Because of the mercury vapor in all fluorescent lights, most
municipalities have designated such bulbs and tubes as hazardous wastes that
should be kept out of the trash. Yet these lights can be good for the
environment in more ways than one (as I noted yesterday) — even as they
threaten to pollute our homes if they break (see my last blog). For those who
want greener lighting — and to keep mercury out of the environment — here’s
some reassuring news.
Free recycling of compact fluorescent bulbs — the palm-size
curly lights that fit into conventional lamps and fixtures — just became widely
available. And should one of these CFLs break, there may soon be a way to render
its mercury harmless.
This chain announced in late June that it was launching a
CFL take-back program in all its
Home Depot is not restricting its take-backs to the CFLs it
sold. I’m guessing the company views this as one way to invite customers in for
impulse buys — perhaps a new house plant or set of replacement drill bits. Then
again, when it comes to light bulbs, Home Depot is the biggest kid on the
block. Last year it sold 75 million CFLs.
Jean Niemi, a spokesperson for the chain, explains that when
someone enters a Home Depot, they’ll find a designated area where they can drop
off batteries, cell phones, or CFLs for recycling. For the fluorescents, “you
just put them in a plastic bag that’s provided for them, and throw them in a
I’m hoping she didn’t mean that literally, because these
bulbs aren’t robust enough to take much physical abuse. Moreover, as chemical
engineer Robert Hurt and his students at
But the Brown engineers might just have a solution for preventing
any leakage of mercury into Home Depot’s air from carelessly tossed CFLs. It’s a
novel recipe for nanomaterials that sop up gaseous mercury and convert it into
an inert compound. Hurt’s team reported its finding in the Aug. 1 Environmental Science & Technology.
Of the commercial materials created to collect spilled
mercury, none had been designed to cope with CFL breaks. So the Brown engineers
tested 28 different chemicals, some of them totally novel. The best performer:
amorphous nanoselenium particles no more than 60 billionths of a meter in
In lab tests, these orange nanoparticles trapped and neutralized
99.9 percent of the mercury vapor they encountered. Indeed, they proved so
potent that just a few milligrams rendered inert a milligram of mercury — an
amount comparable to what a broken CFL would release. Hurt’s team found that for
some other contenders, such as powdered sulfur or zinc, quantities in excess of
10 kilograms (clearly not a commercial option) would be needed to neutralize a
milligram of mercury.
In the nine months since the Brown researchers submitted
their paper to ES&T, they’ve been
breaking bulbs and testing how well prototype treatment strategies perform —
such as covering broken bulbs or spills of CFL debris with fabrics impregnated
with their novel nanoparticles.
And the results? Laying one such fabric atop contaminated carpeting
trapped the mercury it had been emitting. Leaving it on the spill site for a
week, Hurt says, should neutralize virtually all of the mercury while keeping the
toxic vapors from entering the air and moving to other sites.
Once the reactive end product develops, this mercury
selenide “remains stable, under normal conditions. For instance, it should be
stable in landfills,” Hurt says.
But CFLs aren’t the sole raison d’être for Brown’s novel nanoselenium. These particles could be plated onto the inside of boxes that carry fluorescent tubes to stores or recycling centers. Heavily treated cloths might even be used in the final stages of wiping up mercury spills from old thermometers or other equipment, Hurt notes.
Several companies have expressed keen interest in the
technology, Hurt says. So he anticipates nanoselenium treatment kits might find
their way onto store shelves within a year or two.
Johnson, N.C. 2008. Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents. Environmental Science & Technology 42(Aug. 1):5772.
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