阅读说明：本技术 一种赤泥-磷石膏的复合胶凝材料及制备方法 (Red mud-phosphogypsum composite cementing material and preparation method thereof ) 是由 仇伟 唐安江 符远翔 马连刚 舒群威 于 2021-08-02 设计创作，主要内容包括：本发明属于胶凝材料及其制备技术领域,提供了一种赤泥-磷石膏的复合胶凝材料及制备方法,包括如下步骤：步骤1、将赤泥与碱激发剂混合进行陈化,得到活化赤泥；步骤2、将磷石膏与盐类激发剂混合进行陈化,得到可以提高活化赤泥混合物硬度的活化磷石膏；步骤3、将步骤1得到的活化赤泥混合物与步骤2中到的活化磷石膏混合物进行混合均匀,制备赤泥-磷石膏的复合胶凝材料；该复合胶凝材料通过盐类激发剂和碱激发剂促进磷石膏和赤泥的活化作用获得,拓展磷石膏与赤泥综合利用渠道,开发低成本而简单的活化工艺,且容易操作、成本低廉、生产过程清洁、环保。(The invention belongs to the technical field of cementing materials and preparation thereof, and provides a red mud-phosphogypsum composite cementing material and a preparation method thereof, wherein the preparation method comprises the following steps: step 1, mixing red mud and an alkali activator for aging to obtain activated red mud; step 2, mixing the phosphogypsum and a salt activator for aging to obtain activated phosphogypsum capable of improving the hardness of the activated red mud mixture; step 3, uniformly mixing the activated red mud mixture obtained in the step 1 with the activated phosphogypsum mixture obtained in the step 2 to prepare the red mud-phosphogypsum composite cementing material; the composite cementing material is obtained by promoting the activation of the phosphogypsum and the red mud through a salt activator and an alkali activator, expands the comprehensive utilization channel of the phosphogypsum and the red mud, develops a low-cost and simple activation process, and has the advantages of easy operation, low cost, clean production process and environmental protection.)

1. The preparation method of the red mud-phosphogypsum composite cementing material is characterized by comprising the following steps:

step 1, mixing red mud and an alkali activator, adding water, stirring to a slurry shape, and aging to obtain an activated red mud mixture;

step 2, mixing the phosphogypsum and a salt activator, adding water, stirring to a slurry shape, and aging to obtain an activated phosphogypsum mixture capable of improving the hardness of the activated red mud mixture;

and 3, mixing the activated red mud mixture obtained in the step 1 with the activated phosphogypsum mixture obtained in the step 2, and uniformly stirring to obtain the red mud-phosphogypsum composite cementing material.

2. The method for preparing the red mud-phosphogypsum composite cementing material according to the claim 1, which is characterized in that in the step 1, the alkali activator is one or more of sodium hydroxide, calcium oxide, calcium hydroxide and potassium hydroxide.

3. The preparation method of the red mud-phosphogypsum composite cementing material according to claim 2, which is characterized in that in the step 1, the dosage of the alkali-activator is 4-8% of the mass of the red mud.

4. The method for preparing the red mud-phosphogypsum composite cementing material according to the claim 3, wherein in the step 2, the salt excitant is one or more of aluminum sulfate, ferric sulfate, calcium chloride and calcium phosphate.

5. The preparation method of the red mud-phosphogypsum composite cementing material according to claim 4, which is characterized in that in the step 2, the salt activator accounts for 3-8% of the mass of the phosphogypsum.

6. The preparation method of the red mud-phosphogypsum composite cementing material according to claim 5, which is characterized in that in the step 1 and the step 2, the aging time is 12-48 h.

7. The preparation method of the red mud-phosphogypsum composite cementing material according to claim 6, which is characterized in that in the step 3, the mixing mass ratio is 1-3: 1-3.

8. The composite cementing material for preparing red mud-phosphogypsum by the method of claim 1.

Technical Field

The invention belongs to the technical field of cementing materials and preparation thereof, and particularly relates to a red mud-phosphogypsum composite cementing material and a preparation method thereof.

Background

The phosphogypsum is solid waste residue generated in the production of phosphoric acid, the main component of the phosphogypsum is calcium sulfate dihydrate and is acidic, the red mud is industrial waste residue generated by extracting aluminum oxide in the aluminum production industry, the composition of the industrial waste residue is similar to that of clay, and the industrial waste residue is alkaline. According to incomplete statistics, the utilization rate of phosphogypsum in most areas of China is less than 20 percent at present, and the accumulated accumulation amount exceeds 3 hundred million tons; the comprehensive utilization rate of the red mud is even less than 10 percent, and the accumulated accumulation amount is over 3.5 hundred million tons. With the development of phosphorus chemical industry and the annual increase of alumina yield in China and the gradual reduction of the grades of phosphorite and bauxite, the annual production of phosphogypsum and red mud is continuously increased. Not only does these industrial residues occupy a large amount of land, but the harmful components therein also cause serious pollution to surrounding soil, vegetation, water systems and air. As early as 2009, phosphogypsum has been listed as a dangerous solid waste by the national environmental protection agency,

because the phosphogypsum contains soluble phosphorus pentoxide and free acid and is acidic, the main component of the phosphogypsum is calcium sulfate dihydrate, and the phosphogypsum has good gelling property different from the hemihydrate gypsum, so that the treatment difficulty is increased. The red mud contains more alkali metal oxides, so that the alkalinity of the red mud is very strong, the main components are aluminum oxide, ferric oxide and silicon oxide, a large number of research reports are reported on the comprehensive treatment, development and utilization of the red mud in various industries at home and abroad, the red mud is difficult to be efficiently used in a large scale due to the characteristics of strong alkalinity, coating property among components and the like of the red mud, the treatment means of the phosphogypsum in many enterprises are still in a primary stage, the comprehensive utilization of the phosphogypsum is not smooth, and the comprehensive utilization of the phosphogypsum and the red mud is not promoted in a large scale, so that the comprehensive utilization of the phosphogypsum and the red mud is realized, the innovation strength of a new technology is increased, and the problem of the industry urgent need to be solved for fundamentally treating the influence and pollution caused by the stacking of the red mud and the phosphogypsum.

Aiming at the problems that the existing phosphogypsum and red mud have low utilization rate and are accumulated in large quantity to seriously restrict the sustainable development of the phosphorus chemical industry and the aluminum industry and protect the environment, the invention prepares the red mud-phosphogypsum composite cementing material by combining the characteristics of the acid phosphogypsum and the alkaline red mud, utilizing the salt excitant generated between the acid phosphogypsum and the alkaline red mud and promoting the activation of the phosphogypsum and the red mud by adding a proper salt excitant and a proper alkali excitant, develops the low-cost and simple activation process technology, is favorable for expanding the comprehensive utilization channel of the red mud-phosphogypsum composite cementing material, and has guiding significance for the comprehensive utilization of the phosphogypsum and the red mud in other fields.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a red mud-phosphogypsum composite cementitious material and a preparation method thereof, combines the characteristics of acid phosphogypsum and alkaline red mud, promotes the activation of the phosphogypsum and the red mud by a salt activator and an alkali activator to obtain the composite cementitious material, expands the comprehensive utilization channel of the phosphogypsum and the red mud, and develops a low-cost and simple activation process.

One of the purposes of the invention is to provide a preparation method of a red mud-phosphogypsum composite cementing material, which comprises the following steps:

step 1, mixing red mud and an alkali activator, adding water, stirring to a slurry shape, and aging to obtain an activated red mud mixture;

step 2, mixing the phosphogypsum and a salt activator, adding water, stirring to a slurry form, and aging to obtain an activated phosphogypsum mixture capable of improving the hardness of the activated red mud mixture;

and 3, mixing the activated red mud mixture obtained in the step 1 with the activated phosphogypsum mixture obtained in the step 2, uniformly stirring, and adjusting the pH value to obtain the red mud-phosphogypsum composite cementing material.

Preferably, in step 1, the alkali-activating agent is one or more of sodium hydroxide, calcium oxide, calcium hydroxide and potassium hydroxide.

Preferably, in the step 1, the dosage of the alkali-activator is 4-8% of the mass of the red mud.

Preferably, in step 2, the salt exciting agent is one or more of aluminum sulfate, ferric sulfate, calcium chloride and calcium phosphate.

Preferably, in the step 2, the salt excitant accounts for 3-8% of the weight of the phosphogypsum.

Preferably, in the step 1 and the step 2, the aging time is 12-48 h.

Preferably, in the step 3, the mixing mass ratio is 1-3: 1-3.

The invention also aims to provide the composite cementing material for preparing the red mud-phosphogypsum by the preparation method.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention obtains the composite gelled material by promoting the activation of the phosphogypsum and the red mud through the salt activator and the alkali activator, expands the comprehensive utilization channel of the phosphogypsum and the red mud, develops the low-cost and simple activation process, and has the advantages of easy operation, low cost, clean production process and environmental protection.

2. The alkali excitant effectively excites the red mud to generate aluminate, silicate and other substances, latent hydraulicity is stored in the aluminosilicate substances, the red mud can be promoted to be condensed, cemented and hardened, the cementing effect promotes the formation of cemented objects, the internal structure of the system is tighter, the strength of the red mud is greatly improved, and the salt excitant can promote the inert dihydrate gypsum to be converted into active hemihydrate gypsum; and the salt excitant can adjust the pH value of the activated red mud, the pH value can also influence the crystal growth rate and the crystal form, the dehydration rate of the hemihydrate gypsum can be gradually increased along with the reduction of the pH value, the time of the crystal induction stage and the crystal growth stage of the hemihydrate gypsum can be shortened, and the strength of the red mud phosphogypsum composite cementing material can be effectively improved.

Drawings

FIG. 1 is a scanning electron microscope atlas of a composite cementing material before activation and after activation, wherein the mass ratio of red mud to phosphogypsum is 2: 3; wherein a and c are used before activation, and b and d are used after activation;

FIG. 2 is an X-ray diffraction pattern before and after the red mud is activated by the alkali-activator in the invention;

FIG. 3 is X-ray diffraction pattern of various salts exciting agent activated phosphogypsum in the invention;

FIG. 4 is a scanning electron microscope atlas of the composite cementitious material of the salt excitant of the invention after calcium chloride sample activation and before and after activation with the mass ratio of red mud and phosphogypsum being 1: 1; wherein (a) is performed before activation and (b) is performed after activation;

FIG. 5 is an X-ray diffraction pattern of the composite cementing material of the salt excitant of the invention, which is activated by calcium chloride sample, and the mass ratio of red mud and phosphogypsum is 1:1 before activation and after activation.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, in the present invention, NaOH is sodium hydroxide and CaO is calcium oxide, and the terminology used in the present invention is only for the purpose of describing specific examples and is not intended to limit the scope of the present invention, unless otherwise specifically indicated, and all of the raw materials, reagents, apparatuses and equipment used in the following examples of the present invention may be commercially available or prepared by existing methods.

Example 1

A preparation method of a red mud-phosphogypsum composite cementing material comprises the following steps:

mixing 100g of red mud and 6g of sodium hydroxide, adding 200mL of water, stirring to a slurry form, and aging for 12h to obtain an activated red mud mixture; mixing 100g of phosphogypsum, 2.5g of ferric sulfate and 2.5g of aluminum sulfate, adding 200mL of water, stirring to a slurry form, and aging for 24h to obtain an activated phosphogypsum mixture; and mixing the obtained activated red mud mixture with the activated phosphogypsum mixture obtained in the step (2: 3) in a mass ratio, and uniformly stirring to obtain the red mud-phosphogypsum composite cementing material.

Example 2

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: and mixing the activated red mud mixture and the activated phosphogypsum mixture according to the mass ratio of 3: 1.

Example 3

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: and mixing the activated red mud mixture and the activated phosphogypsum mixture according to the mass ratio of 1: 2.

Example 4

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: and mixing the activated red mud mixture and the activated phosphogypsum mixture according to the mass ratio of 1: 1.

Example 5

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 4, and the difference is that: the salt excitant is calcium chloride, and the calcium chloride accounts for 3 percent of the weight of the phosphogypsum.

Example 6

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 4, and the difference is that: the excitant is calcium phosphate, and the calcium chloride accounts for 5 percent of the mass of the phosphogypsum.

Example 7

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the salt excitant is ferric sulfate, and the ferric sulfate accounts for 5% of the phosphogypsum in mass.

Example 8

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the sodium hydroxide accounts for 4 percent of the mass of the red mud, and the activated red mud mixture is obtained after aging for 48 hours.

Example 9

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the alkali activator is calcium oxide and sodium hydroxide, and the calcium oxide and the sodium hydroxide are respectively 3 percent of the mass of the red mud.

Example 10

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the salt excitant is aluminum sulfate and ferric sulfate which are respectively 4 percent of the mass of the red mud.

Comparative example 1

Adding 100g of red mud into 200mL of water, and stirring to form slurry; adding 100g of phosphogypsum into 200mL of water and stirring to form slurry; and mixing the obtained red mud mixture and the phosphogypsum mixture according to the mass ratio of 2:3, and uniformly stirring to obtain the red mud-phosphogypsum composite cementing material.

Comparative example 2

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the comparative example 1, and is characterized in that: the mass ratio of the red mud mixture to the phosphogypsum mixture is 3: 1.

Comparative example 3

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the comparative example 1, and is characterized in that: the mass ratio of the red mud mixture to the phosphogypsum mixture is 1: 2.

Comparative example 4

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the comparative example 1, and is characterized in that: the mass ratio of the red mud mixture to the phosphogypsum mixture is 1: 1.

Comparative example 5

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the activated red mud mixture (6% NaOH) was mixed with the activated phosphogypsum mixture in a mass ratio of 1:0 (pure activated red mud).

Comparative example 6

The method for preparing the red mud-phosphogypsum composite cementing material is the same as the example 1, and the difference is that: the activated red mud mixture was mixed with activated phosphogypsum (2.5% ferric sulphate, 2.5% aluminium sulphate) in a mass ratio of 0:1 (pure activated phosphogypsum).

Uniformly filling the cementing materials prepared in the examples 1-10 and the comparisons 1-6 into a mold, and performing mechanical property test after curing all samples filled with the mold for a certain time at normal temperature; the mechanical test is a compressive strength test, the compressive strength measured by a UTM5305H type multifunctional material universal testing machine is calculated according to the formula:

P＝F/S

wherein, P is the compressive strength/MPa of the sample;

f is pressure/N;

s is the stressed area/m of the sample²。

TABLE 1 influence of activating examples of alkali activator and salt activator on the strength of composite cement materials in different ratios before and after activation

From the comparison in table 1, it can also be seen that the strength obtained by mixing red mud and phosphogypsum in any proportion is not very high, provided that neither is it activated. Because of the influence of soluble impurities in the phosphogypsum, when the phosphogypsum is mixed in too much, the surface of a product is pulverized, the structure is loose, and the strength of the product is seriously influenced. However, the strength of the red mud and the phosphogypsum before and after activation is the highest in the proportion of 2:3 no matter the 7d early strength or the 28d strength. It can also be seen from the comparison in table 1 that, when the phosphogypsum content is more than that of the red mud before or after activation, the strength is generally high, but the phosphogypsum content is not too high due to the influence of soluble impurities; it can also be seen that in examples 1-4, the pH value can affect the crystal growth rate and the crystal form, the dehydration rate of the hemihydrate gypsum gradually increases with the decrease of the pH value, the time of the crystal induction stage and the crystal growth stage of the hemihydrate gypsum can be shortened, and the strength of the red mud-phosphogypsum composite cementing material is effectively improved.

And analyzing the microscopic morphology of the product with the red mud and phosphogypsum ratio of 2:3 before and after activation. As shown in fig. 1, it can be seen from a and b that the interior of the non-activated sample is also cemented with each other, but the formation of large lumps of cement is not seen, and the formation of a large amount of large lumps of cement inside the activated sample enhances the strength of the product. And (3) further amplifying the unactivated sample and the activated sample, wherein crystals in the unactivated sample are trivial, are relatively loose and are not tightly bonded with each other, and crystals in the activated sample are bonded into a large block, so that the strength of the product can be greatly improved.

From the comparison of the XRD patterns in fig. 2, it can be found that each characteristic peak is weakened to a different extent from the characteristic peak of the red mud blank sample after NaOH is added to the red mud, which also indicates that gibbsite and other substances in the red mud are transformed to generate a certain amount of aluminate after NaOH is added.

From the comparison of the XRD patterns of figure 3 it can also be seen that the characteristic peaks of the incorporated aluminium sulphate are significantly weaker than those of the unactivated phosphogypsum, i.e. the aluminium sulphate activation is illustrated to make the conversion of dihydrate gypsum to hemihydrate larger than otherwise. The strength of the combined action of the aluminum sulfate and the ferric sulfate is slightly different from the strength of the independent action of the aluminum sulfate, which shows that the aluminum sulfate and the ferric sulfate have certain synergistic action and are beneficial to the change of the dihydrate gypsum to the hemihydrate gypsum.

TABLE 2 Strength Effect of composite cementitious Material after activation and pH adjustment with different activators and amounts

As can be seen from Table 2, the addition of the activator can greatly improve the strength of the red mud-phosphogypsum composite gelled system, and the influence of the existence of calcium chloride and calcium oxide on the improvement of the strength of the composite gelled system is most obvious no matter the early strength of curing for 7 days or the strength of curing for 28 days.

As shown in figure 4 from the microscopic appearance of the product, on the basis of no addition of an exciting agent, the appearance of the mixture (a) of the red mud and the phosphogypsum in a ratio of 1:1 is not cemented into blocks, and the whole product is loose. After the red mud and the calcium chloride activated phosphogypsum (b) are activated by adding NaOH, the phosphogypsum (b) can be clearly seen to be bonded into blocks with strength, so that the strength of the system is greatly improved. XRD analysis of the mixed blank sample and the calcium chloride sample clearly shows that the characteristic peak of the dihydrate gypsum is obviously weaker than that of the blank sample after the calcium chloride is added, which shows that the calcium chloride is added to promote the conversion of the dihydrate gypsum to the hemihydrate gypsum, and the dihydrate gypsum is cemented into a substance shown as (b) in figure 4 in a composite system, so that the strength of the composite cementing material is improved.

It should be noted that, when the present invention relates to a numerical range, it should be understood that two endpoints of each numerical range and any value between the two endpoints can be selected, and since the steps and methods adopted are the same as those in the embodiment, in order to prevent redundancy, the present invention describes a preferred embodiment. While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.