of industrialization and the like, and opens up a new way for large-scale reduction and utilization of the red mud.)

1. A method for efficiently recycling red mud comprises the following steps:

step 1: grinding the red mud, and sieving to obtain red mud powder;

step 2: repeatedly washing the red mud powder with water to remove the attached alkali in the red mud, and filtering to obtain the solid of the washed red mud;

and step 3: stirring and dissolving the cleaned red mud by using a sulfuric acid solution;

and 4, step 4: introducing air into the solution in the step 3 for an aeration reaction, and after aeration; filtering and separating to obtain primary filtrate and filter residue, and drying the filter residue to obtain gypsum;

and 5: preserving heat of the primary filtrate, aging for a period of time, and then filtering and separating to obtain secondary filtrate and silica gel; the secondary filtrate is mainly acidic solution containing aluminum, iron and sodium ions;

step 6: adding concentrated sulfuric acid into the secondary filtrate, adjusting the concentration of the sulfuric acid to be 1-6 mol/L, and then circularly performing the step 4 and the step 5 to perform primary circular acid leaching and dissolving out to obtain circular acid leaching and dissolving out;

and 7: adding hydrogen peroxide into the cyclic acid leaching solution obtained in the step 6, continuously stirring, slowly adding lime milk until the pH value of the cyclic acid leaching solution is adjusted to 1.5-4.5, stirring for a certain time at a certain temperature, and filtering and separating to obtain the polymeric aluminum ferric sulfate water purifying agent and gypsum.

2. The efficient resource utilization method for red mud according to claim 1, wherein in step 1, the ground red mud is sieved into 200-300-mesh red mud powder, and the red mud is a mixture of any one, two or three of Bayer process red mud, sintering process red mud or combination process red mud.

3. The method for efficiently recycling red mud according to claim 1, wherein in step 2, the pH value after washing with water is neutral, and the washing is stopped.

4. The efficient resource utilization method of red mud of claim 1, which is characterized in that,

in the step 3, the concentration of a sulfuric acid solution is 1-6 mol/L, the sulfuric acid solution and the red mud are added according to the liquid-solid ratio of 4-15: 1, and the stirring and dissolving time is 1-10 min.

5. The efficient resource utilization method for red mud of claim 1, wherein in the step 4, the flow of the introduced air is 30-60 mL/min, and the aeration reaction time is 60-100 min.

6. The efficient resource utilization method for red mud of claim 1, wherein in the step 4, the temperature for drying the filter residue is 60-80 ℃ for 1-2 h.

7. The efficient resource utilization method for red mud of claim 1, wherein in the step 5, the aging is carried out in a water bath, the temperature of the water bath is between normal temperature and 100 ℃, and the aging time is 0.5 to 10 hours.

8. The efficient resource utilization method of red mud of claim 1, wherein in step 6, the concentration of concentrated sulfuric acid is 8-15 mol/L, and the related process parameters are the same as the values of the corresponding parameters in step 4 and step 5.

9. The efficient resource utilization method of red mud as claimed in claim 1, wherein in step 7, the addition amount of hydrogen peroxide is such that the molar ratio of ferrous ions in the secondary mud is 1: 2, stirring for 5-10 min, and adding lime milk.

10. The efficient resource utilization method of red mud as claimed in claim 1, wherein in step 7, Ca (OH) in the lime milk₂The mass fraction of (A) is 10-40%; stirring for 0.5-5 h at the temperature of 45-95 ℃.

Technical Field

The invention relates to a method for efficiently recycling red mud, belonging to the technical field of solid waste recycling.

Background

Red mud is a very fine particle strongly basic solid waste generated in the production process of alumina. According to the difference of alumina production process, red mud can be divided into three types of Bayer process red mud, sintering process red mud and combination process red mud. According to statistics, each 1 ton of alumina is produced, 0.8-1.5 tons of red mud is discharged by a Bayer process, and 1.5-2.5 tons of red mud is discharged by a sintering process or a combination process. As the first alumina producing country in China, the red mud discharged every year is as high as 7000 million tons, and most of the red mud is disposed in a damming and stockpiling mode, so that a large amount of land resources are occupied, environmental pollution is easily caused, and potential safety hazards exist.

In order to solve the problem of red mud discharge and accumulation, China successively goes out a series of relevant policies such as guidance for comprehensive utilization of red mud, 2016 (2016) year 2020 industrial green development plan, and notices about promotion of accumulation and development of the bulk solid waste comprehensive utilization industry, and is used for promoting comprehensive utilization of red mud.

In recent years, domestic scholars have conducted a lot of research and achieved numerous results aiming at the comprehensive utilization of red mud. Generally, the comprehensive utilization method of red mud can be divided into four types: firstly, valuable metal elements such as aluminum, iron, titanium, gallium, scandium and the like are extracted; secondly, preparing building materials such as cement, bricks and the like; the method is mainly used for preparing environment restoration materials (and is applied to the agricultural field such as soil restoration, silicon-calcium compound fertilizer production and the like), but the existing method has the problems of high cost, complex process, poor adaptability to different types of red mud, small treatment capacity and the like, and most of the methods are in the laboratory research stage.

Disclosure of Invention

Technical problem to be solved

In order to solve the problems in the prior art, the invention provides a method for efficiently recycling red mud, which can extract most useful components such as aluminum, iron, silicon, calcium and the like in the red mud and convert the useful components into high-value-added products, thereby realizing reduction, recycling and harmlessness of the red mud.

(II) technical scheme

In order to achieve the purpose, the invention adopts the main technical scheme that:

a method for efficiently recycling red mud comprises the following steps:

step 1: grinding the red mud, and sieving to obtain red mud powder;

step 2: repeatedly washing the red mud powder with water to remove the attached alkali in the red mud, and filtering to obtain the solid of the washed red mud;

and step 3: stirring and dissolving the cleaned red mud by using a sulfuric acid solution;

and 4, step 4: introducing air into the solution in the step 3 for an aeration reaction, and after aeration; filtering and separating to obtain primary filtrate and filter residue, and drying the filter residue to obtain gypsum;

and 5: aging the primary filtrate for a period of time, and then filtering and separating to obtain secondary filtrate and silica gel; the secondary filtrate is mainly acidic solution containing aluminum, iron and sodium ions;

step 6: adding concentrated sulfuric acid into the secondary filtrate, adjusting the concentration of the sulfuric acid to be 1-6 mol/L, and then circularly performing the step 4 and the step 5 to perform primary circular acid leaching and dissolving out to obtain circular acid leaching and dissolving out;

and 7: adding hydrogen peroxide into the cyclic acid leaching solution obtained in the step 6, continuously stirring, slowly adding lime milk until the pH value of the cyclic acid leaching solution is adjusted to 1.5-4.5, stirring for a certain time at a certain temperature, and filtering and separating to obtain the polymeric aluminum ferric sulfate water purifying agent and gypsum.

Preferably, in the step 1, the red mud is ground and sieved into 200-300-mesh red mud powder, wherein the red mud is a mixture of any one, two or three of bayer process red mud, sintering process red mud and combination process red mud.

In the method for efficiently recycling red mud as described above, it is preferable that in step 2, the pH value after washing with water is neutral, and the washing is stopped.

Preferably, in the step 3, the concentration of the sulfuric acid solution is 1-6 mol/L, the sulfuric acid solution and the red mud are added according to the liquid-solid ratio of 4-15: 1, and the stirring and dissolving time is 1-10 min.

Preferably, in the step 4, the flow rate of the introduced air is 30-60 mL/min, and the aeration reaction time is 60-100 min.

According to the efficient resource utilization method of the red mud, preferably, in the step 4, the drying temperature of the filter residue is 60-80 ℃, and the time is 1-2 hours.

Preferably, in the step 5, the aging is carried out in a water bath, the temperature of the water bath is normal temperature to 100 ℃, and the aging time is 0.5 to 10 hours.

According to the efficient resource utilization method for the red mud, preferably, in the step 6, the concentration of concentrated sulfuric acid is 8-15 mol/L, and related relevant process parameters are the same as corresponding parameters in the step 4 and the step 5 respectively.

Preferably, in step 7, the addition amount of hydrogen peroxide is such that the molar ratio of the ferrous ions in the secondary sludge is 1: 2, stirring for 5-10 min, and adding lime milk.

Preferably, in step 7, the red mud is recycled, and Ca (OH) in the lime milk₂The mass fraction of (A) is 10-40%; stirring for 0.5-5 h at the temperature of 45-95 ℃.

(III) advantageous effects

The invention has the beneficial effects that:

the efficient resource utilization method of the red mud provided by the invention can be used for carrying out full-scale treatment on the red mud, converting useful components such as aluminum, iron, silicon, calcium and the like in the red mud into products such as a water purifying agent, silica gel, gypsum and the like, and realizing efficient resource utilization of the red mud. Wherein, the silica gel can be directly used as a water-retaining agent, and can be further processed into high value-added silicon products such as water glass, white carbon black and the like, and the application range is wide.

The efficient resource utilization method of the red mud provided by the invention is applicable to various types of red mud, has the advantages of simple process flow, good controllability of process parameters, good economic benefit, no discharge of harmful substances in reaction, no generation of secondary wastes, easy realization of industrialization and the like, and opens up a new way for large-scale reduction utilization of the red mud.

Detailed Description

For a better understanding of the present invention, reference will now be made in detail to the present invention by way of specific embodiments thereof.

Example 1

The red mud adopted in the embodiment is sintering red mud of Shanxi river jin alumina plant, and the main chemical components of the red mud are measured by a conventional chemical measurement method and comprise: SiO 2₂：30.53％，Al₂O₃：22.43％，Fe₂O₃：7.78％，CaO：27.25％，FeO：5.4％。

A method for efficiently recycling red mud comprises the following steps:

step 1: grinding the red mud, sieving with a 200-mesh sieve to obtain red mud powder,

step 2: repeatedly cleaning the red mud powder with water to remove the attached alkali in the red mud, stopping cleaning after the pH value of the washing water is neutral, filtering, and removing the filtrate to obtain the cleaned red mud;

and step 3: according to the liquid-solid ratio of 4: 1, adding a sulfuric acid solution with the concentration of 6mol/L into the cleaned red mud, and stirring and dissolving the solution for 1 min;

and 4, step 4: then introducing air for an aeration reaction, wherein the flow rate of the introduced air is 40mL/min, and the aeration time is 100min later; filtering and separating to obtain primary filtrate and filter residue, and drying the filter residue at 80 deg.C for 90min to obtain gypsum; wherein the primary filtrate is mainly an acidic solution containing silicon, aluminum, iron and sodium;

the sulfuric acid solution and the main components in the red mud react as follows:

Al₂O₃+3H₂SO₄+aq＝Al₂(SO₄)₃+3H₂O+aq

Fe₂O₃+3H₂SO₄+aq＝Fe₂(SO₄)₃+3H₂O+aq

CaO+H₂SO₄+aq＝CaSO₄↓+H₂O+aq

SiO₂+2H₂O+aq＝H₄SiO₄+aq

FeO+H₂SO₄+aq＝FeSO₄+H₂O+aq

when air is introduced, an oxidation reaction occurs: FeSO₄+O₂→Fe₂(SO₄)₃；

According to the soil cation exchange sequence: fe³⁺>Al³⁺>Ca²⁺>Na⁺

And (3) replacement reaction: fe₂(SO₄)³⁺[Na⁺，Al³⁺，Ca²⁺]·RM→Na₂SO₄+Al₂(SO₄)₃+[Fe³⁺]·RM↓+CaSO₄↓；

And 5: aging the primary filtrate at normal temperature for 8h, and then filtering and separating to obtain secondary filtrate and silica gel; the secondary filtrate is mainly acidic solution containing aluminum, iron and sodium ions;

ortho silicic acid (H) upon aging of the primary filtrate₄SiO₄) Gradually polymerize to form dimer, trimer and cyclic polymer until they are coagulated into silica gel. The silica gel takes silicon dioxide as a framework to form a three-dimensional network structure, wraps a large amount of water and has excellent water absorption and water retention performances.

Step 6: adding 12mol/L concentrated sulfuric acid into the secondary filtrate, adjusting the concentration of the sulfuric acid to 6mol/L, and circularly performing the step 4 and the step 5 to perform primary circular acid leaching and dissolving to obtain a circular acid leaching solution;

and 7: adding hydrogen peroxide into the circulating acid leaching solution obtained in the step 6, wherein the adding amount of the hydrogen peroxide isThe molar ratio of the ferrous ions in the secondary mud is 1: 2, stirring continuously, and slowly adding Ca (OH)₂Adjusting the pH value of the circulating acid leaching solution to 1.5 by lime milk with the mass fraction of 10%, stirring for 60min at the temperature of 95 ℃, and filtering and separating to obtain the polymeric aluminum ferric sulfate water purifying agent and gypsum.

The purpose of the hydrogen peroxide is to increase n (Fe)³⁺) The equation for the reactive ion involved is:

H₂O₂+2Fe²⁺+2H⁺＝2H₂O+2Fe³⁺

when lime milk is added into the circulating acid leaching solution to adjust the pH value, aluminum sulfate and ferric sulfate in the solution can generate hydrolysis-polymerization reaction to form polymeric aluminum ferric sulfate.

Reaction equation of hydrolysis stage:

2Al₂(SO₄)₃+2nH₂O+aq＝2Al₂(OH)n(SO₄)_3-n/2+nH₂SO₄+aq

2Fe₂(SO₄)₃+2nH₂O+aq＝2Fe₂(OH)n(SO₄)_3-n/2+nH₂SO₄+aq

reaction equation of the polymerization stage:

m[Al₂(OH)_n(SO₄)_3-n/2]+aq＝[Al₂(OH)_n(SO₄)_3-n/2]_m+aq

m[Fe₂(OH)_n(SO₄)_3-n/2]+aq＝[Fe₂(OH)_n(SO₄)_3-n/2]_m+aq

and 8: adding hydrogen peroxide into the third filtrate to obtain the polyaluminum ferric sulfate water purifying agent and plaster, adding water and filtering to obtain the polyaluminum ferric sulfate water purifying agent.

In this embodiment, the gypsum obtained in step 4 comprises the following main components: CaO: 33.5%, SO₃: 49.51%, loss on ignition: 6.5 percent; the dried silica gel obtained in the step 5 comprises the following main components: SiO 2₂: 93.21%, loss on ignition: 5.0 percent; al of the Water purifying agent obtained in step 7₂O₃And Fe₂O₃The content is 15.2 percent, the basicity is 35 percent, the density at normal temperature is 1300g/mL, and the pH value is 1.8; the gypsum obtained in the step 7 comprises the following main components: CaO: 37.24%, SO₃: 53.42%, loss on ignition: 7.8 percent; the products can meet the relevant industrial standards.

Example 2

The red mud adopted in the embodiment is bayer process red mud of shanxi river jin alumina plant, and the main chemical components of the red mud are measured by a conventional chemical measurement method and comprise: SiO 2₂：19.64％，Al₂O₃：25.66％，Fe₂O₃：4.58％，CaO：12.1％，FeO：5.4％，Na₂O：8.54％。

A method for efficiently recycling red mud comprises the following steps:

step 1: grinding the red mud, sieving with a 250-mesh sieve to obtain red mud powder,

step 2: repeatedly washing the red mud powder with water to remove the attached alkali in the red mud; filtering, and discarding filtrate to obtain cleaned red mud;

and step 3: stirring and dissolving the cleaned red mud for 10min by using a sulfuric acid solution with the concentration of 1mol/L according to the liquid-solid ratio of 15;

and 4, step 4: introducing air for an aeration reaction, wherein the flow rate of the introduced air is 50mL/min, and the aeration time is 90min later; filtering and separating to obtain primary filtrate and filter residue, and drying the filter residue at 65 ℃ for 1.5h to obtain gypsum; wherein the primary filtrate is mainly an acidic solution containing silicon, aluminum, iron and sodium;

and 5: aging the primary filtrate at normal temperature for 10h, and then filtering and separating to obtain secondary filtrate and silica gel; the secondary filtrate is mainly acidic solution containing aluminum, iron and sodium ions;

step 6: adding sulfuric acid into the secondary filtrate, adjusting the concentration of the sulfuric acid to 1mol/L, and circularly performing the step 4 and the step 5 to perform primary circular acid leaching and dissolving to obtain circular acid leaching and dissolving;

and 7: continuously stirring the circulating acid leaching solution obtained in the step 6, adding hydrogen peroxide and hydrogen peroxideThe molar ratio of ferrous ions in the secondary sludge is 1: 2, after stirring for 8min, slowly adding Ca (OH)₂And (3) adjusting the pH value of the circulating acid leaching solution to 3 by using lime milk with the mass fraction of 40%, and filtering and separating to obtain the polymeric aluminum ferric sulfate water purifying agent and gypsum.

In this embodiment, the gypsum obtained in step 4 comprises the following main components: CaO: 30.38%, SO₃: 45.69%, loss on ignition: 9.8 percent; the dried silica gel obtained in the step 5 comprises the following main components: SiO 2₂: 92.0%, loss on ignition: 7.7 percent; al of the Water purifying agent obtained in step 7₂O₃And Fe₂O₃The content is 6.14 percent, the basicity is 47 percent, the density at normal temperature is 1340g/mL, and the pH value is 4.5; the gypsum obtained in the step 7 comprises the following main components: CaO: 35.78%, SO₃: 52.73%, loss on ignition: 10.6 percent; the products can meet the relevant industrial standards.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art can change or modify the technical content disclosed above into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.