CN113617330B - Low-cost and fast Pb adsorption device 2+ Preparation method of Na-SUZ-4 molecular sieve - Google Patents

Abstract

The object of the present invention is to provide a method for preparing Na-SUZ-4 molecular sieves with low preparation cost and selective fast and efficient removal of heavy metal ^Pb in wastewater, which belongs to the technical field of wastewater treatment. The present invention uses industrial waste residue—— Silica fume and aluminum fume are used as raw materials. By adding a certain amount of K ⁺ to the synthesis system, the amount of organic template in the system is only 3% of the original amount, and 100% K-SUZ-4 molecular sieve can be obtained. Then through ion exchange, Na-SUZ-4 molecular sieve is obtained, which is used for the adsorption and removal of Pb ²⁺ in wastewater. The Na-SUZ-4 molecular sieve adsorption material in the present invention has obvious specific adsorption for Pb ²⁺ , faster equilibrium speed and higher adsorption capacity, and the removal rate does not decrease significantly after cyclic adsorption for 5 times. The greatly reduced usage of the organic template makes the preparation cost of the molecular sieve low, and the preparation process is environmentally friendly.

Description

Preparation method of Na-SUZ-4 molecular sieve with low cost and rapid adsorption of Pb2+

technical field

The invention belongs to the technical field of waste water treatment, and in particular relates to a method for preparing Na-SUZ-4 molecular sieves with low cost and rapid adsorption of Pb2 ⁺ .

Background technique

Water is an essential element for human survival. With the rapid development of industry and the continuous acceleration of urbanization, the problem of heavy metal pollution in water is becoming more and more serious. Among them, the discharge of heavy metal lead (Pb) accounts for more than 35% of the total discharge of all heavy metals. Pb is a heavy metal element that seriously endangers human health. It can affect the nervous, hematopoietic, urinary, reproductive and other systems of the human body, especially the growth and intellectual development of children. Due to the illegal discharge of lead-containing wastewater by lead mining and smelting enterprises and battery manufacturing enterprises, lead pollution incidents have occurred frequently, resulting in excessive blood lead and poisoning of children and even adults. Therefore, it is an urgent task in the environmental field to remove lead in waste water economically, effectively, safely and environmentally friendly, and reduce its accumulation and harm in the environment. Among the many methods for treating Pb(II) in wastewater, the adsorption method has become one of the effective means due to its advantages of low energy consumption, high efficiency, convenient operation, and no secondary pollution. Commonly used adsorbents include activated carbon, minerals, polymer organic substances, zeolites, biomass, etc. The existing adsorption materials generally have problems such as slow adsorption rate, low adsorption capacity, and poor selectivity. Patent CN 111229181 A reports an organic material that efficiently and rapidly adsorbs heavy metal Pb(II), but the preparation method of this material is complicated and the cost is high. Therefore, the research and development of low-cost, specific, fast and efficient adsorbents is the key factor for the practical application of adsorption methods.

K-SUZ-4 is a microporous silica-alumina molecular sieve with SZR structure, which can effectively remove heavy metal cations in water through electrostatic attraction and ion exchange. Our research group (Journal of Cleaner Production 312(2021) 127825.) previously reported that K-SUZ-4 was synthesized from industrial waste residues—silica fume and aluminum ash, and found that the molecular sieve was stable under neutral conditions (pH =7) The maximum adsorption capacity of Cd(II) in water can reach 256.3 mg/g. However, the use of a large amount of organic templates in the above K-SUZ-4 synthesis method not only increases the preparation cost of the molecular sieve, but also pollutes the environment and endangers human health. In addition, the time required for the above adsorption reaction to reach equilibrium is as long as 2 h.

Contents of the invention

The purpose of the present invention is to provide a method for preparing Na-SUZ-4 molecular sieve with low preparation cost and selective fast and efficient removal of heavy metal ^Pb in wastewater. The present invention adds inorganic substances to the SUZ-4 synthesis system K ⁺ reduces the usage of organic template tetraethylammonium hydroxide to 3% of the original dosage, greatly reduces the synthesis cost of molecular sieves, and uses Na-SUZ-4 molecular sieves to realize the removal of heavy metal Pb ² in wastewater ⁺ Specific, fast and efficient adsorption removal.

The present invention adopts following technical scheme:

A kind of preparation method of the Na-SUZ-4 molecular sieve of low-cost and quick adsorption ^Pb , comprises the steps:

The first step, the preparation of K-SUZ-4 molecular sieve: mix silica fume, aluminum ash, tetraethylammonium hydroxide, potassium hydroxide and deionized water in proportion to obtain a mixture, then add potassium salt to the mixture to obtain Gel mixture, put the formed gel mixture into a reaction kettle, and dynamically crystallize at 150°C for 4.5-5 days at 20 rpm. After the crystallization is completed, the obtained product is separated, dried, and calcined to obtain K- SUZ-4 molecular sieve;

The second step, the preparation of Na-SUZ-4 molecular sieve: put the K-SUZ-4 molecular sieve obtained above in 10 mL, 0.1~2mol/L Na ⁺ solution, ion exchange at 30~150℃ for 2~24 h After the exchange is completed, the product is separated and dried to obtain Na-SUZ-4 molecular sieve;

The third step, the adsorption of heavy metal Pb ²⁺ : add 0.003~0.04 g Na-SUZ-4 molecular sieve to 50 mL, 10~70 mg/L Pb ²⁺ solution, adjust the pH to 2~8, shake The bed was oscillated for 0-30 min, samples were taken at regular intervals, the concentration of Pb ²⁺ in the solution was detected by flame atomic absorption spectrometer, and the adsorption capacity was calculated based on the mass of the adsorbent and the concentration of heavy metal ions before and after adsorption.

Further, the silica fume, aluminum ash, tetraethylammonium hydroxide, potassium hydroxide and deionized water described in the first step are SiO ₂ :Al ₂ O ₃ :TEAOH:KOH:H ₂ O=21.2:1.0: 0.078:7.9:498.6 molar ratio mixing.

Further, the potassium salt in the first step is added in a molar ratio range of K ⁺ :TEAOH=20~40.

Further, the potassium salt in the first step includes any one or a combination of potassium chloride, potassium sulfate, and potassium nitrate.

Further, the sodium ion solution in the second step includes any one or a mixture of sodium chloride, sodium carbonate, sodium bicarbonate, and sodium hydroxide.

The beneficial effects of the present invention are as follows:

1. The present invention greatly reduces the use of organic templates and the synthesis cost of SUZ-4 molecular sieves by adding K ⁺ to the synthesis system, and the increase of tetraethylammonium hydroxide is 3% of the addition amount of the normal synthesis method .

2. The present invention uses low-cost Na-SUZ-4 molecular sieves to adsorb heavy metal lead ions in wastewater, which has obvious specificity, large adsorption capacity, and fast adsorption rate, and the adsorption equilibrium can be reached within 5 minutes.

3. The Na-SUZ-4 molecular sieve prepared by the present invention undergoes desorption-resorption cycles for 5 times, and the adsorption capacity remains basically unchanged.

4. The Na-SUZ-4 molecular sieve prepared by the present invention can resist the interference of Zn ²⁺ , Cu ²⁺ , Ni ²⁺ , and Mn ^{2 +} heavy metal ions when adsorbing and removing Pb ²⁺ in water.

Description of drawings

Fig. 1 is the adsorption reaction kinetic curve of the Na-SUZ-4 molecular sieve prepared by the present invention.

Fig. 2 is a graph showing the relationship between the dosage of Na-SUZ-4 molecular sieve prepared by the present invention, the adsorption capacity and the adsorption rate.

Fig. 3 is a graph showing the relationship between the initial concentration and the adsorption capacity of the Pb ²⁺ solution.

Fig. 4 is a graph showing the relationship between the pH value and the adsorption capacity of the Pb ²⁺ solution.

Figure 5 shows the selectivity of Na-SUZ-4 molecular sieves to Pb ²⁺ .

Fig. 6 is a diagram of the cycle use of the Na-SUZ-4 molecular sieve prepared in the present invention.

Detailed ways

A kind of preparation method of the Na-SUZ-4 molecular sieve of low-cost and quick adsorption ^Pb , comprises the steps:

The first step, the preparation of K-SUZ-4 molecular sieve: mix silica fume, aluminum ash, tetraethylammonium hydroxide, potassium hydroxide and deionized water in proportion to obtain a mixture, then add potassium salt to the mixture to obtain Gel mixture, put the formed gel mixture into a reaction kettle, and dynamically crystallize at 150°C for 4.5-5 days at 20 rpm. After the crystallization is completed, the obtained product is separated, dried, and calcined to obtain K- SUZ-4 molecular sieve;

The second step, the preparation of Na-SUZ-4 molecular sieve: put the K-SUZ-4 molecular sieve obtained above in 10 mL, 0.1~2mol/L Na ⁺ solution, ion exchange at 30~150℃ for 2~24 h After the exchange is completed, the product is separated and dried to obtain Na-SUZ-4 molecular sieve;

The third step, the adsorption of heavy metal Pb ²⁺ : add 0.003~0.04 g Na-SUZ-4 molecular sieve to 50 mL, 10~70 mg/L Pb ²⁺ solution, adjust the pH to 2~8, shake The bed was oscillated for 0-30 min, samples were taken at regular intervals, the concentration of Pb ²⁺ in the solution was detected by flame atomic absorption spectrometer, and the adsorption capacity was calculated based on the mass of the adsorbent and the concentration of heavy metal ions before and after adsorption.

1. Effect of preparation conditions of Na-SUZ-4 molecular sieve on adsorption performance

Example 1

1) Mix 0.32 g aluminum ash, 1.92 g potassium hydroxide and 10 g deionized water, stir for 30 min, then add 4.60 g silica fume, 0.2 g 25% tetraethylammonium hydroxide aqueous solution and 23 g mixed solution of deionized water.

The initial gel molar ratio was SiO ₂ :Al ₂ O ₃ :TEAOH:KOH:H ₂ O=21.2:1.0:0.078:7.9:498.6, and then 1 g of potassium chloride was added to the mixed solution. After continuing to stir for 30 min, the resulting mixture was transferred to a 50 mL hydrothermal kettle, and was dynamically crystallized at 150 °C for 4.5 days at a speed of 20 rpm. After the above reaction is completed, the solid phase is separated from the liquid phase, washed, dried, and calcined to obtain K-SUZ-4 molecular sieve solid particles.

2) Place 0.2 g of K-SUZ-4 molecular sieve obtained above in 10 mL of 0.5 mol/L Na ₂ CO ₃ solution, and perform ion exchange at 30°C for 2 h. After the exchange is completed, the product is separated and dried to obtain Na-SUZ-4 molecular sieve.

3) Add 0.01 g of Na-SUZ-4 molecular sieve into 50 mL of 50 mg/L Pb ²⁺ solution, and shake on the shaking bed for 5 min. The concentration of Pb ²⁺ in the solution was detected by flame atomic absorption spectrometer. The adsorption capacity of Pb ²⁺ was measured to be 168.4 mg/g at equilibrium.

Example 2

Repeat Example 1, but change 1 g potassium chloride in step 1 to 0.68 g potassium nitrate, and the resulting mixture is dynamically crystallized at 150 °C for 5 days; put the K-SUZ-4 molecular sieve in step 2) in 10 mL, In 0.1 mol/L NaCl solution, ion exchange at 150°C for 24 h. The measured adsorption capacity of Pb ²⁺ in water was 175.5 mg/g.

Example 3

Repeat Example 1, but change 1 g of potassium chloride in step 1) to a mixture of 0.58 g of potassium sulfate and 0.68 g of potassium nitrate, and place the K-SUZ-4 molecular sieve in step 2) in 10 mL of 2mol/L NaOH The solution was ion-exchanged at 60°C for 8 h. After equilibrium, the measured adsorption capacity of ^Pb in water was 148.4 mg/g.

Example 4

Repeat Example 2, but place the K-SUZ-4 molecular sieve in step 2) in 10 mL, 0.5 mol/L Na ₂ CO ₃ and NaHCO ₃ mixed solution. After equilibration, the measured adsorption capacity of ^Pb in water was 158.5 mg/g.

2. Effect of adsorption conditions on adsorption performance

Example 5

Repeat Example 1, but change the oscillation for 5 minutes in step 3) to oscillation for 30 minutes, and take samples at regular intervals. The kinetic curve of the adsorption reaction is shown in Fig. 1 . It can be seen from Figure 1 that the adsorption reaction has a relatively fast rate, and the adsorption equilibrium can be reached within 5 min.

Example 6

Repeat Example 1, but the amount of Na-SUZ-4 molecular sieve added in step 3) is changed to 0.003~0.04 g. The relationship between the amount of adsorbent dosage and the adsorption capacity and adsorption rate is shown in Figure 2.

Example 7

Repeat Example 1, but the concentration of Pb ²⁺ solution in step 3) is 10-70 mg/L. The relationship between the initial concentration of the heavy metal solution and the adsorption capacity is shown in Fig. 3.

Example 8

Repeat Example 1, but the pH value of the solution in step 3) is adjusted to 2, 3, 4, 5, 6, 7, 8. The relationship between solution pH and adsorption capacity is shown in Fig. 4.

3. Effect of other heavy metal ions in the solution on the adsorption of Pb ²⁺

Example 9

Repeat Example 1, but in step 3), add 0.01 g of Na-SUZ-4 molecular sieve to 50 mL, 50 mg/L of Zn ²⁺ \Pb ²⁺ , Cu ²⁺ \Pb ²⁺ , Ni ²⁺ \Pb ²⁺ , Mn ²⁺ \Pb ²⁺ binary mixed solution. The result is shown in Figure 5. It can be seen from Figure 5 that Na-SUZ-4 molecular sieve has good specificity for Pb ²⁺ , and the presence of other heavy metal cations has little effect on the adsorption of Pb ²⁺ .

4. Recycling of Na-SUZ-4 molecular sieve adsorbent

Example 10

Repeat example 1. Dry the Na-SUZ-4 molecular sieve after adsorbing Pb ²⁺ at 110°C for 6.0 h, weigh 0.01 g, put it into the EDTA analysis solution containing 1 mol/L, shake it at 30°C for 480 min, filter and wash. The obtained filter residue (Na-SUZ-4 molecular sieve) was dried at 110°C for 6.0 h, and then step 3 in Example 1 was repeated). The above desorption and resorption process was repeated five times, and the results are shown in Figure 6. It can be seen from the figure that after repeating 5 times, the adsorption capacity of the adsorbent does not decrease significantly, which shows that the Na-SUZ-4 molecular sieve adsorbent has good recycling performance.

Comparative example 1

Repeat example 1. But no K ⁺ was added, and the increase of organic template TEAOH was 5.67g. After adsorption equilibrium, the measured adsorption capacity of Pb ²⁺ in water was 147.6 mg/g.

Comparative example 2

1) Repeat step 1) in Example 1.

Add 0.01 g of K-SUZ-4 molecular sieve into 50 mL, 50 mg/L Pb ²⁺ solution, and shake on the shaking bed for 5 min. The concentration of Pb ²⁺ in the solution was detected by flame atomic absorption spectrometer. The measured equilibrium adsorption capacity of Pb ²⁺ is 135.6 mg/g, which is lower than that of Na-SUZ-4 molecular sieve.

Claims (3)

1. a low-cost and fast adsorption of ^Pb The preparation method of the Na-SUZ-4 molecular sieve, is characterized in that: comprise the steps: The first step, the preparation of K-SUZ-4 molecular sieve: mix silica fume, aluminum ash, tetraethylammonium hydroxide, potassium hydroxide and deionized water in proportion to obtain a mixture, then add potassium salt to the mixture to obtain Gel mixture, put the formed gel mixture into a reaction kettle, and dynamically crystallize at 150°C for 4.5-5 days at 20 rpm. After the crystallization is completed, the obtained product is separated, dried, and calcined to obtain K- SUZ-4 molecular sieve; The second step, the preparation of Na-SUZ-4 molecular sieve: put the K-SUZ-4 molecular sieve obtained above in 10 mL, 0.1~2 mol/L Na ⁺ solution, ion exchange at 30~150℃ for 2~24 h, after the exchange is completed, the product is separated and dried to obtain Na-SUZ-4 molecular sieve; Silica fume, aluminum fume, tetraethylammonium hydroxide, potassium hydroxide and deionized water described in the first step are SiO ₂ :Al ₂ O ₃ :TEAOH:KOH:H ₂ O=21.2:1.0:0.078:7.9 : 498.6 molar ratio mixing; Potassium salt described in the first step is added by the molar ratio range of K ⁺ :TEAOH=20～40; The potassium salt described in the first step includes any one or a combination of potassium chloride, potassium sulfate and potassium nitrate. 2. a kind of low cost according to claim 1 and the preparation method of the Na-SUZ-4 molecular sieve of fast adsorption ^Pb , it is characterized in that: the sodium ion solution described in the second step comprises sodium chloride, sodium carbonate , sodium bicarbonate, sodium hydroxide in any one or a combination of several. 3. A Na-SUZ-4 molecular sieve prepared by the preparation method according to claim 1 is applied to the adsorption of heavy metal Pb ²⁺ , it is characterized in that: comprising the steps of: using 0.003 ~ 0.04g of Na-SUZ-4 molecular sieve Add it to 50 mL, 10-70 mg/L Pb ²⁺ solution, adjust the pH to 2-8, oscillate on the shaking bed for 0-30 min, take samples at regular intervals, and detect Pb ²⁺ in the solution by flame atomic absorption spectrometer ⁺ concentration, and then calculate the adsorption capacity based on the mass of the adsorbent and the concentration of heavy metal ions before and after adsorption.

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