Chemical Engineering May 2016 - 11

Extremophilic algae selectively recovers
precious metals from solution
T
he research group of Ayumi Minoda
at the University of Tsukuba
(Japan, plmet.biol.tsukuba.ac.jp)
has discovered that the cellular
surface layer of the sulfothermophilic
red algae, Galdieria sulphuraria, can efficiently
adsorb gold and palladium ions,
even in highly acidic conditions.
G. sulphuraria lives on the rock surRO-3066I
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faces of sulfate springs (such as those
found in Kusatsu and Noboribetsu,
Japan), under extreme conditions (low
pH and temperatures up to 56°C). The
researchers found that more than 90%
of gold and palladium ions can be adsorbed
by the algae from solutions with
concentrations in the range of 0.5 parts
per million (ppm) and strong acidic conditions
(0.4 M HCl, with pH of 0.5). This
low concentration is one order of magnitude
lower than the 5-30 ppm concentration
range that can be economically
recovered by existing adsorption
techniques, such as activated charcoal
and ion-exchange resins.
The researchers confirmed that G.
and Industrial Science and Technology
Organization (NEDO; Kawasaki, Japan;
www.nedo.go.jp), under the authority
of the Ministry of Economy, Trade and
Industry (METI), the researchers plan to
develop a low-cost algae system for industrial
use.
7.0 "
sulphuraria selectively recovers Au3+
and Pd2+ from 0.6 M nitrohydrochloric
acid (royal water) waste-metal solution,
which contains other metal
ions (68 ppm Fe2+/3+, 380 ppm Cu2+,
6 ppm Pt4+, 61 ppm Au3+, 59 ppm
Ni2+, 7 ppm Sn2+, 18 ppm Pd2+ and
12 ppm Zn2+). The recovery efficiency
is the same, even if dead algae cells
are used. After the absorption step,
the absorbed metals can be recovered
from the algae as chloride complexes,
by elution with NH4Cl and NH3. After
30 minutes, 48% of the gold and 77%
of the palladium is recovered from the
algae - a net recovery of 90% for both
metals. The entire process of absorption
and elution takes about 1 h.
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(Continues on p. 12)
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ChemiCal engineering www.Chemengonline.Com may 2016
11

http://plmet.biol.tsukuba.ac.jp http://www.nedo.go.jp http://www.StaticMixers.com/Learn http://www.mixers.com/web-app http://adlinks.chemengonline.com/61495-05 http://www.Chemengonline.Com

Chemical Engineering May 2016

Table of Contents for the Digital Edition of Chemical Engineering May 2016