CN112569900A

CN112569900A - Preparation method and application of novel municipal sludge biochar

Info

Publication number: CN112569900A
Application number: CN202011225821.7A
Authority: CN
Inventors: 刁增辉; 钱伟
Original assignee: Zhongkai University of Agriculture and Engineering
Current assignee: Zhongkai University of Agriculture and Engineering
Priority date: 2020-11-05
Filing date: 2020-11-05
Publication date: 2021-03-30
Anticipated expiration: 2040-11-05
Also published as: CN112569900B

Abstract

The invention relates to a preparation method and application of novel municipal sludge biochar.A sludge biochar material co-modified by iron and acid is obtained by taking acid mine wastewater generated by exploiting pyrite as a modifier of the municipal sludge biochar; the introduction of the acid mine wastewater can obviously improve the adsorption performance of the sludge biochar material and can efficiently remove the heavy metal lead and the organic matter atrazine by single or simultaneous adsorption; when single heavy metal lead and organic atrazine are adsorbed and removed, the adsorption capacity can reach 18.30 mg/g and 6.20 mg/g respectively; when the removal is carried out synchronously, the adsorption capacity can be respectively as high as 13.90 mg/g and 4.02 mg/g. The invention realizes the treatment and recycling of the acid mine wastewater and the municipal sludge, realizes the single and synchronous adsorption removal of various pollutants, and finally realizes the environmental management concept of treating wastes with processes of wastes against one another.

Description

Preparation method and application of novel municipal sludge biochar

Technical Field

The invention belongs to the field of resource utilization and treatment of solid waste and wastewater in environmental engineering, and particularly relates to a preparation method and application of novel municipal sludge biochar.

Background

Along with the increase of urban scale and the rapid development of industrialization, toxic pollutants discharged to environmental water bodies are increased, which causes more and more serious water body pollution, especially heavy metals and organic pollutants which are the most serious harm to the environment, and the heavy metals and the organic pollutants coexist in the environmental water bodies, thereby bringing serious threat to human health and safety, and the treatment of the water bodies polluted by the heavy metals and the organic matters is urgent. In addition, the increasing environmental pollution also causes municipal sewage plants to generate the rapidly growing municipal sludge, and how to properly dispose the sludge and realize the recycling is one of the difficult problems of solid waste treatment. Research shows that the sludge pyrolysis method can effectively reduce the sludge amount and obtain a resource product, namely sludge biochar, which is widely used as an adsorbent for removing toxic pollutants such as heavy metals and organic matters. However, the original sludge biochar has the defects of small specific surface area, high ash content, multiple micropores, small pore volume, poor adsorption selectivity and the like, and certain defects exist in chemical properties, surface functional groups and the like, so that the capacity of adsorbing pollutants is limited, and the requirement of quickly repairing environmental pollution cannot be met. Therefore, the structure and the property of the biochar are modified by physical and chemical means to improve the adsorption capacity of the biochar to pollutants. At present, the main methods for modifying the biochar are chemical modification, including metal salt modification, oxidation modification, reduction modification and acid-base modification. Iron is an environment-friendly element, so that commercial ferric chloride and ferric sulfate are widely applied to modification of biochar, and on one hand, modification of ferric salt cannot cause environmental pollution; on the other hand, the modified biochar surface can be loaded with iron oxide and oxyhydroxide, which is beneficial to enhancing the combination of the biochar with heavy metals and organic pollutants, thereby improving the pollution adsorption capacity of the sludge biochar. Therefore, there is an urgent need to find iron-rich inexpensive raw materials as iron modifiers instead of commercial iron salts.

In recent decades, the water and soil environmental pollution caused by pyrite acid mine wastewater is also receiving more and more extensive attention at home and abroad, and the acid mine wastewater is mine wastewater which has a pH value of about 2, contains high-concentration iron ions and also contains some heavy metal ions such as copper, manganese and the like. Such acidic waste water can acidify the surrounding water and soil, seriously endanger the environment and human health and safety, and at present, the waste water is treated by a coagulating sedimentation method and a biological method. However, the pyrite acid mine wastewater integrates two significant characteristics of high acidity and high iron content, which are required for acid and iron salt modification in a common modification method for biochar. However, no patent technology for preparing municipal sludge biochar by utilizing acid mine wastewater to modify and applying the same has been reported so far.

Disclosure of Invention

The invention provides a preparation method and application of novel municipal sludge biochar, which can effectively solve the problems in the background art.

In order to solve the problems, the technical scheme adopted by the invention is as follows: a preparation method of novel municipal sludge biochar comprises the following steps:

preparing sludge biochar:

s1: centrifugally dewatering the sludge in the secondary sedimentation tank of the municipal sewage plant, drying to constant weight, and grinding to obtain dewatered sludge;

s2: heating the dewatered sludge to 650 ℃ at the speed of 5 ℃/min in a tubular furnace under the protection of nitrogen, and performing pyrolysis at high temperature for 180 min to obtain carbonized sludge;

s3: grinding the carbonized sludge and sieving the ground carbonized sludge with a 100-mesh sieve to obtain sludge biochar;

preparing modified sludge biochar:

s4: stirring and mixing the filtered and pretreated acidic mine wastewater for 1440 min according to a certain solid-to-liquid ratio of the sludge biochar to the acidic mine wastewater, and then drying at 150 ℃;

s5: pyrolyzing for 180 min at 650 ℃ under the protection of nitrogen, grinding and sieving with a 100-mesh sieve to obtain the modified sludge biochar.

In a further preferred embodiment of the present invention, the mass concentration of iron in the acid mine wastewater in step S4 is 0.89-1.02 g/L.

As a further preferable scheme of the invention, the solid-to-liquid ratio of the sludge biochar to the acidic mine wastewater in the step S4 is 3-5: 1.

as a further preferable scheme of the invention, the application method of the sludge biochar comprises the following steps: adding the modified sludge biochar into a water body containing heavy metal lead and/or organic matter atrazine, reacting for 120 min, and adsorbing the heavy metal lead and the organic matter atrazine singly or synchronously.

As a further preferable scheme of the invention, the mass concentration of lead in the polluted water body is 10-120 mg/L; the mass concentration of the atrazine is 5-30 mg/L, and the dosage of the modified sludge biochar material is 1-4 g/L.

As a further preferred scheme of the invention, before adding the modified sludge biochar material, the modified sludge biochar material must be ground and sieved to ensure that the particles are in a range of less than 150 mu m.

As a further preferable scheme of the invention, before adding the modified sludge biochar material, the pH value of the water body is adjusted to 3-9.

As a further preferable scheme of the invention, the dosage of the modified sludge biochar material added into the water body polluted by lead and/or atrazine is 3 g/L.

As a further preferable scheme of the invention, the mass concentration of lead in the polluted water body is 60 mg/L; the mass concentration of the atrazine in the polluted water body is 20 mg/L.

As a further preferable scheme of the invention, in the mixed solution, the mass concentration of lead in the polluted water body is 60 mg/L, and the mass concentration of atrazine is 5-30 mg/L.

Compared with the prior art, the invention provides a preparation method and application of novel municipal sludge biochar, and the preparation method has the following beneficial effects:

1. the preparation cost is low, and the raw materials are cheap and easy to obtain; the invention adopts the acid mine wastewater to replace commercial ferric salt and acid reagent to modify the municipal sludge biochar, thereby realizing the treatment and reclamation of the acid mine wastewater.

2. The treatment process is simple to operate and low in operation cost; the method adopts the acid mine wastewater modified municipal sludge biochar to remove heavy metal lead and organic matter atrazine, can realize higher removal effect in single or synchronous removal, and realizes the environmental idea of 'treating waste with waste' of acid mine wastewater and municipal sludge.

3. The range of applicable target objects is wide; the invention is not only suitable for the polluted water body containing lead and/or atrazine, but also suitable for other water bodies containing heavy metals and other organic pollutants.

Drawings

FIG. 1 is a scanning electron microscope image of the sludge biochar modified by the acidic mine wastewater prepared by the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

In the following embodiments, before analyzing and determining a water sample, a water sample is subjected to filtration pretreatment, and the concentration of lead in the water sample is determined by an atomic absorption spectrophotometry; the atrazine is measured by a high performance liquid chromatography.

Example 1:

the preparation method of the novel municipal sludge biochar is described in detail by the embodiment; in this example, the preparation procedure was as follows:

centrifugally dewatering the sludge in the secondary sedimentation tank of the municipal sewage plant, drying to constant weight, and grinding to obtain dewatered sludge; then, pyrolyzing the dewatered sludge at the high temperature of 650 ℃ for 180 min in a tubular furnace under the protection of nitrogen, grinding and sieving by a 100-mesh sieve to obtain sludge biochar; filtering and pretreating acid mine wastewater with the mass concentration of iron of 0.95 g/L, mixing and stirring 1440 min according to the solid-to-liquid ratio of the sludge biochar to the acid mine wastewater of 4:1, drying at 150 ℃, pyrolyzing at 650 ℃ for 180 min under the protection of nitrogen, grinding and sieving with a 100-mesh sieve to obtain the modified sludge biochar material.

Example 2:

in this example, the single adsorption effect of different sludge biochar on lead and atrazine was compared, and the steps were as follows: adding unmodified and modified sludge biochar into a lead or atrazine-containing polluted water body to remove the lead or atrazine from the water body, adopting a 100 mL beaker as a reactor, treating the water body with the lead concentration of 60 mg/L or the atrazine concentration of 20 mg/L and the pH value of the water body of 5, wherein the lead concentration is 50 mL. Adding 3 g/L of unmodified or modified sludge biochar into a beaker, and placing the beaker on a stirrer, wherein the rotating speed is 120 rpm, and the reaction time is 120 min. Example 2 the results are shown in table 1.

As can be seen from the table, the lead adsorption removal rate of the unmodified sludge biochar in the reaction time of 120 min is only 15.83 percent, and the corresponding adsorption amount is 3.13 mg/g, while the removal rate of the municipal sludge biochar modified by the acid mine wastewater is up to 92.40 percent, and the corresponding adsorption amount is 18.30 mg/g, which is more than five times that of the unmodified sludge biochar. In addition, the adsorption removal rate and the adsorption amount of the unmodified sludge biochar to the atrazine are respectively 27.50 percent and 1.82 mg/g, and the adsorption capacity to the atrazine is remarkably improved after the modified sludge biochar is modified. The result shows that the high acidity and the high iron content in the acid mine wastewater are key for the success of modifying the sludge biochar, on one hand, the high acidity can remove impurities on the surface of the biochar, and on the other hand, iron oxide and hydroxide particles are formed on the surface of the biochar, which is beneficial to the adsorption and complexation of pollutants. Therefore, the municipal sludge biochar modified by the acidic mine wastewater is feasible for improving the adsorption effect of the biochar on heavy metal lead and organic atrazine.

Example 3:

the difference from example 2 was that the pH was adjusted to 3, 5, 7 and 9, and the change in lead or atrazine in the water before and after the reaction was measured under the same conditions as in example 2. Example 3 the results are shown in table 2. As can be seen from the table, the adsorption of lead depends on the change of pH conditions, and the adsorption effect is superior to neutral and alkaline in acidic conditions. Wherein pH =5 is the optimum pH reaction condition, the lead removal rate is up to 92.40%, and the corresponding adsorption quantity is 18.30 mg/g. In addition, the adsorption of atrazine also has a similar tendency, and the adsorption effect of biochar on atrazine is the best in acidity.

Example 4:

the difference from example 3 is that the amount of the sludge biochar was adjusted to 1-4 g/L, the other conditions were the same as in example 3, and the change in lead or atrazine in the water before and after the reaction was measured. Example 4 the results are shown in table 3. As can be seen from the table, the adsorption removal rates of lead and atrazine both increased with the increase of the sludge biochar dose, and when the dose was 3 g/L, the removal rates of both reached a higher level, and further increasing the dose did not change much.

Example 5:

the difference from example 4 is that the lead concentration was adjusted to 10-120 mg/L or the atrazine concentration was adjusted to 5-30 mg/L, the other conditions were the same as example 4, and the change in lead or atrazine in the water before and after the reaction was measured. The results of example 5 are shown in Table 4. As can be seen from the table, the adsorption removal rates of lead and atrazine both decreased with the increase of the respective concentrations thereof, and the removal rates of both reached higher levels, 92.40% and 93.96%, when the concentrations of lead and atrazine were 60 mg/L and 20 mg/L, respectively.

Example 6:

the difference from the example 2 is that the polluted water body is a mixed solution of lead and atrazine, the fixed lead concentration is 60 mg/L, and the atrazine concentration is adjusted to be 5-30 mg/L. The other conditions were the same as in example 2, and the changes in the concentrations of lead and atrazine in the water body before and after the reaction were measured each time. The results of example 7 are shown in Table 5. As shown in the table, the adsorption removal effect of the sludge biochar on lead is reduced along with the increase of the concentration of the added atrazine, when the concentration of the atrazine is less than or equal to 10 mg/L, the lead removal rate can be maintained at 83.14%, and the atrazine can also achieve the removal rate of 74.27%. The result shows that the lead and the atrazine can realize single removal of the modified sludge biochar in the acid mine wastewater and synchronous and efficient removal of the lead and the atrazine.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. a preparation method of novel municipal sludge biochar, its method comprises the following steps:

Sludge biochar production:

S1: centrifugally dehydrate the sludge in the secondary sedimentation tank of the municipal sewage plant, dry it to a constant weight, and grind it to obtain dewatered sludge;

S2: Under nitrogen protection, the dewatered sludge was raised to 650 °C at a rate of 5 °C/min in a tube furnace, and the carbonized sludge was obtained by maintaining high temperature for pyrolysis for 180 min;

S3: Grind the carbonized sludge through a 100-mesh sieve to obtain sludge biochar;

Modified sludge biochar production:

S4: The acid mine wastewater after filtering and pretreatment is stirred and mixed for 1440 min according to a certain solid-liquid ratio of sludge biochar and acid mine wastewater, and then dried at 150 °C;

S5: Under nitrogen protection, pyrolyzed at a high temperature of 650 °C for 180 min, and ground through a 100-mesh sieve to obtain modified sludge biochar.

2. A new type of municipal sludge biochar according to claim 1, wherein the method is that in step S4, the mass concentration of iron in the acid mine wastewater is 0.89-1.02 g/L.

3. A new type of municipal sludge biochar according to claim 1, wherein the method is that in step S4, the solid-liquid ratio of sludge biochar to acid mine wastewater is 3-5:1.

4. a kind of novel municipal sludge biochar according to claim 1, its application method is: in the water body containing heavy metal lead and/or organic matter atrazine, add modified sludge biochar, react 120 min , single or simultaneous adsorption removal of heavy metal lead and organic atrazine.

5. the application of a kind of novel municipal sludge biochar according to claim 4, its method is, the mass concentration of lead in the polluted water body is 10-120 mg/L; the mass concentration of atrazine is 5-30 mg /L, the dosage of the modified sludge biochar material is 1-4 g/L.

6. The application of a new type of municipal sludge biochar according to claim 4, the method of which is that before adding the modified sludge biochar material, it must be ground and sieved to ensure that its particles are in the less than 150 μm range.

7 . The application of a new type of municipal sludge biochar according to claim 4 , wherein the method is to adjust the pH value of the water body to 3-9 before adding the modified sludge biochar material. 8 .

8. the application of a kind of novel municipal sludge biochar according to claim 4, its method is, in lead-containing and/or atrazine polluted water body, add modified sludge biochar material dosage is 3 g/ L.

9. the application of a kind of novel municipal sludge biochar according to claim 4, its method is, the mass concentration of lead in the polluted water body is 60 mg/L; the mass concentration of atrazine in the polluted water body is 20 mg/L L.

10. the application of a kind of novel municipal sludge biochar according to claim 4, its method is, in the mixed solution, the mass concentration of lead in the polluted water body is 60 mg/L, the mass concentration of atrazine is 5 -30 mg/L.