阅读说明：本技术 一种水热炭强化洗涤脱除土壤中多环芳烃的方法 (Method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing ) 是由 顾峥 李利兴 梁玺静 于 2021-07-23 设计创作，主要内容包括：本发明公开了一种水热炭强化洗涤脱除土壤中多环芳烃的方法,利用破碎机将水热炭、土壤分别破碎、筛分；两者的粒径不同,便于后续混合后筛分；向土壤中加入洗涤剂进行洗涤,再加入水热炭,在反应器中进行反应；反应结束后,固液分离,固体部分用筛分法分离回收土壤中的水热炭,用该水热碳吸附液体部分,即洗涤废液中的污染物质；从洗涤废液中分离出水热炭,洗涤再生后回收利用,对富集污染物的洗涤废液进行有机物提取。本发明工艺简单,装置组成简单,易于操作,脱除率高,一体化实现了洗涤废液的后处理,污染较小,且吸附后的再生液可以继续循环用于洗涤脱除土壤污染物,大大降低了洗涤废液的后处理成本,实现了了资源的可循环利用。(The invention discloses a method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon reinforced washing, which comprises the steps of respectively crushing and screening hydrothermal carbon and soil by a crusher; the particle sizes of the two are different, so that the subsequent mixing and screening are facilitated; adding a detergent into the soil for washing, adding hydrothermal carbon, and reacting in a reactor; after the reaction is finished, carrying out solid-liquid separation, separating and recovering the hydrothermal carbon in the soil from the solid part by using a screening method, and adsorbing the liquid part, namely the pollutants in the washing waste liquid by using the hydrothermal carbon; and (3) separating the hydrothermal carbon from the washing waste liquid, washing and regenerating the hydrothermal carbon, recycling the hydrothermal carbon, and extracting organic matters from the washing waste liquid rich in pollutants. The method has the advantages of simple process, simple device composition, easy operation and high removal rate, integrally realizes the post-treatment of the washing waste liquid, has less pollution, and the absorbed regeneration liquid can be continuously recycled for washing and removing soil pollutants, thereby greatly reducing the post-treatment cost of the washing waste liquid and realizing the recycling of resources.)

1. A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing is characterized by comprising the following steps:

step 1): crushing and screening the hydrothermal carbon and the soil by using a crusher; the particle sizes of the two are different, so that the subsequent mixing and screening are facilitated;

step 2): adding a detergent into the soil for washing, adding hydrothermal carbon, and reacting in a reactor;

step 3): after the reaction is finished, carrying out solid-liquid separation, separating and recovering the hydrothermal carbon in the soil from the solid part by using a screening method, and adsorbing the liquid part, namely the pollutants in the washing waste liquid by using the hydrothermal carbon;

step 4): and (3) separating the hydrothermal carbon from the washing waste liquid, washing and regenerating the hydrothermal carbon, recycling the hydrothermal carbon, and extracting organic matters from the washing waste liquid rich in pollutants.

2. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 1, wherein the preparation method of the hydrothermal carbon in the step 1) comprises the following steps: mixing the waste biomass, water and the modified additive, stirring, heating, keeping the temperature, performing solid-liquid separation, washing a solid part, drying, grinding and screening.

3. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 2, wherein the waste gas biomass is at least one of straw, waste wood chips, fruit shells, rice hulls and the balance of the ingredients; the modified additive is glucose, the addition amount is 1-5% of mass concentration, or ferric chloride, the addition amount is 1-10% of mass concentration; the mass ratio of solid to liquid after mixing is 1:10-1: 100, respectively; the heating temperature is 180 ℃ and 300 ℃, and the heat preservation is carried out for 1-8 h.

4. The method for removing polycyclic aromatic hydrocarbons in soil by using hydrothermal carbon through enhanced washing as claimed in claim 1, wherein the mesh number of the hydrothermal carbon obtained in step 1) is 60-120, the mesh number of the soil is 180-240, and the particle size difference between the two is greater than 120 meshes.

5. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 1, wherein the detergent in the step 2) adopts at least one of SDBS, SDS, Tween 80, span and Triton.

6. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 1, wherein the concentration of the washing agent in the step 2) is 20-50g/L, and the addition amount is as follows: the mass ratio of the soil to the detergent is 1:10-1:35, and the washing time is 1-8 h.

7. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 1, wherein the adding amount of the hydrothermal carbon in the step 2) is 1-20% of the mass of the soil.

8. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon enhanced washing as claimed in claim 1, wherein after the reaction in the step 2), the removal rate of pollutants in soil is 60-85%.

9. The method for removing polycyclic aromatic hydrocarbons in soil through hydrothermal carbon reinforced washing as claimed in claim 1, wherein the adding amount of the hydrothermal carbon in the step 3) in the washing waste liquid is 1-10g/L, and the adsorption time is 24-48 h.

10. The method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing as claimed in claim 1 or 9, wherein the removal rate of PAHs in washing waste liquid by hydrothermal carbon in step 3) is 50% -70%.

Technical Field

The invention relates to a polycyclic aromatic hydrocarbon contaminated soil remediation technology, in particular to a method for improving organic matter removal rate by using modified hydrothermal carbon to intensively wash polycyclic aromatic hydrocarbons in soil, and belongs to the technical field of environmental remediation.

Background

Polycyclic aromatic hydrocarbon is aromatic hydrocarbon containing two or more than two benzene rings, most of which are colorless, white or light yellow crystals, are slightly soluble or insoluble in water, have poor water solubility, higher octanol-water distribution coefficient and stable physicochemical properties, are persistent organic pollutants which are difficult to degrade, have low bioavailability, are mainly present in soil environment, have strong biological toxicity and have the 'triple effect' of teratogenesis, causing outburst and causing canceration. Polycyclic aromatic hydrocarbon exists in soil, destroys the physical and chemical properties of the soil, hinders the normal physiological metabolism function of animals, plants and microorganisms in the soil, is easy to accumulate through food chain enrichment and damages the health of human body. The search for suitable treatment methods for polycyclic aromatic hydrocarbon-contaminated soil is urgent.

The restoration technology of polycyclic aromatic hydrocarbon polluted soil is mainly divided into three types: physical repair techniques, chemical repair techniques and biological repair techniques. The physical remediation technology is to separate or remove polycyclic aromatic hydrocarbons in soil by physical means, and the method cannot completely remove the polycyclic aromatic hydrocarbons in the soil, only generates interphase transformation and needs subsequent treatment operation. The study of Ni Ni et al (Ni N, Wang F, Song Y, et al. mechanisms of biochemical reduction of PAHs in rim from soil: Degradation catalysis [ J ] Chemosphere,2018,196: 288-. The chemical remediation technology is to utilize some chemical reagents to oxidize, reduce or degrade PAHs in soil into low-toxicity or non-toxic substances. The method can effectively remove the polycyclic aromatic hydrocarbon in the soil, but can cause the problem of secondary pollution. The combination of surfactant washing and active persulfate chemical oxidation was proposed to remove PAHs from soil by the Young Li Y (Liao X Y, Huling S G, et al, the combined effects of surfactant solvation and chemical oxidation on the removal of cyclic aromatic hydrocarbons from soil [ J ]. Science of the Total environmental, 2019,647:1106 1112.) the results showed that surfactant-bound persulfate solutions had the best effect on reducing polycyclic aromatic hydrocarbon concentrations in sand and silty clays, and that treatment of PAHs in wash liquors by exploiting the strong oxidizing power of active persulfate, but also introduced new pollutants. Bioremediation technology refers to the degradation of polycyclic aromatic hydrocarbons into low-toxicity or harmless substances by utilizing the fixation of plants or the metabolic activity of microorganisms. Most of the bioremediation technologies are environment-friendly, economical and safe, have small harm to the environment, but have high requirements on plants or microorganisms and long remediation period. Fu Chen et al (Chen F, Tan M, Ma J, et al. effective repair of PAH-metal co-contaminated soil using microbial-plant combination: A greenhouse study [ J ]. J. Hazard Mater,2016,302:250- > 261.) in greenhouse for 2 years, Lolium perenne induced crop alternation of Seduce alfrederii in the co-contaminated soil, periodically repeated KL5 micro-bacteria and Candida C10, can remove polycyclic aromatic hydrocarbon to the maximum extent (96.4%), but the period is longer and the microbial growth condition is not easy to control. At present, a remediation method for soil polluted by polycyclic aromatic hydrocarbon is in urgent need of a new remediation technology for thoroughly separating pollutants from soil and completely reducing the pollution of pollutants to the soil.

The chemical washing method is a common chemical remediation method, and is characterized in that a detergent is mixed with polluted soil to promote pollutants attached to the surfaces of particles to be transferred to a liquid phase, so that polycyclic aromatic hydrocarbons are separated from the soil. The washing liquid comprises a surfactant, an organic solvent, an acid-base solution, a complexing agent, a chelating agent and the like. The method has good treatment effect and quick reaction, but the washing liquid can not be recycled, further treatment is needed, and the detergent is lost. The hydrothermal carbon is a biological carbon material prepared by suspending biomass in high-pressure water with relatively low temperature (150-. The two are combined, and the hydrothermal carbon competes with soil in the washing process to adsorb the eluted polycyclic aromatic hydrocarbon, so that the desorption process of pollutants from the soil is promoted, the re-adsorption amount of the soil to the polycyclic aromatic hydrocarbon is reduced, and the removal effect of the soil to the polycyclic aromatic hydrocarbon can be obviously improved. Meanwhile, the hydrothermal carbon can be applied to the treatment of the washing liquid due to the good adsorption performance, the defects of a chemical washing method are overcome to a certain extent, and the washing liquid after adsorption treatment can be reused for washing and repairing soil.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: how to improve the removal rate of polycyclic aromatic hydrocarbon organic matters in soil.

In order to solve the technical problems, the invention provides a method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing, which comprises the following steps:

step 1): crushing and screening the hydrothermal carbon and the soil by using a crusher; the particle sizes of the two are different, so that the subsequent mixing and screening are facilitated;

step 2): adding a detergent into the soil for washing, adding hydrothermal carbon, and reacting in a reactor;

step 3): after the reaction is finished, carrying out solid-liquid separation, separating and recovering the hydrothermal carbon in the soil from the solid part by using a screening method, and adsorbing the liquid part, namely the pollutants in the washing waste liquid by using the hydrothermal carbon;

step 4): and (3) separating the hydrothermal carbon from the washing waste liquid, washing and regenerating the hydrothermal carbon, recycling the hydrothermal carbon, and extracting organic matters from the washing waste liquid rich in pollutants.

Preferably, the preparation method of the hydrothermal carbon in the step 1) comprises the following steps: mixing the waste biomass, water and the modified additive, stirring, heating, keeping the temperature, performing solid-liquid separation, washing a solid part, drying, grinding and screening.

More preferably, the waste gas biomass is at least one of straw, waste wood chips, fruit shells, rice hulls and middlings; the modified additive is glucose, the addition amount is 1-5% of mass concentration, or ferric chloride, the addition amount is 1-10% of mass concentration; the mass ratio of solid to liquid after mixing is 1:10-1: 100, respectively; the heating temperature is 180 ℃ and 300 ℃, and the heat preservation is carried out for 1-8 h.

Preferably, the mesh number of the hydrothermal carbon obtained in the step 1) is 60-120, the mesh number of the soil is 180-240, and the particle size difference between the two is more than 120 meshes.

Preferably, the detergent in step 2) is at least one of SDBS, SDS, tween 80, span and triton.

Preferably, the concentration of the detergent in the step 2) is 20-50g/L, and the addition amount is as follows: the mass ratio of the soil to the detergent is 1:10-1:35, and the washing time is 1-8 h.

Preferably, the adding amount of the hydrothermal carbon in the step 2) is 1-20% of the mass of the soil.

Preferably, after the reaction in the step 2) is finished, the removal rate of the pollutants in the soil is 60-85%.

Preferably, the adding amount of the hydrothermal carbon in the step 3) in the washing waste liquid is 1-10g/L, and the adsorption time is 24-48 h.

Preferably, the removal rate of the hydrothermal carbon in the step 3) on PAHs in the washing waste liquid is 50-70%.

According to the invention, the hydrothermal carbon material is added in the conventional washing operation process, and the washed pollutants PAHs are adsorbed by competing with soil in the washing process, so that the pollutants are promoted to be desorbed from the soil, and the re-adsorption amount of the soil to the polycyclic aromatic hydrocarbon is reduced. Meanwhile, pollutants in the washing waste liquid are treated by utilizing the good adsorption performance of the hydrothermal carbon, the pollutants are transferred from the washing liquid to the hydrothermal carbon, and the hydrothermal carbon is separated by utilizing a screening method and recycled.

The technical principle and technical advantages of the invention are as follows:

first, principle of removing polycyclic aromatic hydrocarbon from soil by conventional washing method

By mixing the chemical detergent with the polluted soil, pollutants attached to the surfaces of the particles are transferred to a liquid phase due to dissolution or migration, so that the polycyclic aromatic hydrocarbon is separated from the soil. The method has good treatment effect and quick reaction, but the washing liquid needs further treatment. The washing effect on the soil with high viscosity is poor, and in the washing process, the resolved pollutants can be re-adsorbed by the soil to a certain extent, so that the elution rate of the pollutants in the washing process is influenced.

Secondly, the principle and technical advantages of removing the polycyclic aromatic hydrocarbon in the soil by a hydrothermal carbon adsorption enhanced washing method

Aiming at the defects of the conventional washing method, the washing effect is improved by adding the hydrothermal carbon in the conventional washing process. Firstly, the hydrothermal carbon competes with soil in the washing process to adsorb the eluted polycyclic aromatic hydrocarbon, so that the desorption process of pollutants from the soil is promoted, and the re-adsorption amount of the polycyclic aromatic hydrocarbon by the soil is reduced. Secondly, the hydrothermal carbon is a green and environment-friendly functional carbon material, and can improve the physical and chemical properties of soil and enhance the soil fertility when applied to the polluted soil, thereby being beneficial to the reutilization of the polluted soil. Finally, the hydrothermal carbon can be used for treating pollutants in the washing waste liquid, and the hydrothermal carbon rich in pollutants can be removed and then reused, so that the cost is greatly saved, and the cyclic multiple use of resources is realized.

Thirdly, principle of separating water, heat and carbon in soil

The hydrothermal carbon in the soil can be recovered by a screening method. The key point of the technology is that on the premise of ensuring the adsorption effect of the hydrothermal carbon and considering the cost, the hydrothermal carbon is separated by utilizing the particle size difference of the hydrothermal carbon and the soil and utilizing a screen under the action of water flow. The magnetic activated carbon is also used for replacing common biological carbon and is recovered by magnetism.

Compared with the prior art, the invention has the beneficial effects that:

(1) the removal rate is high, and the condition that the soil can reach the soil quality standard after being washed for many times is avoided;

(2) the post-treatment of the washing waste liquid is integrally realized, the pollution is less, and the absorbed regeneration liquid can be continuously and circularly used for washing and removing soil pollutants;

(3) greatly reduces the post-treatment cost of the washing waste liquid and realizes the recycling of resources;

(4) the technology has simple process, simple device composition and easy operation.

Drawings

FIG. 1 is a process flow diagram of the method for removing soil polluted by polycyclic aromatic hydrocarbons by hydrothermal carbon enhanced washing.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

Examples

A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing (as shown in figure 1):

1) firstly, preparing hydrothermal carbon, wherein the mass ratio of the waste biomass corn straws to water is 1: 10. mixing modified additive glucose (the addition amount is 5 wt% of the mass of the mixture), stirring, heating to a preset temperature of 180 ℃, preserving heat for 8 hours, performing solid-liquid separation, washing, drying, grinding and screening for later use;

2) then crushing and screening the hydrothermal carbon and the soil by using a crusher, and controlling the mesh number of the hydrothermal carbon to be 60 and the mesh number of the soil to be 180; adding a certain concentration of detergent (SDBS concentration is 20g/L) into polluted soil, wherein the solid-liquid ratio (soil mass: washing liquid mass) is 1: 15, washing for 6 hours, adding 12% soil mass fraction hydrothermal carbon, and reacting in a reactor; solid-liquid separation, wherein the solid part is separated and recovered by a screening method to obtain hydrothermal carbon in the soil, and the hydrothermal carbon is reused for adsorbing the liquid part, namely pollutants in the washing waste liquid; the removal rate of the single chemical detergent SDBS on the soil polycyclic aromatic hydrocarbon is 40%, and after the single chemical detergent SDBS is added into the hydrothermal carbon, the removal rate can reach 75%;

3) adding separated hydrothermal carbon into a washing liquid obtained by washing soil, wherein the adding amount is 5g/L, and the adsorption time is 36h, the removal rate of PAHs in the washing liquid reaches 50% (high performance liquid chromatography for measuring polycyclic aromatic hydrocarbon of HJ 784-one 2016 soil and sediment).

Example 2

A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing (as shown in figure 1):

1) firstly, preparing hydrothermal carbon, wherein the mass ratio of the waste biomass corn straws to water is 1: 50. mixing modified additive glucose (the addition amount is 1 wt% of the mass of the mixture), stirring, heating to a preset temperature of 180 ℃, preserving heat for 8 hours, performing solid-liquid separation, washing, drying, grinding and screening for later use;

2) then crushing and screening the hydrothermal carbon and the soil by using a crusher, and controlling the mesh number of the hydrothermal carbon to be 60 and the mesh number of the soil to be 180; adding a certain concentration of detergent (SDBS concentration is 20g/L) into polluted soil, wherein the solid-liquid ratio (soil mass: washing liquid mass) is 1: 15, washing for 6 hours, adding 12% soil mass fraction hydrothermal carbon, and reacting in a reactor; solid-liquid separation, wherein the solid part is separated and recovered by a screening method to obtain hydrothermal carbon in the soil, and the hydrothermal carbon is reused for adsorbing the liquid part, namely pollutants in the washing waste liquid; the removal rate of the single chemical detergent SDBS on the soil polycyclic aromatic hydrocarbon is 40%, and after the single chemical detergent SDBS is added into the hydrothermal carbon, the removal rate can reach 95%;

3) adding separated hydrothermal carbon into a washing liquid obtained by washing soil, wherein the adding amount is 5g/L, and the removal rate of PAHs in the washing liquid reaches 85% under the condition that the adsorption time is 24 h.

Example 3

A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing (as shown in figure 1):

1) firstly, preparing hydrothermal carbon, wherein the mass ratio of waste wood chips to water is 1: 50. mixing modified additive glucose (the addition amount is 3 wt% of the mass of the mixture), stirring, heating to a predetermined temperature of 250 ℃, keeping the temperature for 6 hours, performing solid-liquid separation, washing, drying, grinding and screening for later use;

2) then crushing and screening the hydrothermal carbon and the soil by using a crusher, and controlling the mesh number of the hydrothermal carbon to be 100 and the mesh number of the soil to be 220; adding a detergent with a certain concentration (SDS concentration is 30g/L) into polluted soil, wherein the solid-liquid ratio (soil mass: washing liquid mass) is 1: 30, washing for 4 hours, adding 12% of hydrothermal carbon by mass of soil, and reacting in a reactor; solid-liquid separation, wherein the solid part is separated and recovered by a screening method to obtain hydrothermal carbon in the soil, and the hydrothermal carbon is reused for adsorbing the liquid part, namely pollutants in the washing waste liquid; the removal rate of the soil polycyclic aromatic hydrocarbon by the single chemical detergent SDS is 60%, and the removal rate can reach 85% after the hydrothermal carbon is added;

3) adding separated hydrothermal carbon into a washing liquid obtained by washing soil, wherein the adding amount is 10g/L, and the removal rate of PAHs in the washing liquid reaches 70% under the condition that the adsorption time is 48 h.

Example 4

A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing (as shown in figure 1):

1) firstly, preparing hydrothermal carbon, wherein the mass ratio of waste wood chips to water is 1: 100. mixing modified additive ferric trichloride (the addition amount is 5 wt% of the mass of the mixture), stirring, heating to a preset temperature of 260 ℃, keeping the temperature for 2 hours, performing solid-liquid separation, washing, drying, grinding and screening for later use;

2) then crushing and screening the hydrothermal carbon and the soil by using a crusher, and controlling the mesh number of the hydrothermal carbon to be 120 and the mesh number of the soil to be 240; adding a certain concentration of detergent (SDBS: SDS: Tween 80 mass ratio 1: 1:1, total concentration 30g/L) into the polluted soil, wherein the solid-liquid ratio (soil mass: washing liquid mass) is in a ratio of 1: 30, washing for 4 hours, adding 12% of hydrothermal carbon by mass of soil, carrying out solid-liquid separation in a reactor, separating and recovering the hydrothermal carbon in the soil from the solid part by using a screening method, and reusing the hydrothermal carbon for adsorbing the liquid part, namely pollutants in the washing waste liquid; the removal rate of single chemical detergents SDBS, SDS and Tween 80 to soil polycyclic aromatic hydrocarbon is 55%, and the removal rate can reach 85% after hydrothermal charcoal is added;

3) adding separated hydrothermal carbon into a washing liquid obtained by washing soil, wherein the adding amount is 10g/L, and the removal rate of PAHs in the washing liquid reaches 70% under the condition that the adsorption time is 48 h.

Example 5

A method for removing polycyclic aromatic hydrocarbons in soil by hydrothermal carbon enhanced washing (as shown in figure 1):

1) firstly, preparing hydrothermal carbon, wherein the mass ratio of waste wood chips to water is 1: 1. mixing modified additive ferric trichloride (the addition amount is 2 wt% of the mass of the mixture), stirring, heating to a preset temperature of 270 ℃, preserving heat for 3 hours, carrying out solid-liquid separation, washing, drying, grinding and screening for later use;

2) then crushing and screening the hydrothermal carbon and the soil by using a crusher, and controlling the mesh number of the hydrothermal carbon to be 90 and the mesh number of the soil to be 170; adding a certain concentration of detergent (triton: SDS: Tween 80 mass ratio 1: 1:1, total concentration 30g/L) into the polluted soil, wherein the solid-liquid ratio (soil mass: washing liquid mass) is in a ratio of 1: 30, washing for 4 hours, adding 12% of hydrothermal carbon by mass of soil, and reacting in a reactor; solid-liquid separation, wherein the solid part is separated and recovered by a screening method to obtain hydrothermal carbon in the soil, and the hydrothermal carbon is reused for adsorbing the liquid part, namely pollutants in the washing waste liquid; triton, a chemical detergent alone: SDS (sodium dodecyl sulfate): the removal rate of tween to the soil polycyclic aromatic hydrocarbon is 70 percent, and the removal rate can reach 85 percent after the hydrothermal carbon is added;

3) adding the separated hydrothermal carbon into a washing liquid obtained by washing soil, wherein the adding amount is 10g/L, and the removal rate of PAHs in the washing liquid reaches 95% under the condition that the adsorption time is 48 h.