Reduction and adsorption of Pb2+ in aqueous solution by nano-zero-valent iron - A SEM, TEM and XPS study

Article abstract of DOI:10.1016/j.materresbull.2010.06.046

This study reports the synthesis, characterisation and application of nano-zero-valent iron (nZVI). The nZVI was produced by a reduction method and compared with commercial available ZVI powder for Pb²⁺ removal from aqueous phase. Comparing with commercial ZVI, the laboratory made nZVI powder has a much higher specific surface area. XRD patterns have revealed zero-valent iron phases in two ZVI materials. Different morphologies have been observed using SEM and TEM techniques. EDX spectrums revealed even distribution of Pb on surface after reaction. The XPS analysis has confirmed that immobilized lead was present in its zero-valent and bivalent forms. 'Core-shell' structure of prepared ZVI was revealed based on combination of XRD and XPS characterisations. In addition, comparing with Fluka ZVI, this lab made nZVI has much higher reactivity towards Pb²⁺ and within just 15 min 99.9% removal can be reached. This synthesized nano-ZVI material has shown great potential for heavy metal immobilization from wastewater.

Full text of DOI:10.1016/j.materresbull.2010.06.046

Materials Research Bulletin 45 (2010) 1361–1367
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Materials Research Bulletin
journal homepage: www.elsevier.com/locate/matresbu
Reduction and adsorption of Pb2+ in aqueous solution by nano-zero-valent iron—A
SEM, TEM and XPS study
Yunfei Xi a,b, , Megharaj Mallavarapu a,b, Ravendra Naidu a,b
*
a Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia, Mawson Lakes, SA 5095, Australia
b Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), University of South Australia, Mawson Lakes, SA 5095, Australia
A R T I C L E I N F O
A B S T R A C T
Article history:
This study reports the synthesis, characterisation and application of nano-zero-valent iron (nZVI). The
nZVI was produced by a reduction method and compared with commercial available ZVI powder for Pb2+
removal from aqueous phase. Comparing with commercial ZVI, the laboratory made nZVI powder has a
much higher specific surface area. XRD patterns have revealed zero-valent iron phases in two ZVI
materials. Different morphologies have been observed using SEM and TEM techniques. EDX spectrums
revealed even distribution of Pb on surface after reaction. The XPS analysis has confirmed that
immobilized lead was present in its zero-valent and bivalent forms. ‘Core–shell’ structure of prepared
ZVI was revealed based on combination of XRD and XPS characterisations. In addition, comparing with
Fluka ZVI, this lab made nZVI has much higher reactivity towards Pb2+ and within just 15 min 99.9%
removal can be reached. This synthesized nano-ZVI material has shown great potential for heavy metal
immobilization from wastewater.
Received 23 October 2009
Received in revised form 17 June 2010
Accepted 18 June 2010
Available online 25 June 2010
Keywords:
Metals
Chemical synthesis
Electron microscopy
Photoelectron spectroscopy
X-ray diffraction
Microstructure
ß 2010 Elsevier Ltd. All rights reserved.
Surface properties
1. Introduction
an issue. In the last decade, zero-valent iron (ZVI) has been
increasingly used in ground water remediation and hazardous
The presence of heavy metal ions, which are the most toxic
inorganic pollutants in the environment especially in water
system, is becoming a major concern due to their acute toxicity.
These ions are usually from natural weathering processes and
industries. Some of these ions can be very toxic even at very low
concentration and their toxicity may increase with their
accumulation in water and soil. Among these heavy metal ions,
Pb2+ is one of the major environmental pollutants. It can be
introduced to the water system through corrosion of household
plumbing, effluents from lead smelters, battery manufacturers,
mining and many other industries. The problems associated with
heavy metal pollution could be reduced or minimized by
precipitation, ultra-filtration, electrode-deposition, reverse os-
mosis, etc., but these processes have disadvantages such as high
cost, generation of secondary pollutants and poor removal
efficiency. Adsorption has been found to be an effective and
economic method with high potential for the removal, recovery
and recycle of metals from wastewater [1], although desorption is
waste treatment. Laboratory studies have demonstrated that ZVI
can effectively transform chlorinated solvents, organochlorine
pesticides, PCBs, organic dyes and heavy metals [2–9] into
nontoxic forms. These zero-valent iron (ZVI) materials were
proposed as a reactive material in permeable reactive barriers
(PRBs) due to its great ability in reducing and stabilizing different
types of pollutants [10–12]. It has many advantages, such as
nontoxic – as iron is abundant in nature, lower price and high
activity. And this material with particle size at nano-scale could
exhibit superior activity because of their larger surface area and
higher reactivity [2]. However, there is significant scope for
research on nano-ZVI particularly its ability to remove toxic heavy
metals from wastewater.
In this study, sodium borohydride reduction method was used
for nano-ZVI preparation with a view to testing the synthesized
material for the removal of Pb2+ from aqueous phase under
laboratory conditions. The material was also compared with a
commercially available ZVI powder. X-ray photoelectron spec-
troscopy (XPS) was used for surface element investigation to
determine the distribution and valence states of heavy metals and
iron on ZVI material surface.
A series of characterisation
* Corresponding author at: Centre for Environmental Risk Assessment and
Remediation (CERAR), University of South Australia, Mawson Lakes Boulevard,
Mawson Lakes, SA 5095, Australia. Tel.: +61 8 8302 6232; fax: +61 8 8302 3786.
E-mail address: yunfei.xi@unisa.edu.au (Y. Xi).
methods—XRD, surface analysing and SEM with EDX were carried
out to characterise the surface properties of the prepared
materials.
0025-5408/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2010.06.046

1362
Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
2. Experimental
2.1. Materials
‘Peakfit’ software package. This software enabled the type of fitting
function to be selected and allows specific parameters to be fixed
or varied accordingly. Band fitting was done using a Lorenz–Gauss
cross-product function with the minimum number of component
bands used for the fitting process.
In this study, iron (II) chloride tetrahydrate (FeCl2ꢀ4H2O) 99%,
sodium borohydride (NaBH4) 98.5%, absolute ethanol and hydro-
gen chloride were obtained from Sigma–Aldrich and used without
further purification. A reduced iron powder was obtained from
Fluka with a purity of 99%. Lead solutions of different concentra-
tions were made by dilution of 10 g Lꢁ1 stock solution prepared
from analytical grade Pb(NO3)2 with deionized water (MilliQ
system) and the initial pH was adjusted using nitric acid and
sodium hydroxide.
2.4. Pb2+ removal tests
Because of the reliability and simplicity of batch model,
adsorption measurements were carried out by a batch technique
at room temperature. ZVI was weighed into 50 mL centrifuge tube
containing 40 mL of metal ion solution of known concentration and
pH. The initial pH of all heavy metal solutions were adjusted to
about 4 by addition of dilute HNO3 solution, as there is no
precipitation of Pb2+ at this pH value. The solutions were
2.2. Preparation of nZVI
equilibrated on
adsorbent was separated using 0.45
a
rotary shaker at room temperature. The
m PTFE syringe filter. Pb2+
In a typical procedure of nZVI preparation, 21.36 g of FeCl2ꢀ4H2O
was dissolved in a mixture of absolute ethanol and deionized water
(96 mL ethanol + 24 mL H2O), this mixture was denoted as solution
A while 12.2 g of NaBH4 was dissolved in 400 mL of H2O to form 1 M
solution, denoted as solution B. Then solution B was added drop by
drop to solution A in a fume hood, the resulting reaction can be
expressed as Fe2+ + 2BH4ꢁ + 6H2O ! Fe0 + 2B(OH)3 + 7H2", black
particles of nZVI appeared and then the mixture was further stirred
for 2 h. Prepared iron powder was separated from the solution by
centrifugation at 3000 rpm and then the sediment was washed with
400 mL ethanol twice and dried in a 50 8C oven without air
evacuation overnight. The prepared sample was kept in vacuum
desiccator prior touse. Asreportedinsomeliteratures, using ethanol
to wash samples instead of using water is critical in stabilizing ZVI
against immediate oxidation [2,13], and drying in atmosphere oven
haspassivation effect forZVIapplication which mayotherwise catch
fire on exposure to atmospheric oxygen [13].
m
concentrations in the supernatant liquid were determined using an
ICP-OES. All assays were carried out in 2% nitric acid background.
The residual amount of metal ions was calculated by the difference
between the amount initially added and that of remaining
following equilibration. Solid-phase loading of metal, qe (mg/g)
was computed from the mass balance: qe = V(Ci ꢁ Ce)/M where Ci
and Ce are total dissolved and equilibrium liquid phase metal
concentration (mg/L), respectively, and M is the dose of adsorbent
(g/L), V is the volume of metal solution. All working solutions were
prepared from lead stock solution diluted with deionized water
and all experiments were carried out in duplicate.
3. Results and discussion
3.1. Characterisation of the synthesized material
The XRD patterns are shown in Fig. 1. Laboratory synthesized
nZVI and commercially available ZVI both show strong reflections
2.3. Characterisation methods
˚
at about 2.01 A and 2.03 A, respectively, which is a characteristic
[(Fig._1T)D$FI]G
˚
The samples were pressed in stainless steel sample holders. X-
ray diffraction (XRD) patterns were recorded using CuK
a
radiation
(n = 1.5418 A) on a Panalytical X’Pert diffractometer operating at
40 kV and 40 mA between 58 and 908 (2 ) at a step size of 0.01678.
˚
u
Adsorption and desorption experiments using N2 were carried out
at 77 K on a Gemini 2380 surface analyser. Prior to each
measurement the samples were degassed at 353 K for 24 h. The
specific surface area (SA) was determined using multipoint BET
method [14]. A Philips XL30 scanning electron microscope (SEM)
with integrated energy dispersive X-ray analyser (EDX) system
was used for morphological studies. Samples were dried at room
temperature and sprinkled onto adhesive carbon tapes supported
on metallic stub and then coated with carbon. A Philips CM 200
transmission electron microscope (TEM) at 200 KV was used to
investigate the microstructure of the lab made nZVI. This nZVI
material was dispersed in acetone and then dropped on carbon-
coated films and dried at room temperature for TEM study. A
PerkinElmer Optima 5300V optical emission spectrometer (ICP-
OES) was employed to measure the residual metal ion concentra-
tions. The pH of the solutions was measured with Thermo Orion pH
meter with a glass electrode. The X-ray photoelectron spectrosco-
py (XPS) analyses were performed on a Kratos AXIS Ultra DLD with
a monochromatic Al X-ray source at 130 W. Each analysis started
with a survey scan from 0 to 1320 eV with a dwell time of 55 ms,
pass energy of 160 eV at steps of 0.5 eV with three sweeps. For
the high-resolution analysis, the number of sweeps was increased,
the pass energy was lowered to 20 eV at steps of 100 meV, and the
dwell time was changed to 158 ms with 8 sweeps for Fe, 332 ms
with 8 sweeps for O and 397 ms with 5 sweeps for Pb respectively.
Band component analyses were undertaken using the Jandel
Fig. 1. XRD patterns of laboratory made nZVI and ZVI from Fluka.

Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
1363
reflection for ZVI [13] and is from the diffraction of 110 plane of Fe.
This also indicates that for both ZVIs, Fe is mainly in its Fe0 state
(only characterised by the basic reflection appearing at a 2-theta
value of 44.8–44.78) [15]. Some researchers have suggested a core–
shell structure [7,15–18] where the Fe nanoparticles may form a
core of main zero-valent iron with a shell made of iron oxides. Due
to surface hydroxylation, FeOOH was also observed in some study
[15], however, they were not detected in this study using XRD,
which may due to the low crystallinity of iron oxides phases. Small
specific surface area (0.11 m2/g) obtained from BET surface area
analysis. The laboratory made iron particles as shown in Fig. 2c,
however, demonstrates very different morphology where chain-
like structure with floc aggregates can be observed similar to that
reported by others [2,20]. The morphology and size difference of
the two types of ZVIs also illustrate the large difference in surface
areas obtained as discussed above.
3.2. Effect of Pb on the surface properties of the synthesized material
˚
˚
reflections at about 1.43 A (2 0 0 plane) and 1.17 A (2 1 1 plane)
were also observed on both samples from iron which was in
accordance with the literature [19].
Fig. 2d shows the synthesized nZVI after reaction with Pb2+ and
in this case, chain-like morphology is replaced with flakes/
aggregates. This may be attributed to the formation of elemental
lead and lead oxides via redox reaction, which changes the
morphology of nZVI surface. Fig. 2e and f shows energy dispersive
X-ray (EDX) spectrum of nZVI and nZVI reacted with Pb2+. It was
observed that peak from Pb was present after ZVI treatment with
Pb from aqueous phase (in Fig. 2f, 2–3 KeV). Imaging of EDX (as
shown in Fig. 3) further shows a series of elements distributions on
the surface of material, where Fig. 3a shows a SEM image of the
studied area, Fig. 3b shows the distribution of C element (shown by
the bright points) which is mainly from the coating and adhesive
carbon tape, as most of this element is observed not on the surface
of nZVI. Fig. 3c and d shows the Fe K and Fe L signals, respectively,
Adsorption and desorption experiments using N2 were carried
out at 77 K. The N2 isotherms were used to calculate the specific
surface area (SA) using multipoint BET [14] method. ZVI purchased
from Fluka has a specific surface area only at 0.11 m2/g, however,
laboratory prepared nZVI showed a much higher specific surface
area at 80.4 m2/g.
The SEM images of Fluka ZVI and laboratory prepared nZVI are
shown in Fig. 2a–c. The ZVI obtained from Fluka shows large
particles with sizes at around several tens of microns with irregular
shapes (Fig. 2a). Fig. 2b shows details of a Fluka ZVI particle at
10,000ꢂ magnifications which demonstrates solid and relatively
smooth surface; this observation is also consistent with the small
[(Fig._2)TD$FIG]
Fig. 2. (a) SEM image of Fluka ZVI; (b) Fluka ZVI–10,000ꢂ magnifications; (c) laboratory made nZVI; (d) laboratory made nZVI reacted with Pb2+; (e) EDX element analysis of
laboratory made nZVI; (f) EDX element analysis of laboratory made nZVI reacted with Pb2+
.

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Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
Fig. 3. (a) SEM image of a selected area of laboratory made nZVI reacted with Pb2+; (b) EDX mapping of C (K) on this area; (c) EDX mapping of Fe (K) on this area; (d) EDX
mapping of Fe (L) on this are; (e) EDX mapping of O (K) on this area; (f) EDX mapping of Pb (M) on this area.
Fig. 3e shows the signal of O K, and it also confirmed the existence
of oxides. The oxides may come from iron oxides on nZVI surface
and lead oxides after redox reaction. Even distribution of element
Pb was observed on the surface of nZVI material as shown in Fig. 3f
from Pb M signal. For comparison reason, Fig. 4a shows SEM image
of a studied area of nZVI and its elements distributions (from
Fig. 4b–f), respectively, where it can be observed that comparing
with that of nZVI reacted with Pb2+, distributions of elements of C,
Fe, O are quite similar, except no Pb element distribution was
observed on pure nZVI sample.
Fig. 5 shows the TEM image of the synthesized nZVI which
permits the direct observation of microstructural features of this
material confirming SEM observation of the presence of chain-like
morphology from iron aggregations. It is likely that this type of
chain is connected with pieces of iron and/or iron oxides particles,
and the chain can be as long as several tens of microns (figure not
shown).
take place to a certain extent, as the standard reduction potential of
Pb2+ (ꢁ0.13 V) is greater than that of Fe2+ (ꢁ0.44 V), insoluble
Pb(0) may be observed on the surface of nZVI. XPS technique was
applied to study the binding energy of element, which may be used
as a ‘fingerprint’ for discrimination of different chemical environ-
ments of certain element. The XPS analysis in this study has firstly
confirmed that lead on the surface of ZVI was present in both its
zero-valent and bivalent forms. As shown in Fig. 6, the observed Pb
4f peaks are located at 136.2 and 137.2 eV, respectively, where the
former value corresponds to the zero-valent Pb and the latter is
from PbO, and these values are little lower than those obtained in a
study [22], where 136.7, 138.1 eV were reported, respectively.
While in Fig. 7, for nZVI reacted with Pb2+, the photoelectron peak
of O 1s can be decomposed into three peaks at 527.5, 528.7 and
530.3 eV, respectively which is in accordance with that in a
literature, where these peaks represented binding energies of O2ꢁ
,
OHꢁ and chemically or physically adsorbed water, respectively
[23]. While for nZVI only, as shown in Fig. 8 the decomposed peaks
from O 1s are located at 527.2, 528.6 and 530.0 eV, respectively. It
can be observed that there was no significant shift of peak
positions before and after ZVI reacted with Pb2+. However, further
examination of the peak area % using Peakfit software in this region
suggested that there was noticeable change on area % of each
decomposed peak. Area % can be used as a guide to calculate
3.3. Lead adsorption mechanism
It was reported in some literatures that nZVI can remove metal
ions from aqueous solutions by various mechanisms including
electrostatic adsorption, complex formation, reduction and pre-
cipitation [18,21]. In this study, redox reaction was expected to

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Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
1365
Fig. 4. (a) SEM image of a selected area of laboratory made nZVI; (b) EDX mapping of C (K) on this area; (c) EDX mapping of Fe (K) on this area; (d) EDX mapping of Fe (L) on this
area; (e) EDX mapping of O (K) on this area; (f) EDX mapping of Na (K) on this area.
composition % change, because the number of photoelectron of a
certain element is dependent on the atomic concentration of that
element in the sample, so XPS can be used to quantify the relative
chemical composition using the peak area. In this study, area % of
O2ꢁ, OHꢁ and H2O of nZVI changed from 5.9%, 58.5% and 35.6%,
respectively to 21.1%, 45.9% and 33%, respectively after its reaction
with Pb2+. It can be noticed that there was no significant change of
area % on O 1s peak of water which only changed from 35.6% to 33%
after reaction with Pb2+. But area % of O 1s peak from O2ꢁ increased
from only 5.9% to 21.1%, which may be ascribed to the increased
oxides percentage after nZVI reacted with Pb2+, as lead oxide
formed after reaction, so the percentage of this part increased
[(Fig._5)TD$FIG]
[F(ig._6)TD$FIG]
Fig. 6. XPS spectroscopy of Pb 4f in lab made nZVI reacted with Pb2+
.
Fig. 5. TEM image of laboratory made nZVI.

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Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
9
Fig. 7. XPS spectroscopy of O 1s in lab made nZVI reacted with Pb2+
.
Fig. 9. XPS spectroscopy of Fe 2p in lab made nZVI.
significantly. Area % of peak at around 528 eV did not change a lot
before and after reaction, which meant the FeOOH content % was
relative stable. FeOOH was a result of surface hydroxylation and
subsequent dehydration of the exposed shell when iron nano-
particles were in contact with aqueous solution [2]. Based on the
discussion above, it could be suggested that Pb2+ undergo partial
reduction following its immobilization on nZVI surface resulting in
precipitation on the surface as PbO. The Fe 2p spectra consists of
both 2p3/2 peaks at about 708 eV in binding energy (BE) and 2p1/2
at about 720 eV in BE, but both energies are lower than those
reported in literature [18], where 711 and 725 eV were observed,
respectively. In this study, it was noticed that the BE of Fe 2p3/2
peaks increased with Pb2+ immobilized on Fe surface, from 708.3
and 710.1 eV on ZVI as shown in Fig. 9 to 708.5 and 710.4 eV (see
Fig. 10), respectively (towards higher BE). Where peak at 708.3 eV
is ascribed to Fe2O3 + FeO, and after reaction with Pb, the peak at
708.5 is ascribed to Fe2O3. The peak at 710 eV is from Fe2+ and
changed to Fe3+ at 710.4 eV after Pb immobilization.
individually proved the existence of Fe(0) and iron oxides,
respectively. The reason for why iron oxide phase was not
observed using XRD was because of its low crystallinity, at the
same time, the reason why Fe(0) was not detected using XPS was
because of the limitation of XPS technique – only a surface
technique, so iron as ‘core’ was not detected in XPS. However, the
combination of these two techniques together has strongly
supported the ‘core–shell’ theory.
3.4. Pb removal tests results
For optimising adsorption time, at around pH 4 (no precipita-
tion for Pb2+ at this value), a set of experiments were conducted by
equilibrating 40 mL of 200 mg/L Pb2+ solution with 0.1 g of ZVI
materials at 25 8C. Following equilibration for periods ranging from
15 min to 360 min, solution concentration of Pb2+ was determined
to calculate immobilized Pb2+ on ZVIs. The effect of mixing time on
removal density shows that only very small amount of Pb2+
(usually less than 2 mg/g) can be immobilized onto the commercial
ZVI powder with increase in contact time (figure not shown). This
demonstrated that commercial ZVI with large particles at micron
level and very small surface area (only at 0.11 m2/g) had very
limited reactivity/adsorption capacity for Pb2+ at this pH value.
However, the laboratory synthesized nZVI powder showed large
capacity for Pb2+ immobilization with the amount of Pb removed
being 99.9% within 15 min (figure not shown).
A similar tendency is reported on Fe 2P1/2, where peaks at
721.9 and 723.8 eV (see Fig. 9) shifted to 722 and 723.9 eV (as
shown in Fig. 10), respectively. It was reported that the binding
energy of Fe will shift to higher BE with the decease of Fe content
[24]. In this study, the Pb was immobilized on Fe surface and at the
same time some iron ions were released to the solution (though
only very small amount of Fe released, see details below), so the
percentage of Fe content was decreased. Zero-valent iron peak at
about 706.4–707 eV was not distinguished in the XPS spectrum,
which may because XPS is a truly surface analysis technique with
only 2–5 nm probing depth, however, this observation when
combined with XRD results has strongly supported our speculation
on ‘core–shell’ structure: because XRD and XPS techniques have
In order to optimise the amount of adsorbent/catalyst material
required for most efficient removal of Pb2+ from aqueous solution,
a series of experiments were undertaken with varying solid
concentrations in the reaction mixtures containing 40 mL of
2+
solution at pH 4. The Pb2+ concentrations were
5[(Fgi_.1DT)0IF$]G 00 mg/L Pb
[(Fig._8)TD$FIG]
Fig. 10. XPS spectroscopy of Fe 2p in lab made nZVI reacted with Pb2+
.
Fig. 8. XPS spectroscopy of O 1s in lab made nZVI.

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Y. Xi et al. / Materials Research Bulletin 45 (2010) 1361–1367
1367
ꢃ
ꢃ
TEM image has confirmed the observation in SEM study.
The XPS analysis confirmed that immobilized lead was present in
its zero-valent and bivalent forms, and iron oxides were also
detected. Based on both XRD and XPS results, ‘core–shell’
structure of ZVI was supported.
ꢃ
Comparing with Fluka ZVI, this lab made nZVI had much higher
reactivity towards Pb2+ at studied pH value and within just
15 min the removal rate at 99.9% can be reached. And material
amount effect showed only 0.05 g of ZVI can remove Pb2+ at up to
>99% (401.8 mg/g).
In summary, this study demonstrates a great potential for heavy
metal immobilization using nano-zero-valent iron.
Acknowledgements
Fig. 11. Influence of added amount of nZVI on Pb2+ removal amount and % rate.
The authors would like to acknowledge the financial and
infrastructural support of the Centre for Environmental Risk
Assessment and Remediation (CERAR, University of South
Australia) and the Cooperative Research Centre for Contamina-
tion Assessment and Remediation of the Environment (CRC
CARE).
tested after 24 h of equilibration at 25 8C. The amount of Pb2+
adsorbed on the centrifuge tubes was found to be negligible.
Relationship between the added laboratory made nZVI and the
amounts of Pb2+ immobilized rates (%) are shown in Fig. 11. It was
demonstrated that Pb2+ immobilized amount (mg/g) decreased
with increasing adsorbent concentration (g). The rate of Pb
immobilized (%) increased with an increase in the amount of
adsorbent (g). As shown in Fig. 11, removal rate of Pb2+ on only
0.05 g of nZVI can reach up to >99%, which corresponds to
401.8 mg/g. And at the same time, though at acidic condition, the
released iron concentration in solution after reaction is only from
0.27 mg/L (when 0.05 g of nZVI was added) to 0.75 mg/L (when
0.35 g of nZVI was added), which should not have any negative
effects considering Fe is an abundant element in natural
environment.
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4. Conclusions
In this study, nano-zero-valent iron (nZVI) prepared using
reduction method together with a commercially available ZVI
(Fluka) was used for Pb2+ removal from aqueous phase.
ꢃ
Compared to commercial ZVI (0.11 m2/g), the laboratory made
nZVI powder has much higher specific surface area, which is at
80.4 m2/g as determined by BET method.
ꢃ
ꢃ
XRD patterns have revealed iron phases in these two ZVI
materials.
SEM images have shown different morphologies between two
ZVIs, where Fluka ZVI shows big particles with sizes at around
several tens of microns with irregular shapes, the laboratory
made iron particles, however, demonstrate chain-like structure
with floc aggregates. And morphology of flakes/aggregates was
[21] C. Uzum, T. Shahwan, A.E. Eroglu, K.R. Hallam, T.B. Scott, I. Lieberwirth, Appl. Clay
Sci. 43 (2009) 172–181.
[22] H. Abdel-Samad, P.R. Watson, Appl. Surf. Sci. 136 (1998) 46–54.
[23] X.-Q. Li, D.W. Elliott, W.-X. Zhang, Crit. Rev. Solid State Mater. Sci. 31 (2006) 111–
122.
observed after treated with Pb2+
.
ꢃ
Energy dispersive X-ray (EDX) spectrum study shows even
distribution of Pb on the surface.
[24] A.N. Hattori, K. Hattori, H. Daimon, Surf. Interface Anal. 40 (2008) 988–992.