What are the common treatment methods for mercury-containing wastewater?

At present, the treatment methods of mercury-containing wastewater include precipitation method, electrolysis method, ion exchange method, activated carbon adsorption method and combined process treatment method. The following editor will introduce several methods for you in detail.

1. Precipitation method:

Precipitation method is divided into two types: coagulation precipitation and vulcanization precipitation. The principle of the coagulation sedimentation method is to add coagulants (lime, iron salt, aluminum salt) to mercury-containing wastewater to form hydroxide floccules under weak alkaline conditions with a pH of 8-10, and use the floccules to make mercury Co-precipitation precipitated. The vulcanization precipitation method is a precipitation method that has been reported more frequently. The method is to put sodium sulfide into mercury-containing wastewater, utilize the strong affinity of Hg2+ and S2- to generate mercury sulfide with extremely small solubility and remove mercury from the solution, which can be promoted in small and medium-sized chemical industries. This method is suitable for the treatment of different concentrations and types of mercury salts. When the concentration of mercury ions is high, the chemical precipitation method should be the first choice. According to reports, the removal rate of mercury by precipitation method can reach 95%-99.9%.
The shortcomings of this method: easy to cause water quality hardening, incomplete treatment of waste water containing low concentrations of mercury, and easy to cause secondary pollution; affected by precipitants, environmental conditions and process control parameters, it is difficult for the concentration of effluent to reach the discharge standard Therefore, further processing is required.

2. Electrolysis method:

The electrolysis method uses the electrochemical properties of metals. Under the action of direct current, mercury compounds dissociate into mercury ions at the anode and reduce to metallic mercury at the cathode to remove mercury in the waste water. The method is suitable for treating wastewater containing high-concentration inorganic mercury. The disadvantage of this method is that the concentration of mercury ions in the water cannot be reduced very low, the power consumption is relatively large, the investment cost is high, mercury vapor is easily generated, and secondary pollution is formed.

The ion exchange method is carried out in an ion exchanger, using macroporous sulfhydryl ion exchange resin to adsorb mercury ions in mercury-containing wastewater. The mercapto group on the resin has a strong adsorption capacity for mercury ions. The mercury adsorbed on the resin can be eluted with concentrated hydrochloric acid and recovered quantitatively. It is suitable for treating waste water containing low-concentration mercury. Studies have shown that the ion exchange effect is good after the first-level treatment and then the ion exchange method. After the ion exchange method treats mercury-containing wastewater, the low effluent content of inorganic mercury is 1-5ug/L. This method is affected by the impurities in the wastewater, as well as the limitation of the variety, output and cost of the exchanger.

Activated carbon adsorption method is a relatively mature mercury-containing wastewater treatment method. It can effectively adsorb mercury in wastewater. Some factories in our country have used this method to treat mercury-containing wastewater, but this method is expensive and only suitable for treating low-concentration mercury-containing wastewater. When the concentration of wastewater is too high, it can be treated with a primary treatment first, and then treated with activated carbon adsorption. According to relevant data, this method is suitable for wastewater with a mercury content of 1-2mg·L-1 or less. After being treated by the activated carbon adsorption method, the mercury concentration in the effluent water can be reduced to 0.01-0.05mg·L-1. Disadvantages of this treatment method: the supply of activated carbon is relatively tight, the regeneration equipment is less, and the regeneration cost is high.

5. Application of combined treatment technology:

Activated carbon adsorption method is a relatively mature mercury-containing wastewater treatment method. It can effectively adsorb mercury in wastewater. Some factories in our country have used this method to treat mercury-containing wastewater, but this method is expensive and only suitable for treating low-concentration mercury-containing wastewater. When the concentration of wastewater is too high, it can be treated with a primary treatment first, and then treated with activated carbon adsorption. According to relevant data, this method is suitable for wastewater with a mercury content of 1-2mg·L-1 or less. After being treated by the activated carbon adsorption method, the mercury concentration in the effluent water can be reduced to 0.01-0.05mg·L-1. Disadvantages of this treatment method: the supply of activated carbon is relatively tight, the regeneration equipment is less, and the regeneration cost is high.

6. ​​Other methods:

Superconducting magnetic separation technology is a newly developed superconducting magnet application technology. This technology is a technology that uses the force of a magnetic field to separate materials with different magnetic properties. The use of superconducting high-gradient magnetic separation technology can purify and separate mercury-containing wastewater. The technology is currently in the scientific research stage and has not yet been industrialized.

Further reading: What are the prevention and control measures for mercury-containing wastewater?

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