CN113213632B - Nano-hydroxyapatite loofah sponge composite filler and preparation method and application thereof - Google Patents

Abstract

The invention discloses a nano-hydroxyapatite loofah composite filler and its preparation method and application, and relates to the technical field of wastewater treatment; the method comprises the following steps: taking loofah with a water content of 5-10% and soaking it in a mass concentration In 30% hydrogen peroxide, soak it for 2 hours and take it out to dry; soak the dried loofah in Ca(NO ₃ ) ₂ 4H ₂ O solution for 8 hours; the molar ratio of Ca and P is 1.67:1 Add diammonium hydrogen phosphate dropwise to the Ca(NO ₃ ) ₂ 4H ₂ O solution, then use ammonia water with a volume concentration of 10-15% to adjust the pH to 9-9.5, and stir for 4-5h; the loofah obtained in the previous step After washing, dry at 75-78°C for 24 hours; repeat the above steps three times to obtain nano-hydroxyapatite loofah composite filler. The nano-hydroxyapatite loofah composite filler of the present invention is used to adsorb heavy metals in landfill leachate, and the optimal adsorption rate of Pb is as high as 59%, and the optimal adsorption rate of Cr is as high as 92.31%, and the adsorption effect is remarkable.

Description

A kind of nano-hydroxyapatite loofah composite filler and its preparation method and application

technical field

The invention relates to the technical field of wastewater treatment, in particular to a nano-hydroxyapatite loofah composite filler and a preparation method and application thereof.

Background technique

Around 2000, my country's urban domestic waste increased rapidly. For this reason, the country vigorously built waste landfills. So far, most landfills have been used for 20 years. With the increase of landfill time, the content of heavy metals in landfill leachate shows an increasing trend, and the content of heavy metals such as As, Mn, Zn, Pb, Cd, Cr and Ni is relatively high. .

In order to solve this problem, some people use biochemical methods to treat landfill leachate. However, due to the poor biodegradability of landfill leachate, and most heavy metals have an inhibitory effect on the nitrifying and denitrifying bacteria, leading to the gradual emergence of CMBR in the later stage of operation and maintenance. Poor microbial flora activity, unstable effluent, etc.

For the treatment of high ammonia nitrogen and high heavy metal organic wastewater, since most heavy metals have a certain inhibitory effect on nitrification and denitrification bacteria, the biochemical A2/O process is currently the main application technology for landfill leachate treatment. In order to improve the treatment effect of microorganisms, most of the project site construction uses ordinary fillers in the O pool to increase the contact area between microorganisms and wastewater and improve the effect of sewage treatment, but its effect is single.

As an environmentally friendly and low-cost material, loofah has been widely used in various water treatment fields as a biofilm carrier or carbon source. The directions involved include heavy metal adsorption, fiber modification, petroleum pollutant adsorption, and biological contact oxidation bed carrier. , porous microbial carrier, etc. Some scholars use the high-temperature drying method to modify the loofah with hydroxyapatite and make it into a powdered form, which has a certain heavy metal adsorption effect, but destroys the original porous shape of the loofah, and cannot realize the biological filler as activated sludge. The effect of hanging the net.

Contents of the invention

In order to solve the above problems, the present invention provides a nano-hydroxyapatite loofah composite filler and its preparation method and application.

In order to achieve the above object, one of the technical solutions adopted in the present invention is to provide a preparation method of nano-hydroxyapatite loofah composite filler, said method comprising the following steps:

S1: Take the loofah with a water content of 5-10% and soak it in hydrogen peroxide with a mass concentration of 30%, take it out and dry it after soaking for 2 hours;

S2: Soak the dried loofah in step S1 in Ca(NO ₃ ) ₂ ·4H ₂ O solution for 8 hours;

S3: Add diammonium hydrogen phosphate dropwise to the solution in step S2 according to the molar ratio of Ca and P of 1.67:1, then adjust the pH to 9-9.5 with ammonia water with a volume concentration of 10-15%, and stir for 4-5h;

S4: Wash the loofah obtained in step S3 and dry it at 75-78°C for 24 hours;

S5: Repeat steps S2-S4 three times to obtain nano-hydroxyapatite loofah composite filler.

Further, the concentration of the Ca(NO ₃ ) ₂ ·4H ₂ O solution is 0.0334moL/L.

Furthermore, the concentration of diammonium hydrogen phosphate is 0.02moL/L.

In order to achieve the above object, the second technical solution adopted by the present invention is to provide a nano-hydroxyapatite loofah composite filler prepared by the method of the present invention.

In order to achieve the above purpose, the third technical solution adopted by the present invention is: the nano-hydroxyapatite loofah composite filler prepared by the present invention is applied to but not limited to the treatment of landfill leachate.

In order to achieve the above object, the fourth technical solution adopted by the present invention is to provide a bioreactor for treating landfill leachate, the filler used in the reactor is the nano-hydroxyapatite loofah composite filler prepared by the present invention .

Further, the bioreactor is also provided with a plurality of porous suspension balls, and the nano-hydroxyapatite loofah composite filler is filled in the porous suspension balls.

Beneficial effects of the present invention:

The nano-hydroxyapatite loofah composite material prepared by the method of the present invention is used as the filler of the bioreactor, which effectively solves the problem of heavy metal pretreatment in landfill leachate, reduces engineering equipment, and shortens the hydraulic retention time (HRT); It solves the problem that the traditional adsorption method will produce a large amount of heavy metal-containing sludge and the cost of sludge treatment is high.

The invention utilizes the porous multi-level structure of loofah to realize integrated synchronous nitrification and denitrification, and replaces the traditional A2/O pool with one reaction pool, which not only reduces the size of the pool, simplifies the equipment, but also reduces energy consumption. The cost is reduced. In addition, the denitrification effect of simultaneous nitrification and denitrification is better, which avoids the problem of insufficient C/N ratio of leachate in old landfills, and avoids the problem of difficult operation or the need to add C sources. At the same time, loofah Composed of 65.5% cellulose, 17.5% hemicellulose and 15.2% lignin, it can be used as part of the C source to supply nitrifying bacteria and denitrifying bacteria for metabolic reproduction; loofah is a rural solid waste with low price, so it can be used as a raw material The prepared composite material is an environment-friendly and low-cost material. Moreover, microorganisms degrade the lignin in the loofah, which can realize the resource utilization and reduction of the loofah.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail below.

Description of drawings

The accompanying drawings constituting a part of this application are used to provide further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention.

Fig. 1 is the outward appearance figure of the luffa raw material of the embodiment of the present invention;

Fig. 2 is the scanning electron micrograph of the loofah raw material of the embodiment of the present invention;

Fig. 3 is the scanning electron micrograph of the nano-hydroxyapatite loofah composite filler of the embodiment of the present invention;

4 is a schematic diagram of nano-hydroxyapatite loofah composite filler filled in porous suspension balls according to an embodiment of the present invention;

Fig. 5 is the synchronous nitrification and denitrification biological denitrification system diagram of the external anaerobic, intermediate anoxic and internal aerobic synchronous nitrification and denitrification formed on the surface of the nano-hydroxyapatite loofah composite filler of the embodiment of the present invention;

Fig. 6 is the structural representation of the bioreactor of the embodiment of the present invention;

Fig. 7 is the figure of removal effect of Pb in landfill leachate by loofah before and after the process of the inventive method;

Fig. 8 is a graph showing the removal effect of Cr in landfill leachate by loofah before and after treatment by the method of the present invention.

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.

Example 1

A preparation method of nano-hydroxyapatite loofah composite filler, said method comprising the following steps:

Refer to Figure 1, S1: Take a loofah with a water content of 5-10% and soak it in hydrogen peroxide with a mass concentration of 30%, soak it for 2 hours, take it out and dry it; specifically, you can directly buy the finished loofah and dry it until it contains water The water content of the loofah is 5-10%, and the picked loofah can also be dried until the water content is 5-10%, then peeled, removed the seeds, and the two ends are removed to obtain the loofah; then the loofah with the water content of 5-10% Soak in hydrogen peroxide with a mass concentration of 30%. The purpose is to remove the colloid in the loofah and increase the fiber content of the loofah. After soaking for 2 hours, take it out and dry it.

S2: Soak the dried loofah in step S1 in Ca(NO ₃ ) ₂ ·4H ₂ O solution for 8 hours; specifically, first, weigh Ca(NO ₃ ) ₂ ·4H ₂ O and adjust to paste, then add water at a temperature of 60-65°C and stir until the concentration of Ca(NO ₃ ) ₂ 4H ₂ O is 0.0334moL/L; then soak the dried loofah in step S1 in Ca(NO 3 ) 2 ·4H 2 O ₃ ) In ₂ ·4H ₂ O solution, the purpose is to make the calcium ions evenly distributed around the functional groups of the loofah, so as to locate the site where hydroxyapatite is formed, and soak for 8 hours.

S3: Add diammonium hydrogen phosphate dropwise to the solution in step S2 according to the molar ratio of Ca and P of 1.67:1, then adjust the pH to 9-9.5 with ammonia water with a volume concentration of 10-15%, and stir for 4-5h; specifically Yes, first prepare the diammonium hydrogen phosphate solution with a concentration of 0.02moL/L, and then add the prepared diammonium hydrogen phosphate solution to the Ca(NO ₃ ) In _{2.4H 2} O solution, combine phosphate ions with calcium ions on the surface of the loofah to form hydroxyapatite, then use ammonia water with a volume concentration of 10-15% to adjust the pH to 9-9.5, and stir at a low speed for 4 -4.5h.

S4: Wash the loofah obtained in step S3 and dry it at 75-78° C. for 24 hours; specifically, the water used for cleaning the loofah is pure water, and the drying is performed in an oven.

S5: Repeat steps S2-S4 three times to obtain nano-hydroxyapatite loofah composite filler.

For verifying the modification effect of the inventive method to loofah, the nano-hydroxyapatite loofah composite filler prepared by the loofah raw material and the present invention is observed under SEM, the results are shown in Fig. 2 and Fig. 3, as can be seen from the figure It is found that porous hydroxyapatite attachment material has been obviously formed on the surface of the nano-hydroxyapatite loofah composite filler modified by the method of the present invention, the pore diameter is clear, the size distribution is uniform, and the specific surface area for adsorption is greatly increased.

Example 2

The bioreactor shown in Figure 6 is used to treat the landfill leachate of a waste incineration plant. The filler used in the bioreactor is the nano-hydroxyapatite loofah composite filler prepared in Example 1. First, the nano-hydroxyapatite The loofah composite filler is cut into a square with a side length of 80mm, and then filled into PP porous suspension balls of φ100, and the porous suspension balls are connected by yarn, as shown in Figure 4.

After analysis, the COD value in the landfill leachate is high, the B/C ratio is 0.22, and the biodegradability is poor. The water quality is shown in Table 1.

Table 1 Water quality of landfill leachate

As can be seen from Table 1, the main heavy metal pollution in the landfill leachate is Cr and Pb, so the nano-hydroxyapatite loofah composite filler of the present invention and the loofah raw material not processed by the method of the present invention are used to fill the same Quantity of porous suspension balls for comparative adsorption experiments on Cr and Pb in landfill leachate.

Adjust the pH of landfill leachate to be 6.5-7.5, under continuous aeration, absorb respectively 30min, 1h, 2h, 4h, 8h, 12h, 24h, 48h, investigate the effect of loofah before and after the process of the inventive method on landfill leachate The adsorption effect of Cr and Pb, the experimental effect is as shown in Figure 7, as can be seen from Figure 7, the nano-hydroxyapatite loofah composite filler prepared by the method of the present invention has an optimal adsorption rate of Pb in landfill leachate up to 59%, which is 41.85% higher than the best adsorption rate of loofah raw material 17.15%; the concentration of Pb in the effluent after adsorption is as low as 0.098mg/L. It can meet the first-level A standard of "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB 18918-2002).

As can be seen from Figure 8, the nano-hydroxyapatite loofah composite filler prepared by the method of the present invention has an optimal adsorption rate of Cr in landfill leachate up to 92.31%, which is 57.69% higher than the optimal adsorption rate of the loofah raw material. Increased by 34.7%; the concentration of Cr in the effluent after adsorption is as low as 0.02mg/L. It can meet the first-level A standard of "Pollutant Discharge Standards for Urban Sewage Treatment Plants" (GB 18918-2002).

The nano-hydroxyapatite loofah composite material prepared by the method of the present invention is used as the filler of the bioreactor, which effectively solves the problem of heavy metal pretreatment in landfill leachate, reduces engineering equipment, and shortens the hydraulic retention time (HRT); It solves the problem that the traditional adsorption method will produce a large amount of heavy metal-containing sludge and the cost of sludge treatment is high.

As shown in Figure 5, the present invention utilizes the porous multi-level structure of loofah to realize integrated synchronous nitrification and denitrification, and replaces the traditional A2/O pool with a reaction pool, which not only reduces the pool size, simplifies the equipment, It also reduces energy consumption and cost. In addition, the denitrification effect of synchronous nitrification and denitrification is better, avoiding the problem of insufficient C/N ratio of leachate in old landfills, and avoiding difficult operation or the need to add C source Problem, at the same time, loofah is composed of 65.5% cellulose, 17.5% hemicellulose and 15.2% lignin, which can be used as part of the C source to supply nitrifying bacteria and denitrifying bacteria for metabolic reproduction; loofah is rural solid waste, the price Low, the composite material prepared as a raw material is environmentally friendly and low-cost material. Moreover, microorganisms degrade the lignin in the loofah, which can realize the resource utilization and reduction of the loofah.

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

Claims (7)

1. A preparation method of a nano hydroxyapatite and loofah sponge composite filler is characterized by comprising the following steps:

s1: soaking retinervus Luffae fructus with water content of 5-10% in 30% hydrogen peroxide for 2 hr, taking out, and air drying;

s2: placing the loofah sponge dried in the step S1 in Ca (NO) ₃ ) ₂ ·4H ₂ Soaking in the O solution for 8 hours;

s3: dropwise adding diammonium hydrogen phosphate into the solution obtained in the step S2 according to the molar ratio of Ca to P of 1.67, then adjusting the pH value to 9-9.5 by adopting ammonia water with the volume concentration of 10-15%, and stirring for 4-5h;

s4: cleaning the loofah obtained in the step S3, and drying for 24 hours at 75-78 ℃;

s5: and repeating the steps S2-S4 for three times to obtain the nano hydroxyapatite and loofah sponge composite filler.

2. The method for preparing nano hydroxyapatite and loofah sponge composite filler according to claim 1, wherein the Ca (NO) is ₃ ) ₂ ·4H ₂ The concentration of the O solution was 0.0334moL/L.

3. The method for preparing nano hydroxyapatite and loofah sponge composite filler according to claim 1, wherein the concentration of diammonium phosphate is 0.02moL/L.

4. A nano hydroxyapatite and loofah sponge composite filler, which is characterized in that the nano hydroxyapatite and loofah sponge composite filler is prepared by the method of any one of claims 1 to 3.

5. An application of the nano-hydroxyapatite and loofah sponge composite filler of claim 4 in landfill leachate treatment.

6. A bioreactor for treating landfill leachate, wherein the filler in the bioreactor is the nano hydroxyapatite and loofah sponge composite filler according to claim 4.

7. The bioreactor for treating landfill leachate according to claim 6, wherein a plurality of porous suspension balls are further disposed in the reactor, and the nano hydroxyapatite and loofah sponge composite filler is filled in the porous suspension balls.

Images