A bone biochar-based ceramsite for phosphorus removal from sewage and its preparation method

Abstract

The present invention discloses a bone biochar-based ceramsite for phosphorus removal from sewage and a preparation method thereof, and belongs to the technical field of material preparation. The present invention abandons the traditional path of phosphorus removal by adsorption, adopts crystallization precipitation for phosphorus removal, utilizes the characteristics of bone biochar that is similar to hydroxyapatite in structure and can reduce the crystallization nucleation barrier, uses it as the main active component of phosphorus removal ceramsite, and acts synergistically with an alkali activator. The alkali activator in the raw material can slowly release alkalinity into the sewage, which can prevent phosphorus leakage caused by too low pH of the influent, and can achieve deep treatment of phosphorus without additional addition of agents. It can reduce the phosphorus content in water in a short time and has the ability of long-term and efficient phosphorus removal, and has a long service life; applying it to artificial wetlands can significantly improve the phosphorus removal efficiency of artificial wetlands, and achieve the effect of cost reduction and expansion of application scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a bone biochar-based ceramsite for removing phosphorus from sewage and a preparation method thereof. Background Art

[0002] Phosphorus is an important element for the growth and reproduction of organisms. However, excessive phosphorus discharged into water will cause serious ecological problems such as eutrophication. At present, the methods for removing phosphorus in water can generally be divided into two categories: biological methods and physicochemical methods.

[0003] The biological method has a high removal rate of phosphorus and organic matter in wastewater under suitable conditions. However, since this method relies on the action of microorganisms, it has strict requirements for environmental conditions. The temperature, pH value, etc. of the wastewater will all affect the treatment effect, and it is difficult for the effluent to meet the phosphorus discharge standard. Therefore, secondary phosphorus removal treatment of the effluent is often required.

[0004] The physicochemical method mainly uses chemical precipitation, or the adsorption, crystallization, etc. of materials to separate phosphorus elements in water into insoluble solid substances from the water. On the one hand, the precipitates generated by the physicochemical method have almost no utilization value and can only be stacked and landfilled as waste residues, which will cause secondary pollution to the environment. On the other hand, the reagent cost is relatively high, and a large amount of difficult-to-treat sludge, etc., are also the main obstacle factors affecting the application of chemical phosphorus removal technology. The treatment effect of the adsorption method mainly depends on the performance conditions of the adsorbent. Once the adsorbent reaches adsorption saturation, the phosphorus removal efficiency will drop linearly and the long-term phosphorus removal ability will be poor. How to obtain an adsorbent with good adsorption capacity and capable of being used stably for a long time has become a problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a bone biochar-based ceramsite for removing phosphorus from sewage and a preparation method thereof, so as to solve the technical problem of poor phosphorus removal effect of the existing adsorbent.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a bone biochar-based ceramsite for removing phosphorus from sewage, and the raw materials used include, by weight: 8-12 parts of bone biochar powder, 30-50 parts of fly ash, 12-24 parts of binder, 20-40 parts of cement, 30-50 parts of sand, 5-10 parts of gypsum, and 2-5 parts of alkali activator.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows:

[0008] Further, the raw materials used include, by weight: 8 parts of bone biochar powder, 50 parts of fly ash, 24 parts of binder, 20 parts of cement, 30 parts of sand, 10 parts of gypsum, and 5 parts of alkali activator.

[0009] Further, the raw materials used include, by weight: 12 parts of bone biochar powder, 30 parts of fly ash, 12 parts of binder, 40 parts of cement, 50 parts of sand, 5 parts of gypsum, and 2 parts of alkali activator.

[0010] Further, the raw materials used include, by weight: 10 parts of bone biochar powder, 40 parts of fly ash, 18 parts of binder, 30 parts of cement, 40 parts of sand, 8 parts of gypsum, and 3 parts of alkali activator.

[0011] Further, the bone biochar powder is prepared by the following method: cleaning animal bones, crushing them after drying, and then carbonizing them at 380 - 520 °C for 6 - 10 h in a protective atmosphere to obtain the bone biochar powder.

[0012] Further, the cleaning agent used in the cleaning process is at least one of acetone, petroleum ether, or gasoline.

[0013] Further, the animal bones are the bones of medium - sized or large - sized beasts.

[0014] Further, the medium - sized or large - sized beasts are cattle, pigs, sheep, or horses.

[0015] Further, the drying temperature is 180 - 220 °C and the time is 22 - 26 h.

[0016] Further, the gas used in the protective atmosphere is nitrogen or argon.

[0017] Further, the heating rate during carbonization is 6 - 8 °C / min.

[0018] Further, the carbonization temperature is 450 °C and the time is 8 h.

[0019] Further, the binder is water glass, dextrin, or sodium metasilicate.

[0020] Further, the alkali activator is sodium hydroxide and calcium oxide, and the mass ratio of sodium hydroxide to calcium oxide is 2 - 3:2 - 3.

[0021] The present invention also discloses a preparation method of bone biochar - based ceramsite for sewage dephosphorization, comprising the following steps:

[0022] S1. Dissolve the binder in water to obtain a binder solution; mix fly ash, cement, sand, gypsum, and alkali activator in proportion to form a ash material, and then spray 40 - 50% of the binder solution on the surface of the ash material to obtain ceramsite spheres through granulation;

[0023] S2. Place the ceramsite spheres in the bone biochar powder, continue to spray the remaining binder solution, and obtain the green ceramsite through granulation.

[0024] S3. Place the green pellets of ceramsite at room temperature for aging for 4 - 6 h, and then cure them at an air humidity of 80% - 90% and a temperature of 20 - 25 °C for 24 - 48 h to obtain bone biochar - based ceramsite.

[0025] Furthermore, the air humidity for curing is 85%, the temperature is 23 °C, and the time is 36 h.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention abandons the traditional path of phosphorus removal by adsorption, adopts crystallization precipitation for phosphorus removal, and utilizes the characteristic that bone biochar is similar to hydroxyapatite in structure and can reduce the crystallization nucleation barrier. It is used as the main component of the phosphorus - removing ceramsite and acts synergistically with the alkali activator. The alkali activator in the raw materials can slowly release alkalinity into the sewage, preventing phosphorus leakage caused by too low influent pH. It can achieve in - depth treatment of phosphorus without additional dosing of agents, can reduce the phosphorus content in water in a short time and has the ability of long - term and efficient phosphorus removal, with a long service life.

[0028] 2. The raw materials used in the present invention are cheap and easily available, and the kitchen waste solid waste can be utilized for resource recycling; the preparation process is simple, without a firing step. The prepared bone biochar - based ceramsite is green and environmentally friendly. Applying it to constructed wetlands can significantly improve the phosphorus - removing efficiency of constructed wetlands, achieving the effects of cost reduction and expanded application scenarios. Description of the Drawings

[0029] Figure 1 is the process flow schematic diagram of the present invention;

[0030] Figure 2 is the SEM Mapping of bone biochar - based ceramsite; among them, Figure (a) is the distribution map of P element, Figure (b) is the distribution map of Ca element, Figure (c) is the distribution map of O element, Figure (d) is the distribution map of Al element, and Figure (e) is the distribution map of Si element;

[0031] Figure 3 is the total number spectrum diagram of the distribution map of bone biochar - based ceramsite;

[0032] Figure 4 is the 24 - h crystallization phosphorus - removing efficiency diagram of bone biochar - based ceramsite;

[0033] Figure 5 is the scanning electron microscope image of bone biochar - based ceramsite after crystallization phosphorus removal; among them, Figure (a) is the SEM image of bone biochar - based ceramsite with a scale of 20 μm, and Figure (b) is the SEM image of bone biochar - based ceramsite with a scale of 500 μm;

[0034] Figure 6 is the XRD diagram of bone biochar - based ceramsite after crystallization phosphorus removal;

[0035] Figure 7 Verification diagram of the long-term phosphorus removal effect of bone biochar-based ceramsite. Specific implementation mode

[0036] The specific implementation mode of the present invention will be described below to facilitate those skilled in the art of the present technology to understand the present invention. For those conditions not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase. However, it should be clear that the present invention is not limited to the scope of the specific implementation mode. For those ordinary skilled in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0037] Example 1

[0038] A kind of bone biochar-based ceramsite for sewage phosphorus removal, the raw materials used include, by weight: 8 parts of bone biochar powder, 50 parts of fly ash, 24 parts of binder, 20 parts of cement, 30 parts of sand, 10 parts of gypsum, 3 parts of sodium hydroxide and 2 parts of calcium oxide.

[0039] The preparation method of the bone biochar-based ceramsite is as Figure 1 shown, and includes the following steps:

[0040] S1. Remove the residual tissue parts on the bovine bones, then wash the bovine bones with acetone, dry them at 180 °C for 26 h, then crush them, place the crushed materials in a nitrogen atmosphere, raise the carbonization temperature from room temperature to 380 °C at a heating rate of 6 °C / min, and carbonize for 10 h, and grind the carbonized bone biochar particles to obtain bone biochar powder;

[0041] S2. Dissolve sodium silicate in water to obtain a sodium silicate solution with a concentration of 10 wt%; put fly ash, cement, sand, gypsum, sodium hydroxide and calcium oxide into a granulator in proportion and mix them evenly to form ash materials, where fly ash, cement and sand are the main raw materials for the ball core; then close the granulator, spray 40% of the sodium silicate solution on the surface of the ash materials, and finally turn on the granulator to obtain ceramsite spheres through granulation;

[0042] S2. Place the ceramsite spheres in the bone biochar powder, then turn on the granulator, and continue to spray the remaining binder solution to obtain green ceramsite through granulation;

[0043] S3. Age the green ceramsite at room temperature for 4 h, then transfer it to a constant temperature and humidity curing box, and cure it at an air humidity of 80% and a temperature of 20 °C for 48 h to obtain the bone biochar-based ceramsite.

[0044] Example 2

[0045] A bone biochar-based ceramsite for phosphorus removal from sewage, the raw materials used include, by weight: 12 parts of bone biochar powder, 30 parts of fly ash, 12 parts of binder, 40 parts of cement, 50 parts of sand, 5 parts of gypsum, 1 part of sodium hydroxide, and 1 part of calcium oxide.

[0046] The preparation method of the bone biochar-based ceramsite is as Figure 1 shown, and includes the following steps:

[0047] S1. Remove the residual tissue parts on the pig bones, then wash the pig bones with gasoline, dry them at 220 °C for 22 h, then crush them, place the crushed material in an argon atmosphere, raise the carbonization temperature from room temperature to 520 °C at a heating rate of 8 °C / min, and carbonize for 6 h. Grind the carbonized bone biochar particles to obtain bone biochar powder;

[0048] S2. Dissolve water glass in water to obtain a water glass solution with a concentration of 20 wt%. Put fly ash, cement, sand, gypsum, sodium hydroxide, and calcium oxide into a granulator in proportion and mix them evenly to form ash material, where fly ash, cement, and sand are the main raw materials for the ball core. Then close the granulator, spray 50% of the water glass solution on the surface of the ash material, and finally turn on the granulator to obtain ceramsite spheres through granulation;

[0049] S2. Place the ceramsite spheres in the bone biochar powder, then turn on the granulator and continue to spray the remaining binder solution to obtain green ceramsite through granulation;

[0050] S3. Age the green ceramsite at room temperature for 6 h, then transfer it to a constant temperature and humidity curing box, and cure it at an air humidity of 90% and a temperature of 25 °C for 24 h to obtain the bone biochar-based ceramsite.

[0051] Example 3

[0052] A bone biochar-based ceramsite for phosphorus removal from sewage, the raw materials used include, by weight: 10 parts of bone biochar powder, 40 parts of fly ash, 18 parts of binder, 30 parts of cement, 40 parts of sand, 8 parts of gypsum, 1.5 parts of sodium hydroxide, and 1.5 parts of calcium oxide.

[0053] The preparation method of the bone biochar-based ceramsite is as Figure 1 shown, and includes the following steps:

[0054] S1. Remove the residual tissue parts on the sheep bones, then wash the sheep bones with acetone and petroleum ether in sequence, dry them at 200 °C for 24 h, then crush them, place the crushed material in a nitrogen atmosphere, raise the carbonization temperature from room temperature to 450 °C at a heating rate of 7 °C / min, and carbonize for 8 h. Grind the carbonized bone biochar particles to obtain bone biochar powder;

[0055] S2. Dissolve sodium silicate in water to obtain a sodium silicate solution with a concentration of 15 wt%. Put fly ash, cement, sand, gypsum, sodium hydroxide and calcium oxide into a granulator in proportion and mix them evenly to form ash material, where fly ash, cement and sand are the main raw materials for the ball core. Then close the granulator, spray 45% of the sodium silicate solution on the surface of the ash material, and finally turn on the granulator to obtain ceramsite spheres through granulation.

[0056] S3. Place the ceramsite spheres in bone biochar powder, then turn on the granulator and continue to spray the remaining binder solution to obtain green ceramsite through granulation.

[0057] S3. Age the green ceramsite at room temperature for 5 h, then transfer it to a constant temperature and humidity curing box and cure it at an air humidity of 85% and a temperature of 23 °C for 36 h to obtain bone biochar-based ceramsite.

[0058] Comparative Example

[0059] A kind of bone biochar, the preparation process of which is the same as that of step S1 in Example 3.

[0060] Use the bone biochar-based ceramsite prepared in Example 3 to conduct the following experiments.

[0061] Structural Characterization of Example 1

[0062] To verify the element distribution in the bone biochar-based ceramsite, conduct structural characterization on the bone biochar-based ceramsite. Its EDS-Mapping diagram is as Figure 2 shown. It can be seen from the figure that elements such as Ca, P, Al, O, and Si are evenly distributed on the surface of the ceramsite. The total number spectrum diagram of the distribution map is as Figure 3 shown. The content of each element is basically the same as the design concept, indicating that the ceramsite prepared by the present invention is basically successfully synthesized in terms of structure.

[0063] Experimental Example 2 Verification of Crystallization Phosphorus Removal Effect

[0064] Verify whether the mechanism of using the bone biochar-based ceramsite prepared by the present invention for phosphorus removal is crystallization. First, let the ceramsite be saturated in a solution with a certain phosphate concentration to exclude the effect of adsorption phosphorus removal, and then change the experimental conditions to conduct crystallization phosphorus removal experiments under the same phosphate concentration and a certain amount of calcium ion concentration. The specific steps are as follows:

[0065] (1) Adsorption shielding experiment: To rule out the mechanism of phosphorus removal by ceramsite being adsorption, an adsorption shielding experiment was set up before the crystallization phosphorus removal experiment, as follows: Weigh 10 g of ceramsite into a 250 mL beaker, add a phosphorus solution with a concentration of 2 mg / L, adjust the pH to 7.8, then place it on a magnetic stirrer. After mixing evenly, use a UV-Vis spectrophotometer to detect the absorbance of the sample solution. If the result shows a decrease in phosphorus concentration, replace the phosphorus solution and continue the adsorption experiment until the phosphorus concentration remains unchanged, that is, the bone biochar-based ceramsite reaches adsorption saturation.

[0066] (2) Crystallization phosphorus removal experiment: After ruling out the effect of adsorption phosphorus removal, weigh 10 g of ceramsite into a 250 mL beaker, add a mixed solution containing 2 mg / L PO 4 3- -P and 50 mg / L Ca 2+ . Adjust the pH to 7.8 to simulate the alkalinity and phosphorus concentration in actual wastewater, then place it on a magnetic stirrer. Take samples every 30 minutes from 0 to 4 hours after the reaction, and then take samples at 8 hours and 24 hours of the reaction. Use a UV-Vis spectrophotometer to detect the absorbance of the sample solution, calculate the phosphate concentration, and the crystallization phosphorus removal curve is as Figure 4 shown. It can be seen that the main mechanism of the bone biochar-based ceramsite prepared in the present invention for removing phosphate is not by adsorption, but by relying on crystallization to remove phosphate. And 80.1% of the phosphate can be removed within 4 hours, and the phosphate concentration after 24 hours can be reduced from 2 mg / L to 0.04 mg / L, and the phosphate removal efficiency reaches 98.0%.

[0067] By performing SEM on the surface of the bone biochar-based ceramsite after the crystallization phosphorus removal experiment, the result is as Figure 5 shown. The surface of the ceramsite is irregular and has a stacked lamellar structure. Further observation based on the TEM image shows that the bone biochar-based ceramsite has many wrinkles and edges, which are speculated to be hydroxyapatite crystals formed after phosphorus removal.

[0068] By performing XRD analysis on the surface of the bone biochar-based ceramsite after the crystallization phosphorus removal experiment, the result is as Figure 6 shown. The diffraction curve of the surface crystal is basically fitted with the standard hydroxyapatite curve, indicating that the crystal product on the surface of the bone biochar-based ceramsite is hydroxyapatite crystal.

[0069] Experimental Example 3 Verification of Long-term Phosphorus Removal Effect and High Phosphorus Removal Performance

[0070] By comparing the phosphorus removal effect of the bone biochar-based ceramsite prepared in Comparative Example 3 with that of the comparative example, and setting a control group (pure gravel), to explore whether the bone biochar-based ceramsite prepared in the present invention has the ability of long-term phosphorus removal.

[0071] Three groups of filter columns were set up, and the running time was 60 days. The change in phosphate concentration was continuously monitored. The fillers of each group of filter columns were as follows:

[0072] (1) 1000 g of bone biochar-based ceramsite + gravel;

[0073] (2) 1000 g of bone biochar + gravel;

[0074] (3) Gravel;

[0075] The influent was set to the effluent of a sewage treatment plant (without chemical phosphorus removal), with a COD concentration of 60 mg / L, a PO 4 3- -P concentration of 2 mg / L, and a Ca 2+ concentration of 50 mg / L. The hydraulic retention time was 3 days. After filtration with a 0.45 μm filter head, the concentration of phosphate in the effluent was detected using a UV-visible spectrophotometer, and the results are as Figure 7 shown.

[0076] As can be seen from the figure, during the continuous operation of 60 days, the phosphorus removal effects of both bone biochar-based ceramsite (Example 3) and bone biochar (control) were significantly higher than that of the traditional gravel filler (control group). Both could stably reduce the phosphate concentration to about 0.3 mg / L, and the change in phosphate concentration during the process was not significant, indicating that bone biochar-based ceramsite has the ability of efficient and long-term phosphorus removal; compared with bone biochar, bone biochar-based ceramsite could reduce the phosphate concentration to 0.3 mg / L, higher than 0.2 mg / L of bone biochar, but the difference between the two was not large. Pure bone biochar is the main effective component of the ceramsite of the present invention, and it has a good phosphorus removal effect, but it is expensive. The present invention does not reduce the phosphorus removal effect while reducing the dosage of the effective component. The final results prove that on the basis of a large reduction in the dosage of bone biochar, the effect is not significantly weakened.

Claims

1. A bone biochar-based ceramsite for wastewater phosphorus removal, characterized in that: The raw materials used include, by weight: 8-12 parts of bone biochar powder, 30-50 parts of fly ash, 12-24 parts of adhesive, 20-40 parts of cement, 30-50 parts of sand, 5-10 parts of gypsum and 2-5 parts of alkali activator; the alkali activator is sodium hydroxide and calcium oxide, and the mass ratio of sodium hydroxide to calcium oxide is 2-3:2-3; The method for preparing the bone biochar-based ceramsite comprises the following steps: S1, dissolving the binder in water to obtain a binder solution; mixing fly ash, cement, sand, gypsum and alkali activator in proportion to form ash material, then spraying 40-50% of the binder solution on the surface of the ash material, and obtaining ceramsite spheres by granulation; S2, placing the ceramsite spheres in the bone biochar powder, continuing to spray the remaining binder solution, and obtaining ceramsite green bodies by granulation; S3. The ceramsite green body is aged at room temperature for 4-6 hours, and then cured at an air humidity of 80%-90% and a temperature of 20-25°C for 24-48 hours to obtain bone biochar-based ceramsite.

2. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 1, characterized in that: The raw materials used for the bone biochar-based ceramsite include, by weight: 10 parts of bone biochar powder, 40 parts of fly ash, 18 parts of adhesive, 30 parts of cement, 40 parts of sand, 8 parts of gypsum and 3 parts of alkali activator.

3. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 1 or 2, characterized in that: The bone biochar powder is prepared by the following method: cleaning animal bones, drying and crushing them, and then carbonizing them in a protective atmosphere at 380-520° C. for 6-10 hours to obtain the bone biochar powder.

4. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 3, characterized in that: The drying temperature is 180-220° C. and the drying time is 22-26 hours.

5. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 3, characterized in that: The heating rate during the carbonization is 6-8°C / min.

6. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 3, characterized in that: The carbonization temperature is 450° C. and the time is 8 hours.

7. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 1 or 2, characterized in that: The adhesive is water glass, dextrin or sodium metasilicate.

8. The bone biochar-based ceramsite for wastewater phosphorus removal according to claim 1, characterized in that: The air humidity of the curing is 85%, the temperature is 23° C., and the curing time is 36 hours.

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