General Characteristic of Cyanide
In general, we can observe Hydrogen cyanide, sodium cyanide, and potassium cyanide easily in the environment where we have industrial activities.
* Cyanide is a powerful and rapid-acting
* Hydrogen cyanide has been used in gas-chamber executions and as a war gas.
Hydrogen cyanide is a colorless gas with a faint, bitter, almond-like odor.
Is anybody know what the almond-like odor?
Sodium cyanide and potassium cyanide are both white solids with a slight, bitter, almond-like odor in damp air.
Cyanide salt and hydrogen cyanide are used in electroplating, metallurgy, production of organic chemicals, photographic developing, in making plastics, fumigating ships, and some mining process.
In this project we discuss mainly about the mining process.
The recipe of precious metal extraction is not so complicated.
The chemical reaction occurring in this process is very complicated. Because Cyanide will change its form through the process.
Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard
Hazard Hazard Hazard Hazard
General Characteristic of Cyanide
The common cyanide:
Sodium Cyanide: White powder, A slight, bitter, almond-like odor in dump air.
Potassium Cyanide: White powder, A slight, bitter, almond-like odor in dump air.
Hydrogen Cyanide: Colorless Gas, A faint, bitter, almond-like odor.
Chemical composition of Sodium Cyanide
CNNa * Na+ + CN-
Produced by carbon monoxide and ammonia.
yHazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazard
Hazard Hazard Hazard Hazard Hazard Hazard Hazard Hazardp
Biological Treatment of Cyanide
at Precious and Heavy Metal Mines.
My peers and I researched the use of cyanide in gold leach mining last
quarter. (Energies Research Project, CYANIDE, Fall 97) I specifically
looked up the chemistry of cyanide and found the complexity of it associated
with hydrology and geochemistry. The process is what follows: cyanide (CN)
is mixed with sodium (Na), then this sodium cyanide (NaCN) meets water
(H2 O), then sodium cyanide solution meets crashed
rocks that contains gold (Au) and many other heavy metals such as silver,
arsenic and mercury. The negatively charged cyanide (CN2
) attract positively charged metals. Various cyanide compounds such as
K2 Fe(CN)2 , and other metal
cyanide complexes will be created in the results.
Simplified process of gold extraction by cyanide
recipe of precious metal extraction
|1. Put the low grade ore
into the super heavy duty grinder.
2. Add the sodium cyanide solution. Then, grind and mix them very well.
+ 4NaCN +2H2O
| 3. Pour
the slurry into the large bowl. Let it rest for a while.
+ 2NaOH +H2O2
4. Then add some zinc (Zn) dust.
Zn + 4NaCN + NaAu(CN)2 = Au + Na2Zn(CN)2+ 2NaCN
5. Gold is recovered by electrowinning.
The detail of gold dissolution
was discussed in the first report of
The Chemistry of Free and Complexed Cyanide, Fall 97.
(This site is under construction.)
Bioremediation is the process of breaking and transforming hazardous
materials into simple nontoxic substances by a biological treatment. Cyanide
can be broken in to simpler substances by microorganisms in the wastewater,
piles and in the soil. Some bacteria and fungus can decompose cyanide and
cyanide compounds. The biological treatment methods do not depend on the
supply of electricity or other energy sources. The bacterial detoxification
would be safer, quicker, and less costly than the chemical treatment to
handle cyanide wastes. The process that demands oxygen is an aerobic biodegradation
and the process that occurs in the absence of oxygen is an anaerobic biodegradation.
HIGHLIGHTS OF BIOREMEDIATION
COMPOSITION OF CYANIDE
chemistry of cyanide is CN. The biodegradation of cyanide seems very
simple: it breaks into carbon and nitrogen.
BIODEGRADATION OF CYANIDE
The bacteria oxidizes the cyanide, breaking it down into harmless compounds. In many cases, cyanide-oxidizing bacteria are naturally present in processing ponds and waste piles.
1. Under aerobic conditions, biological process may consume hydrogen cyanide and generate hydrogen cyanate as shown in the equation below. The hydrogen cyanate is in turn hydrolysed into ammonia and carbon dioxide.
Equations of aerobic biodegradation of hydrogen cyanide (HCN):
1) 2HCN + O2 + enzyme = 2 HCNO
2) HCNO + H2 O = NH2+ CO2
The direct oxidation of cyanide CN2 requires a mineralogical, bacteriological, or photochemical (sunlight) catalyst, and produces cyanate ions (CNO2):
3) 2CN2 + O2 + catalyst = 2CNO2
2. Anaerobic biodegradation of cyanide and hydrogen cyanide is restricted to the moderately to strongly reduced portions of the heap environment and can only occur if HS2 or H2 S are present. The sulphur species present will depend on pH. At a pH value greater that 7, HS2 is the dominant species. At a lower pH, H2 S will be present.
Equations of anaerobic biodegradation of cyanide:
4) CN2 + H2 S = HCNS
5) HCN + HS2 = HCNS + H2
The HCNS will then hydrolyze to form NH2 , H2 S and CO2 . Compared to the aerobic biodegradation of cyanide, anaerobic biodegradation is much slower and anaerobic bacteria have a cyanide toxicity threshold of only 2 mg/l compared to 200 mg/l for aerobic bacteria. Consequently anaerobic biodegradation is a much less effective cyanide removal mechanism. (The Chemistry and Treatment of Cyanidation Wastes by Adrian Smith and Terry Mudder, Mining Journal Books Limited, 1991)
Wastewaters in the mining industry, in which CN serves as an ore extractanct,
are often high in Ni, Cu, Zn, and Fe. The following cyanide degrading bacteria
occurs readily in nature. They eat cyanide, CN, as a sole nitrogen source.
(Toxicity and Environmental Fate of Cyanate, Thiocyanate and Cyanogen Chloride
by Dean Boening and Christine Coffey, ICF Kaiser Engineers, Inc., 1994)
|Pseudomonas putida||Sewage sludge, Soil, Creek water|
|Pseudomonas paucimobilis||Mining wastewater|
|Klebsiella pneumoniae||Soil, Creek water|
|Klebsiella sp.||Creek water|
There are some other enzymes capable of CN transformation. Cyanase is an enzyme that catalyzes the hydrolysis of cyanate to ammonia and bicarbonate. Escherichia coli (E. coli), and Flavobacterium speicies also eats cyanate as a sole nitrogen source.
Ammonia and carbon dioxide are the major end products of aerobic CN metabolism. The primary end products from anaerobic cyanide transformation are formate and bicarbonate, but the mechanisms of adaptation to and degradation of cyanide in anaerobic systems are not well understood.
Nutrients for bacteria.
Phosphates encourage bacterial populations to grow and to break the cyanide down into carbon and nitrogen. (Bacteria eat mining wastes, News Notes Geotimes, 1993)
Environment for biodegradations
It is known that the pH in particular plays a significant role in the and reactivity of these compounds, although further studies must be conducted. (The Chemistry and Treatment of Cyanidation Wastes, Smith and Mudder, 1991)
Many biological treatment application have been developed to clean up various hazardous, wastes such as arsenic, cyanide and radioactive materials. This application should involve hydrology, geochemistry, and micro-organisms, and therefore the results are complex. In the next century, developing biological treatments will be the very exciting and the potential area in Research & Development arena not only in science but in economic as a proficient, economically feasible, technically viable, applications as well as environmentally sound. Currently serious R & D efforts are underway to find leachants that are less toxic and dissolve precious metals at faster rates than cyanide.
The Chemistry and Treatment of Cyanidation Wastes
by Adrian Smith and Terry Mudder
Mining Journal Books Limited, 1991
Bacteria eat mining wastes, Geotimes, News Notes
by Sandy Cleva, Office of Public Informations
U.S. Bureau of Mines, December ,1993
Let them eat cyanide, Geotimes, News Notes
by Sandra Cleva
U.S. Bureau of Mines, July, 1995
Tosicity and Environmental Fate of Cyanate, Thiocyanate
and Cyanogen Chloride by Dean Boening and Christine Coffey
ICF Kaiser Engineers, Inc., 1994
Microscopic Secret Agents
by Jeannie Woodring
Alaska Magazine, June 1992
Use bacterial degradation to get rid of cyanide
by S.M. Kang and D. J. Kim
Korea Steel Chemical Co.,
Biotechnol Letter, 1993
In-situ Groundwater Biodegradation - Vendor Companies.
ENSR CONSULTING AND ENGINEERING
GEO-MICROBIAL TECHNOLOGIES, INC.
GAIA RESOURCE, INC.
GROUNDWATER TECHNOLOGY, INC.
YELLOWSTONE ENVIRONMENTAL SCIENCE, INC.
WASTE STREAM TECHNOLOGY, INC.
MICRO-BAC INTERNATIONAL, INC.
Comments and feedback are welcome. Email me
|Astrobiology||Oort Cloud||Dark Matter||SEM||TEC||ZAMS||Wonderland||Resume||Ann||Essay||Purchasing Website|
Back to Home
This page is produced and maintained by Moko.
Last update: 10/03/2000
Moko's Home Page
This page created with Netscape Navigator Gold