Environmental Engineering Reference
In-Depth Information
TABLE 6.3
Cyanide Removal Technologies
Technology (and Type*)
Short Description
Basic Reagents
Basic Products
A. OXIDATIVE
Alkaline Chlorination (C)
Oxidation to CNO
and then N
2
and CO
2
with Cl
2
or ClO
at pH
11
Cl
2
/ClO
, NaOH
CNO
, CO
2
, N
2
SO
2
/Air (C)
SO
2
, air, Cu catalyst
Oxidation to CNO
with SO
2
/Air and
soluble Cu catalyst; INCO process
CNO
Oxidation to CNO
with H
2
O
2
and Cu
2
catalyst; Degussa Process
CNO
, CO
2
, NH
4
Hydrogen Peroxide (C)
H
2
O
2
Caro's Acid (C) (C)
Oxidation to CNO
with H
2
SO
5
H
2
SO
5
CNO
Activated Carbon (C & P)
Oxidation to CNO
and then partially to CO
2
and
NH
4
Activated carbon, air/O
2
,
Cu catalyst
CNO
, CO
2
, NH
4
with activated carbon and Cu catalyst
Biodegration (B)
Oxidation to CO
2
and NH
4
and then NO
3
using
indigenous micro-organisms
Na
2
CO
3
, H
3
PO
4
CO
2
, NH
4
, NO
3
, PO
x
with air at mild temperatures
(
130
o
C) and pressures (550 kPa) with a catalyst
UOP Catalytic Oxidation (C)
Oxidation to CO
2
, N
2
and NH
4
Catalyst
CO
2
, N
2
, and NH
4
Oxidation to CO
2
and N
2
with O
3
CO
2
, N
2
Ozonation (C)
O
3
Oxidation to CO
2
and N
2
at high temperatures (175 - 320
o
C)
and high pressures (2,100 - 20,700 kPa)
Wet Air Oxidation (C)
none
CO
2
,
N
2
Photocatalytic Oxidation
(C & P)
Oxidation to CNO
and then NO
3
and CO
2
using
uv/visible light and semiconductor type substrate,
e.g. TiO
2
, ZnO or CdS
B. NON-OXIDATIVE
Natural Degradation (B, C & P)
Mainly volatilization of HCN from tailing dams
none
Mainly HCN
AVR (C & P)
Acidification-Volatilization-Reneutralization. After acidification to
pH
3, HCN(g) is volatilized and absorbed in NaOH and recy-
cled. Metals are precipitated after reneutralization
H
2
SO
4
, NaOH
HCN, SCN
CYANISORB® (C & P)
Similar to AVR bur HCN(g) stripped at higher pH values
(5.5-7.5)
H
2
SO
4
, NaOH
HCN, SCN
CRP (C & P)
Cyanide Regenaration Process; similar to AVR but with better
HCN(g) stripping and metal precipitation
H
2
SO
4
, NaOH
HCN, SCN
Thermal Hydrolysis (C)
Hydrolysis to NH
4
and formate at high temperatures
none
NH
4
, HCOO
Alkaline Hydrolysis (C)
and formate at high temperatures
(100-250
o
C) and high pH
NaOH
Hydrolysis to NH
4
NH
4
, HCOO
GM-IX (C & P)
Gas Membrane-Ion Exchange; Ion Exchange concentrates CN.
After regeneration the Gas Membrane recovers pure CN.
Resin
CN
Prussion Blue Precipitation (C)
Precipitation of Fe
4
[Fe(CN
6
)]
3
on addition of FeSO
4
FeSO
4
Fe
4
[Fe(CN
6
)]
3
(Continued)
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