CN110327874B - Core-shell structure composite iron-cerium oxide dearsenic adsorbent and preparation method and application thereof - Google Patents

Abstract

The invention discloses a core-shell structure composite iron-cerium oxide dearsenic adsorbent. The magnetic nano-Fe ₃ O ₄ is used as the core, and the surface of the magnetic nano-Fe ₃ O ₄ is covered with a composite iron-cerium oxide layer; The molar ratio of iron element and cerium element in the oxide layer is 1:(0.04-0.12). The preparation method of the arsenic removal adsorbent of the present invention: adding magnetic nano-Fe ₃ O ₄ , m-phenylenediamine and formaldehyde into the solution, performing in-situ polymerization reaction to obtain sample A; carbonizing sample A at high temperature to obtain sample B ; The mixed solution of ferric nitrate and cerium nitrate is loaded on the sample B by the impregnation method to obtain the sample C; the sample C is subjected to oxidative roasting to obtain the dearsenic adsorbent. The core-shell structure composite iron-cerium oxide dearsenic adsorbent of the invention can directly capture gaseous arsenic in a large temperature range, and the adsorption efficiency of arsenic can reach more than 80%, and the stability of arsenic after adsorption is relatively high. High, reducing the secondary pollution of arsenic.

Description

A core-shell structure composite iron-cerium oxide dearsenic adsorbent and its preparation method and application

technical field

The invention belongs to the field of adsorbents, and in particular relates to an adsorbent suitable for treating arsenic-containing flue gas generated in the non-ferrous metal smelting pyro-smelting process.

Background technique

Because arsenic is highly toxic, how to achieve efficient control of arsenic pollution has become an urgent problem to be solved. my country's "National Arsenic Pollution Prevention and Control Technology Policy", "Twelfth Five-Year Plan for Comprehensive Prevention and Control of Heavy Metal Pollution", "Comprehensive Plan for Heavy Metal Pollution Prevention and Control (2011-2015)", "Thirteenth Five-Year Plan for Ecological Environmental Protection", etc. A series of documents have clearly listed arsenic as the main prevention and control object, and the prevention and control of arsenic pollution has become the focus of attention at home and abroad and a major livelihood issue in my country. In the smelting process of metal minerals, most of the arsenic in the ore is oxidized and volatilized into the flue gas in the form of arsenic trioxide, thereby forming arsenic-containing flue gas.

At present, arsenic in smelting flue gas is mainly removed in the process of dust removal and wet scrubbing. Arsenic is transferred from flue gas to soot and polluted acid, and there is still a risk of arsenic pollution. Therefore, the direct capture of gaseous arsenic from flue gas And selective separation has become the main research direction to control arsenic pollution. Chinese Patent No. 201711220671.9 discloses a preparation method of a flue gas dearsenic adsorbent. The adsorbent is prepared by uniformly mixing calcium oxide, metallurgical slag, zeolite and fly ash, granulating, heating, etc.; Chinese Patent No. 201810285567.6 discloses an arsenic An adsorbent and its preparation method and application, which are impregnated with an alumina carrier with iron element and calcined at high temperature to prepare a gaseous arsenic adsorbent. Although the above-mentioned adsorbents can realize the adsorption of gaseous arsenic, the adsorbents after adsorbing arsenic are still mixed with soot or polluted acid, which is difficult to controllable separation, and faces the problem of secondary arsenic pollution. In addition, the adsorption capacity and adsorption rate of gaseous arsenic for traditional adsorption materials are not high, which is difficult to meet the actual industrial demand. Therefore, there is an urgent need to develop stable, efficient and easy-to-recycle adsorbents.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and to provide a preparation method of a recyclable high-efficiency dearsenic adsorbent and an application method for the adsorbent to capture gaseous arsenic, which is suitable for high-temperature and high-sulfur smelting smoke Efficient capture and separation of gaseous arsenic in gas.

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A core-shell structure composite iron-cerium oxide dearsenic adsorbent, which uses magnetic nanometer Fe ₃ O ₄ as a core, and a composite iron-cerium oxide layer is coated on the surface of the magnetic nano-Fe ₃ O ₄ ; The molar ratio of the element and the cerium element is 1:(0.04-0.12).

The present invention also provides a method for preparing the above-mentioned dearsenic adsorbent, comprising the following steps:

(1) adding magnetic nanometer Fe ₃ O ₄ , m-phenylenediamine and formaldehyde into the solution, ultrasonically mixing uniformly, and performing in-situ polymerization under mechanical stirring to obtain sample A;

(2) carbonizing sample A at high temperature to obtain sample B wrapped with porous carbon material;

(3) the mixed solution of ferric nitrate and cerium nitrate is loaded on the sample B by the dipping method, and dried to obtain the sample C loaded with ferric cerium;

(4) The sample C is oxidatively roasted in an oxidizing atmosphere to obtain the arsenic removal adsorbent.

In the above preparation method, preferably, in the step (1), the particle size of the magnetic nano Fe ₃ O ₄ is 50-200 nm.

In the above preparation method, preferably, in the step (1), the molar ratio of m-phenylenediamine and formaldehyde is 1:(1.5～3), the pH of the mixed solution is 8～9, and the in-situ polymerization reaction time is 18～ 30h.

In the above-mentioned preparation method, preferably, in the step (2), the calcination temperature of the high-temperature carbonization is 600-700 ° C, and the holding time is 1.5-3 hours; the high-temperature carbonization is carried out under the protection of nitrogen, and the nitrogen flow rate is 0.5-1L /min.

In the above preparation method, preferably, in the step (3), the molar ratio of iron ions to cerium ions is 1:(0.04～0.12), and the volume ratio of the mixed solution of ferric nitrate and cerium nitrate to sample B is 1:(1 ～1.5), the immersion temperature is 25～50℃, and the immersion time is 30～60min.

In the above preparation method, preferably, in the step (4), the temperature of oxidative roasting is 600-800° C., the roasting time is 20-40 min, and the oxygen concentration is 20-40%.

As a general inventive concept, the present invention also provides the application of the above-mentioned dearsenic adsorbent or prepared by the above preparation method in high-temperature and high-sulfur flue gas. The arsenic is sprayed into the flue gas, the adsorbent after adsorbing arsenic and the flue gas enter the flue gas together in the dust removal system to obtain the arsenic-containing mixed flue gas, and then the composite magnetic adsorbent is recovered from the arsenic-containing mixed flue gas through magnetic separation.

In the above application, preferably, the temperature of the flue gas is 400-1200° C. when the arsenic-removing adsorbent performs the de-arsenic removal, and the concentration of sulfur dioxide in the flue gas is not higher than 10%.

The core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention uses magnetic Fe ₃ O ₄ particles as the core, forms a layer of resin wrapped on the surface of the Fe ₃ O ₄ particles through surface in-situ polymerization, and forms a surface after high temperature carbonization The loose and porous carbon shell forms various functional groups such as amino groups and carboxyl groups during the high-temperature carbonization process, which has a certain adsorption capacity for metal ions, ensuring the effective loading of iron and cerium through the impregnation method. Finally, the porous carbon layer is oxidized and decomposed by oxidative roasting. And the adsorbed iron-cerium is converted into a porous and highly active x(CeO ₂ )·y(Fe ₂ O ₃ ) (where x/y is (0.08～0.24):1) composite oxide, that is, the final product is Fe ₃ O ₄ is the composite adsorption material with the inner core and the porous x(CeO ₂ )·y(Fe ₂ O ₃ ) composite oxide as the outer shell. The gaseous As ₂ O ₃ in the flue gas can be efficiently oxidized to As ₂ O ₅ by CeO ₂ . Forms stable ferric arsenate with _Fe2O3 , enabling efficient capture _of gaseous arsenic. The small size of the composite adsorbent and the physical characteristics of rich pores ensure the adsorption rate of arsenic, the high-activity iron-cerium composite oxide ensures the efficient capture of arsenic, and the magnetic core of the composite adsorbent ensures the recyclability of the adsorbent.

Compared with the prior art, the advantages of the present invention are:

(1) The core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention can realize the direct capture of gaseous arsenic in a relatively large temperature range, and the adsorption efficiency of arsenic can reach more than 80%, and the adsorption of arsenic can reach more than 80%. High stability, reducing the secondary pollution of arsenic.

(2) The core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention can be widely used in the fields of smelting and coal-fired flue gas dearsenic removal, and has a wide range of applications. Existing treatment processes need to be changed.

(3) The core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention can be recycled after desorption, thereby reducing the cost of dearsenic.

(4) The present invention has the advantages of simple preparation process, high adsorption efficiency, and environmental friendliness.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

Example 1:

The preparation method of the core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention comprises the following steps:

(1) Take 30 mg of Fe ₃ O ₄ particles with a particle size of 100 nm, place it in a solution containing 0.02 mol of m-phenylenediamine and 0.04 mol of formaldehyde, use ammonia water to mix the solution to pH 8.5, and in continuous mechanical stirring The reaction was carried out for 24 hours, dried in a vacuum drying oven, placed in a tube furnace, and carbonized at 650 °C for 3 hours under a nitrogen protective atmosphere to obtain Fe ₃ O ₄ @C adsorbent wrapped in porous carbon.

(2) 20 mL of mixed solutions with different molar ratios of iron and cerium were prepared, mixed with the prepared Fe ₃ O ₄ @C, immersed in Fe ₃ O ₄ @C with iron and cerium ions, dried to remove moisture, and finally obtained Composite adsorbents with different iron and cerium impregnation amounts;

(3) The composite adsorbent material was placed in a tube furnace, and a gas with an oxygen content of 30% was introduced, heated to 650°C at a heating rate of 10°C/min, and then the holding time was 30min, and finally different iron-cerium ratios were obtained. The core-shell structured Fe ₃ O ₄ @x(CeO ₂ )·y(Fe ₂ O ₃ ) adsorbent.

Take 20 mg of Fe ₃ O ₄ @x(CeO ₂ )·y(Fe ₂ O ₃ ) adsorbents with different iron-cerium ratios respectively, and inject the adsorbent and simulated arsenic-containing flue gas into the quartz tube in the muffle furnace , install a filter cloth at the end of the quartz tube to collect the adsorbent. The conditions during the experiment are: the arsenic content in the simulated flue gas is 0.2mg, the flue gas flow rate is 0.1L/min, the flue gas temperature is 600°C, and the gas in the flue gas becomes 20%O ₂ +5%SO ₂ +55%N _2. The arsenic capture efficiencies of the synthesized different adsorbents are shown in Table 1.

Table 1 Comparison of arsenic adsorption efficiency of composite adsorbents with different iron-cerium ratios

Table 1 shows the comparison of the arsenic capture efficiency of the composite adsorbents with different iron-cerium ratios. It can be seen from the table that when the content of cerium in the adsorbent is low (the ratio of iron to cerium is 1:0.02), the capture efficiency of arsenic is only 30.6%. Improve the capture efficiency of arsenic. When the iron-cerium ratio is 1:0.16, the arsenic capture efficiency decreases, which indicates that the appropriate iron-cerium ratio plays a key role in the capture efficiency of the composite adsorbent for arsenic.

Example 2:

The preparation method of the core-shell structure composite iron-cerium oxide dearsenic adsorbent of the present invention comprises the following steps:

(1) Take 30 mg of Fe ₃ O ₄ particles with a particle size of 100 nm, place it in a solution containing 0.02 mol of m-phenylenediamine and 0.04 mol of formaldehyde, use ammonia water to mix the solution to pH 8.5, and in continuous mechanical stirring The reaction was carried out for 24 hours, dried in a vacuum drying oven, placed in a tube furnace, and carbonized at 650 °C for 3 hours under a nitrogen protective atmosphere to obtain Fe ₃ O ₄ @C adsorbent wrapped in porous carbon;

(2) Prepare 20 mL of a mixed solution with a molar ratio of iron-cerium 1:0.06, mix it with the prepared Fe ₃ O ₄ @C, impregnate iron-cerium ions on Fe ₃ O ₄ @C, and dry it to remove moisture , to obtain a composite material;

(3) The composite material was placed in a tube furnace, and a gas with an oxygen content of 30% was introduced, heated to 650°C at a heating rate of 10°C/min, and then the holding time was 30min, and finally Fe ₃ with a core-shell structure was obtained. O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ) adsorbent. Take 20mg Fe ₃ O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ) adsorbent.

Take 20 mg of Fe ₃ O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ) prepared in this example, and spray the adsorbent and simulated arsenic-containing flue gas into the quartz tube in the muffle furnace. A filter cloth is installed at the end to collect the adsorbent. The conditions during the experiment were: the arsenic content in the simulated flue gas was 0.2 mg, the flue gas flow rate was 0.1 L/min, and the flue gas temperature was 600 °C. By changing the flue gas composition and reaction temperature, Fe ₃ O ₄ @ under different conditions was investigated. The capture efficiency of 0.12(CeO ₂ )·(Fe ₂ O ₃ ) for arsenic is shown in Table 2.

Table 2 Comparison of arsenic adsorption efficiency under different process conditions

Table 2 shows the comparison of arsenic capture performance under different atmospheres and capture temperatures. It can be seen from the table that the presence of oxygen and sulfur dioxide in the flue gas both promote the capture of arsenic, while the actual smelting flue gas contains both oxygen and arsenic. Therefore, the core-shell structure Fe ₃ O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ) composite adsorbent is very suitable for capturing arsenic in smelting flue gas. The capture temperature is also an important parameter in practical applications. The lower and higher flue gas temperatures are not conducive to the capture of arsenic. The optimal arsenic capture temperature is 600-800 °C, and the capture efficiency of arsenic is above 80%. However, the capture efficiency of arsenic remains above 60% when the reaction temperature is between 400 and 1200°C, that is, it still has practical application value.

Take 40 mg of prepared Fe ₃ O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ), and inject the adsorbent and simulated arsenic-containing flue gas into the quartz tube placed in the muffle furnace. A filter cloth is installed at the end of the tube to collect the adsorbent. The experimental conditions were as follows: the arsenic content in the simulated flue gas was 0.2 mg, the flue gas flow rate was 0.1 L/min, the flue gas temperature was 600 °C, the sulfur dioxide concentration was 5%, and the oxygen concentration was 20%. After this adsorption experiment, the adsorbent was regenerated by alkali desorption and desorption of arsenic and thermal activation, and the capture efficiency of the adsorbent for gas phase arsenic was measured under the same conditions. This cycle was repeated 5 times. The specific results are shown in Table 3. . It can be seen from Table 3 that although the capture efficiency of the composite adsorbent for arsenic decreases with the increase of the number of cycles, after 5 cycles, the adsorption efficiency of the adsorbent for arsenic can still be maintained at 64.23%. It also shows that the core-shell structure composite iron-cerium oxide adsorbent prepared by the present invention has excellent recycling performance.

Table 3 Cycling performance of magnetic composite Fe ₃ O ₄ @0.12(CeO ₂ )·(Fe ₂ O ₃ ) adsorbent

Claims (9)

1. The core-shell structure composite iron-cerium oxide dearsenic adsorbent applied to high-temperature high-sulfur flue gas is characterized in that the dearsenic adsorbent is magnetic nano Fe₃O₄As core, in the magnetic nano Fe₃O₄Surface coating with compoundA layer of iron cerium oxide; the molar ratio of the iron element to the cerium element in the iron-cerium oxide layer is 1 (0.08-0.12).

2. A method of preparing the de-arsenic adsorbent of claim 1, comprising the steps of:

(1) magnetic nano Fe₃O₄Adding m-phenylenediamine and formaldehyde into the solution, uniformly mixing by ultrasonic, and carrying out in-situ polymerization reaction under mechanical stirring to obtain a sample A;

(2) carbonizing the sample A at high temperature to obtain a sample B wrapped by a porous carbon material;

(3) loading the mixed solution of ferric nitrate and cerium nitrate on the sample B by an impregnation method, and drying to obtain a sample C loaded with iron and cerium;

(4) and oxidizing and roasting the sample C in an oxidizing atmosphere to obtain the dearsenic adsorbent.

3. The method according to claim 2, wherein in the step (1), the magnetic nano Fe₃O₄Has a particle diameter of 50 to 200 nm.

4. The method according to claim 2, wherein in the step (1), the molar ratio of m-phenylenediamine to formaldehyde is 1: (1.5-3), the pH value of the mixed solution is 8-9, and the in-situ polymerization reaction time is 18-30 h.

5. The preparation method according to claim 2, wherein in the step (2), the roasting temperature of the high-temperature carbonization is 600-700 ℃, and the holding time is 1.5-3 hours; the high-temperature carbonization is carried out under the protection of nitrogen, and the flow rate of the nitrogen is 0.5-1L/min.

6. The preparation method according to claim 2, wherein in the step (3), the molar ratio of the iron ions to the cerium ions is 1 (0.08-0.12), and the volume ratio of the mixed solution of the ferric nitrate and the cerium nitrate to the sample B is 1: (1-1.5); the dipping temperature in the dipping process is 25-50 ℃, and the dipping time is 30-60 min.

7. The preparation method according to claim 2, wherein in the step (4), the oxidizing roasting temperature is 600-800 ℃, the roasting time is 20-40 min, and the oxygen concentration is 20-40%.

8. The application of the arsenic-removing adsorbent according to claim 1 or the arsenic-removing adsorbent prepared by the preparation method according to any one of claims 2 to 7 in high-temperature and high-sulfur flue gas is characterized in that the arsenic-removing adsorbent is directly and uniformly sprayed into the flue gas at the front end of a flue gas dust collection process, the adsorbent adsorbing arsenic and the flue gas enter the flue gas in a dust removal system together to obtain arsenic-containing mixed flue gas, and then the composite magnetic adsorbent is recovered from the arsenic-containing mixed flue gas through magnetic separation.

9. The application of claim 8, wherein the temperature range of the flue gas when the arsenic removal adsorbent is used for removing arsenic is 400-1200 ℃, and the concentration of sulfur dioxide in the flue gas is not higher than 10%.