How liquid salt could be the answer to oilsands tailings ponds

Wastewater from oilsands mining operations have long been a challenge for Canada's energy industry, much of it ending up inindustrialtailings ponds.

But scientists and engineers at theUniversity of Calgary aretakingaimateliminatingwatery tailings from the oilsands production process with the help of specialized liquid salt.

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Hot water is used in oilsands mining operations to extract the oily bitumen from the sand, with the resulting wastewater ending upintailings ponds to settle and later be reused. Alberta hasan estimated 1.3 trillion litres of fluid tailingssitting in tailings ponds.

Paula Berton and Steven Bryantbelieve ionicliquids, orliquid salt, offera possible solution.

By using ionicliquids instead of water in the extractionprocess, the researcherssay theycan eliminate the production of watery tailings, while the ionic liquids can be recycled. They anticipatetheleftover sand can be returned tothe ground.

The ionic liquids andthe resulting sand are not toxic, they say.

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"We have found a way, using advanced materials, to do the extraction of bitumen from oilsands efficiently, using much less energy and without using any water at all, and thereby eliminating the tailings issue," said Bryant, a part of the university's Schulich School of Engineering.

Taking it out of the lab

They believe the ionic liquid process couldbe used by in-situ projects as well. The team, whichreceivedfunding from the Canada Excellence Research Chairs Program, has obtained a patent and thework was recently published by the American Chemical Society.

The team's nextgoal is to test the work outside thelaboratory in a pilot project,and scale up their research.

"We're quite optimistic about the need for new approaches," Bryant said. "If we can eliminate tailings from future developments that would be a huge advantage over existing processes."

Scientists have been researching ionic liquids (salts with organic cationsthat melt at low temperatures) for decades, but theyhave become a major subject of study for modern chemistry.

Becausethey can dissolve many things andhave a low volatility, some of them have beenreferred to as "green"solvents and used in chemical processes including separation and purification.

"Another property of these materials in general, I would say, is that they are really stable," Berton said.

Recycled liquids

The researchers say theionic liquids will also work at ambient temperature, meaning less energy is needed in the process and, therefore, fewer carbon emissions.

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Because the ionic liquidsare recycled immediately, Bryant explained, the volumes required are much smaller than the volumes of water used in current processes.

"There are lots of reasons these are not your granddad's solvents," Bryant said.

Nina Lothian,director of the fossil fuel program of the Pembina Institute, a green energy think tank, said mining oilsands without tailings is a concept that industry has been exploring for a long time.

"I think there's a lot of potential in it," Lothiansaid.

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"I would applaud efforts to figure out technology that would mine oilsands without producing tailings, but that doesn't eliminate the [existing]tailings that we have on the landscape today."

Tailings are a priority

Alberta's oilsands tailings pondshave faced criticism fromenvironmentalists for years,gaininginternational attention in 2008 afterthe deaths of 1,600 ducks.

The water in tailings ponds contains contaminants ranging from salt and heavy metals to polycyclic aromatic hydrocarbons andnaphthenic acids.

Canada's Oil Sands Innovation Alliance (COSIA), which coordinates research for 13 oilsands companies, has identified tailings as one of its key environmental priority areas.

A COSIA spokesman said theyare aware of the U of C researchers' work.

"The use of ionic liquids... is one of the numerous treatment technologies that are being researched and developed to improve tailings management,"Rob Gray said in a statement.

"This work is in the early stages and is not currently a COSIA project, but ionic liquids may become a tailings treatment of interest for COSIA in the near future."