阅读说明：本技术 一种土壤放射性元素污染的修复装置和修复方法 (Remediation device and remediation method for soil radioactive element pollution ) 是由 李翔 王雷 席北斗 王金生 闫政 郑明霞 李一葳 余红 李艳平 郭可昕 胡妍玢 于 2020-09-17 设计创作，主要内容包括：本发明公开了一种土壤污染的修复装置和修复方法,包括对污染土壤施加修复剂并种植修复性植物,以及任选接种微生物,所述修复剂包括有机调理剂和生物质碳源,所述有机调理剂由表面活性剂和腐殖酸钠组成。本发明提供的修复装置和修复方法,以热解碳作为调理剂的基底材料,同时结合有机调理剂,能够广泛地应用于放射性元素和重金属污染的土壤修复,减少了修复土壤的二次污染,同时原材料简单易得,制备过程易操作,成本低、对环境影响小、能够实现原位同时修复多重土壤污染源。(The invention discloses a soil pollution remediation device and a remediation method, which comprises the steps of applying a remediation agent to polluted soil, planting a remediation plant and optionally inoculating microorganisms, wherein the remediation agent comprises an organic conditioner and a biomass carbon source, and the organic conditioner consists of a surfactant and sodium humate. According to the restoration device and the restoration method provided by the invention, pyrolytic carbon is used as a base material of the conditioner, and an organic conditioner is combined, so that the restoration device and the restoration method can be widely applied to restoration of soil polluted by radioactive elements and heavy metals, secondary pollution of the restored soil is reduced, raw materials are simple and easy to obtain, the preparation process is easy to operate, the cost is low, the influence on the environment is small, and in-situ simultaneous restoration of multiple soil pollution sources can be realized.)

1. A method for remediating contaminated soil, comprising applying a remediation agent to the contaminated soil and growing plants, and optionally inoculating a microbial inoculum.

2. The method of claim 1, wherein the remediation agent comprises an organic conditioning agent and a biomass carbon source, the organic conditioning agent being co-applied with the biomass carbon source, preferably produced by soaking the biomass carbon source in the organic conditioning agent.

3. A method according to claim 2, characterized in that the organic conditioning agent consists of a surfactant, which may be an alkylammonium salt, preferably octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide, and sodium humate.

4. The method according to claim 3, wherein the surfactant is formulated into a solution having a concentration of 0.5 to 5%, and then sodium humate is added thereto in a mass ratio of 1:0.5 to 5.

5. The method according to one of claims 2 to 4, characterized in that the biomass carbon source is pyrolytic carbon, preferably in a mixture with inorganic pellets.

6. The method according to claim 5, wherein the mixing of pyrolytic carbon with inorganic granules in situ is performed in a reconditioning device, preferably a pyrolysis plant comprising a pyrolysis furnace, wherein the charging, pyrolysis, venting, conveying and cooling of pyrolytic carbon is performed and a closed cycle of gases is achieved.

7. The method of claim 1, wherein the doped pyrolytic carbon is obtained by adding calcium oxide and/or calcium carbonate simultaneously with or after adding the plant carbon source in the pyrolysis furnace and before separating the pyrolytic carbon particles, and is in the form of microspheres, strips or rods, for example, with a particle size of 0.5mm to 10mm, soaking the doped pyrolytic carbon in an organic conditioner solution for several hours, taking out and standing at room temperature to obtain the doped pyrolytic carbon with repairing activity.

8. The method according to one of claims 1 to 7, characterized in that the restorative plant is a crop plant, a commercial crop plant, or another herbaceous plant, preferably rice, wheat, ryegrass, sorghum, corn, castor-oil plant, ramie, or the like.

9. The method according to any one of claims 1 to 8, wherein the inoculum comprises Phanerochaete chrysosporium and gloeostereum parvum, preferably a spore suspension, which is inoculated multiple times in an amount of 0.5-2 g/m²。

10. A soil pollution repairing device is a pyrolysis device comprising a pyrolysis furnace, wherein plant carbon sources are fed, pyrolyzed, discharged, conveyed and cooled, gas is circulated in a closed loop, and pyrolytic carbon and inorganic granules are mixed in situ.

Technical Field

The invention relates to a device and a method for repairing soil polluted by radioactive elements and/or heavy metals, belonging to the technical field of soil repair and improvement.

Background

The radioactive elements and the heavy metals are two pollution sources of the current soil, according to statistics, the area of the soil polluted by the heavy metals in China currently reaches more than 5000 ten thousand mu, various heavy metal elements in the soil exceed the standard to different degrees, and the heavy metal pollutants have the characteristics of poor mobility, long detention time, difficulty in degradation and the like in the soil, so that the radioactive elements and the heavy metals have great influence on the self-circulation capability of the soil, and are easy to finally influence the health of human beings through media such as water, plants and the like. The radioactive element pollution mainly comes from nuclear tests, nuclear energy production, nuclear accidents, production and application of radioactive isotopes, mining, smelting and application of minerals and the like.

Radioactive dust generated by atmospheric nuclear tests has hitherto caused a major source of radioactive contamination of the soil environment. Nuclear test explosion and nuclear leakage accidents with long-term residual radionuclides, e.g. contaminated soil¹³⁷Cs, etc., present in the soil. For large-area radioactive contaminated soil, a shoveling method, a clay-cutting method, a strippable membrane method, a leaching method, a precipitation method, an electrochemical method, a magnetization method, and the like are generally used. In addition, the restoration may be performed by a method such as plant microorganism. The repairing method of radioactive pollution in soil mainly includes phytoremediation, mycorrhiza remediation and microbial remediation.

The prior repair technology generally has the problems of low repair efficiency, high cost, easy secondary pollution, easy damage to soil structure and the like. Therefore, it is urgent to explore technical methods and systems for soil remediation to comprehensively regulate and control radioactive element pollution and heavy metal pollution.

Disclosure of Invention

In order to overcome the above problems, the inventors have studied and found that: the method has the advantages that the remediation agent is applied to the polluted soil, plants are planted, the microbial inoculum is optionally inoculated for remediation, the pyrolytic carbon is used as a base material of the conditioner, and meanwhile, the organic conditioner is combined, so that the method can be widely applied to remediation of soil polluted by radioactive elements and heavy metals, the secondary pollution of the remedied soil is reduced, meanwhile, the raw materials are simple and easy to obtain, the preparation process is easy to operate, the cost is low, the environmental influence is small, and the in-situ simultaneous remediation of multiple soil pollution sources can be realized.

Specifically, the invention provides a method for remediating contaminated soil, which comprises the steps of applying a remediation agent to the contaminated soil, planting plants and optionally inoculating a microbial inoculum.

According to the invention, the repairing agent comprises an organic conditioner and a biomass carbon source, wherein the organic conditioner and the biomass carbon source are applied together, and the repairing agent is preferably prepared by soaking the biomass carbon source in the organic conditioner.

According to the invention, the organic conditioner consists of a surfactant, which may be an alkylammonium salt, preferably octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide, and sodium humate.

In the present invention, the surfactant is formulated into a solution having a concentration of 0.5 to 5%, and then sodium humate is added thereto so that the mass ratio of sodium humate to surfactant is 1:0.5 to 5, preferably 1:2 to 4. .

According to the invention, the biomass carbon source is pyrolytic carbon, preferably used in a mixture with inorganic granules, preferably the pyrolytic carbon and inorganic granules are mixed in situ in a remediation device, preferably a pyrolysis plant comprising a pyrolysis furnace, wherein the charging, pyrolysis, discharge, transport and cooling of the pyrolytic carbon are performed and a closed cycle of gases is achieved.

According to a preferred embodiment, the doped pyrolytic carbon obtained by adding calcium oxide and/or calcium carbonate simultaneously with or after the addition of the vegetable carbon source in the pyrolysis furnace and before the separation of the pyrolytic carbon particles is in the form of microspheres, strips or rods, for example, with a particle size of 0.5mm to 10 mm.

According to the invention, the pyrolytic carbon is soaked in the organic conditioner solution for several hours, such as 3-8 hours, and the soaked pyrolytic carbon is taken out and placed at room temperature for 1-24 hours, so that the doped pyrolytic carbon with repair activity is obtained.

According to the invention, the reparative plant can be a crop, a commercial crop, or other herbaceous plants, preferably rice, wheat, ryegrass, sorghum, corn, castor-oil plant, ramie, etc.

In the invention, the applied microbial inoculum comprises Phanerochaete chrysosporium and gloeostereum furiosum, preferably spore suspension, and can be inoculated for multiple times, wherein the inoculation amount is 0.5-2 g/m²。

The invention also provides a soil pollution remediation device, which is a pyrolysis device comprising a pyrolysis furnace, wherein the plant carbon source is fed, pyrolyzed, discharged, conveyed and cooled, the gas is circulated in a closed loop, and the pyrolytic carbon and the inorganic granules are mixed in situ.

The invention has the advantages that:

1) according to the soil radioactive element pollution repairing device and method provided by the invention, pyrolytic carbon is used as a base material of the conditioner, and the radioactive element and heavy metal elements are adsorbed by utilizing the adsorption performance of the pyrolytic carbon;

2) according to the restoration device and the restoration method provided by the invention, the planting restoration of the plants not only beautifies the environment, but also effectively improves the soil quality of the polluted soil, avoids pollutants from entering a food chain, reduces the secondary pollution of the restored soil to the maximum extent, has low cost and small influence on the environment, can stabilize the surface of the ground for a long time, eliminates the pollutants in the atmosphere and the water body around the polluted soil while eliminating the soil pollution, is favorable for improving the ecological environment and improves the biological diversity of the polluted soil;

3) the regulation and control method provided by the invention can realize in-situ simultaneous remediation of multiple soil pollution sources, and meanwhile, the raw materials are simple and easy to obtain, the preparation process is easy to operate, and the industrial production of the conditioner can be realized.

Detailed Description

The present invention will be described in further detail below with reference to preferred embodiments and examples. The features and advantages of the present invention will become more apparent from the description.

According to the present invention there is provided a method of remediating contaminated soil comprising applying a remediation agent to the contaminated soil and planting a remediating plant, and optionally inoculating a microorganism.

According to the invention, the repairing agent comprises an organic conditioner and a biomass carbon source, wherein the organic conditioner consists of a surfactant and sodium humate.

In the present invention, the surfactant may be an alkylammonium salt, preferably octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide.

According to a preferred embodiment, the surfactant is formulated as a solution with a concentration of 0.5 to 5%, and then sodium humate is added thereto so that the mass ratio of sodium humate to surfactant is 1:0.5 to 5, preferably 1:2 to 4.

In the invention, the surfactant can adsorb a certain amount of radioactive elements and/or heavy metals through a complexing reaction, so that the adsorption capacity of the repairing agent is improved; humic acid is taken as an organic macromolecule, so that the repairing agent is easy to form a three-dimensional network structure, organic groups on the repairing agent can further perform complexation and chelation reactions with radioactive elements and/or heavy metals, and the adsorption capacity of the conditioner is greatly enhanced.

According to the invention, the organic conditioning agent is co-applied with the biomass carbon source. The biomass carbon source is used as a substrate of the conditioner, is preferably a solid material, and mainly has the functions of fixing and dispersing the organic conditioner, the adsorbed radioactive elements and heavy metals and preventing the conditioner adsorbing the radioactive elements and the heavy metals from integrally migrating in the polluted soil.

In the invention, the biomass carbon source is soaked in the organic conditioner to endow the carbon source with repairing activity.

In the present invention, the biomass carbon source is preferably pyrolytic carbon, which may be in the form of granules, preferably mixed with other granules, such as inorganic granules. The mixing may be physical mixing of the pyrolytic carbon and the inorganic granules, respectively, in a finished product, or in-situ mixing during the preparation process.

According to the invention, a device for carrying out the restoration is also provided, which is used for mixing pyrolytic carbon with inorganic granules in situ, preferably a pyrolytic device, and comprises a pyrolytic furnace, plant carbon sources and additives enter the pyrolytic furnace together, the generated semi-coke and preliminary pyrolysis gas containing carbon dioxide react with calcium oxide in the additives, the final pyrolysis gas is discharged through a pipeline, calcium carbonate and pyrolytic carbon in reaction products are discharged and sent to a cooling zone, the pyrolysis gas is contacted with cooling gas and conducts heat exchange, warm flue gas passes through a cyclone separator and is converged with sweeping gas entering from a gas supply pipeline and returns to the pyrolytic furnace together, the feeding, pyrolysis, discharge, transmission and cooling of pyrolytic carbon are completed, and closed cycle of the gas is realized.

In the invention, the plant carbon source is a biomass material or material capable of providing carbon elements, and is selected from herbaceous plants or woody plants, the herbaceous plants can be harvested or harvested terrestrial or aquatic crops or plants, such as rice straws, sorghum straws and maize straws, harvested materials of wheat, ryegrass, castor-oil plants and ramie, reeds or cattails, and the woody plants can be forestry biomass, such as roots, branches and leaves of various trees, branches and leaves of shrubs, or other forestry waste or wood waste. More preferably, cut or harvested reparative plants and their waste are used.

According to the present invention, the plant carbon source is subjected to appropriate treatments including drying and pulverization. The plant carbon source is dried to remove moisture, such as by sun drying or natural air drying, preferably the plant carbon source is air dried so that the plant moisture content is 10% to 20%, and then chopped. Before drying the plants, they are washed, preferably with deionized water, and then soaked in dilute hydrochloric acid.

In the invention, the plant carbon source is pyrolyzed in a pyrolysis furnace at a medium-low temperature. The plant carbon source may be directly pyrolyzed, preferably by purging with an inert gas such as nitrogen or carbon dioxide gas in advance, and then heating with an external heat source, and the temperature of the pyrolysis furnace is raised to 200 ℃ or more, more preferably 300 to 600 ℃. The low temperature is not favorable for volatilization and stripping of low-boiling-point organic matters, and the higher temperature is easy to cause excessive coking or complete carbonization. The process is maintained for several tens of minutes to several hours while maintaining the circulation of nitrogen to carry away the gaseous products generated by pyrolysis while maintaining an oxygen-deficient environment.

The pyrolysis is mainly carried out in three main stages of dehydration drying, preheating and volatile component separation. Dehydration drying is to remove internal crystal water; then entering a short preheating stage, and continuously increasing the number of active structures of raw material molecules; volatile components are separated and separated out gradually after preheating, light hydrocarbon compounds are cracked and separated out continuously to generate carbon monoxide, methane, hydrogen, carbon dioxide and the like, and the proportion of the residual fixed carbon is increased gradually. The obtained crystal water, the generated volatile gas and most of tar steam (collectively called pyrolysis gas) can be discharged out of the pyrolysis furnace, the pyrolysis gas can be used as heating fuel, and volatile gas liquid can be separated out through condensation, namely pyrolysis oil.

Preferably, calcium oxide and/or calcium carbonate is added to the pyrolysis furnace simultaneously with or after the addition of the plant carbon source, prior to separation of the pyrolysed carbon particles.

The reacted material is discharged to a cooling area, can be naturally cooled, and preferably, the incandescent pyrolytic carbon is directly cooled by inert gas to obtain pyrolytic carbon particles and hot gas. The cooling gas is preferably the same inert gas used for purging, and may be nitrogen, carbon dioxide, or a mixture of both, with an amount of carbon dioxide that aids in the formation of calcium carbonate upon pyrolysis.

According to the invention, the solid separated after cooling is a pyrolytic carbon, in granular form, possibly comprising, in addition to the pyrolytic carbon particles, calcium carbonate, in which case a part of it originates from the added calcium carbonate and another part from calcium carbonate formed by calcium oxide and carbon dioxide. The addition of the calcified substance can reduce the content of carbon dioxide in the pyrolysis gas, can also mix the pyrolytic carbon particles with calcium carbonate together, increases the density of particle materials, promotes the dispersion of the pyrolytic carbon, avoids agglomeration, and is very favorable for the load solidification of bacteria liquid, because the uniformly distributed carrier material is compact and porous.

According to the invention, the produced pyrolytic carbon contains organic substances with higher boiling points, is not large in density, low in mechanical strength, easier to crush than biomass raw materials, consumes less energy for crushing, and is preferably crushed for better forming, and can be directly pressed into a certain shape, preferably pressed into a certain shape together with calcium carbonate, such as microspheres, strips or rods, for example, with a particle size or a cross-sectional diameter of 0.5mm to 10mm, preferably 1mm to 5mm, for example 2mm to 4 mm.

In the preferred embodiment of the invention, the pyrolytic carbon and the calcium carbonate are pressed together with the pyrolytic oil, so that the pyrolytic oil can play a role of an adhesive, carbon powder is easy to adhere, the loose situation of a formed product is avoided, meanwhile, the pyrolytic oil is a pyrolysis product of the raw material, no additional material is needed, and the cost is reduced. In addition, the heavy carbon organic matters in the pyrolysis oil are slowly decomposed or degraded in the soil improvement process, and a carbon source or nutrient is continuously provided, so that the effect of fertilizer maintaining and slow release is generated, and the effective repair of the soil is promoted.

According to the invention, in order to combine the organic conditioner and the doped pyrolytic carbon, the pyrolytic carbon is soaked in the organic conditioner solution, and the soaking time can be several hours, for example, 1-10 hours, preferably 3-8 hours, according to the actual needs.

And then, taking out the soaked pyrolytic carbon, standing for a period of time, preferably at room temperature for 1-24 hours, preferably 6-12 hours, to obtain the doped pyrolytic carbon with repairing activity, and applying the doped pyrolytic carbon to the polluted soil to be repaired.

The doped pyrolytic carbon obtained by the method of the invention has lighter calcium carbonate (with a sedimentation volume of about 2.4-2.8mL/g) relative to heavy calcium carbonate (with a sedimentation volume of about 1.1-1.9mL/g) produced by a mechanical method, so that the calcium carbonate is light calcium carbonate and is used as a carrier together with the pyrolytic carbon, and can provide enough surface area for the contained or adsorbed organic conditioning agent to further adsorb and treat radioactive elements or heavy metals, and the pyrolytic carbon can effectively improve the activity and the treatment capacity of the organic conditioning agent on one hand and play a good role in curing and protecting the organic conditioning agent on the other hand.

According to the invention, the prepared repairing agent is applied to the polluted soil to be regulated and controlled, and the addition amount of the repairing agent is 0.1-5 kg/m²Preferably 0.5 to 2kg/m². The soil is then turned deep 15-30cm, preferably 20-25cm, for days to weeks, for example one to two weeks.

According to the invention, a restorative plant is planted on the soil after the above treatment, and optionally a microorganism is applied, for example in the form of a microbial inoculum.

According to the invention, the reparative plant can be a crop, a commercial crop, or other herbaceous plants.

According to the invention, preferably, rice, wheat, ryegrass, sorghum, corn, castor-oil plant, ramie and the like can be planted according to the conditions of regions, water conservancy and the like.

According to an optional embodiment of the invention, a bacterial agent, comprising Phanerochaete chrysosporium and glomus parvulus, preferably a spore suspension, is applied several days after planting the restorative plant, depending on the plant type and growth, for example within 5 to 30 days. In the present invention, Phanerochaete chrysosporium and glomus parvifolium are commercially available, and the spore suspension can be prepared by a method generally used in the art. In the present invention, the application position of the microbial inoculum varies depending on the plant species, for example, a position 5 to 20cm, preferably 8 to 18cm deep from the surface layer of the soil. The seed can be inoculated multiple times, for example, in layers, preferably, one layer is inoculated every about 2cm of thickness, and 1-4 layers can be inoculated.

According to the invention, the inoculation amount of the microbial inoculum is 0.5-2 g/m²Preferably 1.0 to 1.5g/m²The application can be performed by flowing irrigation or pumping.

Preferably, the planted restorative plants are subjected to normal field management including watering, fertilizing, weeding, and harvesting on time.

Examples

The present invention is further described below by way of specific examples, which are merely exemplary and do not limit the scope of the present invention in any way.

Example 1

Washing corn stalk with water, soaking in 0.01M dilute hydrochloric acid for 2 hr, air drying to water content of 15-18%, and cutting. Introducing nitrogen into a pyrolysis furnace for purging, then adding straws and a calcium mixture (the weight ratio of calcium oxide to calcium carbonate is 2: 1) which accounts for one fifth of the weight of the straws through a feeding port, heating to 450-550 ℃, and carrying out heat preservation reaction for 2 hours while keeping the circulation of nitrogen.

And then cooling to room temperature to obtain pyrolytic carbon, crushing the pyrolytic carbon, and pressing the pyrolytic carbon and the antipyretic oil obtained by condensing the pyrolytic gas into granules with the particle size of 2-4 mm.

Preparing hexadecyl trimethyl ammonium bromide into a 2% aqueous solution, adding sodium humate (the mass ratio of the sodium humate to the surfactant is 1:3), soaking semicoke particles in the obtained soil conditioner for 5 hours, taking out the soaked pyrolytic carbon, and standing at room temperature for 8-10 hours to obtain the doped pyrolytic carbon with repairing activity.

Selecting an experimental soil area polluted by radioactive elements and heavy metals, dividing the samples, wherein the length and the width of each sample are 5m, ridges with the width of 0.8m are reserved between every two samples, and each sample is provided with 5 sampling points according to a diagonal principle. And (4) adopting 0-25cm soil on the surface layer of the test field, cooling in the shade, ventilating and drying, and removing impurities. The soil pH value is determined to be 7.5, the radioactive element cesium concentration is 0.0238mg/kg, and the concentrations of heavy metals Zn, Pb, Cd and As are 440.2, 290.5, 85.2 and 64.6mg/kg respectively.

Adding the repairing agent into soil at an amount of 1.5kg/m²Turning over the soil deeply for 18-22cm, and standing for 10 days.

Then planting ramie in the soil, after 12 days of planting, irrigating a microbial inoculum which is spore suspension obtained after activation of phanerochaete chrysosporium and glomus pusillus (the concentration of the phanerochaete chrysosporium spore suspension is 2.7 multiplied by 10)⁶Per mL, concentration of the spore suspension of glomus minor was 3.1X 10⁶The volume ratio of the seed to the seed is 2:3), and the inoculation amount is 1.2g/m²The inoculation is divided into 3 times. And harvesting the ramie after the ramie is mature. After 15 days, the soil was sampled and analyzed. The results of the measurement were as follows: the soil pH dropped to 7.2, the cesium concentration was 0.0086mg/kg, and the Zn, Pb, Cd, and As concentrations were 155.6, 82.3, 1.35, and 25.1mg/kg, respectively.

The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention.