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A D V A N C E D
M A T E R I A L S
&
P R O C E S S E S |
S E P T E M B E R
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titanium. For biomedical implants, for
example, two key measures are bio-
compatibility and wear resistance.
Because titanium and gold by them-
selves are among the most biocom-
patible metals and are often used in
medical implants, the team believed
titanium-3-gold would be comparable.
In fact, tests determined that the new
alloy was even more biocompatible
than pure titanium. The story proved
much the same for wear resistance:
Titanium-3-gold also outperformed
pure titanium. rice.edu.
NONTOXIC METHOD
EXTRACTS RARE EARTHS
Researchers from the Harvard
John A. Paulson School of Engineer-
ing and Applied Sciences (SEAS), Cam-
bridge, Mass., may have found a clean
alternative to extracting rare earth met-
als. David Clarke, the materials profes-
sor at SEAS, and his graduate student
William Bonificio, developed a method
to separate rare earths using bacteria
filters and solutions with pH no lower
than hydrochloric acid. They immo-
bilized a bacteria from marine algae
on an assay filter and passed a solu-
tion of mixed rare earths (lanthanides)
through it. The bacteria bioabsorbed all
of the elements as they passed—pluck-
ing them out of the solution and fixing
them to their surface.
Next, researchers pumped solu-
tions of various pH balances through
the filter. With each successive pH
wash, different rare earths detached.
Researchers found that lighter lan-
thanides, such as europium and pra-
seodymium, desorbed with higher-pH
washes while heavier lanthanides, such
as thulium, lutetium, and ytterbium,
desorbed with lower pH. For more
information: David Clarke, clarke@seas.
harvard.edu, .
Rare earth metals are used in everything fromwind turbines and cell phones to electric cars
and precision weapons. Courtesy of Wikicommons.