CN117985909B - Treatment and Reuse of River Sediment - Google Patents

Abstract

The invention discloses a method for treating and reusing riverbed mud, comprising the following steps: step 1, sampling the riverbed mud, screening out debris, and obtaining a mud sample; step 2, modifying activated carbon with nitric acid, and then compounding it with polyethylene glycol to form a film, preparing a polyethylene glycol composite carbon-based filter membrane, and using it to filter the mud sample multiple times, adsorbing heavy metal ions, and air-drying and sieving the solid separated by filtration to obtain air-dried mud; step 3, uniformly mixing the air-dried mud with normal soil after air-drying to obtain a mixed matrix, which is used as a plant culture matrix. The present invention treats and reuses the riverbed mud to obtain a plant culture matrix, protects the environment, and saves costs.

Description

Treatment and Reuse of River Sediments

Technical Field

The present invention relates to the technical field of riverbed mud treatment, and more specifically, to a method for treating and reusing riverbed mud.

Background Art

Bottom mud is the product of long-term accumulation and precipitation at the bottom of the river. Excessive bottom mud can easily cause river siltation. In addition to external pollution sources, the secondary pollution caused by the release of bottom mud accumulation is also an important factor affecting the water quality of the reservoir. Bottom mud pollutants are roughly divided into four parts: (1) nutrients: nitrogen and phosphorus compounds; (2) large amounts of organic matter: carbohydrates; (3) heavy metals: Cd, Mn, etc.; (4) non-metals, Se, etc. Bottom mud has the characteristics of large amount of sedimentation, high water content, serious pollution, and a variety of nutrients and harmful components. If it is not properly disposed of, randomly piled up and landfilled, it will not only occupy land resources, but also cause secondary pollution to the environment through rainwater scouring. The nutrients in the bottom mud cannot be fully utilized. Therefore, the resource utilization of bottom mud is very important. In the prior art, a patent application with application publication number CN110451758A discloses a method and system for resource utilization of river bottom mud. The method removes organic matter in the bottom mud by breaking the wall and sterilizing it, so that the treated bottom mud can be fully utilized. However, in actual application, it was found that after removing organic matter, the nutritional content of the sediment was greatly reduced, which is not conducive to its application in crop planting, and the heavy metals contained in the sediment will also cause secondary pollution to the environment.

Summary of the invention

The invention provides a method for treating and reusing riverbed mud, wherein the treated mud can be used as a plant culture matrix to achieve the purpose of resource utilization.

In order to achieve these purposes and other advantages according to the present invention, a method for treating and reusing riverbed mud is provided, comprising the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2: Modify activated carbon with nitric acid, and then compound the activated carbon with polyethylene glycol to form a film to prepare a polyethylene glycol composite carbon-based filter membrane, and use the membrane to filter the sediment sample multiple times to adsorb heavy metal ions, and air-dry and sieve the filtered and separated solids to obtain air-dried sediment;

Step 3: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, which is used as a plant culture matrix.

Preferably, the screening process in step 2 uses a vibrating screen with a pore size of 1 cm for separation.

Preferably, in step three, the weight percentage of the air-dried sludge in the mixed matrix is 10% to 25%.

Preferably, in the step 2, the specific process of modifying the activated carbon with nitric acid is: placing the powdered activated carbon in concentrated nitric acid at 80° C. and reflux for 12 hours, filtering under reduced pressure until the pH of the filtrate is neutral, and the solid collected after filtration is the nitric acid-modified activated carbon, and the weight ratio of the activated carbon to the concentrated nitric acid is 1:(150-200).

Preferably, in step 2, the compounding process with polyethylene glycol is specifically as follows:

Take the nitric acid-modified activated carbon, add dimethylformamide, ultrasonically disperse for 2 hours, and then stir at 0°C. Pass nitrogen into the system for protection, and slowly drop oxalyl chloride, heat to 25°C for reaction for 2 hours, heat to 70°C for stirring for 10 to 14 hours, continue to heat to 100°C, add polyethylene glycol, stir and react for 6 to 24 hours to obtain a polyethylene glycol composite modified carbon solution, wherein the weight ratio of the nitric acid-modified activated carbon, oxalyl chloride and polyethylene glycol is 1:(55 to 65):(8 to 12).

Preferably, the mass ratio of dimethylformamide to polyethylene glycol is (45-55):1.

Preferably, the molecular weight of the polyethylene glycol is 10,000-20,000.

Preferably, the film forming process in step 2 is specifically as follows: standing the polyethylene glycol composite modified carbon solution for degassing, casting the solution into a film, and drying the solution to obtain the polyethylene glycol composite carbon-based filtration membrane.

Preferably, the average pore size of the polyethylene glycol composite carbon-based filter membrane is 50 to 120 nm.

The present invention includes at least the following beneficial effects: the method for treating and reusing riverbed mud of the present invention treats and recycles riverbed mud, removes harmful substances such as heavy metals in the mud, retains the original nutrient content, and uses it as a plant culture matrix, thereby achieving the purpose of resource utilization, protecting the environment, and saving costs.

Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified; in the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected, set, or detachably connected, set, or connected and set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood in specific circumstances. The orientation or position relationship indicated by the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or position relationship shown, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

Example 1

A method for treating and reusing riverbed mud comprises the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2: Place the powdered activated carbon in concentrated nitric acid at 80° C. and reflux for 12 hours, and filter under reduced pressure until the pH of the filtrate is neutral. The solid collected after filtration is nitric acid-modified activated carbon, and the weight ratio of the activated carbon to concentrated nitric acid is 1:180;

Step 3: Take the nitric acid-modified activated carbon, add dimethylformamide, ultrasonically disperse for 2 hours, and then stir at 0°C. Pass nitrogen into the system for protection, and slowly drop oxalyl chloride, heat to 25°C and react for 2 hours, heat to 70°C and stir for 12 hours, continue to heat to 100°C, add polyethylene glycol with a molecular weight of 15,000, and stir for 12 hours to obtain a polyethylene glycol composite modified carbon solution, wherein the weight ratio of the nitric acid-modified activated carbon, oxalyl chloride, and polyethylene glycol is 1:50:10, and the mass ratio of dimethylformamide to polyethylene glycol is 50:1;

Step 4: degassing the polyethylene glycol composite modified carbon solution, casting it into a film, and drying it to obtain a polyethylene glycol composite carbon-based filter membrane with an average pore size of 80 nm, using it to filter the sediment sample multiple times to adsorb heavy metal ions, and air-drying the solid separated by filtration, and sieving it with a vibrating screen with a pore size of 1 cm to obtain air-dried sediment;

Step 5: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, wherein the air-dried sludge accounts for 10% by weight of the mixed matrix, and the mixed matrix is used as a plant culture matrix.

Example 2

A method for treating and reusing riverbed mud comprises the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2: Place the powdered activated carbon in concentrated nitric acid at 80° C. and reflux for 12 hours, and filter under reduced pressure until the pH of the filtrate is neutral. The solid collected after filtration is nitric acid-modified activated carbon, and the weight ratio of the activated carbon to concentrated nitric acid is 1:150;

Step 3: Take the nitric acid-modified activated carbon, add dimethylformamide, ultrasonically disperse for 2 hours, and then stir at 0°C. Pass nitrogen into the system for protection, and slowly drop oxalyl chloride, heat to 25°C and react for 2 hours, heat to 70°C and stir for 10 hours, continue to heat to 100°C, add polyethylene glycol with a molecular weight of 10,000, and stir for 6 hours to obtain a polyethylene glycol composite modified carbon solution, wherein the weight ratio of the nitric acid-modified activated carbon, oxalyl chloride, and polyethylene glycol is 1:55:8, and the mass ratio of dimethylformamide to polyethylene glycol is 45:1;

Step 4: degassing the polyethylene glycol composite modified carbon solution, casting it into a film, and drying it to obtain a polyethylene glycol composite carbon-based filter membrane with an average pore size of 50 nm, using it to filter the sediment sample multiple times to adsorb heavy metal ions, and air-drying the solid separated by filtration, and sieving it with a vibrating screen with a pore size of 1 cm to obtain air-dried sediment;

Step 5: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, wherein the air-dried sludge accounts for 25% by weight of the mixed matrix, and the mixed matrix is used as a plant culture matrix.

Example 3

A method for treating and reusing riverbed mud comprises the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2: Place the powdered activated carbon in concentrated nitric acid at 80° C. and reflux for 12 hours, and filter under reduced pressure until the pH of the filtrate is neutral. The solid collected after filtration is nitric acid-modified activated carbon, and the weight ratio of the activated carbon to concentrated nitric acid is 1:200;

Step 3: Take the nitric acid-modified activated carbon, add dimethylformamide, ultrasonically disperse for 2 hours, and stir at 0°C. Pass nitrogen into the system for protection, and slowly drop oxalyl chloride, heat to 25°C and react for 2 hours, heat to 70°C and stir for 14 hours, continue to heat to 100°C, add polyethylene glycol with a molecular weight of 20,000, and stir for 24 hours to obtain a polyethylene glycol composite modified carbon solution, wherein the weight ratio of the nitric acid-modified activated carbon, oxalyl chloride, and polyethylene glycol is 1:65:12, and the mass ratio of dimethylformamide to polyethylene glycol is 55:1;

Step 4: degassing the polyethylene glycol composite modified carbon solution, casting it into a film, and drying it to obtain a polyethylene glycol composite carbon-based filter membrane with an average pore size of 120 nm, using it to filter the sediment sample multiple times to adsorb heavy metal ions, and air-drying the solid separated by filtration, and sieving it with a vibrating screen with a pore size of 1 cm to obtain air-dried sediment;

Step 5: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, wherein the air-dried sludge accounts for 10% by weight of the mixed matrix, and the mixed matrix is used as a plant culture matrix.

Example 4

A method for treating and reusing riverbed sediment, which differs from Example 1 in that the weight percentage of the air-dried sediment in step five to the mixed matrix is 25%.

Comparative Example 1

A method for treating and reusing riverbed sediment, which differs from Example 1 in that the weight percentage of the air-dried sediment in step five to the mixed matrix is 50%.

Comparative Example 2

A method for treating and reusing riverbed mud, which differs from Example 1 in that in step five, only the air-dried mud is used as a plant culture matrix.

Comparative Example 3

Only normal soil after air drying was used as plant culture medium.

Comparative Example 4

A method for treating and reusing riverbed sediment, which differs from Example 1 in that a polyethylene glycol filter membrane is used to filter the sediment sample, and specifically comprises the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2: Take polyethylene glycol with a molecular weight of 15,000, add dimethylformamide, stir, the mass ratio of dimethylformamide to polyethylene glycol is 50:1, let the polyethylene glycol solution stand for degassing, cast into a film, and after drying, obtain a polyethylene glycol composite carbon-based filter membrane with an average pore size of 80 nm, use it to filter the sediment sample multiple times, air-dry the solid after filtration and separation, and sieve it with a vibrating sieve with a pore size of 1 cm to obtain air-dried sediment;

Step 3: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, wherein the air-dried sludge accounts for 10% by weight of the mixed matrix, and the mixed matrix is used as a plant culture matrix.

Comparative Example 5

A method for treating and reusing riverbed sediment, which differs from Example 1 in that activated carbon is used to adsorb and separate the sediment sample, and then a polyethylene glycol filter membrane is used to filter the sediment sample, and specifically comprises the following steps:

Step 1: Sampling the riverbed sediment, screening out debris, and obtaining sediment samples;

Step 2, taking activated carbon and mixing it with the sediment sample;

Step 3: Take polyethylene glycol with a molecular weight of 15,000, add dimethylformamide, stir, the mass ratio of dimethylformamide to polyethylene glycol is 50:1, let the polyethylene glycol solution stand for degassing, cast into a film, and after drying, obtain a polyethylene glycol composite carbon-based filter membrane with an average pore size of 80 nm, use it to filter the mixture of the sediment sample and activated carbon multiple times, air-dry the solid after filtration and separation, and sieve it with a vibrating sieve with a pore size of 1 cm to obtain air-dried sediment;

Step 4: Evenly mix the air-dried sludge with the air-dried normal soil to obtain a mixed matrix, wherein the air-dried sludge accounts for 10% by weight of the mixed matrix, and the mixed matrix is used as a plant culture matrix.

The coordinates of the sampling points in the above-mentioned embodiments and comparative examples are 39°8′21″N and 117°5′21″E. The sampling personnel collected the surface sediment of the river with a grab-type mud sampler washed with clean water, and the sampling depth was 0-30 cm. In order to ensure that the wet weight of the sediment after filtration was not less than 3000 g, multiple samples were collected within a range of 20 m around the point. The normal soils in the above-mentioned embodiments and comparative examples were all collected from the cultivated layer of the National Field Scientific Observation and Research Station for Soil Quality in Changping, Beijing, and the soil type was brown tidal soil.

Soil physical and chemical properties determination

The sediment samples used in each embodiment, normal soil, and the air-dried sediment obtained in Examples 1 to 3 and Comparative Examples 4 to 5 were taken for soil physical and chemical property analysis, and their nutrient content and heavy metal content were measured, respectively. The results are shown in Table 1.

Table 1

The results show that compared with normal soil, riverbed mud is rich in a large amount of nutrients, but it is also an important carrier of heavy metal pollutants. The riverbed mud treatment and reuse method of the present invention is used to treat riverbed mud samples. The polyethylene glycol composite carbon-based filter membrane is compounded with activated carbon and polyethylene glycol to improve its wettability with the water system and has good adsorption to heavy metals. Since polyethylene glycol is biodegradable, it is convenient to analyze the attachment after the membrane is used, so that the activated carbon can be reused and resources are saved. In addition, the polyethylene glycol composite carbon-based filter membrane of the present invention can retain the original nutrients while adsorbing heavy metal ions, which provides an important idea for the resource utilization of sediment. In comparative example 4, since only polyethylene glycol is used as the filter membrane, the adsorption rate of heavy metals is low, and other nutrients will be separated during the separation process, so that the nutrient content is reduced. In Comparative Example 5, activated carbon is first used for adsorption and then separated using a polyethylene glycol filter membrane. However, the activated carbon adsorbed with heavy metals is easily retained by the filter membrane and retained together with the bottom mud, so that its heavy metal content is still high. In addition, when filtering with the filter membrane, some nutrients will also be separated, reducing the nutrients.

Agricultural resource utilization experiment

Take the plant culture substrates in Examples 1, 4 and Comparative Examples 1 to 3 respectively, take Chinese cabbage and spinach as test vegetables, and carry out indoor potted experiments in a greenhouse. Take 2.5 kg of each plant culture substrate and put it into plastic flower pots of the same specifications, balance indoors for 5 days, sow 8 seeds in each flower pot after the balance, observe the plant growth after 40 days of growth, and keep the water content of the matrix in the flower pot at 70% of the field water holding capacity. Observe the emergence and growth of the two vegetables. After harvesting the vegetables, study and measure the growth and development related indicators of vegetable crops, including plant height, aboveground biomass, emergence rate and average fresh weight. The results of the determination of Chinese cabbage are shown in Table 2, and the results of the determination of spinach are shown in Table 3.

Table 2 Growth and development indicators of Chinese cabbage

The results showed that the aboveground biomass and average fresh weight of Chinese cabbage showed a trend of first increasing and then decreasing. Among them, the aboveground biomass and average fresh weight were the largest when 10% or 25% of air-dried sludge was added. This is because the nutrient supply of the treatment after adding sludge is higher than that of pure soil planting, while the weight of the plants treated with 50% and 100% air-dried sludge showed a clear downward trend, which is lower than that of pure soil planting. From the results of plant height, it can be seen that the plant height of Chinese cabbage generally shows a downward trend with the increase of sludge application. This is because the content of certain elements in the sludge may have an inhibitory effect on the plant growth of Chinese cabbage, resulting in slow plant growth. For the germination rate index, Comparative Examples 1 and Comparative Examples 2 showed a downward trend. This is because the particle size of the main canal sludge is small, and when the water content is high, it is easy to stick together into blocks, and the ventilation performance is poor, which affects the crop germination rate.

Table 3 Spinach growth and development indicators

The results showed that the aboveground biomass, average fresh weight and average plant height of spinach showed a trend of first increasing and then decreasing. Among them, the aboveground biomass and average fresh weight were the largest when 10% or 25% of air-dried sludge was added. This is because the nutrient supply after adding sludge is higher than that of pure soil planting, while the plant weight and plant height of 50% and 100% air-dried sludge treatments showed a significant downward trend, but were still higher than pure soil planting. For the germination rate index, it showed an overall downward trend. This is because the particle size of the main canal sludge is small, and when the water content is high, it is easy to stick together and form blocks, and the ventilation performance is poor, which affects the crop germination rate.

The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims (4)

1. The method for treating and recycling the river sediment is characterized by comprising the following steps of:

step one, sampling river sediment, and screening impurities to obtain a sediment sample;

Secondly, modifying the activated carbon by using nitric acid, compositing the activated carbon with polyethylene glycol to form a film, preparing a polyethylene glycol composite carbon-based filtering film, filtering the substrate sludge sample for multiple times by using the polyethylene glycol composite carbon-based filtering film to adsorb heavy metal ions, and air-drying and sieving the filtered and separated solid to obtain air-dried substrate sludge;

Step three, uniformly mixing the air-dried bottom mud with the air-dried normal soil to obtain a mixed matrix which is used as a plant culture matrix;

wherein the wind dry sediment in the third step accounts for 10-25% of the weight of the mixed matrix;

In the second step, the specific process of the nitric acid modified activated carbon is as follows: placing powdery active carbon into concentrated nitric acid at 80 ℃ for reflux for 12h, carrying out reduced pressure suction filtration until the pH value of the filtrate is neutral, and collecting solid after filtration to obtain nitric acid modified active carbon, wherein the weight ratio of the active carbon to the concentrated nitric acid is 1 (150-200);

in the second step, the compounding process with polyethylene glycol specifically comprises the following steps:

Adding dimethylformamide into the nitric acid modified activated carbon, performing ultrasonic dispersion for 2 h, then placing the mixture under the condition of 0 ℃ for stirring, introducing nitrogen for protection, slowly dropwise adding oxalyl chloride, heating to 25 ℃ for reaction 2 h, heating to 70 ℃ for stirring for 10-14 h, continuously heating to 100 ℃, adding polyethylene glycol, and stirring for reaction for 6-24 h to obtain a polyethylene glycol composite modified carbon solution, wherein the weight ratio of the nitric acid modified activated carbon to the oxalyl chloride to the polyethylene glycol is 1 (55-65) (8-12);

the mass ratio of the dimethylformamide to the polyethylene glycol is (45-55): 1;

The molecular weight of the polyethylene glycol is 10000-20000.

2. The method for treating and recycling river sediment according to claim 1, wherein the sieving process in the second step is carried out by adopting a vibrating sieve with the aperture of 1 cm.

3. The method for treating and recycling river sediment according to claim 1, wherein the film forming process in the second step is specifically as follows: and standing the polyethylene glycol composite modified carbon solution for deaeration, casting to form a film, and drying to obtain the polyethylene glycol composite carbon-based filtering film.

4. The method for treating and recycling river sediment according to claim 1, wherein the average pore diameter of the polyethylene glycol composite carbon-based filtering membrane is 50-120 nm.