Method for treating mercury-containing hazardous waste residues by means of combination of low-temperature thermal desorption and chemical stabilization

Abstract

The invention discloses a method for treating mercury-containing hazardous waste residues by means of combination of low-temperature thermal desorption and chemical stabilization. The method comprisesthe steps that the mercury-containing hazardous waste residues are subjected to low-temperature thermal desorption treatment, and then organic combined-state mercury and partial low-boiling-point inorganic combined-state mercury in the mercury-containing hazardous waste residues are removed; then a sulfurizing salt solution is added for a sulfurization reaction, and then a ferrous salt is added for enabling excess S<2-> to be precipitated; and a clay mineral and humus are added for adsorption, a pH regulator is added for adjusting the pH of the mercury-containing hazardous waste residues to range from 6 to 7, and then curing is conducted for three days or above. According to the method, removing of low-boiling-point form mercury and stabilizing of high-boiling-point form mercury in the mercury-containing hazardous waste residues can be achieved, and mobility of mercury in the mercury-containing hazardous waste residues can be greatly reduced; various forms of mercury in the mercury-containing waste residues can be effectively removed and stably solidified, the stabilizing effect is good, energy consumption is low, and the period is short; and reagents adopted in the method are wide in raw material source and low in cost, and wide application is promoted.

Description

technical field [0001] The invention relates to a treatment method for mercury-containing hazardous waste residue, in particular to a method for treating mercury-containing hazardous waste residue through low-temperature thermal desorption combined with chemical stabilization, and belongs to the technical field of solid waste treatment. Background technique [0002] In recent years, with the rapid development of industry and agriculture, a large amount of mercury has been released in the process of production and use, and the "National Waste List" has listed mercury-containing waste as HW29 waste. Mercury-containing hazardous waste mainly refers to mercury-containing solid waste produced in mercury mining and smelting, chlor-alkali industry, battery and thermometer manufacturing and other industries. These mercury-containing wastes have high mercury content. If they are not disposed of properly, they will pollute the atmosphere, surrounding soil, surface water and groundwate...

AI Technical Summary

Problems solved by technology

At present, there are few relevant reports on the stabilization treatment of mercury-containing hazardous waste residues, but there are many studies on the stabilization agents and remediation methods for mercury-contaminated soils. For example, Chinese patent (CN105414166A) discloses a method for remediating mercury-contaminated soils Specifically, plow the off-ground surface soil of mercury-contaminated soil, air-dry, grind, and sieve to obtain the pretreated surface soil; The deactivation agent is fully mixed with the treated surface soil, and placed for 10-20 days until 70% of the mercury content in the surface soil is fixed, and the passivation agent is repaired; the surface soil is leveled and Indian kale is planted. During the vigorous growth period of Indian kale, dissolve calcium thiosulfate in water and spray it evenly into the soil around the root system of Indian kale, and finally harvest the Indian kale

Chinese patent (CN105598145 A) discloses an in-situ remediation method for mercury-contaminated soil. The method selects biochar, calcium polysulfide and sodium selenite as three passivating agents, which are mixed and applied to the soil by using biochar. Effectively improve the soil microenvironment. In alkaline and highly reducing soil, the mobility of mercury is greatly reduced. Biochar with a strong specific surface, porous structure, and complex organic functional groups can absorb a large amount of mercury in the soil. ; Irrigation of calcium polysulfide solution in the soil can further promote the mineralization of mercury. After planting crops, the microenvironmental biological activity of the root soil is strengthened. Sodium selenite solution is applied to weaken its bioavailability by using the antagonistic effect of selenium and mercury.

Mercury has many forms in soil, including: Hg, HgCl 2 , Hg 2 Cl 2 , HgO, HgS, mercury combined with soil inorganically, organically bound mercury, etc., Hg, HgCl 2 , Hg 2 Cl 2 Isomorphic mercury has a low boiling point and can be easily removed by low-temperature thermal desorption, while HgO, HgS and other forms of mercury have a high boiling point and must be heated to a temperature of 700-800°C or higher, and the heat treatment time Often it takes more than 1 hour to effectively remove, therefore, high energy consumption is required for repairing soil at high temperature. In particular, a large number of studies have shown that heat treatment temperatures higher than 350 ° C will seriously damage the structure of the soil

At present, there are many studies on the thermal desorption restoration of mercury-contaminated soil, but most of them are high-temperature thermal desorption methods, and there are few studies on low-temperature thermal desorption. Chinese patent (CN103056157A) discloses a low-temperature pyrolysis treatment of mercury-contaminated soil Repair method and device

In this patent, mercury-contaminated soil with a moisture content of less than 10% is put into a pyrolysis device. The initial temperature of the pyrolysis device is 250°C, and the temperature is raised to 400°C within 30 minutes. After repairing by this method, the mercury content in the soil is still relatively high. High, much higher than the third-level standard of "Soil Environmental Quality Standard" (GB15618-1995), the restoration effect is not ideal

Chinese patent (CN103785682A) discloses a method of using organic acid to promote the thermal treatment and restoration of mercury-contaminated soil. In this method, the organic acid and mercury-contaminated soil are mixed evenly before being put into the pyrolysis device, and the pyrolysis temperature is set at 400-500 °C. The treatment time is 20 to 60 minutes. After repairing by this method, the mercury content in the soil can be lower than the third-level standard of "Soil Environmental Quality Standard" (GB15618-1995). Although this method can properly reduce the pyrolysis temperature by adding organic acids, etc. The removal efficiency of mercury is high, but the pyrolysis temperature of this method is still above 400°C

[0007] Because mercury-containing hazardous waste residue is mercury-enriched residue, the mercury content is much higher than that of general mercury-contaminated soil, and the existing methods for treating mercury-contaminated soil are difficult to adapt to the treatment of mercury-containing hazardous waste residue, and there is no such method in the prior art. See related reports on the combination of low-temperature pyrolysis technology and chemical stabilization technology to efficiently stabilize mercury in waste residue