All that glitters: University of Victoria's Kevin Telmer is helping artisanal gold miners in Nigeria improve extraction of gold from lead-laced ores following an epidemic of lead poisoning that reportedly killed hundreds of children.
The Hausa subsistence farmers and herders of Zamfara had, before children began dying in early 2010, initiated small-scale, artisanal gold mining in response to soaring prices and high demand. They dug shallow mines to bring up ore veined with gold. The men carried chunks of rock back to the villages in sacks. Women and children pounded the ore into fragments for grinding in eight-horsepower flourmills to separate the gold from the ore. Instead of flour dust, the villages were now covered in red rock dust that, unbeknownst to the inhabitants, contained high amounts of lead. This form of lead isn't excreted by the body and quickly builds up to toxic levels. Children, most of them aged five and younger, took sick in the hundreds, convulsing, falling into a coma and, finally, dying. When MSF workers first went to the region, says Mike Fark, operations manager with MSF Canada, one of their first grim tasks was to count the fresh graves. Survivors, Fark says, suffered "significant brain damage and reduced functioning in general, resulting in severe permanent neurological damage similar to cerebral palsy, as well as blindness and deafness."
MSF treated the poisoned children--2,000 by recent counts, making the Zamfara epidemic one of the worst cases of acute heavy metal poisoning in history--with chelation therapy. Chelating drugs such as ethylene diamine tetraacetic acid (EDTA) grab onto heavy metal molecules, which are then expelled in urine.
Clean up was also started. TerraGraphics Environmental Engineering, an Idaho-based consulting firm that cleans heavily polluted sites around the globe, began remediating the soil by scraping off the top level. The group was assisted by a host of international agencies, university students, Nigerian government staff and hundreds of Hausa labourers. By March 2011, 430 residential compounds and 30 ponds had been decontaminated, according to the University of Idaho publication Here We Have Idaho. Still, says Fark, at least 163 Hausa, most of them children, have been confirmed dead from lead poisoning, although some reports put the death toll at 500. Another 1,600 to 1,800 youngsters are in need of medical care but aren't receiving it, Fark says, because they are still living on lead-laced ground. "You cannot treat children that are in a contaminated environment because they just become re-exposed."
An effective health strategy, MSF realized, would have to incorporate not only treatment for poisoning and soil remediation but contamination prevention. So it contacted University of Victoria geochemist Kevin Telmer, co-founder and executive director of the not-for-profit Artisanal Gold Council (AGC), which is dedicated to creating sustainable development and improving the health of artisanal and small-scale gold mining communities worldwide. Small-scale gold mining, practiced by 10 million people in 70 countries, represents a critical global development issue due to pollution and health problems. Telmer has been studying small-scale mining and its effect on the environment since 1995, when he worked as a geologist for the Canadian government surveying Brazilian mining communities. Last July, he travelled at MSF's request to Zamfara to assess the situation. The ores of Zamfara are rich in galena (lead sulfide), lead oxide and lead carbonates. When small chunks of ore are ground up in the flourmills, these minerals settle into the soil around the mud brick homes where the children play. Soil testing showed lead levels of 10 to 20 per cent, Telmer says. Since all small children ingest on average a gram a day of soil from playing outside, "20 per cent of one gram in your mouth--you have lead poisoning," says Telmer, who saw first-hand the injurious effects. "The children are thin and pallid with unhappy, glazed eyes and, like any sick child, not very responsive." But he also saw solutions.
The first, most obvious problem was the dry milling, Telmer says by telephone from AGC's Victoria headquarters. To liberate the gold, villagers would put the dry rock through the grinding plates of the flourmills three times, which created huge amounts of dust. Local Islamic leaders, called emirs, had ordered the flourmills to be moved outside of the residential compounds but lead-heavy dust still drifted into compounds. The miners also re-contaminated the compounds when they returned home in their dusty clothes.
Impoverished Zamfara miners couldn't, economically, simply stop mining. Soaring world gold prices--more than $900 an ounce by 2008, according to Gold News--had pushed the small-scale miners' daily income to $5 from $1. By 2011, 100,000 Zamfara miners had extracted 10 tonnes of gold with a realized profit of about 80 per cent, Telmer says. "The magic of gold is that it transfers wealth almost directly; it's a great mechanism for transferring wealth from rich to poor." Telmer could advise not only on improved gold-recovery techniques and thus potentially greater profits but cleaner, more sustainable mining methods. "The miners were very eager and very happy to meet someone like me," Telmer says, who is a technical advisor to the United Nations on artisanal gold mining.
Nigeria is an oil-rich nation; mining has played little part in its economic history and there are no technical mining schools. Nonetheless, traditional methods of extracting gold had been adopted that are moderately efficacious. After milling the ore and grinding it until it is almost powder, it is mixed with water and washed down a carpeted incline in a classic method called sluicing. Because the gold is heavy, it sticks to the fibers of the carpeting, forming a gravity concentrate.
Several tonnes of rock are reduced to about 20 kilograms at this stage. Mercury, bought in 200-gram glass bottles for $50 each, is now added to the concentrate to create an amalgam. This is heated over small fires to evaporate the mercury, creating "sponge gold," so named because the vaporizing chemical leaves sponge-like holes in the hard, glittering material. This stage of extraction raises more health concerns, says Telmer, as workers inhale toxic mercury vapours that, through prolonged exposure, can cause brain, kidney and lung damage as well as tremors and impaired vision. This is a problem that extends far beyond Zamfara, adds Telmer. Due to the increase globally in small-scale mining, it is now one of the top emitters of mercury in the world, releasing about 1,400 tonnes annually into the environment.
The 20 kilograms of concentrate might yield from 10 to 20 grams of gold, which is taken to a local gold dealer who refines it further for export. But the process is inefficient, says Telmer, and only captures from 20 to 50 per cent of the gold present in the ore. "The flourmills are terrible at liberating the gold effectively and don't produce a consistently fine grind," he says. The miners of Zamfara had just begun to collect the tailings, which Telmer believes could yield more gold by leaching with chemicals such as cyanide, which is often used for gold recovery at large mining operations. Cyanide, although deadly if ingested, oxidizes and transforms via natural processes into less toxic chemicals when exposed to the air. Nonetheless, it must be carefully managed when used in mining operations to mitigate risk, adds Telmer.
Although Telmer's trip to Zamfara was mainly to assess the extent of the problem to determine long-term, inexpensive solutions, he did make suggestions to the miners as "a quick fix measure." Rather than adding water following milling, Telmer recommended adding it at the start. By milling wet rocks and discharging directly onto sluices, workers can dramatically cut down on lead-laden dust. This not only saves time but liberates more gold, he says. In order to lessen exposure to mercury, Telmer suggested using recycling technology such as a closed-retort distilling system to avoid releasing vapours into the atmosphere and allow for mercury recovery. The closed, or non-vented, system is relatively inexpensive and simple and involves using a boiling vessel with cooling tube that catches the mercury and directs it into a catch container. Even simple retorts boast 95 per cent recovery. Although retorts are not currently being used in Zamfara, Telmer believes that, because they are cheap, easy to use and save the miners money, they can easily be adapted into the gold recovery process.
Telmer wrote a report following his Nigeria trip for the World Bank and MSF that provided solutions to assist the villagers modernize their gold extraction techniques to maximize potential profits and reduce contamination. He is also seeking funding so that an organization like AGC can set up pilot processing plants to teach miners how to wet mill and use retorts. This training system, says Telmer, should not only provide instruction to miners but train people how to teach these mining techniques. In the long-term, Telmer says, Zamfara's small-scale mining sector should move to a zero mercury processing system that effectively liberates the gold and provides good concentration. Telmer would also like to see the adoption of high quality sluices or centrifuges or shaker tables to concentrate the gold, possibly by the creation of community processing plants. Such methods, used in other artisanal small-scale mining sites throughout the world, allow for up to 70 per cent gold recovery--all without using mercury, Telmer adds. He estimates that such a processing plant would cost about $200,000 to set up and could be run by local miners.
Thanks to a long history of mining and gold extraction, Canadian mining companies have a deep repository of knowledge to offer the world and could easily assist small-scale miners like those in Zamfara improve their economic lot while ensuring their children grow up healthy. "They just need enhanced training, skills and access to a little bit of capital to move forward," says Telmer.
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|Title Annotation:||BUSINESS: ARTISANAL GOLD MINING|
|Publication:||Canadian Chemical News|
|Date:||Jan 1, 2012|
|Next Article:||Engineering solutions to globe's biggest challenges.|