CN112170472A

CN112170472A - Novel emergency remediation technology for heavy metal contaminated soil

Info

Publication number: CN112170472A
Application number: CN201910588140.8A
Authority: CN
Inventors: 傅开彬; 秦天邦; 龙美樵; 侯普尧; 杜明霞; 李文涛; 吴雨哲; 高德强
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2019-07-02
Filing date: 2019-07-02
Publication date: 2021-01-05

Abstract

The invention relates to an emergency treatment method for rapidly removing heavy metal ions in soil during sudden heavy metal pollution accidents, which is characterized by comprising the following steps of: removing heavy metals in soil by using a self-made nano air flotation device, taking soil polluted by heavy metals in sudden pollution events, sequentially separating coarse-grained and fine-grained stones through twice wet screening, mixing products under the screen, controlling the slurry concentration to be between 15% and 55%, performing 'one-coarse three-fine three-sweep', wherein foam products are removed heavy metal products, recovering the heavy metals from the foam products, adding a vulcanizing agent, a reinforced vulcanizing agent, a collecting agent, a foaming agent and the like into the repaired soil at a proper point in a flow, and the removal rate of the heavy metals (Hg, Cd, Pb, Cr, Cu, Zn, Ni and the like) in the heavy polluted soil is more than 90%. The method is suitable for quickly repairing the heavily polluted soil, has high heavy metal removal rate, and can effectively recover the heavy metals in the soil.

Description

Novel emergency remediation technology for heavy metal contaminated soil

Technical Field

The invention relates to an emergency air-floatation repair technology for heavy metal contaminated soil in the field of mineral processing engineering, which is particularly suitable for emergency repair treatment of heavy contaminated soil caused by sudden heavy metal leakage.

Background

Heavy metal pollution of soil has become one of the major environmental hazards worldwide. The emergency repair treatment method for the heavily polluted soil caused by sudden heavy metal leakage has less research. At present, the technology for removing heavy metals in soil at home and abroad mainly aims at the condition of light pollution degree, and can be roughly divided into three categories of physical remediation, chemical remediation and biological remediation from the remediation principle.

The physical restoration mainly comprises three methods of turning soil, replacing soil, soil dressing and the like, has the characteristics of rapidness, thoroughness and stability, but has larger engineering quantity and large investment. According to the relevant reports, the method has the advantage of 1 hm²The polluted soil in the area is subjected to engineering treatment (soil replacement), the cost of soil body per 1.0 m deep is up to $ 800-2400 ten thousand, and soil fertility is easy to weaken, so that the method is only suitable for a small-area polluted area at present.

The chemical remediation is that heavy metal ions react with coordination compounds to form stable complexes or react with acid radical ions to form precipitates, so that the existence form of the heavy metals in the soil is changed, the bioavailability and the mobility of the heavy metals in the soil are reduced, and the chemical remediation mainly comprises solidification/stabilization, leaching, an electrochemical method and a flotation method. Solidification/stabilization refers to the technique of mixing contaminated soil with a binder that can coalesce into a solid, capturing or immobilizing the contaminant in a solid structure. The soil leaching method is a method for transferring heavy metal pollutants in soil to a liquid phase by using a leaching agent and then treating the generated waste liquid. Electrochemical remediation of soil refers to a technique for in situ remediation of contaminated soil by placing suitable anodes and cathodes vertically underground and applying a low power dc electric field to remove inorganic or organic contaminants from the soil. The bioremediation technology is to utilize certain specific animals, plants and microorganisms to enable the specific animals, plants and microorganisms to absorb or degrade heavy metal pollutants in soil quickly so as to achieve the aim of purifying the soil.

The flotation method is initially applied to separation of useful minerals and gangue, and as early as 1860, Willianm Hayneo applies for the flotation method, which is one of the most important methods for mineral separation, and has more research reports on treatment of wastewater containing heavy metals and less reports on application of the flotation method to heavy metal contaminated soil. The Sunweishi application of a foam flotation method to separate heavy metal in soil, sodium dodecyl sulfate (SDS, 6 mg/g) is used as a foaming agent, potassium amyl xanthate (1 mg/g) or kerosene (15 mg/g) is used as a collecting agent, and when the concentration of sodium sulfide is 3 times that of the heavy metal in the soil, the removal rate of the heavy metal reaches 80%, which indicates that the foam flotation method can effectively remove the heavy metal ions in the soil.

At present, the heavy metal contaminated soil treatment methods mainly aim at the condition of light pollution degree, and have the following defects:

(1) the physical method has large energy consumption and large investment, thereby limiting the application range of the method.

(2) The biological method has long repair period and cannot be used for emergency pollution events.

(3) The chemical method has short restoration time, high efficiency, easy generation of secondary pollution and poor removal effect on heavy metals adsorbed on the surface of the soil.

Disclosure of Invention

At present, emergency repair treatment methods for severely polluted soil caused by sudden heavy metal leakage are few. The conventional methods such as physical remediation, chemical remediation and biological remediation have respective defects and are not suitable for remediation of contaminated soil in sudden pollution events. Therefore, the novel emergency remediation technology for the heavy metal contaminated soil provided by the invention can treat about 0.5-10 tons of soil per hour, is particularly suitable for emergency remediation treatment of the heavily contaminated soil caused by sudden heavy metal leakage, simultaneously recovers the heavy metals in the soil, realizes resource utilization, has the advantages of high treatment efficiency, high treatment speed, capability of simultaneously remedying various heavy metals and the like, does not need to carry the soil for the second time, removes the soil with the heavy metals, stacks the soil in situ after dehydration, and settles and exposes the filtered water to reach the surface water discharge standard.

Drawings

The attached figure 1 is a process flow chart of emergency repair treatment of heavily polluted soil caused by sudden heavy metal leakage, and the process scheme of the invention is explained by combining the process flow chart: an excavator or other similar mechanical equipment feeds polluted soil into a small buffer bin, the polluted soil is washed by a rough screen to separate coarse-particle stones, products under the rough screen enter a fine screen, products on the fine screen are fine-particle stones, products under the fine screen enter a stirring barrel to be subjected to size mixing, a vulcanizing agent, a reinforced vulcanizing agent, a collecting agent, a foaming agent and the like are added, rough-selection foam products enter primary fine selection, rough-selection underflow enters primary scavenging, primary fine-selection foam enters secondary fine selection, secondary fine-selection foam enters third fine selection, third fine-selection underflow flows back to secondary fine selection, secondary fine-selection underflow flows back to primary fine selection, primary fine-selection underflow flows back to rough selection, underflow of primary scavenging flows to secondary scavenging, underflow of secondary scavenging flows into third scavenging, and foam products return sequentially.

Fig. 2 and 3 show a nanobubble flotation device of the present invention, and the structure and the operation principle of the device are described as follows: 3-6 slurry feeding ports are arranged from the bottom surface of the column bottom of the flotation column to 1/3 parts of the cylinder, the top is a foam product overflow port, a foam product groove, the bottom is a mine discharge port, and the flotation column can be connected with the next flotation device to realize series connection. The water pump inhales gas, liquid and solid mixing arrangement with mud, then mud gets into column separator through nanometer air supporting generator, and the nanometer bubble carries adhesion heavy metal sulphide granule to get into the foam product, separates out the heavy metal through scraping the bubble, and the soil after the restoration is stayed in the air supporting device, can change the volume of heavy metal contaminated soil as required, designs the nanometer air supporting device of different models.

Detailed Description

The first embodiment is as follows: a liquid return pipe of an electrolytic tank in an electrolytic workshop of a certain copper industry Limited liability company bursts, electrolyte leaks, and workers directly wash and discharge the copper-containing waste liquid out of a factory, so that soil around the factory is polluted, and the Cu content in the polluted soil is up to 15000 mg/kg. By adopting a self-made nanometer bubble flotation device and through 'one-rough three-fine three-sweep', the consumption of the vulcanizing agent is 3 times of a theoretical value, the concentration of the strengthened vulcanizing agent is 20 mg/L, the concentration of the collecting agent is 60 mg/L, the concentration of the foaming agent is 30 mg/L, the content of copper ions in the restored soil is reduced to 1325 mg/kg, and the removal rate of the copper ions reaches 91.17%.

Example two: in the heap leaching of certain nickel oxide ore, dilute sulfuric acid is adopted for leaching, a dam body of a pregnant solution pool collapses, so that pregnant solution leaks to pollute soil around the pregnant solution pool, and the Ni content in the polluted soil is up to 30000 mg/kg. By adopting a self-made nanometer bubble flotation device and through 'one-rough three-fine three-sweep', the consumption of the vulcanizing agent is 3.5 times of the theoretical value, the concentration of the reinforced vulcanizing agent is 30 mg/L, the concentration of the collecting agent is 80 mg/L, the concentration of the foaming agent is 30 mg/L, the content of nickel ions in the restored soil is reduced to 1405 mg/kg, and the removal rate of the nickel ions reaches 95.32%.

Example three: in the microbial heap leaching of certain secondary copper sulfide ore, as the dam body of the microbial leaching liquid pool collapses due to rain washing, the pregnant solution leaks, the soil around the pregnant solution pool is polluted, and the Cu content in the polluted soil is up to 10000 mg/kg. By adopting a self-made nanometer bubble flotation device and through 'one-rough three-fine three-sweep', the consumption of the vulcanizing agent is 2.5 times of the theoretical value, the concentration of the reinforced vulcanizing agent is 15 mg/L, the concentration of the collecting agent is 50 mg/L, the concentration of the foaming agent is 30 mg/L, the content of copper ions in the restored soil is reduced to 925 mg/kg, and the removal rate of the copper ions reaches 90.75%.

Claims

1. A new technology for emergency remediation of heavy metal contaminated soil is characterized by comprising the following steps:

(1) wet sieving and separating stones: the method adopts twice screening to sequentially separate stones with different granularities, the equipment for coarse screening can select one or more of a vibrating screen, a cylindrical screen, a rotary screen, a shaking screen, a grid screen and the like, and the equipment for fine screening can select a fine screen, a sand washer and the like.

(2) Soil size mixing: according to the content of heavy metal ions in the soil and the degree of argillization, the concentration of the slurry is controlled to be between 10 and 55 percent.

(3) Removing heavy metal by nano air flotation: after size mixing, through 'one-coarse three-fine three-sweep', foam products are removed heavy metal products, the discharge of a flotation device is restored soil, and the removal rate of heavy metals (Hg, Cd, Pb, Cr, Cu, Zn, Ni and the like) in the heavily polluted soil is more than 90%.

(4) Flotation reagent: the flotation reagents comprise vulcanizing agents, strengthening vulcanizing agents, collecting agents, foaming agents and the like, 4 types of reagents are added in rough concentration, the vulcanizing agents and the collecting agents are added in scavenging, and no reagent can be added in a concentration stage.

(5) And (3) recovering heavy metals: the foam product has high heavy metal content, and the metal elements in the foam product can be recovered by a chemical method or sold to a smelting plant, so that the comprehensive utilization of resources is realized.

2. The novel technology for emergency remediation of heavy metal contaminated soil according to claim 1, characterized in that:

(1) self-control nanometer air supporting device: utilize self-control novel controllable nanometer bubble flotation device to be reactor (application number 201811081629.8), its characterized in that, the water pump inhales gas, liquid and solid mixing arrangement with mud, then mud gets into column separator through nanometer air supporting generator, the nanometer bubble carries adhesion heavy metal sulphide granule to get into the foam product, through scraping the bubble and separate out the heavy metal, soil after the restoration is stayed in the air supporting device (see figure 2), can revise the volume of heavy metal soil as required, design the nanometer air supporting device of different models.

(2) The heavy metal removing agent comprises: the vulcanizing agents comprise calcium sulfide, sodium sulfide, barium sulfide, potassium sulfide, sodium hydrosulfide, sodium polysulfide and the like, and the dosage of the vulcanizing agents is 1.5-6 times of the theoretical dosage; the strengthening vulcanizing agent comprises ammonium sulfate, ammonium chloride, ethylenediamine phosphate, ammonium bicarbonate, ammonium nitrate, ammonium carbonate, diammonium hydrogen phosphate and the like, and the concentration of the strengthening vulcanizing agent is 10 mg/L-1000 mg/L; the collecting agent comprises ethyl xanthate, butyl xanthate, Z-200, Sodium Dodecyl Sulfate (SDS), Sodium Dodecyl Benzene Sulfonate (SDBS) and Cetyl Trimethyl Ammonium Bromide (CTAB), and the concentration of the collecting agent is 30 mg/L-1000 mg/L; the blowing agent comprises 2^#Oil, MIBC and 11^#The foaming agent concentration is 10 mg/L to 500 mg/L.

(3) The nano air flotation process structure: the flow of 'one coarse and three fine sweeping' is adopted, and the flotation time is determined according to the flotation time of the self-made nano bubble flotation device.

(4) After the heavy metal ions are converted into sulfide particles, heavy metal ion sulfide particles and soil need to be separated through an air floatation method, so that the heavy metal contaminated soil is repaired. Heavy metal ions in the soil exist in a water-soluble state, an ion exchange state, a carbonate combination state, an iron-manganese oxide combination state, an organic combination state, a sulfide combination state, a residual state and the like, after the vulcanization pretreatment, the particle size of the formed hydrophobic sulfide particles is small, some particles even reach the nanometer level, bubbles matched and coordinated with the nanometer level sulfide particles are formed, and the key for efficiently separating the sulfide particles from the soil is that. Therefore, the nano-bubble flotation equipment is developed into key equipment for repairing heavy metal contaminated soil by a vulcanization-air floatation method (application number 201811081629.8).