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Take a look at the soil remediation technology of industrial polluted sites

judging from the current situation, the pollution of heavy metals and organic matter in China's soil has been very serious, which has been concerned by more and more scholars at home and abroad. This paper mainly studies the soil remediation technology of industrial contaminated sites, hoping to provide some reference for relevant personnel in practical work

main types of industrial pollution sites in China

1. Heavy metal pollution

in chemistry, heavy metals generally refer to metal elements with a relative density of 5.0 or more, but generally there is no strict definition for them. There are 45 kinds of heavy metal elements, including Zn, Ge, Mn, Cu, etc. because the attributes of as are similar to those of heavy metal elements, we also regard as heavy metal elements, This element is also one of the important heavy metal elements in industrial site pollution

relevant studies show that there are mainly 8 kinds of heavy metal elements in the soil of industrial sites, namely as, Ni, Hg, Cu, Zn, CD, Cr and pb These eight heavy metals mainly come from chemical raw materials and related products, smelting, leather and related products, battery manufacturing, etc

2. Organic pollutants

organic pollution in the soil of industrial sites mainly refers to the entry of organic substances that can pollute the soil into the soil of industrial sites and produce relevant polluting organic compounds. The types of organic pollutants mainly include pops (persistent organic pollutants), pesticides, polycyclic aromatic hydrocarbons (PAHs) and petroleum pollution. These organic pollutants mainly come from petrochemical industry, paint Pesticide production and other related industries

3. Compound pollution

compound pollution mainly refers to the compound pollution of heavy metals and organic pollutants, which is also the main form of soil pollution in industrial sites. Its specific forms are relatively diverse, including the compound pollution between different heavy metals, the compound pollution between different organic pollutants, and the compound pollution between different heavy metals and different organic pollutants, At present, the main pollutants in the soil pollution of industrial sites in China are the compound pollution between heavy metals, the compound pollution between petroleum organic pollutants, the pollution of heavy metals and pesticides and other organic pollutants. Once the soil is polluted by these compound pollutants, due to the certain interaction between various pollutants, the relevant soil will change the low-carbon soil environment and groundwater environment, This has also caused serious difficulties in the restoration of industrial sites

soil remediation technology for industrial contaminated sites

at present, China's contaminated soil remediation technology system is mainly composed of biological and physicochemical remediation technologies. At present, the main soil remediation technologies in China are shown in Figure L:

1. Phytoremediation technology

in the process of soil remediation, specific phytoremediation technologies mainly include plant extraction technology, plant stabilization technology and plant volatilization technology. First of all, plant extraction technology mainly refers to the technology that plants that can absorb and accumulate a large number of heavy metals and organic substances in the soil can absorb the heavy metals and organic substances in the soil with long testing cycle and high cost, so that the content of heavy metals and organic substances in the soil can be transferred to the plants as much as possible, and then the plants can be harvested and treated to reduce the content of heavy metals and organic substances in the soil and improve the soil

secondly, plant stabilization technology mainly refers to the effective precipitation or chelation of heavy metals and organic matter in soil by using the secretory properties of relevant microorganisms in the rhizosphere of plants, so as to prevent heavy metals and organic matter from continuing to penetrate into the underground and polluting the groundwater or other animals and plants, and indirectly reduce the damage of heavy metals and organic matter to human health; Finally, plant volatilization technology mainly refers to the direct absorption, accumulation and volatilization of heavy metals and organic matter in soil through the absorption, accumulation and volatilization of plants themselves, so as to reduce the content of heavy metals and organic matter in soil

2. Microbial remediation technology

for microbial remediation technology, it is often a process of cleaning pollutants in soil and water or harmless treatment of pollutants by using the role of some microorganisms. In urban soils, the number and types of microorganisms are relatively large, and their role in the harmless treatment of heavy metals and organic matter can not be ignored. The use of microorganisms to reduce the toxicity of heavy metals and organic compounds in soil or to adsorb the heavy metals and organic compounds accumulated in soil can slowly change the rhizosphere microenvironment, which can increase the efficiency of absorption, volatilization and fixation of heavy metals and organic compounds by plants

3. Thermochemical method for remediation

this method is to heat directly, or steam, infrared and microwave radiation, and slowly heat the substances in the soil to a certain temperature. In this way, some volatile pollutants in the soil can be rapidly vaporized, and then these volatile pollutants can be collected, which can effectively reduce the concentration of pollutants in the soil. This kind of heating method has high requirements for energy consumption, which generally requires that the soil has certain permeability, only for some volatile soil pollutants

4. Solidification stabilization technology

fixes the pollutants in the polluted medium to keep the pollutants in a relatively stable state. This repair technology is the solidification stabilization technology. The technology mixes the solidified stabilizer with the contaminated soil, and reduces the physical and chemical dissolution degree of pollutants or the activity degree in the environment through chemical and physical methods

this solidification stabilization method can be carried out in situ and ectopic respectively. For the in situ solidification stabilization technology, it is more suitable for the remediation of soil polluted by organic substances or heavy metals; Ectopic solidification stabilization technology is usually suitable for the treatment of inorganic pollutants, but not for the remediation of semi volatile organic compounds and pesticide contaminated soil

solidification stabilization technology can treat a variety of complex metal wastes. The solid formed has low toxicity, strong stability and low disposal cost. It is widely used in the rapid control of soil hard metal pollution. It has obvious advantages in the harmless treatment of soil polluted by a variety of heavy metals and organic substances and radioactive substances. In addition, the burial depth of pollutants, soil pH and organic matter content will affect the application and effectiveness of this technology to a certain extent

5. Cleaning method

some surfactants are often used in the implementation of cleaning method. These surfactants include many types: non-ionic surfactants, anionic surfactants and cationic surfactants. Compared with simple hydraulic flushing, the decontamination capacity of these surfactants can be increased by more than 50 times in the process of flushing, which has an excellent decontamination effect

in addition, with the continuous development of biotechnology, biosurfactants are becoming more and more popular. Its decontamination effect is often more environmentally friendly and easier to degrade than some conventional surfactants, and has gradually become a development direction of surfactants in the future. For some pesticide contaminated soils, organic solvents can be used for cleaning to achieve the purpose of decontamination

6. Thermal desorption technology

the main working principle of thermal desorption is to use heat energy to enhance the volatility of pollutants, so as to separate pollutants from contaminated soil or sediment, and conduct centralized treatment for these pollutants first. Generally, the thermal desorption system includes two modules: thermal desorption unit and waste gas treatment system. The thermal desorption process is divided into high-temperature thermal desorption and low-temperature thermal desorption

compared with the traditional technology, the thermal desorption technology has obvious advantages, with a large range of pollutant treatment capacity. Its equipment is mobile and flexible, and the repaired soil can be recycled. It is especially suitable for the separation and treatment of chlorinated organic compounds such as PCBs, which can effectively avoid the production of dioxins. In view of the advantages of thermal desorption technology, many European and American countries have engineered soil thermal desorption technology at this stage, and have made breakthrough progress in the displacement and recovery of highly organic contaminated soil

however, thermal desorption technology has not been widely used in the remediation of persistent organic contaminated soil due to the high price of related equipment, high operating cost, long desorption time and other factors

as we all know, soil is an important non renewable natural resource for human survival. We need to control and eliminate the pollution source at the source when the sensor is under the effect of pull P based on an environmental protection policy of prevention oriented comprehensive treatment

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