Regeneration and recovery of cyanide waste liquid - electrodialysis - acidification

Electrodialysis is widely used in the treatment of brackish water, fluorine-containing water, seawater desalination, salt production, boiler feed water purification, etc. due to its high salt removal efficiency. Kunming Institute of Metallurgy cyanide barren solution for both CN ^- from recovering, Au, Zn, Pb, Cu and the like, and to reduce the amount of processing solution tail explored lean liquid cyanide integrated process flow of FIG.

Figure 1 Electrodialysis-acidification process

Electrodialysis is the orientation movement of ions under the action of an electric field. Through the alternate arrangement of the anion and cation exchange membranes and the rational assembly of the separator, the ions in the lean liquid flowing through the desalination chamber enter the phase through the ion exchange membrane under the action of the electric field. Pro concentrated room. The solutions in the rich and depleted compartments are then passed through the respective water channel ejectors to obtain two different concentrations of solution.

The electrodialyzer for the experiment has a separator of 100 mm × 200 mm and δ = 2 mm. A plastic window gauze is attached to the double-circuit flow channel, and the flow channel is 33 mm wide and 150 mm long. It is assembled into eight stages by eight pairs of anion and cation exchange membranes. The fresh water circulation flow is indicated by the rotameter. After circulating to concentrated water to a certain concentration, it is discharged and subjected to acidification and CN ^- treatment.

The lean liquid used in the experiment contained NaCN 540 mg ∕L. When the power consumption was 3 kW·h/m ³ , the NaCN removal rate in the produced desalinated water was more than 90%. The amount of desalinated water accounts for 75% of the total amount of treated lean liquid, and is used during the return to cyanide operation. Concentrated water accounts for 25% of the total amount of lean liquid. Containing NaCN up to 2090 mg ∕L, enriched 3.9 times.

The acidification and de-cyanide test of concentrated water uses an electrically heated three-necked bottle, and the steam is passed through a first-stage buffer bottle and a two-stage lye absorption bottle in series, and then discharged through an air pump. Concentrated water is injected into the three-necked bottle to add sulfuric acid to adjust pH=1.5, the temperature is about 35 °C, and the vacuum degree during the process is 17 kPa (580 mmHg, local atmospheric pressure is 600-610 mmHg), and 0.5~1 h, the residual in the steam residue NaCN < 50 mg ∕ L, CN recovery rate is greater than 93%. The cyanide anion such as Au, Cu, Zn in concentrated water releases CN-, and the sulfate is enriched in the vapor residue, and lime is added to hydrolyze them to form a hydroxide and precipitate together with CaSO ₄ . The chloride is then used to leach all of the metal in the precipitate and then separated and purified.

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