CN112808761B

CN112808761B - Remediation method of organic matter-heavy metal combined contaminated soil

Info

Publication number: CN112808761B
Application number: CN202011626184.4A
Authority: CN
Inventors: 田全志; 张海军; 贺琼琼; 万克记; 陈长帅; 白颖楚
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2022-09-27
Anticipated expiration: 2040-12-31
Also published as: CN112808761A

Abstract

The invention discloses a method for restoring organic matter-heavy metal combined polluted soil, which comprises the following steps: drying the polluted soil to be restored, and then grinding and crushing; fully and uniformly mixing the crushed polluted soil and an additive according to a certain mass ratio, then calcining at a high temperature, thermally desorbing or partially cracking organic pollutants in the polluted soil into volatile gas in the calcining process, and discharging the volatile gas after collection and purification; and (3) fully and uniformly mixing the calcined soil mixture and the alkali activator according to a certain mass ratio, and obtaining a solidified body after molding and maintenance. According to the invention, organic matters in soil are separated from heavy metal pollutants through thermal desorption at high temperature, the silicon-aluminum material is synchronously activated, then the calcined soil mixture is used as a raw material and is mixed with the alkali activator to prepare the geopolymer solidified body, the heavy metal pollutants can be effectively fixed in the geopolymer network structure, and the prepared solidified body can be used as a building material, and the dual principles of recycling and harmlessness are reflected.

Description

Remediation method of organic matter-heavy metal composite contaminated soil

Technical Field

The invention belongs to the technical field of soil remediation, and particularly relates to a remediation method of organic matter-heavy metal composite contaminated soil.

Background

Soil is the basic material basis and carrier on which human beings rely for survival. With the development of global industrialization in recent decades, the proportion of polluted soil is higher and higher. According to the report, the soil environment condition of China is not optimistic, the total national soil standard exceeding rate is 16.1%, the soil pollution rate of cultivated land is nearly 20%, and therefore, the treatment of soil pollution is not slow at all. Currently, soil pollutants can be classified into four categories by nature: organic pollutants, heavy metal pollutants, radioactive substance pollutants, and pathogenic microorganism pollutants, with sites contaminated with organic and heavy metals being the most common. The organic pollutants in the soil mainly comprise petroleum hydrocarbon, polychlorinated biphenyl, polycyclic aromatic hydrocarbon, polychlorinated biphenyl and some pesticides which are difficult to degrade, and the organic matters are easy to accumulate in a food chain and have potential toxicity and carcinogenicity. For organic matter polluted sites, common remediation methods include soil leaching, chemical oxidation, photocatalytic degradation, phytoremediation, pyrolysis and the like. On the other hand, the heavy metals are not degraded by microorganisms in the soil, have long detention time and are easy to accumulate in the soil, and when the content reaches a certain degree, the content of pollutants in crops exceeds the standard, so that the health of people and livestock is harmed. Heavy metal pollutants mainly comprise cadmium, mercury, arsenic, copper, lead, chromium, zinc and the like, and have diversity of occurrence forms relative to organic pollutants, so that the difficulty of repair and treatment is aggravated. The existing restoration methods comprise three major types, namely physical methods (soil dressing, soil replacement, isolation and the like), chemical methods (solidification, chemical leaching and the like), biological methods (plant fixation, microorganism restoration methods and the like) and the like. The choice of the specific method is determined by the nature of the contaminated site and the surrounding environmental factors.

In actual soil environments, a single pollutant in an absolute sense is difficult to exist, and the current soil pollution presents a situation of complication and diversification of pollutants. Soil co-contamination may be defined as the presence of 2 or more contaminants in the soil at concentrations that have exceeded national relevant standards. And can be classified into organic composite pollution, heavy metal composite pollution and organic-heavy metal composite pollution according to the types of pollutants. Although a great deal of research is already carried out on the remediation of soil polluted by organic matters or heavy metals, the research on the remediation and treatment of the soil polluted by the organic matters and the heavy metals is deficient. Under the organic matter-heavy metal combined pollution system, different types of organic matters and heavy metals can generate interaction, and the leaching, migration and other rules of the organic matters and the heavy metals can be influenced by each other, so that the remediation and treatment of the organic matter-heavy metal combined pollution soil are undoubtedly more difficult. The simultaneous removal of organic pollutants and heavy metal pollutants by a single technical means is often difficult to achieve high remediation efficiency, and two or more methods are usually required to jointly treat the composite polluted soil. The common combined repairing process includes electric-biological, plant-microbial, soil eluting-photocatalysis, chemical leaching-biological and other combined repairing methods. However, these processes have great limitations due to the limitations of their own methods, for example, plant or biological remediation has too long a remediation cycle, and meanwhile, the remediation adaptability to contaminated soils with different properties is poor; the photocatalytic degradation efficiency is low, and certain photocatalysts can cause secondary pollution to soil.

Disclosure of Invention

The invention aims to provide a safe and effective method for repairing organic matter-heavy metal combined polluted soil.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a method for restoring organic matter-heavy metal combined polluted soil comprises the following steps:

(1) drying the polluted soil to be repaired, and then grinding and crushing;

(2) fully and uniformly mixing the crushed polluted soil and an additive according to a certain mass ratio, then calcining at a high temperature, wherein in the calcining process, organic pollutants in the polluted soil are thermally desorbed or partially cracked into volatile gas, collected, purified and then discharged;

(3) and (3) fully and uniformly mixing the calcined soil mixture and the alkali activator according to a certain mass ratio, and obtaining a solidified body after moulding and maintenance.

Preferably, the organic pollutant in the polluted soil is one or more of petroleum hydrocarbon, polycyclic aromatic hydrocarbon, polychlorinated biphenyl, organic chlorine, organic phosphorus and ester compounds, and the heavy metal in the polluted soil is one or more of copper, lead, zinc, chromium, nickel, cobalt, cadmium and tin.

Preferably, the pulverized particle size is 200 mesh or less.

Preferably, the additive is kaolin or coal gangue powder, and the mass ratio of the additive to the polluted soil is 1:0.5 to 4.

Preferably, the calcining temperature is 500-750 ℃ and the calcining time is 1-6 h.

Preferably, the mass ratio of the soil mixture to the alkali-activator is 1:0.5 to 0.8.

Preferably, the alkali activator is sodium silicate or potassium silicate solution with the concentration of 20 wt% to 50 wt%.

According to the method for restoring the organic matter-heavy metal combined polluted soil, the organic matter in the soil is thermally desorbed at high temperature and the heavy metal pollutants are separated, the silicon-aluminum material is synchronously activated, then the calcined soil mixture is used as the raw material and mixed with the alkali activator to prepare the geopolymer solidified body, the heavy metal pollutants can be effectively fixed in the geopolymer net structure, and the prepared solidified body can be used as a building material and simultaneously embodies the double principles of recycling and harmlessness.

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

1. according to the method for restoring the organic matter-heavy metal composite polluted soil, the polluted soil is treated by combining the thermal desorption-solidification/stabilization process, the organic pollutants are thermally desorbed (or partially cracked) at high temperature, and compared with the direct solidification process, the adverse effect of the organic pollutants on the subsequent solidification/stabilization process is reduced, and the solidification effect is improved.

2. According to the method for restoring the organic matter-heavy metal combined polluted soil, the coal gangue is used as the silicon-aluminum additive, so that the coal gangue as the solid waste can be effectively consumed, the pollution to the environment caused by the coal gangue is reduced, the source is wide, and the practicability of the method is improved.

Drawings

FIG. 1 is a flow chart of the remediation method of organic matter-heavy metal combined contaminated soil according to the invention.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

Example 1

As shown in figure 1, the composite contaminated soil containing 9000mg/kg of total petroleum hydrocarbon and 500mg/kg of nickel is placed in a 110 ℃ oven for drying, then ore grinding and crushing are carried out to obtain powder below 200 meshes, kaolin and the soil are uniformly mixed according to the mass ratio of 1:1, then the mixture is calcined at the high temperature of 700 ℃ for 3 hours to obtain a calcined soil mixture, and the calcined soil mixture is subjected to organic pollutant detection, so that the result shows that all harmful substances are purified. And collecting and purifying the flue gas generated in the calcining process, and then discharging.

Then mixing and stirring the calcined soil mixture and an alkali activator (50 wt% of sodium silicate solution) according to a mass ratio of 1:0.7, placing the slurry into a cylindrical mold with a diameter of 50mm and a height of 100mm, discharging bubbles in the slurry through oscillation, sealing and maintaining for 24h at room temperature, then demolding, placing the slurry into a maintenance box with a humidity of 93%, continuing to maintain for 27 days, after demolding, measuring that the compressive strength of the obtained cylindrical body is more than 12MPa, crushing, and then carrying out TCLP leaching toxicity test, wherein the leaching concentration of nickel is less than 0.8mg/L, and the leaching standard specified in GB5085 is achieved.

Example 2

As shown in figure 1, the composite contaminated soil containing 60mg/kg polycyclic aromatic hydrocarbon and 4047mg/kg cadmium is placed in a 110 ℃ drying oven for drying, then ore grinding and crushing are carried out to be less than 200 meshes, coal gangue powder and soil are uniformly mixed according to the mass ratio of 1:4, then calcining is carried out for 4 hours at the high temperature of 750 ℃ to obtain a calcined soil mixture, and the detection of organic pollutants is carried out on the material, so that the result shows that all harmful substances are purified. And the flue gas generated in the calcining process is collected, purified and then discharged.

Then mixing and stirring the calcined soil mixture and an alkali activator (50 wt% sodium silicate solution) according to the mass ratio of 1:0.8, putting the slurry into a cylindrical mold with the diameter of 50mm and the height of 100mm, discharging bubbles in the slurry through oscillation, sealing and maintaining for 24h at room temperature, then demolding, putting into a maintenance box with the humidity of 93%, continuing to maintain for 27 days, after demolding, measuring that the compressive strength of the obtained cylinder is more than 5MPa, and carrying out TCLP leaching toxicity test after crushing, wherein the leaching concentration of cadmium is less than 0.4mg/L, and reaches the leaching standard specified in GB 5085.

Example 3

As shown in figure 1, composite contaminated soil containing 90mg/kg of pyrene, 3234mg/kg of lead, 4205mg/kg of copper and 45mg/kg of cadmium is placed in a 110 ℃ drying oven to be dried, then ground and smashed to be below 200 meshes, certain kaolin-rich tailings and the soil are mixed evenly in a mass ratio of 1:1.2, then the mixture is calcined for 6 hours at a high temperature of 600 ℃ to obtain a calcined soil mixture, and the detection of organic pollutants on the material shows that all harmful substances are purified. And collecting and purifying the flue gas generated in the calcining process, and then discharging.

Then mixing and stirring the calcined soil mixture and an alkali activator (20 wt% of potassium silicate solution) according to the mass ratio of 1:0.6, putting the slurry into a cylindrical mold with the diameter of 50mm and the height of 100mm, discharging bubbles in the slurry through oscillation, sealing and curing for 24h at room temperature, then demolding, putting the cylindrical mold into a curing box with the humidity of 93%, continuing curing for 27 days, after demolding, measuring that the compressive strength of the obtained cylindrical mold is more than 10MPa, crushing, and then carrying out TCLP leaching toxicity test, wherein the leaching concentrations of lead, copper and cadmium are respectively less than 2, 4 and 0.4mg/L, and the leaching standard of GB5085 is achieved.

Example 4

As shown in figure 1, the composite contaminated soil containing 1799mg/kg polychlorinated biphenyl and 15727mg/kg zinc is placed in a 110 ℃ oven for drying, then ore grinding and crushing are carried out to below 200 meshes, certain kaolin-rich tailings and soil are uniformly mixed in a mass ratio of 1:0.8, then calcination is carried out at 650 ℃ for 5 hours to obtain a calcined soil mixture, and the detection of organic pollutants on the material shows that all harmful substances are purified. And collecting and purifying the flue gas generated in the calcining process, and then discharging.

Then mixing and stirring the calcined soil mixture and an alkali activator (20 wt% of potassium silicate solution) according to the mass ratio of 1:0.5, placing the slurry into a cylindrical mold with the diameter of 50mm and the height of 100mm, discharging bubbles in the slurry through oscillation, sealing and maintaining for 24h at room temperature, then demolding, placing the cylindrical mold into a maintenance box with the humidity of 93%, continuing to maintain for 27 days, after demolding, measuring that the compressive strength of the obtained cylindrical mold is more than 15MPa, crushing, and then carrying out TCLP leaching toxicity test, wherein the leaching concentration of zinc is respectively less than 40mg/L, and the leaching standard specified in GB5085 is reached.

Claims

1. The method for restoring the organic matter-heavy metal combined polluted soil is characterized by comprising the following steps of:

(1) drying the polluted soil to be restored, and then grinding and crushing;

(2) uniformly mixing the crushed polluted soil and an additive according to a certain mass ratio, and then calcining at a high temperature, wherein the additive is tailings rich in kaolin, the calcining temperature is 600-650 ℃, the calcining time is 5-6 hours, and in the calcining process, organic pollutants in the polluted soil are thermally desorbed or partially cracked into volatile gases, collected, purified and then discharged;

(3) fully and uniformly mixing the calcined soil mixture with an alkali activator, wherein the alkali activator is a potassium silicate solution with the concentration of 20 wt%, and obtaining a solidified body after molding and maintenance;

the crushing granularity is below 200 meshes;

the mass ratio of the additive to the polluted soil is 1: 0.8-1.2;

the mass ratio of the soil mixture to the alkali activator is 1: 0.5-0.6.

2. The method for remediating organic matter-heavy metal combined contaminated soil as recited in claim 1, wherein the organic pollutants in the contaminated soil are one or more of petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorines, organophosphates and ester compounds, and the heavy metals in the contaminated soil are one or more of copper, lead, zinc, chromium, nickel, cobalt, cadmium and tin.