Malaysiakini Letter

Nonsense to claim someone can get sick from cyanide

Kit Lee  |  Published:  |  Modified:

I refer to the Malaysiakini report Bkt Koman residents fail to stop goldmine .

I have been involved in exploration and mining for 40 years around the world. Half my experience has been in gold mining including in the former Raub Gold Mine (1986 to 1987), the centre of this dispute.

Cyanide was first ever used in gold mining in Bau, Sarawak at the turn of the 20th century by the Borneo Company. Cyanide (sodium cyanide) is used to dissolve gold (including silver) as gold cyanides (cyanide/cyanades/thiocyanides). In the old days, the dissolved gold is recovered with zinc dust (Merrill Crowe Process) and then smelted into gold bars.

In the 1950s, resins were used to absorb the dissolved gold cyanides and gold could then be recovered by electrolysis. This was replaced by activated carbon (most of which is being produced in Malaysia from coconut shells). The cyanides/cyanides/thiocyanides will remain in the tailings water as stable metal complexes.

Internationally, to meet environmental compliance, these are require to be denatured using chlorine, iodine and common hydrogen peroxide before discharge. In fact, these are more harmful to the environment as they will kill plant life and increase BOD (Biological Oxygen Demand).

But all environmental agencies insist on this antiquated law. The regulations also insist in denaturing free cyanide radicals (unused sodium cyanide). These could cause death if a sufficient quantity is consumed.

But all mining operations use a very low concentration of cyanide at 110 to 150 ppm (parts per million) and tailing waters are further diluted by other waters especially storm water many fold. Environmental protection agencies should ensure that cyanide concentrations be kept at such diluted levels.

Cyanide is not a poison as it is a carbon-nitrogen compound and will disintegrate in UV light. It would, however, prevents the blood from absorbing oxygen and anyone consuming too much will die of suffocation. Cyanide occurs naturally in many roots especially unripe tapioca. The indigenous people have been using these to ‘poison' fish and yet the fish is edible.

For more than 100 years since cyanide had been used for gold mining, there have been only two instances of accidental death reported due to cyanide poisoning. Such dangers can be limited by the following:

1. Tight control of the circuit of mine water with safety ponds properly constructed to prevent any overflow due to surges in mine waters during floods. These safety ponds must be constructed and maintained to meet strict safety codes.

2. All mine waters be re-circulated (this is a common practice to use up all the free cyanide as cyanide is expensive) so that only small amounts of concentrated inert cyanide solutions require de-naturing

3. The biggest danger from cyanide is hydrogen cyanide gas that is odourless but deadly (used for gas chambers). Hydrogen cyanide gas will result if cyanide occurs in an acidic environment.

All mines should ensure all mine waters are alkaline and cyanide monitors installed at strategic areas especially enclosed areas. Once in the open, the concentration of hydrogen cyanide gas is so diluted that it will never pose a threat

4. If required, the mine could be operating with zero discharge. There is also technology available to recycle cyanide. This strategy is in the interest of the mine operator as it would save cyanide consumption as the cyanide is recycled.

Several saleable metals (eg, arsenic, copper, lead, zinc) would be recovered as well instead of being discharged. These normally cause serious environmental pollution.

5. The concentration of cyanide solutions used in the mining operation must not exceed 150 ppm. At this concentration, an adult requires to drink 10 Coke cans of the cyanide solution to be affected. So the risk of accidental deaths is minimal.

Some miners use higher concentrations thinking it will speed up the gold dissolution process. Actually, it does not help and even at low concentrations it would soon reach a equilibrium and the kinetics of the chemistry will not improve.

6. Adequate monitoring must be installed to avoid any accidental spills into the environment.

The current concerns by the Bkt Koman villages are due to misinformation, fear-mongering and emotion. It is nonsense to claim someone can get sick from cyanide.

If you consume too much you just ‘suffocate' and die, you do not get sick. I had operated a small ‘Heap Leach' operation in Kelantan in the 1990s with no cyanide hazards. There are so many gold mines using cyanide being operated around the world with no danger or health hazard.

Bukit Koman is immediately downstream from the mining operations. But the mining operations can be designed to minimise any risk. In this case, the environment authorities should insist on a zero discharge of liquid waste and all solid waste must be stored in proper, waterproof, non- biodegradable storage areas that could be rehabilitated effectively at the end of mining operations.

I will be happy to supply any interested party detailed information on cyanide and gold mining operations and cyanide recycling and safety practices.

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