CN108435130A - A kind of synthetic method of pentavalent arsenic (As (V)) adsorbent X-type zeolite - Google Patents

Abstract

The invention belongs to the field of adsorbent material preparation, and discloses a method for synthesizing pentavalent arsenic (As(V)) adsorbent X-type zeolite, which comprises mixing fly ash with low aluminum content and sodium hydroxide particles, grinding them evenly, and calcining; Take out the mixture and cool it down to room temperature naturally, grind it and place it in the liner of a polytetrafluoroethylene reactor, add deionized water and sodium aluminate, stir, and mix thoroughly; after the suspension is left to stand, put the liner in Carry out hydrothermal reaction in an electric thermostat box; take out the reaction kettle and cool it down to room temperature naturally, then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain pentavalent arsenic (As(V)) adsorbent X type Zeolite. The present invention has low cost; in the present invention, the raw material used is low-alumina fly ash, which is a by-product produced after coal combustion and contains a large amount of silicon-alumina; synthesizing fly ash into zeolite solves the problem that it produces Pollution problems turn waste into treasure.

Description

A kind of synthetic method of pentavalent arsenic (As(V)) adsorbent X-type zeolite

technical field

The invention belongs to the field of adsorbent material preparation, in particular to a method for synthesizing pentavalent arsenic (As(V)) adsorbent X-type zeolite.

Background technique

At present, the existing technologies commonly used in the industry are as follows:

Arsenic (As) is one of the most toxic elements. It can enter water bodies through natural effects and some human activities. This will seriously threaten the water environment on which humans and animals depend. At present, arsenic poisoning incidents have occurred in Australia, Canada, the United States, Japan, Argentina and other countries, and my country has also become a country with serious arsenic pollution in recent years. Once arsenic pollution is formed, it will enter the human body or other organisms through the food chain or groundwater and surface water, seriously endangering human health and the entire ecological environment. Therefore, how to effectively remove As has become an urgent problem.

At present, there are many methods for treating As-containing wastewater at home and abroad, and the commonly used methods include chemical precipitation, ion exchange, membrane separation, biological method and adsorption method. Among many methods, the adsorption method has the characteristics of low cost, high efficiency, simple and easy operation, and little or no secondary pollution. The key point of the adsorption method is the adsorbent. At present, commonly used adsorbents include biological adsorbents, metal adsorbents, and mineral adsorbents. Disadvantages such as low adsorption capacity or high cost limit the popularization and use of the above-mentioned adsorbents to a large extent. Therefore, the development of cheap and efficient As adsorbents is particularly important.

Fly ash is the main waste product of coal combustion, that is, the dust brought out from the flue gas duct and collected by the dust collector after the pulverized coal is burned at 1100-1700 °C. At present, the annual output of fly ash in my country is huge and increasing year by year. In 1995, the discharge of fly ash was 125 million tons, in 2000 it was 150 million tons, and in 2009 it was 375 million tons. However, its utilization is mainly in the cement and concrete industries, and the utilization rate accounts for 50% of the total emissions, and the remaining 50% is stockpiled for disposal. The National Development and Reform Commission in 2013 revised the "Management Measures for the Comprehensive Utilization of Fly Ash" to encourage the high value-added utilization of fly ash. Therefore, how to utilize the accumulated fly ash with high added value has become an urgent problem to be solved.

At present, the methods for synthesizing zeolite from fly ash include hydrothermal synthesis, alkali fusion and salt heat. Each method offers improvements over the others in terms of increased fly ash conversion, increased zeolite purity, or reduced synthesis time. However, their synthetic objects are all high-aluminum fly ash, the conversion rate of fly ash and the yield of zeolite are still low, the ion exchange capacity of the obtained zeolite is poor, the synthesis period is long, and some aluminum that is beneficial to the adsorption of arsenic will be released with The filtrate flows out.

In summary, the problems in the prior art are:

(1) In the synthesis technology of cheap and high As(V) adsorption adsorbents, we need to find new cheap raw materials to obtain adsorbents with strong exchange capacity.

(2) The effective activation degree of silica-alumina components in fly ash determines the conversion rate of fly ash, the yield of zeolite and the synthesis cost of zeolite, but the existing X zeolite synthesis method requires a long activation time.

(3) The composition of fly ash is affected by many factors, but at this stage, the technology of using fly ash to synthesize zeolite with high added value is mainly carried out for high-alumina fly ash, and the use of low-aluminum content fly ash There is still a lack of guiding basis for the synthesis of X zeolite with strong ion exchange capacity.

The significance of solving the above technical problems:

Based on considerations of cost, adsorption effect, waste reuse and the like, the present invention uses fly ash as a raw material to prepare an X-type zeolite adsorbent for As(V) adsorption. In the process of synthesizing zeolite, the silicon-aluminum ratio of the system has a great influence on the type of zeolite. Therefore, it is very important to rationally control the ratio of silicon to aluminum. The X zeolite has good adsorption capacity and has a strong application potential for the treatment of heavy (like) metal wastewater.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides a method for synthesizing a pentavalent arsenic (As(V)) adsorbent X-type zeolite.

The present invention is achieved in that a kind of synthetic method of pentavalent arsenic (As(V)) adsorbent X-type zeolite comprises the following steps:

(1) Mix low-aluminum fly ash and sodium hydroxide particles in a mass ratio of 1:0.9 to 1:1.5, grind them evenly, and calcinate;

(2) Take out the mixture and cool it down to room temperature naturally, grind it and place it in the liner of a polytetrafluoroethylene reactor, add 80-90mL of deionized water and 0.019-0.076mol of sodium aluminate, stir for 30-40min, mix well;

(3) After the suspension is left to stand for 20-30 hours, the liner is placed in an electric thermostat for 3-9 hours of hydrothermal reaction; the heating temperature is 75-120°C;

(4) Take out the reaction kettle and cool it down to room temperature naturally, filter to obtain a solid product, rinse the solid product with deionized water, and dry to obtain pentavalent arsenic (As(V)) adsorbent X-type zeolite.

Further, in the step (1), the mass ratio of fly ash to sodium hydroxide particles is 1:1.2; calcining at 550° C. for 1 h.

Further, in the step (2), the volume of deionized water is 85 mL; the dosage of sodium aluminate is 0.038 mol; the stirring time is 35 min.

Further, the standing time in the step (3) is 24h;

The temperature of the hydrothermal reaction in the step (3) is 90°C;

The time of the hydrothermal reaction in the step (3) is 6h.

Another object of the present invention is to provide a pentavalent arsenic (As(V)) adsorbent X-type zeolite.

Another object of the present invention is to provide a kind of pentavalent arsenic (As(V)) adsorbent X-type zeolite adsorption method utilizing said synthetic method, comprising:

Adsorption temperature 25°C;

Adsorption pressure is normal pressure;

The concentration of As(V) is 2.50～43.42mg/L;

The dosage of adsorbent type X zeolite is 0.1g;

The volume of the aqueous solution containing As(V) was 50 mL.

In summary, the advantages and positive effects of the present invention are:

The adsorbent X-type zeolite synthesized in the present invention has a large amount of adsorption active sites on the surface of the zeolite after the Al source is supplemented in the preparation process, which has the following advantages:

(1) Low cost. In the present invention, the raw material used is fly ash, which is a by-product of coal combustion and contains a large amount of silicon and aluminum. Synthesizing fly ash into zeolite not only solves the pollution problem it produces, but also turns waste into treasure;

(2) High value-added utilization of low-aluminum fly ash aluminum. In the present invention, the aluminum content of the used fly ash is about 15.42%, which is not high, and the X-type zeolite is successfully synthesized by adding an external aluminum source.

(3) Low energy consumption. In the present invention, X-type zeolite can be synthesized at low temperature (90° C.) within a short time (6 hours), and only 1 hour is needed for early high-temperature activation, which can reduce power consumption.

(4) Zeolite has high purity. The purity of the zeolite synthesized in the present invention is relatively high, and a large amount of X-type zeolite can be obtained;

(5) Good adsorption effect. Compared with the adsorption effect of fly ash on As(V) (the adsorption efficiency is about 60%), the adsorption effect of the zeolite synthesized by the present invention on As(V) can be increased by more than 20 percentage points on this basis;

The preparation method of the adsorbent X-type zeolite provided by the invention only involves a conventional hydrothermal method, the preparation process is simple, and the prepared adsorbent has good adsorption effect. The efficient adsorption of As(V) at normal temperature and pressure has been realized.

The adsorbent prepared by the invention has great industrial applicability for adsorbing As(V).

Description of drawings

Fig. 1 is a flowchart of a synthetic method of type X zeolite as a pentavalent arsenic (As(V)) adsorbent provided in an example of the present invention.

Fig. 2 is an XRD diagram showing the X-type zeolite product of Example 1 provided by the examples of the present invention.

Fig. 3 is an XRD diagram showing the X-type zeolite product of Example 2 provided by the examples of the present invention.

In Fig. 3: (a) aluminum chloride; (b) aluminum fluoride; (c) aluminum nitrate.

Fig. 4 is an XRD diagram showing the X-type zeolite product of Example 3 provided by the examples of the present invention.

Fig. 5 is an XRD diagram showing the X-type zeolite product of Example 4 provided by the examples of the present invention.

Fig. 6 is an XRD diagram showing the X-type zeolite product of Example 5 provided by the examples of the present invention.

Fig. 7 is an XRD diagram showing the X-type zeolite product of Example 6 provided by the examples of the present invention.

Fig. 8 is an XRD pattern showing the X-type zeolite product of Example 7 provided by the examples of the present invention.

Fig. 9 is an XRD pattern showing the X-type zeolite product of Example 8 provided by the examples of the present invention.

Fig. 10 is an XRD pattern showing the X-type zeolite product of Example 9 provided by the examples of the present invention.

Fig. 11 is an XRD pattern showing the X-type zeolite product of Example 10 provided by the examples of the present invention.

FIG. 12 is a graph showing the adsorption effect of the X-type zeolite prepared in Example 1 and the raw material fly ash on As(V) provided by the example of the present invention.

In the figure: (a) X-type zeolite; (b) FA.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The adsorbent X-type zeolite synthesized in the present invention has a large number of adsorption active sites on the surface of the zeolite after the Al source is supplemented during the preparation process, and has the advantages of low cost. In the present invention, the raw material used is fly ash, which is a by-product of coal combustion and contains a large amount of silicon and aluminum. Synthesizing fly ash into zeolite not only solves the pollution problem it produces, but also turns waste into treasure; the aluminum content of fly ash is low. In the present invention, the aluminum content of the used fly ash is about 15.42%, which is not high, and the X-type zeolite is successfully synthesized by adding an external aluminum source.

The aluminum content and silicon content of the fly ash used in the present invention are respectively: 15.42% and 57.09%.

As shown in Figure 1, the synthetic method of pentavalent arsenic (As(V)) adsorbent X-type zeolite provided by the embodiment of the present invention comprises the following steps:

S101: Mix low-aluminum fly ash and sodium hydroxide particles at a mass ratio of 1:0.9 to 1:1.5, grind them evenly, and calcinate;

S102: Take out the mixture and cool it down to room temperature naturally, grind it and place it in the liner of a polytetrafluoroethylene reactor, add 80-90mL of deionized water and 0.019-0.076mol of sodium aluminate, stir for 30-40min, fully mix;

S103: After the suspension is left to stand for 20-30 hours, the liner is placed in an electric thermostat for hydrothermal reaction for 3-9 hours; the heating temperature is 75-120°C;

S104: Take out the reaction kettle and cool it down to room temperature naturally, filter to obtain a solid product, rinse the solid product with deionized water, and dry to obtain X-type zeolite as a pentavalent arsenic (As(V)) adsorbent.

In the step S101, the mass ratio of fly ash to sodium hydroxide particles is 1:1.2; calcining at 550° C. for 1 h.

In the step S102, the volume of deionized water is 85 mL; the dosage of sodium aluminate is 0.038 mol; the stirring time is 35 min.

The standing time in the step S103 is 24h;

The temperature of the hydrothermal reaction in step S103 is 90°C;

The hydrothermal reaction time in the step S103 is 6 hours.

The embodiment of the present invention provides a pentavalent arsenic (As(V)) adsorbent X-type zeolite adsorption method using the synthesis method, including:

Adsorption temperature 25°C;

Adsorption pressure is normal pressure;

The concentration of As(V) is 2.50～43.42mg/L;

The dosage of adsorbent type X zeolite is 0.1g;

The volume of the aqueous solution containing As(V) was 50 mL.

The present invention will be further described below in conjunction with specific embodiments.

Example 1

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The powder X-ray diffraction (XRD) of the product is shown in Figure 2. The XRD pattern shows that the obtained product coincides with the characteristic peaks of X-type zeolite. This shows that the synthetic method in the present invention successfully produced X-type zeolite.

Example 2

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in the liner of a polytetrafluoroethylene reactor, 85mL of deionized water and 0.038mol of aluminum chloride or aluminum fluoride or aluminum nitrate were added, and stirred for 35 minutes to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90° C. for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 3. The results show that the aluminum ions in aluminum nitrate and aluminum chloride will consume OH ^— in the suspension to form Al(OH) ₃ , which will affect the dissolution of silica-alumina in fly ash and be unfavorable to the formation of zeolite. However, aluminum fluoride is insoluble in water, and it is meaningless to change the silicon-aluminum ratio in the suspension, so it is also not conducive to the formation of zeolite.

Example 3

10g of fly ash and 15g of sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 4. The results show that excessive sodium hydroxide will redissolve or recrystallize the X-type zeolite, and will further reduce the silicon-aluminum ratio, which is conducive to the formation of the A-type zeolite.

Example 4

10g of fly ash and 9g of sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 5. The results show that the insufficient amount of alkali has a certain influence on the dissolution of silicon and aluminum in fly ash, which will affect the formation of X-type zeolite precursor, which is unfavorable for the crystallization of X-type zeolite.

Example 5

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.076 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 6. The results show that the addition of too much aluminum source will reduce the ratio of silicon to aluminum in the suspension, which is beneficial to the formation of type A zeolite.

Example 6

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.019 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 7. The results show that when the addition of aluminum source is small, the ratio of silicon to aluminum in the suspension is still high, which has a certain influence on the formation of X-type zeolite.

Example 7

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 75°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 8. The results showed that the temperature was too low, which affected the crystallization of zeolite.

Example 8

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 120°C for 6 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 9. The results show that the crystallization temperature continues to rise, which will make the X-type zeolite in the metastable phase transform into the more stable phase of hydroxysodalite.

Example 9

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90° C. for 9 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 10. The results show that the XRD peak intensity of X-type zeolite weakens, because the crystallization time increases, the Si content in the suspension remains unchanged, and the Al increases, so that the silicon-aluminum ratio decreases, resulting in a decrease in the purity of X-type zeolite.

Example 10

10g fly ash and 12g sodium hydroxide particles were mixed and ground uniformly, and calcined at 550°C for 1h. After the mixture was cooled to room temperature, it was ground and placed in a polytetrafluoroethylene reactor liner, 85 mL of deionized water and 0.038 mol of sodium aluminate were added, and stirred for 35 min to make it fully mixed. After the suspension was allowed to stand for 24 hours, a hydrothermal reaction was carried out at 90° C. for 3 hours. Then filter to obtain a solid product, wash the solid product with deionized water, and dry it to obtain the X-type zeolite. The XRD of the product is shown in Figure 11. The results show that the prolonged crystallization time has a certain influence on the growth and nucleation of zeolite crystals.

Comparative example one

The X-type zeolite obtained in Example 1 and the raw material fly ash were used to treat the As(V)-containing aqueous solution. The conditions are: the pH of the aqueous solution containing As(V) is 2.14; the concentration of As(V) is 22.83mg/L; the addition amount of X-type zeolite and raw material fly ash is 0.1g; the sampling time is 15, 30, 60 , 90, 120, 180, 240, 360, 480, 720min. The results are shown in Figure 12.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. a synthetic method of pentavalent arsenic (As (V)) adsorbent X-type zeolite, is characterized in that, the synthetic method of described pentavalent arsenic (As (V)) adsorbent X-type zeolite comprises the following steps: (1) Mix low-aluminum fly ash and sodium hydroxide particles in a mass ratio of 1:0.9 to 1:1.5, grind them evenly, and calcinate; (2) Take out the mixture and cool it down to room temperature naturally, grind it and place it in the liner of a polytetrafluoroethylene reactor, add 80-90mL of deionized water and 0.019-0.076mol of sodium aluminate, stir for 30-40min, mix well; (3) After the suspension is left to stand for 20-30 hours, the liner is placed in an electric thermostat for 3-9 hours of hydrothermal reaction; the heating temperature is 75-120°C; (4) Take out the reaction kettle and cool it down to room temperature naturally, filter to obtain a solid product, rinse the solid product with deionized water, and dry to obtain pentavalent arsenic (As(V)) adsorbent X-type zeolite. 2. the synthetic method of pentavalent arsenic (As (V)) adsorbent X type zeolite as claimed in claim 1, is characterized in that, in described step (1), fly ash and sodium hydroxide particle mass ratio are 1 : 1.2; calcined at 550°C for 1h. 3. the synthetic method of pentavalent arsenic (As (V)) adsorbent X type zeolite as claimed in claim 1, is characterized in that, in described step (2), deionized water volume is 85mL; Sodium aluminate consumption is 0.038mol; stirring time is 35min. 4. the synthetic method of pentavalent arsenic (As (V)) adsorbent X type zeolite as claimed in claim 1, is characterized in that, in described step (3), standing time is 24h; The temperature of the hydrothermal reaction in the step (3) is 90°C; The time of the hydrothermal reaction in the step (3) is 6h. 5. a pentavalent arsenic (As(V)) adsorbent X-type zeolite synthesized by the synthetic method of the pentavalent arsenic (As(V)) adsorbent X-type zeolite as claimed in claim 1. 6. A method for absorbing pentavalent arsenic (As (V)) sorbent X-type zeolite utilizing the synthetic method described in claim 1, wherein said pentavalent arsenic (As (V)) sorbent X-type zeolite Adsorption methods include: Adsorption temperature 25°C; Adsorption pressure is normal pressure; The concentration of As(V) is 2.50～43.42mg/L; The dosage of adsorbent type X zeolite is 0.1g; The volume of the aqueous solution containing As(V) was 50 mL.