Not so fast, says Giant Mine Oversight Board of proposed process, which is untested in mine setting
The decision to freeze about 237,000 tonnes of toxic arsenic trioxide dust underground at the former Giant Mine in Yellowknife remains the chosen solution for now — and possibly for the next 100 years — but a researcher at Queen’s University says he and his team have a technology that could render all that toxic dust inert in five years.
“Freezing arsenic underground is a good solution, but in general it’s not a permanent solution,” says Dr. Ahmad Ghahreman, a Queen’s University assistant professor in the department of mining. “Imagine if for any reason you have a power loss … the water body around the arsenic is not frozen anymore and then your arsenic starts to release into the environment.”
Ghahreman says a new process to treat arsenic trioxide and render it into inert could work, and would be relatively affordable compared to another well-established — but prohibitively expensive — hydrogen peroxide treatment.
The new process, which costs about 40 per cent less than the hydrogen peroxide treatment, uses a column of activated charcoal and air to convert an arsenic trioxide solution into an arsenic five-oxide solution, leaving a deposit of “immobilized” arsenic that does not require further treatment.
He says it could work in Yellowknife, rendering the frozen block solution obsolete.
“You remove that arsenic [trioxide] from underground. You convert it to a more stable mineral, which is roughly 10,000 to 100,000-times less soluble, and then you even don’t have to worry about that compound anymore. It’s so stable, even in the rain, the arsenic will remain in the mineral and will not get into underground waters.”
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