CN113000011A

CN113000011A - Heavy metal adsorption material and preparation method and application thereof

Info

Publication number: CN113000011A
Application number: CN202110259457.4A
Authority: CN
Inventors: 侯德义; 李炫儒; 王刘炜
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-03-10
Filing date: 2021-03-10
Publication date: 2021-06-22
Anticipated expiration: 2041-03-10
Also published as: CN113000011B

Abstract

The invention relates to the technical field of heavy metal pollution environment restoration, in particular to a heavy metal adsorption material and a preparation method and application thereof. The preparation method of the heavy metal adsorption material includes the following steps: providing a mixed oxide material, the mixed oxide material includes calcium oxide, aluminum oxide and magnesium oxide, the content of the calcium oxide is 25wt% to 50wt%, the oxide The content of aluminum is 7wt% to 15wt%, and the content of magnesium oxide is 6.5wt% to 50wt%; the mixed oxide material is added into the acid solution to fully react to obtain a solution containing metal ions; An alkaline solution is added to the solution of metal ions, the pH is adjusted to 10-12, and mixed hydroxide is obtained by co-precipitation.

Description

Heavy metal adsorption material and preparation method and application thereof

Technical Field

The invention relates to the technical field of heavy metal polluted environment restoration, in particular to a heavy metal adsorption material and a preparation method and application thereof.

Background

Adsorption is the most common remediation mode for environmental medium heavy metal pollution remediation. Adsorption is a broad concept and may include a number of repair mechanisms: physical adsorption based on Van der Waals force is realized through the large specific surface area of the repair material; the abundant functional groups on the surface of the material are utilized to realize surface complexing fixation; the ion exchange or surface precipitation fixation of heavy metals is realized by mineral components contained in the material. In terms of soil pollution, the adsorption process is often referred to as "stabilization" or "passivation", and the material applied to the soil changes the microscopic morphology of the heavy metal in the soil through the adsorption mechanism, so that the mobility of the heavy metal in the soil is reduced.

Conventional adsorbent materials tend to be effective only against one or more heavy metals of the same type. In the face of scenes that arsenical and oxyacid radical anions, lead cations and the like need to be synchronously adsorbed, the adsorption material often cannot realize synchronous adsorption removal of the anions and the cations in a water body or synchronous stabilization treatment of the anions and the cations in soil due to the fact that the adsorption material has specific electrical property and only contains sites suitable for single type of heavy metals. For example, the most commonly used stabilizing material, lime, can effectively inactivate cationic heavy metals such as cadmium and lead by raising the soil pH, but can activate the oxyanion, arsenic. The addition of ferrous sulfate can effectively passivate arsenic in soil, but can acidify the soil and further activate cationic heavy metals. Although the activated carbon material can realize simultaneous adsorption of various heavy metals, the activated carbon material is high in price and cannot be applied to environmental remediation in a large scale.

Disclosure of Invention

Based on the above, there is a need for a novel heavy metal adsorption material capable of adsorbing lead and arsenic simultaneously, and a preparation method and application thereof.

In one aspect of the invention, a preparation method of a heavy metal adsorption material is provided, which comprises the following steps:

providing a mixed oxide material, wherein the mixed oxide material comprises 25-50 wt% of calcium oxide, 7-15 wt% of aluminum oxide and 6.5-50 wt% of magnesium oxide;

adding the mixed oxide material into an acidic solution for full reaction to obtain a solution containing metal ions; and

and adding an alkaline solution into the solution containing the metal ions, adjusting the pH to 10-12, and performing coprecipitation to obtain a mixed hydroxide.

In one embodiment, the magnesium oxide is present in an amount of 20 wt% to 50 wt%.

In one embodiment, the mixed oxide material is selected from one or more of blast furnace slag, steel slag, red mud, silica fume and industrial magnesia.

In one embodiment, the mixed oxide material is blast furnace slag comprising 45-50 wt% calcium oxide, 10-15 wt% aluminum oxide, 6-7 wt% magnesium oxide.

In one embodiment, the mixed oxide material is blast furnace slag and magnesium oxide, and the mass ratio of the blast furnace slag to the magnesium oxide is 1: (0.25-1), wherein the blast furnace slag comprises 45-50 wt% of calcium oxide, 10-15 wt% of aluminum oxide and 6-7 wt% of magnesium oxide, and the industrial magnesium oxide contains more than 85 wt% of magnesium oxide, less than 5 wt% of calcium oxide and less than 1.5 wt% of aluminum oxide.

In one embodiment, the acidic solution is a hydrochloric acid solution or a nitric acid solution, the concentration of the acidic solution is 1mol/L to 5mol/L, and the solid-to-liquid ratio of the mixed oxide material to the acidic solution is 1: (10-20) g/mL.

In one embodiment, in the step of adding the mixed oxide material into the acidic solution for sufficient reaction, the reaction temperature is 60-80 ℃, and the reaction time is 3-5 hours.

In one embodiment, the reaction condition of the coprecipitation step is 60-80 ℃ for 8 hours or more, or 20-30 ℃ for 24 hours or more.

In one embodiment, the method for preparing the heavy metal adsorption material further comprises the step of calcining the mixed hydroxide.

In one embodiment, in the step of calcining the mixed hydroxide, the calcining temperature is 450-500 ℃, and the calcining time is 1-3 h.

In another aspect of the invention, the heavy metal adsorbing material prepared by the preparation method of the heavy metal adsorbing material is provided.

In a further aspect of the invention, the application of the heavy metal adsorption material in remediation of heavy metal polluted water or soil is also provided.

In one embodiment, the heavy metal comprises arsenic and lead.

Compared with the prior art, the invention has the following technical effects:

the preparation method of the heavy metal adsorption material provided by the invention takes a mixed oxide material with the components of 30-60 wt% of calcium oxide, 15-30 wt% of aluminum oxide and 6.5-50 wt% of magnesium oxide as a raw material, calcium, aluminum and magnesium metal ions are obtained by reacting with an acidic solution, and then calcium-aluminum hydroxide and magnesium-aluminum hydroxide are obtained by coprecipitation in an alkaline solution. The two hydroxides are space layered frameworks, arsenic can be adsorbed/passivated by surface complexation, and lead is adsorbed/passivated by surface precipitation, so that heavy metal lead heavy metal and arsenic in the polluted water body or the polluted soil can be adsorbed/passivated simultaneously, the adsorption efficiency is greatly improved, and the heavy metal adsorption material obtained by the preparation method is particularly suitable for adsorption/passivation of arsenic-lead composite polluted water body and soil.

Drawings

FIG. 1 is a flow chart of a method for preparing a heavy metal adsorption material according to an embodiment of the present invention;

FIGS. 2 and 3 are XRD patterns of the mixed hydroxide and the composite oxide prepared in examples 1 to 3 of the present invention;

FIG. 4 is a comparison of specific surface areas of the mixed hydroxides and the composite oxides prepared in examples 1 to 3 of the present invention;

FIG. 5 is a scanning electron microscope image of the mixed hydroxide and the composite oxide prepared in examples 1 to 3 of the present invention;

FIG. 6 is an infrared spectrum of a mixed hydroxide and a composite oxide;

FIG. 7 is a thermogravimetric analysis curve of the mixed hydroxides prepared in examples 1 to 3 of the present invention;

FIG. 8 shows the adsorption isotherms and kinetics of the composite oxides and mixed hydroxides prepared in examples 1 to 3 of the present invention;

FIG. 9 shows adsorption isotherms and kinetics of the composite oxides and mixed hydroxide lead prepared in examples 1 to 3 of the present invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Other than as shown in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, physical and chemical properties, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". For example, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can be suitably varied by those skilled in the art in seeking to obtain the desired properties utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range and any range within that range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, and the like.

The embodiment of the invention provides a preparation method of a heavy metal adsorption material, which comprises the following steps:

s10, providing a mixed oxide material, wherein the mixed oxide material comprises 25 wt% -50 wt% of calcium oxide, 7 wt% -15 wt% of aluminum oxide and 6.5 wt% -50 wt% of magnesium oxide;

s20, adding the mixed oxide material into an acidic solution for full reaction to obtain a solution containing metal ions; and

s30, adding an alkaline solution into the solution containing the metal ions, adjusting the pH value to 10-12, and carrying out coprecipitation to obtain a mixed hydroxide.

The preparation method of the heavy metal adsorption material provided by the embodiment of the invention takes a mixed oxide material with the components of 30-60 wt% of calcium oxide, 15-30 wt% of aluminum oxide and 6.5-50 wt% of magnesium oxide as a raw material, calcium, aluminum and magnesium metal ions are obtained by reacting with an acidic solution, and then calcium-aluminum hydroxide and magnesium-aluminum hydroxide are obtained by coprecipitation in an alkaline solution. The two hydroxides are space layered frameworks, arsenic can be adsorbed/passivated by surface complexation, and lead is adsorbed/passivated by surface precipitation, so that heavy metal lead heavy metal and arsenic in the polluted water body or the polluted soil can be adsorbed/passivated simultaneously, the adsorption efficiency is greatly improved, and the heavy metal adsorption material obtained by the preparation method is particularly suitable for adsorption/passivation of arsenic-lead composite polluted water body and soil.

The content of calcium oxide in the mixed oxide material may be anywhere between 25 wt% and 50 wt%, and may include, for example and without limitation, 25.5 wt%, 26 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 48 wt%.

The content of alumina in the mixed oxide material may be any value between 7 wt% and 15 wt%, and may include, for example and without limitation, 7.2%, 7.5%, 8%, 9%, 10%, 11%, 12%, 13%, 14%.

The content of magnesium oxide in the mixed oxide material may be any value between 6.5 wt% and 50 wt%, and may include, but is not limited to, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and more preferably 20 wt% to 50 wt%, for example. The magnesium oxide can improve the stability of the heavy metal adsorption material and can further assist the adsorption/passivation of lead. With the increase of the content of the magnesium oxide, particularly the content of the magnesium oxide is in the range of 20 wt% to 50 wt%, the stability of the heavy metal adsorption material and the adsorption/passivation capacity to lead are better.

The mixture oxide material may be selected from one or more of group-granulated blast-furnace slag (GGBS), steel slag, red mud, silica fume, and industrial magnesium oxide.

The blast furnace slag is a waste slag discharged from a blast furnace when smelting pig iron. The blast furnace slag may be one or more of cast raw iron slag, steel-making raw iron slag and special raw iron slag. The blast furnace slag may include silicon dioxide (SiO)₂) Aluminum oxide (Al)₂O₃) Calcium oxide (CaO), magnesium oxide (MgO), manganese oxide (TiO)₂) And ferric oxide (Fe)₂O₃) And the like.

The steel slag is a byproduct in the steel making process. It is composed of various oxides formed by oxidizing impurities in pig iron, such as silicon, manganese, phosphorus, sulfur, etc. in the smelting process, and salts generated by the reaction of these oxides and solvent. The steel slag contains metal iron, calcium oxide, manganese oxide and other components.

The red mud is industrial solid waste discharged during extraction of alumina in the aluminum production industry. The main component of the red mud is silicon dioxide (SiO)₂) Alumina (Al)₂O₃) Calcium oxide (CaO), and iron oxide (Fe)₂O₃). The diameter of the red mud particles is 0.088 mm-0.25 mm.

The silicon ash is a large amount of SiO with strong volatility produced in an ore-smelting electric furnace when ferroalloy is used for smelting ferrosilicon and industrial silicon (metallic silicon)₂And Si gas, which is quickly oxidized, condensed and precipitated with air after being discharged. The main component of the silica fume is silicon dioxide, which can be called as silica fume or silica micropowder. Further, the silica fume may further contain one of sodium oxide, calcium oxide, magnesium oxide, iron oxide and aluminum oxideOr a plurality thereof.

The commercial magnesium oxide may have a purity greater than 80%, preferably greater than 85%, more preferably greater than 90%.

The mixed oxide materials are all industrial solid wastes or industrial materials, and the materials are used as raw materials for preparing the heavy metal adsorption material, so that the cost can be greatly reduced, and the resource recycling is realized.

Preferably, the blast furnace slag contains 45 to 50 wt% of calcium oxide, 10 to 15 wt% of aluminum oxide, and 6 to 7 wt% of magnesium oxide. Further, the blast furnace slag may also contain small amounts of other metal oxides, such as Fe₂O₃、TiO₂The content of said other metal oxide is preferably less than 2 wt%. May also contain non-metal oxide SiO₂Further, it may contain a small amount of non-metal non-oxide impurities such as S, etc.

It is emphasized that the blast furnace slag contains a small amount of metal oxides other than calcium oxide, aluminum oxide and magnesium oxide, and the content of metal ions other than calcium, magnesium and aluminum after the acid reaction is negligible. If the blast furnace slag contains more SiO₂E.g. SiO₂When the content is 10 wt% -30 wt%, step S20, adding the mixed oxide material into the acid solution for full reaction, and then filtering to remove silica gel.

Preferably, the purity of the industrial magnesium oxide is more than 85%, the content of calcium oxide is less than 5%, and the content of aluminum oxide is less than 1.5%. More preferably, the content of the magnesium oxide in the industrial magnesium oxide is 85 wt% to 90 wt%. Further, the industrial magnesium oxide may also contain small amounts of other metal oxides, such as Fe₂O₃、TiO₂And may further contain a non-metal oxide SiO₂The content thereof is preferably less than 5%, and further, a small amount of non-metallic non-oxide impurities such as S and the like may be contained.

In some embodiments, the mixed oxide material is blast furnace slag. In other embodiments, the mixed oxide material is a mixture of blast furnace slag and industrial magnesium oxide, and the mass ratio of the blast furnace slag and the magnesium oxide may be 1: (0.25 to 1).

The purpose of step S20 is to completely convert calcium oxide, aluminum oxide, and magnesium oxide in the mixed oxide material into calcium ions, aluminum ions, and magnesium ions.

In some embodiments, the acidic solution may be a hydrochloric acid solution or a nitric acid solution. The concentration of the acidic solution may be 1mol/L to 5 mol/L. The solid-to-liquid ratio of the mixed oxide material and the acidic solution may be 1: (10-20) g/mL.

In some embodiments, in the step of adding the mixed oxide material into the acidic solution for sufficient reaction, the reaction temperature is 60 ℃ to 80 ℃ and the reaction time is 3h to 5 h.

The purpose of step S30 is to co-precipitate calcium ions, aluminum ions, and magnesium ions in the metal ion-containing solution to form calcium-aluminum hydroxide and magnesium-aluminum hydroxide.

In step S30, the pH of the coprecipitation reaction may be any value between 10 and 12, for example, 10.5, 11, or 11.5.

In some embodiments, the reaction conditions of the co-precipitation step are 60 ℃ to 80 ℃ for 8h and more.

In other embodiments, the reaction conditions of the coprecipitation step are 20 ℃ to 30 ℃ for 24 hours or more.

In some preferred embodiments, the preparation method of the heavy metal adsorption material further comprises step S40: calcining the mixed hydroxide. Through the calcination step, the mixed hydroxide loses moisture in the crystal lattice and is converted into a composite oxide. The composite oxides can absorb water again when being added into polluted water or polluted soil, and the original space layered framework is restored through a recombination lattice structure: hydroxyl in the original space layered framework is replaced by arsenate in the adsorbed polluted water body or soil, and divalent ions such as magnesium/calcium in the original space layered framework are replaced by lead cations. Therefore, by adopting the method of further calcining the mixed hydroxide, the water phase adsorption/soil passivation effect of heavy metals arsenic and lead can be further improved by directly embedding the heavy metals into a recombinant lattice structure.

In some embodiments, the mixed hydroxide may be calcined at a temperature of 450 ℃ to 500 ℃ for 1h to 3h in step S40.

In another aspect of the invention, the heavy metal adsorption material prepared by the preparation method of the heavy metal adsorption material is also provided.

Further, the invention also provides application of the heavy metal adsorption material in remediation of heavy metal polluted water bodies or soil. Particularly preferably, the heavy metals include arsenic and lead.

The following are specific examples. The present invention is intended to be further described in detail to assist those skilled in the art and researchers to further understand the present invention, and the technical conditions and the like do not limit the present invention. Any modification made within the scope of the claims of the present invention is within the scope of the claims of the present invention.

The compositions of oxides in blast furnace slag (100 mesh) and magnesia (100 mesh) selected in the following examples are detailed in Table 1.

TABLE 1

Oxide compound	Blast furnace slag	Magnesium oxide
			CaO	49.03wt％	4.96wt％
SiO₂	26.90wt％	4.62wt％
			Al₂O₃	13.17wt％	1.34wt％
MgO	6.51wt％	86.08wt％
			TiO₂	0.93wt％	0.07wt％
Fe₂O₃	0.65wt％	1.79wt％
			Non-metal non-oxide impurities	2.81％	1.14％

Example 1

1. Blast furnace slag (100g) having the oxide composition shown in Table 1 was used as a raw material.

2. According to the following steps: blast furnace slag (100g) was added to 3mol/L hydrochloric acid (2L) at a liquid ratio of 1:20g/mL, reacted at 80 ℃ for 4 hours, and filtered to obtain a filtrate.

3. 4mol/L sodium hydroxide was gradually added dropwise to the obtained filtrate to bring the pH of the reaction system to 11.5. And heating the solution after the pH is adjusted at 80 ℃ for 24h, crystallizing to separate out crystals, and drying to obtain the mixed hydroxide a.

4. And (3) placing the mixed hydroxide a in a muffle furnace, and calcining for 2h at 500 ℃ to obtain the composite oxide a.

Example 2

1. Blast furnace slag (80g) and magnesium oxide (20g) composed of the oxides shown in Table 1 were used as raw materials and mixed well under dry conditions for 30 min.

2. According to the following steps: adding the mixed solid (100g) obtained in the step 1 into 3mol/L hydrochloric acid (2L) according to the liquid ratio of 1:20g/mL, reacting at 80 ℃ for 4 hours, and filtering to obtain filtrate.

3. 4mol/L sodium hydroxide was gradually added dropwise to the obtained filtrate to bring the pH of the reaction system to 11.5. And heating the solution after the pH is adjusted at 80 ℃ for 24h, crystallizing to separate out crystals, and drying to obtain the mixed hydroxide b.

4. And (3) placing the mixed hydroxide b into a muffle furnace to be calcined for 2h at 500 ℃ to obtain the composite oxide b.

Example 3

1. Blast furnace slag (50g) and magnesium oxide (50g) composed of the oxides shown in Table 1 were used as raw materials and mixed well under dry conditions for 30 min.

3. 4mol/L sodium hydroxide was gradually added dropwise to the obtained filtrate to bring the pH of the reaction system to 11.5. And heating the solution after the pH is adjusted at 80 ℃ for 24h, crystallizing to separate out crystals, and drying to obtain the mixed hydroxide c.

4. And (3) placing the mixed hydroxide b in a muffle furnace, and calcining for 2h at 500 ℃ to obtain the composite oxide c.

Example 4

The production method of example 4 is substantially the same as that of example 3 except that the pH is adjusted to 10 in step 3 to obtain a mixed hydroxide d, and the mixed hydroxide b is calcined in a muffle furnace at 500 ℃ for 2 hours to obtain a composite-type oxide d.

Example 5

The production method of example 5 is substantially the same as that of example 3 except that the pH is adjusted to 12 in step 3 to obtain a mixed hydroxide e, and the mixed hydroxide b is calcined in a muffle furnace at 500 ℃ for 2 hours to obtain a composite-type oxide e.

Comparative example 1

The preparation method of comparative example 1 is substantially the same as that of example 3 except that: and 3, adjusting the pH value to 9.5 to obtain a mixed hydroxide f, and calcining the mixed hydroxide b in a muffle furnace at 500 ℃ for 2h to obtain the composite oxide f.

Comparative example 2

The preparation method of comparative example 2 is substantially the same as that of example 3 except that: and 3, adjusting the pH value of China to 12.5 to obtain a mixed hydroxide g, and calcining the mixed hydroxide b in a muffle furnace at 500 ℃ for 2h to obtain a composite oxide g.

The list of raw materials and process parameters in the preparation methods of examples 1 to 5 and comparative examples 1 to 3 is shown in table 1 below:

TABLE 1

Group of	Blast furnace slag	Magnesium oxide	pH
				Example 1	100g	-	11.5
Example 2	80g	20g	11.5
				Example 3	50g	50g	11.5
Example 4	50g	50g	10
				Example 5	50g	50g	12
Comparative example 1	50g	50g	9.5
				Comparative example 2	50g	50g	12.5
Comparative example 3	60g	40g	11.5

Structural characterization

1. The mixed hydroxides a, b and c and the composite oxides a, b and c obtained in examples 1 to 3 were mineralogically analyzed by XRD test, and the results are shown in FIGS. 2 and 3.

As can be seen from fig. 2 and 3, the mixed hydroxides a, b and c are mainly calcium-aluminum hydroxide and magnesium-aluminum hydroxide, and as the dosage of magnesium oxide increases (from a to c), the mineralogical characteristics gradually change from calcium-aluminum hydroxide to magnesium-aluminum hydroxide. When the mass ratio of magnesium oxide to blast furnace slag reached 1:1, the mixed hydroxide c exhibited a peak of magnesium hydroxide. The three mixed hydroxides are calcined to obtain the composite oxides, and diffraction peaks of various oxides are generated. For example, the composite oxide a shows magnesium oxide and calcium carbonate, the composite oxide b shows magnesium oxide, calcium carbonate and calcium-aluminum mixed oxide material, and the composite oxide c mainly shows a magnesium oxide diffraction peak.

2. The mixed hydroxides a, b and c and the composite oxides a, b and c prepared in the examples 1 to 3 are subjected to N treatment at a temperature of 77K₂The BET specific surface area was calculated by adsorption-desorption, and the result graph is shown in fig. 4. Compared with the mixed hydroxides a, b and c, the specific surface areas of the composite oxides a, b and c are all increased, which shows that the calcined material has high specific surface area, so that the calcined material has stronger adsorption performance and is more suitable for adsorption/passivation of heavy metals.

3. The mixed hydroxides a, b and c and the composite oxides a, b and c prepared in the embodiments 1 to 3 are observed for morphology by a scanning electron microscope, as shown in fig. 5. The material mixed hydroxides a, b and c before calcination all have sheet structures, and calcination destroys these sheet structures. The formed composite oxides a, b and c are broken off, which is caused by that water molecules in crystal lattices are removed in the heating process, and the lattice structure is broken.

5. The mixed hydroxides a, b and c and the composite oxides a, b and c prepared in examples 1 to 3 were analyzed by infrared spectroscopy, and the results are shown in FIG. 6. As can be seen from fig. 6, hydroxyl is the most dominant functional group of these materials, and arsenic and lead can be adsorbed/passivated by complexing with the hydroxyl surface or precipitating. It is to be noted that the infrared absorption peak (M-OH) between the metal (here, calcium, magnesium, aluminum) and the hydroxyl group in the composite oxides a, b and c after calcination disappears, and an absorption peak representing Ca — O appears, and from another point of view, the calcination causes lattice collapse to some extent, and a metal oxide-like substance is produced.

6. The results of thermogravimetric analysis of the mixed hydroxides a, b and c obtained in examples 1 to 3 are shown in FIG. 6. As can be seen from fig. 7, the weight loss curve of the mixed hydroxide material gradually shifted to the right with increasing magnesium oxide content, indicating that higher temperatures are required to destroy the original material. The weight loss peak at about 100 ℃ represents the process of losing free water of the material, and the weight loss peak at about 300-400 ℃ represents the damage of the hydroxyl of the lattice structure. The calcination temperature in step S40 of the present invention is higher than this temperature, which ensures that the mixed hydroxide is completely converted into the composite oxide. It can also be seen that magnesium oxide can improve the stability of the material.

Application example 1 adsorption of heavy metals in arsenic and lead polluted water body

Using Pb (NO)₃)₂And Na₂HAsO₄·7H₂And O, preparing Pb (II), As (V) solutions, and carrying out adsorption isotherm and adsorption kinetics experiments.

Adsorption isotherm: 0.1g of adsorbing material is added into 20mL of polluted water, and the pollution ranges of arsenic and lead are respectively 25-500 mg/L and 25-30000 mg/L until adsorption balance is achieved.

Adsorption kinetics: 0.1g of adsorbing material is added into 20ml of polluted water, the pollution concentration of arsenic and lead is 500mg/l and 5000mg/l respectively, and samples are taken at different time periods.

The adsorbing materials are respectively the mixed hydroxides a, b and c and the composite oxides a, b and c prepared in the examples 1-3.

The adsorption isotherms and kinetics of arsenic and lead are shown in fig. 8, fig. 9 and table 2.

TABLE 2

As can be seen from the graph, the adsorption performance of the composite oxides a, b, and c after calcination is improved compared to the adsorption performance of the mixed hydroxides a, b, and c before calcination. This is because arsenic is directly embedded into a new crystal lattice, thereby promoting adsorption. The adsorption rate of the composite oxides a, b and c to arsenic and lead can reach more than 95%. Higher magnesium oxide content is not good for arsenic adsorption, but can promote lead adsorption to some extent.

The adsorption kinetics are in accordance with a quasi-second-order model, which shows that the speed-determining step of the process is adsorption rather than diffusion. The mixed hydroxides a, b with a small content of magnesium oxide, the composite oxides a, b are Langmuir type isotherms, which indicates that they are monolayer adsorption on a homogeneous surface. The mixed hydroxide c and the composite oxide c with high magnesium oxide content are Freundlich type adsorption, which shows that the heterogeneity of the material is increased by the high magnesium oxide content, and the material is changed into multilayer adsorption.

Comparative application examples 1 to 1

The adsorbing material is replaced by a mixture of 0.1g of oxides (0.02 g of magnesium oxide, 0.05g of calcium oxide and 0.03g of aluminum oxide), and the adsorption rates of arsenic and lead are respectively 30-44% and 35-51%.

Comparative application examples 1 to 2

The adsorption material is replaced by 0.1g of magnesium oxide, and the adsorption rates of arsenic and lead are respectively 22% -29% and 61% -78%.

Comparative application examples 1 to 3

The adsorption material is replaced by 0.1g of blast furnace slag, and the adsorption rates of arsenic and lead are respectively 18-40% and 26-38%.

The adsorption rates of comparative application examples 1-1 to 1-3 were obtained by adsorption isotherm and adsorption kinetics experiments, and the adsorption rates obtained by the two methods were different from each other, so that the adsorption rate values were in a range. But this does not affect the comparison of the adsorption effect of the heavy metal adsorption material and the heavy metal adsorption material. From the obtained range data, even if the maximum value is in the range, the adsorption rate of the adsorption material of the application examples 1-3 to arsenic and lead is far lower than that of the heavy metal adsorption material of the invention.

Application example 2 passivation of arsenic-lead composite contaminated soil

Drying the arsenic-lead composite contaminated soil, sieving the soil by a 40-mesh sieve, adding an adsorbing material (5 g of the adsorbing material is added into 100g of the soil) according to the proportion of 5% of the soil mass fraction, adding 30g of water, and then culturing for 7 days. Sampling, leaching by using a HJ557 horizontal oscillation method, testing the concentrations of arsenic and lead in leachate, and comparing with soil without added materials to obtain the passivation rate, wherein the results are shown in Table 3.

The adsorbent materials were each the adsorbent materials listed in table 3.

TABLE 3

As can be seen from the above Table 3, the passivation effect of the calcined composite oxide (92% -97% for arsenic and 91% -99% for lead) is better than that of the mixed hydroxide before calcination (46% -61% for arsenic and 75% -80% for lead). With the increase of the content of magnesium oxide, the passivation effect of arsenic is slightly reduced, and the passivation effect of lead is greatly improved.

The adsorption effect of the mixed hydroxides a, b, c, d and e formed in the range of the pH value of the coprecipitation is 10-12 and is better than that of the mixed hydroxides f and g which are not formed in the range and are determined. On the other hand, on the one hand, the adsorption effect of the adsorption material prepared by simply mixing magnesium oxide, calcium oxide and aluminum oxide as the adsorption material on arsenic and lead is far lower than that of the adsorption material prepared in examples 1-5, and the structure and composition of the adsorption material prepared by the invention are different from those of the mixture of oxides. On the other hand, the adsorption effect of the magnesium oxide and the blast furnace slag as the adsorption materials or the mixture of the magnesium oxide and the blast furnace slag as the adsorption materials on arsenic and lead is far lower than that of the adsorption materials prepared in the embodiments 1 to 5.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The preparation method of the heavy metal adsorption material is characterized by comprising the following steps:

2. The method for preparing a heavy metal adsorbing material according to claim 1, wherein the content of the magnesium oxide is 20-50 wt%.

3. The method for preparing a heavy metal adsorption material according to claim 1, wherein the mixed oxide material is selected from one or more of blast furnace slag, steel slag, red mud, silica fume and industrial magnesium oxide.

4. The method for producing a heavy metal-adsorbing material according to claim 3, wherein the mixed oxide material is blast furnace slag comprising 45 to 50 wt% of calcium oxide, 10 to 15 wt% of aluminum oxide, and 6 to 7 wt% of magnesium oxide.

5. The method for producing a heavy metal-adsorbing material according to claim 3, wherein the mixed oxide material is a mixture of blast furnace slag and industrial magnesium oxide, and the mass ratio of the blast furnace slag to the industrial magnesium oxide is 1: (0.25-1), wherein the blast furnace slag comprises 45-50 wt% of calcium oxide, 10-15 wt% of aluminum oxide and 6-7 wt% of magnesium oxide, and the industrial magnesium oxide contains more than 85 wt% of magnesium oxide, less than 5 wt% of calcium oxide and less than 1.5 wt% of aluminum oxide.

6. A preparation method of the heavy metal adsorbing material as claimed in claim 3 to 5, wherein the acidic solution is a hydrochloric acid solution or a nitric acid solution, the concentration of the acidic solution is 1mol/L to 5mol/L, and the solid-to-liquid ratio of the mixed oxide material to the acidic solution is 1: (10-20) g/mL.

7. A preparation method of the heavy metal adsorbing material according to claim 3-5, wherein in the step of adding the mixed oxide material into the acidic solution for sufficient reaction, the reaction temperature is 60-80 ℃, and the reaction time is 3-5 h.

8. A preparation method of the heavy metal adsorbing material according to claim 3-5, wherein the reaction condition of the coprecipitation step is 60-80 ℃ standing for 8 hours or more, or 20-30 ℃ standing for 24 hours or more.

9. The method for producing a heavy metal adsorbing material according to claim 1, further comprising calcining the mixed hydroxide.

10. The method for preparing a heavy metal adsorption material according to claim 9, wherein in the step of calcining the mixed hydroxide, the calcining temperature is 450 to 500 ℃ and the calcining time is 1 to 3 hours.

11. The heavy metal adsorbing material prepared by the preparation method of the heavy metal adsorbing material according to any one of claims 1 to 10.

12. The application of the heavy metal adsorbing material according to claim 11 in remediation of heavy metal polluted water bodies or soil.

13. Use according to claim 12, wherein the heavy metals comprise arsenic and lead.