What technology is used to support soil pollution remediation?

▇ Physical restoration technology: saving money, high yield and sustainability.

Characteristics and application of physical separation remediation: Physical separation technology is mainly used for remediation of inorganic pollutants in contaminated soil. It is most suitable for treating soil polluted by shooting range in a small area, separating heavy metals from soil, sediment and waste residue, purifying soil and restoring its normal function. Most physical separation and repair technologies have the advantages of simple equipment, low cost, sustainable and high output. However, in the specific separation process, the technical feasibility should consider the influence of various factors.

Characteristics and application of steam leaching repair: this technology can be operated in situ, which is relatively simple and can limit the interference to the surrounding as little as possible; Very effective removal of volatile organic compounds; Be able to treat as much contaminated soil as possible within an acceptable cost range; The system is easy to install and transfer; Easy to combine with other technologies. Leaching technology is mainly used to repair halogenated and non-halogenated volatile organic compounds. The pollutants commonly used are volatile organic compounds with Henry coefficient greater than 0.0 or vapor pressure greater than 66.7Pa, and are sometimes used to remove pollutants such as oils, heavy metals and their organics, polycyclic aromatic hydrocarbons, etc. In the United States, steam leaching has almost become the "standard" technology for repairing groundwater and soil polluted by gas stations. The main factors limiting the application effect of soil steam extraction technology are the heterogeneity of lower soil, soil permeability, groundwater level and exhaust gas that need further treatment.

Characteristics and application of electrodynamics remediation: electrodynamics technology is mainly used for the remediation of low-permeability soil (the application of traditional technology is limited due to hydraulic conduction problems), and it is suitable for most inorganic pollutants, and can also be used for the treatment of radioactive substances and strongly adsorbed organic substances. Electrokinetic technology can effectively remove heavy metal ions in soil and groundwater, as well as polar organic substances with strong adsorption in soil, such as phenol and acetic acid. The latest development trend is to combine electrodynamics with other technologies to strengthen electrodynamics repair.

Characteristics and application of thermal remediation: The pollutants mainly treated by high-temperature primary heating technology include semi-volatile halogenated organic compounds and non-halogenated organic compounds, polychlorinated biphenyls and high-density non-aqueous liquid organic compounds. The pollutants treated by in-situ heating at low temperature mainly include semi-volatile halogenated compounds, non-halogenated compounds and concentrated insoluble liquid substances, and volatile organic compounds can also be treated by this method. In addition, in-situ electromagnetic wave heating remediation technology belongs to high-temperature in-situ heating technology, which uses electromagnetic wave energy generated by high-frequency voltage to heat in-situ soil, and uses heat-enhanced soil steam leaching technology to desorb pollutants in soil particles, thus achieving the purpose of remediation of contaminated soil.

▇ Chemical remediation technology: Various ways and strong applicability, and prevention of secondary pollution is the key.

Characteristics and application of solidification stabilization technology: This technology is to fix pollutants in polluted media and make them in a long-term stable state. Immobilization technology is to encapsulate pollutants in inert matrix or add low-permeability materials outside pollutants, and limit the migration of pollutants by reducing the leaching area exposed by pollutants. Stabilization refers to the transformation of pollutants from the effectiveness of pollutants into insoluble, less migratory or toxic forms, so as to reduce the risk of harm to ecosystems. It is a rapid control and remediation method widely used in soil heavy metal pollution, and has obvious advantages in treating soil polluted by multiple heavy metals at the same time. Its advantages are simple process operation, low price, easily available curing agent, etc. The cure product is convenient to transport; However, stabilization does not necessarily change the physical properties of contaminated soil, thus improving the overall efficiency and economy of hazardous waste treatment and disposal system. It can be seen that stabilization technology is expected to become the main force in the field of soil heavy metal pollution remediation technology.

Characteristics and application of chemical leaching remediation technology: Soil leaching remediation technology is a process of injecting water or aqueous solution containing washing AIDS, acid-base solutions, complexing agents or surfactants into contaminated soil or sediments to elute and clean pollutants in the soil. After treatment, the leaching wastewater is discharged up to the standard, and the treated soil can be safely reused. Suitable for heavy metal pollution or multi-pollutant mixed pollution media. Its advantages are high applicability. At present, this remote restoration technology has been applied in many countries. Its disadvantage is that it needs water, so the repair site is required to be close to the water source, and the cost increases because of the need to treat wastewater.

Characteristics and application of redox technology: This technology purifies soil by adding chemical oxidants (Fenton reagent, ozone, hydrogen peroxide, potassium permanganate, etc.). ) or reducing agent (SO2, FeO, gaseous H2S, etc. ) make them react with pollutants. It is suitable for simultaneous remediation of soil and groundwater polluted by organic matter. Remediation of organic pollutants sensitive to reduction by chemical reduction. Its advantage is that it takes 3~24 months to clean up the pollution source area relatively quickly. The technical disadvantage is that there are still some problems in the application of zero-valent iron reduction dechlorination technology to degrade chlorine-containing organic compounds, such as active passivation of iron surface and polymerization failure caused by soil adsorption.

Characteristics and application of photocatalytic degradation technology: soil photocatalytic degradation (photolysis) technology is a new type of deep oxidation remediation technology of soil, which can be applied to the remediation of pesticides and other contaminated soil. Soil texture, particle size, iron oxide content, soil moisture, soil pH value and soil thickness have obvious effects on photocatalytic oxidation of organic pollutants: the migration rate of pollutants in high porosity soil is fast, and the lower the clay content, the faster the photolysis; Iron oxide in natural soil plays an important role in regulating the photolysis of organic matter; Organic matter can be used as light stabilizer; Soil moisture can adjust the absorption band; Soil thickness affects filtration rate and incident light rate.

Characteristics and application of electrochemical dynamic remediation technology: Electrokinetic remediation (referred to as electrokinetic remediation) is a process of driving pollutants to concentrate in the electrode area for centralized treatment or separation through the combined action of electrochemistry and electrodynamics (electroosmosis, electromigration, electrophoresis, etc.). ). It is suitable for remediation of organic contaminated soil such as copper and chromium, phenanthrene and pentachlorophenol. Its advantages are fast electroremediation and low cost, and it is especially suitable for the remediation of small cohesive soil polluted by various heavy metals and soluble organic substances. The disadvantage is that insoluble organic pollutants need chemical solubilization, which is easy to produce secondary pollution. It will be a subject worth studying to develop the combined remediation technology of composite polluted soil by electric reinforcement.

▇ Phytoremediation technology: it is suitable for large-scale treatment and has the function of bioenergy.

Phytoremediation technologies include plant absorption remediation using plant super accumulation or accumulation function, plant stable remediation using plant root system to control pollution diffusion and restore ecological function, plant degradation remediation using plant metabolic function, plant volatilization remediation using plant transformation function, and plant filtration remediation using plant root system adsorption. Suitable for heavy metals, pesticides, petroleum and persistent organic pollutants, explosives, radionuclides, etc. Among them, the phytoremediation technology of heavy metal contaminated soil has been widely studied at home and abroad, and it has been applied to the remediation of soil contaminated by heavy metals such as arsenic, cadmium, copper, zinc, nickel and lead and polycyclic aromatic hydrocarbons, showing a set of integrated technologies, including complex-induced enhanced remediation, interplanting different plants for joint remediation, and plant treatment and disposal after remediation.

Technical advantages: Phytoremediation technology is not only suitable for removing pollutants from farmland soil, but also suitable for the construction of constructed wetlands, the surface coverage and ecological restoration of landfill sites, and the reconstruction of biological habitats. In recent years, phytoremediation technology is considered to be a more acceptable and widely used plant technology, which is conducive to the ecological restoration of soil at the edge of mining areas. It is also considered as a plant carbon fixation technology and biomass energy production technology.

Disadvantages: Although the phytoremediation of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and petroleum hydrocarbons by alfalfa, ryegrass and other plants has been carried out, the field research on phytoremediation technology of organic contaminated soil is still less, and the phytoremediation research on soil contaminated by explosives and radionuclides needs to be strengthened.

▇ Joint restoration technology: give full play to joint advantages and solve governance problems.

Microbial/animal-plant combined remediation technology: microbial (bacteria, fungi)-plant, animal (earthworm)-plant combined remediation is a soil bioremediation technology.

Combined chemical/physical-chemical-biological remediation technology: give full play to the rapid advantages of chemical or physical-chemical remediation and combine the characteristics of non-destructive biological remediation. Chemical leaching-combined bioremediation is based on the role of chemical leaching solvent, which can improve the efficiency of bioremediation by increasing the bioavailability of pollutants. Most of these technologies are in the stage of indoor research.

Physical and chemical combined remediation technology: Soil physical and chemical combined remediation technology is a remediation technology suitable for ectopic treatment of contaminated soil. Solvent extraction-photodegradation combined remediation technology is a new physical and chemical combined remediation technology that uses organic solvents or surfactants to extract organic pollutants and then photolyses them. For example, polycyclic aromatic hydrocarbons (PAHs) in polluted soil can be extracted with cyclohexane and ethanol, and then photocatalytic degradation can be carried out. In addition, the combined technology of catalysis-thermal desorption or microwave pyrolysis-activated carbon adsorption supported by PdPRh can be used to remediate PCB contaminated soil, and photo-regulated titanium dioxide can also be used to catalyze the remediation of pesticide contaminated soil.