De-Cyanide System

Most of the current methods to destroy cyanide hardly can meet the discharge standard in China. Furthermore, it hardly control the waste stream volume and the costs are too high.

Therefore, we recommend our client to use Metabisulfite Air process to treat mid-high

density of cyanide waste water. This process has advantages of destroy cyanide entirely,

operate simply, safe, less chemicals, low fees, etc. It will use half of the operating cost

comparing with current methods.

Sodium Metabisulfite - Air Process is based on using

SO2-O2 as oxidation, and using Cu2+ as catalyst. Keep the PH as curtain level and make the

CN- into CNO- which is way less toxic. The CNO- will be turned into NH3 and HCO3-

by hydrolysis. SO2 can be added as Metabisulfite, Cu2+ can be added as CuSO4·5H2O,

CaO or NaOH can be used to adjust PH.

The equation is:

S2O52- + 2CN- + 2O2 + H2O Cu2+ 2CNO-+2H+ + 2SO42-

èCNO-+2H2O èHCO3- + NH3

The reaction normally need the PH around 7-10 (8-9.5 is the best)

The sequence of oxidization is:

CN->Zn(CN)42->Fe(CN)34->Ni(CN)42->Cu(CN)42->SCN-

The CN- will be oxidized and the heavy metals will be precipitated as XFe(CN)6, X(OH)2,

XCO3 from the water (X for any metal). The destruction rate for CN- can be over 95%.