Purification of cyanide-containing wastewater by hydrogen peroxide

Aqueous located in densely populated area fishing waters developed a Hubei gold ore, heap leaching tail cyanide-containing water 1.15mg / L, purification with bleach (alkaline chlorination), can be reduced to 0.26mg / L, although lower It is based on industrial wastewater discharge standard (0.5mg/L), but much higher than the water quality standard of fishery waters (0.02mg/L). To ensure that human, animal, fish and industrial and agricultural production is not harmed or affected. The Hubei Institute of Geological Experiments carried out research on the purification of cyanide-containing wastewater by hydrogen peroxide, with the aim of allowing the heap leaching tail water to reach the national fishery water area water quality standard.

1. Mechanism of decomposition and oxidation of cyanide by hydrogen peroxide

Hydrogen peroxide first oxidizes the cyanide to cyanate, and then the cyanate is hydrolyzed to ammonium carbonate. The reaction formula is:

CN ^- +H ₂ O ₂ →CNO ^- +H ₂ O

CNO ^- +2H ₂ O→NH ₄ ⁺ +CO ₃ ^{2 -}

The reaction is very rapid. H ₂ O ₂ does not produce any harmful toxic products after reaction with cyanogen.

Second, the experiment and results

It was observed that when the cyanide-containing wastewater (CN 3.73 mg/L) was added to a hydrogen peroxide having a volume ratio of 1.0%, the treated liquid had a cyanide content of less than 0.002 mg/L. When the stabilizer was added to reduce the amount of hydrogen peroxide, it was observed that the amount of hydrogen peroxide was reduced from 0.01% to 0.005%, and the amount of stabilizer was increased from 0.002% to 0.005%, which could reduce the cyanide wastewater of 2.2mg/L to 0.003. Mg/L, its cyanide removal effect is satisfactory.

Third, expand the test results

After the experimental parameters of the small test are selected, the expansion test is carried out. The test tail water is used. 55 g of hydrogen peroxide and 55 g of stabilizer are added per m ³ of cyanide-containing wastewater, and the mixture is stirred for 0.5 h to make the total cyanide content 3.32 mg/ The tail water of L is reduced to 0.004mg/L at one time, which is not only lower than the water quality standard of the fishery water area, but also lower than the national source water quality standard (0.005mg/L).

Fourth, the cost estimate

Purification tests were carried out on the tailwater of a gold mine in Hubei Province using hydrogen peroxide and bleaching powder methods, respectively. The results comparison and the cost estimate of the medicament are listed in Table 1. The comparison results show that the hydrogen peroxide method plus the stabilizer has a lower cost and better purification effect than the bleaching powder, and is a promising method.

Table 1 Comparison of the cost of the two purification methods and the effect of removing cyanide