Net water sludge / sodium silicate composite adsorbent, preparation method thereof and application in treating ammonia nitrogen in water

Abstract

The present invention belongs to the field of sewage treatment technology, and specifically relates to a purified water sludge / sodium silicate composite adsorbent, its preparation method and application in treating ammonia nitrogen in water bodies. After mixing powdered purified water sludge with an aqueous sodium silicate solution and standing, a precipitate is obtained. Then, the precipitate is washed with water until neutral and granulated to obtain purified water sludge / sodium silicate composite particles; the purified water sludge / sodium silicate composite particles are then dried and calcined to obtain a purified water sludge / sodium silicate composite adsorbent. The present invention makes resource utilization of purified water sludge, which can not only solve the pollution problem caused by purified water sludge, but also save costs and generate economic benefits, and has good prospects.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment technology, and particularly relates to a composite adsorbent of purified water sludge / sodium silicate, a preparation method thereof, and an application in removing ammonia nitrogen in water. Background Art

[0002] Ammonia nitrogen is one of the main oxygen-consuming pollutants in water bodies. When household or industrial wastewater containing excessive ammonia nitrogen is discharged into rivers due to improper treatment, it often leads to eutrophication of water bodies and deterioration of water quality. In addition, ammonia nitrogen in over-fertilized farmland leaks into the groundwater system under the action of rainwater, causing serious damage to the aquatic ecosystem. In addition, ammonia nitrogen is converted into nitrate by biological nitrification. When the concentration of nitrite exceeds 10 mg∙L -1 it is harmful to human health. At the same time, the increase in the ammonia nitrogen content in water will also cause the growth of algae and bacteria, further consuming the dissolved oxygen in the water, making the water body turn black and stinky.

[0003] Purified water sludge is a by-product generated during the sedimentation and filtration washing processes in water treatment plants. The amount of purified water sludge generated from water treatment plants is increasing annually, and the output is huge. If not properly treated, directly discharging or landfilling the purified water sludge will not only waste the useful resources in the purified water sludge, but also cause new pollution to the environment. With the increase in the output of purified water sludge and the increasingly strict relevant environmental standards, the treatment of purified water sludge has become an increasingly severe challenge.

[0004] In the early stage, the treatment of purified water sludge mainly focused on direct discharge and landfilling, which would not only cause the riverbed in the discharge area to rise and the river channel to be blocked, but also the aluminum salts and some heavy metal particles in it would cause poisoning and death of animals and plants, accumulate in the human body and cause lesions, affecting human survival, and causing long-term pollution and damage to the ecological environment. With the aggravation of environmental pollution and the implementation of relevant environmental protection policies, domestic and foreign countries have attached great importance to the treatment of purified water sludge. At present, the treatment of purified water sludge mainly focuses on its harmless treatment, and on this basis, resource utilization has become the main trend of current research.

[0005] At present, domestic and foreign countries have focused on how to recycle purified water sludge. Recycling purified water sludge can not only solve the pollution problem caused by purified water sludge, but also save costs and generate economic benefits, showing good prospects. At present, the research on purified water sludge mainly focuses on its adsorption performance for toxic substances in water. Summary of the Invention

[0006] The present invention adopts the following technical solutions:

[0007] The water purification sludge / sodium silicate composite adsorbent, and its preparation method includes the following steps: Mix powdered water purification sludge with an aqueous sodium silicate solution and let it stand to obtain a precipitate. Then wash the precipitate with water until it is neutral and granulate it to obtain water purification sludge / sodium silicate composite particles. Then dry and calcine the water purification sludge / sodium silicate composite particles to obtain the water purification sludge / sodium silicate composite adsorbent.

[0008] A method for treating ammonia-nitrogen-containing water bodies includes the following steps: Mix powdered water purification sludge with an aqueous sodium silicate solution and let it stand to obtain a precipitate. Then wash the precipitate with water until it is neutral and granulate it to obtain water purification sludge / sodium silicate composite particles. Then dry and calcine the water purification sludge / sodium silicate composite particles to obtain the water purification sludge / sodium silicate composite adsorbent. Add the water purification sludge / sodium silicate composite adsorbent to the ammonia-nitrogen-containing water body to complete the treatment of the ammonia-nitrogen-containing water body.

[0009] In the adsorption process of the water purification sludge / sodium silicate composite adsorbent of the present invention, surface adsorption, ion adsorption and surface particle coordination reaction occur simultaneously. Especially after high-temperature calcination, the porosity increases and it has a strong adsorption capacity. Therefore, the present invention discloses the application of the above-mentioned water purification sludge / sodium silicate composite adsorbent in treating ammonia nitrogen in water bodies.

[0010] In the present invention, the dosage ratio of the powdered water purification sludge to the aqueous sodium silicate solution is 1 g∶25 mL; the mass concentration of the aqueous sodium silicate solution is 0.5% - 12%, preferably 5% - 10%.

[0011] In the present invention, the mixing is carried out by oscillating at room temperature for 1.5 - 2.5 h. The specific oscillation is a conventional technique as long as it can mix the materials. The calcination temperature is 200 - 500 °C, preferably 300 - 400 °C; the time is 3 - 5 hours, preferably 4 hours.

[0012] In the present invention, the particle size of the powdered water purification sludge is 100 - 200 mesh.

[0013] In the present invention, when treating the ammonia-nitrogen-containing water body, the dosage ratio of the water purification sludge / sodium silicate composite adsorbent to the ammonia-nitrogen-containing water body is (10 - 40) g∶1 L; preferably (20 - 30) g∶1 L.

[0014] The water purification sludge / sodium silicate composite adsorbent of the present invention contains SiO2 and Al2O3, has a lamellar structure, and has a good adsorption effect on ammonia nitrogen. In addition, after the water purification sludge is calcined at high temperature, the lamellar structure becomes looser, the porosity increases, and the specific surface area becomes larger, which is beneficial to the adsorption process. After being modified with sodium silicate, Na + replaces Ca with a larger atomic radius in the water purification sludge 2+ and K + , and has a smaller steric hindrance, so that the adsorption capacity of the water purification sludge modified with sodium silicate for NH4 + increases. Description of the Drawings

[0015] Figure 1 It is a physical photo of the purified water sludge / sodium silicate composite adsorbent;

[0016] Figure 2 It is the XRD patterns of the purified water sludge adsorbent and the purified water sludge / sodium silicate composite adsorbent;

[0017] Figure 3 It is the SEM images of the purified water sludge adsorbent (a) and the purified water sludge / sodium silicate composite adsorbent (b). Detailed Description of the Invention

[0018] The preparation method of the purified water sludge / sodium silicate composite adsorbent of the present invention is as follows: mix powdered purified water sludge with an aqueous sodium silicate solution and let it stand to obtain a precipitate, then wash the precipitate with water until it is neutral and granulate it to obtain purified water sludge / sodium silicate composite particles; then dry and calcine the purified water sludge / sodium silicate composite particles to obtain the purified water sludge / sodium silicate composite adsorbent.

[0019] The method for treating ammonia-nitrogen water body of the present invention is as follows: mix powdered purified water sludge with an aqueous sodium silicate solution and let it stand to obtain a precipitate, then wash the precipitate with water until it is neutral and granulate it to obtain purified water sludge / sodium silicate composite particles; then dry and calcine the purified water sludge / sodium silicate composite particles to obtain the purified water sludge / sodium silicate composite adsorbent; add the purified water sludge / sodium silicate composite adsorbent to the ammonia-nitrogen water body to complete the treatment of the ammonia-nitrogen water body; the obtained adsorption capacity and adsorption rate for NH4 + are the average values of three parallel experiments (the error meets the requirements)

[0020] The purified water sludge taken from the waterworks (existing raw material) is dried at 100 °C for 24 h, then crushed by a pulverizer, and the particles with a particle size of 100-200 mesh are taken as powdered purified water sludge for the following examples and comparative examples. The present invention only uses purified water sludge and sodium silicate (Na2SiO3·9H2O) as raw materials, without other raw materials. Through mixing, granulation, drying, and calcination, the purified water sludge / sodium silicate composite adsorbent is obtained, which has good ammonia-nitrogen treatment effect. The raw materials of the present invention are all conventional products, and the specific operation methods and testing methods are all conventional technologies. Oscillation and calcination are carried out in a conventional air environment. Examples

[0021] Add 100 g of the above-mentioned powdered purified water sludge into 2500 mL of sodium silicate aqueous solutions with different mass concentrations, and oscillate it conventionally at room temperature for 2 h; then let it stand for sedimentation, suck off the supernatant, wash the lower-layer precipitate with distilled water until it is neutral (neutral pH value), and then put it into a granulator for conventional extrusion molding to obtain purified water sludge / sodium silicate composite particles; then dry the purified water sludge / sodium silicate composite particles at 105 °C, and then put them into a muffle furnace for roasting at different temperatures for 4 hours (heating from room temperature to the roasting temperature at a heating rate of 16 °C / min, and then keeping warm for 4 hours, in an air environment) to prepare a purified water sludge / sodium silicate composite adsorbent. The physical picture is shown in Figure 1 , and it is brown after roasting; Table 1 shows the parameters of the examples and the ammonia nitrogen treatment results.

[0022] Control example

[0023] Extrude the powdered purified water sludge into particles with a granulator (add water conventionally, which is common sense for granulation) to obtain purified water sludge particles; then dry the purified water sludge particles at 105 °C, and then put them into a muffle furnace for roasting at 350 °C for 4 hours (heating from room temperature to 350 °C at a heating rate of 16 °C / min, and then keeping warm for 4 hours, in an air environment) to prepare a purified water sludge adsorbent; Table 1 shows the parameters of the examples and the ammonia nitrogen treatment results, which is the seventh group.

[0024] Preparation of ammonia nitrogen simulated water samples

[0025] Use a 50 mg∙L -1 ammonium chloride aqueous solution to simulate actual wastewater; use the Nessler reagent-spectrophotometry method to measure the concentration of ammonia nitrogen. Weigh 1 g of the adsorbent respectively and put it into different conical flasks, then add 50 mL of the previously prepared ammonia nitrogen simulated water sample respectively. After oscillating the conical flasks at room temperature for 12 h (oscillation rate is 120 r / min), let it stand, suck 5 mL for centrifugation with a disposable dropper, and take 1 mL of the upper-layer clear liquid for absorbance measurement, and calculate the adsorption capacity of the adsorbent for NH4 + under different modification conditions. The results are shown in Table 1.

[0026]

[0027] Use a 50 mg∙L -1 ammonium chloride aqueous solution to simulate actual wastewater; use the Nessler reagent-spectrophotometry method to measure the concentration of ammonia nitrogen. Weigh 1.5 g of the purified water sludge / sodium silicate composite adsorbent of Group 6 (calcined at 5%, 400 °C), put it into a conical flask, then add 50 mL of the previously prepared ammonia nitrogen simulated water sample. After oscillating the conical flask at room temperature for 12 h (oscillation rate is 120 r / min), let it stand, suck about 5 mL for centrifugation with a disposable dropper, and take 1 mL of the upper-layer clear liquid for absorbance measurement, and calculate the adsorption capacity of the modified purified water sludge for NH4 under different adsorbent dosage conditions+ The removal rate was 95.1%; the NH4 removal rate of the 1 g group 6 of the purified water sludge / sodium silicate composite adsorbent (calcined at 5%, 400 °C) + was 91.6%; the NH4 removal rate of the 0.5 g group 6 of the purified water sludge / sodium silicate composite adsorbent (calcined at 5%, 400 °C) + was 67.5%.

[0028] Compared with the existing 20-mesh to 60-mesh zeolite adsorbents available in the market in this research group, the NH4 removal rate of the purified water sludge / sodium silicate composite adsorbents of the examples of the present invention (groups 1 to 6) + is significantly better than that of the commercially available 20-mesh to 60-mesh zeolite adsorbents.

[0029] From Figure 2 it can be seen that the purified water sludge / sodium silicate composite adsorbent (group one) includes the SiO2 and Al2O3 structures. The oxygen atoms in the internal crystal structure of the purified water sludge are not yet saturated, so it carries a negative charge, generating electrostatic attraction to NH4 + ; after being modified with sodium silicate, Na + replaces Ca with a larger atomic radius in the purified water sludge 2+ and K + , with a smaller steric hindrance, thus increasing the adsorption capacity of the sodium silicate-modified purified water sludge for NH4 + .

[0030] From Figure 3 it can be seen that the purified water sludge was originally a tightly structured flaky structure, stacked in a staggered manner. After high-temperature calcination, the tightly packed lamellar structure of the purified water sludge was significantly damaged, the structure became loose and large pores were generated. This is because the water in the purified water sludge volatilized and the organic matter decreased during high-temperature roasting, forming pores. The flat-layered structure of the sodium silicate-modified purified water sludge (group one) is looser and the pores become larger. This is because Na in the sodium silicate + exchanged with the metal active sites in the purified water sludge. The atomic radius of Na + is smaller, so larger pores are formed, and at the same time, the original lattice structure is damaged, making the flat-layered structure looser.

Claims

1. A water purification sludge / sodium silicate composite adsorbent, characterized in that, The preparation method of the purified water sludge / sodium silicate composite adsorbent comprises the following steps: adding 100 g of powdery purified water sludge into 2500 mL of sodium silicate aqueous solution, oscillating at room temperature for 2 h; then standing for sedimentation, sucking off the supernatant, washing the lower-layer precipitate with distilled water until neutral, and then putting it into a granulator for conventional extrusion molding to obtain purified water sludge / sodium silicate composite particles; then drying the purified water sludge / sodium silicate composite particles at 105 °C, and then putting them into a muffle furnace for roasting for 4 hours, heating from room temperature to the roasting temperature at a heating rate of 16 °C / min, and then holding for 4 hours in an air environment to prepare the purified water sludge / sodium silicate composite adsorbent; the mass concentration of the sodium silicate aqueous solution is 5% - 10%; the roasting temperature is 350 °C - 400 °C.

2. A method for treating ammonia-nitrogen water body, characterized in that, Comprising the following steps: adding the purified water sludge / sodium silicate composite adsorbent described in claim 1 into the ammonia-nitrogen-containing water body to complete the treatment of the ammonia-nitrogen-containing water body; when treating the ammonia-nitrogen-containing water body, the dosage ratio of the purified water sludge / sodium silicate composite adsorbent to the ammonia-nitrogen-containing water body is (10 - 40) g∶1 L.

3. The method for treating ammonia-nitrogen water body according to claim 2, characterized in that, The particle size of the powdery purified water sludge is 100 - 200 mesh.

4. Application of the purified water sludge / sodium silicate composite adsorbent described in claim 1 in treating ammonia nitrogen in water bodies.

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