JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

The Recovery of Precious Metals Using Biomass
Adsorbents
D. Parajuli, N. Seko and K. Hirota
Environmental and Industrial Materials Research Division, QuBS, JAEA
1. Introduction
The recovery of precious metals from electric and
electronic wastes, urban mine, is very important for the
elemental strategy of Japan because we don’t have few
mineral resources. Conventional methods for recovery of
precious metals from urban mine are solvent extraction and
use of ion exchange resins. However, these methods have
disadvantages of huge chemical and energy requirement,
1)
lack of required selectivity, and costly . Biomass
adsorbents is expected to be superior materials for
recovering precious metals with lower capital cost and
2)
higher efficiency . In the present work, lignophenol
modified with ethylenediamine by electron-beam irradiation
was uses as biomass adsorbents. Their performance for the
recovery of precious metals has been studied and the results
are compared with that of chemically modified derivative.
2. Experimental
2-1 Synthesis of Biomass Adsorbents
3)
Lignophenol was extracted from cedar wood powder
and treated with paraformaldehyde to obtain crosslinked
lignophenol gel (CLP). In order to obtain ethylenediamine
modified crosslinked lignophenol, the CLP matrix was
irradiated by electron beam at a dose of 20 kGy and then
directly treated with ethylenediamine in dimethylsolfoxide
(DMSO) as shown in Scheme 1. It is named as
EN-CLP(EB). Chemically modified CLP with
ethylenediamine group (EN-CLP(Chem)) was also prepared
by following the same scheme without pre-irradiation for
comparison of adsorption performance with EN-CLP(EB).
HO
2-06
CH 2
C
H 2
CH CH
LIGNIN
O
CLP
CH 2OH
OCH 3
20 kGy EB
EN, DMSO, 348 K
EN =
H2N OCH 3
2-2 Adsorption Test
The adsorption performence of the EN-CLP(EB),
EN-CLP(Chem) was tested batchwise by mixing 5 mL of
0.5 mM different metal chloride solutions at various
hydrochloric acid concentrations with 10 mg sorbents.
The sorbents at 10 mg in the sample solution was
continuously shaked for 24 h at 303 K in a thermostatic
shaking incubator. After filtration, the amount adsorbed
was evaluated by measuring the residual metal
HO
CH 2
C
H 2
H
N
H2C CH CH
LIGNI
O
EN-CLP
Scheme 1 Preparation of EN-CLP using electron beam.
NH 2
JAEA-Review 2010-065
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concentration in the filtrate solution. Similarly, the
adsorption isotherm was examined to evaluate the maximum
loading capacities of the sorbents for Au(III), Pt(IV), and
Pd(II).
3. Results and Discussion
The adsorption behavior of various metals on
EN-CLP(EB) modified by electron-beam irradiation at
varying hydrochloric acid concentration in Fig. 1. The
adsorption of Au(III) and Pt(IV) was more than 80 % even
at 5 M hydrochloric acid medium. However, Pd(II)
adsorption was decreased with an increase in acid
concentration. Interestingly, the adsorption of other metal
ions is near around zero. It was found that the sorbent of
EN-CLP(EB) can be used for adsorption of gold and
platinum even in highly acidic condition.
Adsorption %
100
80
60
40
20
0
Au(III)
Pt(IV)
Pd(II)
Fe(III)
Ni(II)
Zn(II)
Cu(II)
Co(II)
0 1 2 3 4 5 6 7 8
[HCl] (M)
Fig. 1 Adsorption behavior of EN-CLP(EB) for
various metals in hydrochloric acid. Sorbent:
10 mg, solution: 5 mL of 0.5 mM each metal.
The maximum loading capacity for Au(III), Pt(IV), and
Pd(II) were found to be 3.1, 2.3, and 0.85 mol/kg for
EN-CLP(EB). These capacity was higher than those of 2.4,
1.9, and 0.42 mol/kg for EN-CLP(Chem). These
differences suggest that the degree of modification can be
enhanced by the application of electron beam.
References
1) Y. Goksungur et al., Bioresource Technol. 96 (2005)
103.
2) C. Mack et al., Biotechnol. Adv. 25 (2007) 264.
3) M. Funaoka, Polymer International, 47 (1998) 277.