Treatment of mercury-containing household wastewater

There are many methods for treating mercury-containing wastewater. The effectiveness and cost of various treatment methods depend on the form in which mercury exists, its initial concentration, the ions present in the wastewater, and the standards required for the quality of the treated water. (1) Reduction method: (1) NaBH4 (sodium borate) reduction method: The non-metallic reducing agent—sodium borate—reacts with mercury to produce mainly mercury and boric acid, while hydrogen gas is released. Hg2+ + BH4- + 2OH- → Hg↓ + 3H2↑ + BO2-. (2) Metal reduction method: For metals whose redox potential is lower than that of Hg2+, such as Cu, Zn, Fe, Mn, Mg, Al, etc., the corresponding metal shavings can be used as a filler in a packed tower to displace Hg2+ ions from wastewater. Taking iron as an example: Fe + Hg2+ → Fe2+ + Hg↓. (II) Sulfidation method: H2+ + S2- → HgS↓; 2Hg2+ + S- → Hg2S + Hg↓. (III) Adsorption method: Activated carbon is commonly used as the adsorbent. The process involves first converting mercury ions into mercury sulfide precipitate using sodium sulfide, and then using activated carbon to absorb this precipitate. The purified liquid resulting from this treatment contains residual mercury levels that meet the specified emission standards. (IV) Ion exchange method: Several types of resins are installed in columns to form a wastewater purification system; in this way, after the mercury-containing wastewater passes through these exchange columns, no mercury is detected in the effluent. (5) Coagulation and precipitation method: Lime is added to mercury-containing wastewater; the resulting Ca(OH)2 has a coagulating and adsorbing effect on mercury, and this effect is even better in the presence of trivalent iron ions. Using aluminum sulfate as a coagulant to treat mercury-containing wastewater also yields good results. After coagulation and precipitation, the mercury content in the effluent water can be reduced to below 0.05 mg/L. (VI) Solvent extraction method: Currently, abroad, triisooctylamine-dimethyltoluene is used to extract mercury-containing wastewater; after extraction, the residual mercury concentration in the purified liquid is below 0.017 mg/L. In addition, abroad, mercury is recovered using microorganisms, electrolysis, ferrite precipitation, and sulfide precipitation-flotation separation; in China, methods such as conversion for mercury removal and adsorption using humic acid-containing coal are under investigation.

Hello, are there any examples of mercury-containing wastewater treatment in the chlor-alkali industry? How is the treatment effect?

This post was last edited by sigui1201 on 2012-4-19 at 17:57. Using chelating resins to treat mercury-containing wastewater yields good results and stable performance; the initial cost of using these resins is higher, but the mercury in the wastewater can be recovered. In the chlor-alkali industry, mercury-containing wastewater is generally treated to recover mercury using the two chelating resins CH-95 and CH-97. CH-95 cannot be regenerated, while CH-97 can be regenerated; both have an exchange capacity of 150 g/L. CH-95 is used within a pH range of 0–7. CH-97 can be used in a pH range of 0-14. Using CH-97, regeneration is carried out with a low concentration of hydrochloric acid, simultaneously eluting mercury. Mercury can then be recycled. In the case of CH-95, the mercury-containing resin is usually melted, and what remains is mercury. You can reach out to me if needed