Synergistic construction of green tea biochar supported nZVI for
immobilization of lead in soil: a mechanistic investigation
Sandip Mandal1, Shengyan Pu1,2[footnoteRef:1], Lixiang Shangguan
1, Shibin Liu1, Hui Ma 1, 3, Sangeeta Adhikari4, Deyi Hou5 [1:
Corresponding author at: Prof. Pu Shengyan, State Key Laboratory of
Geohazard Prevention and Geoenvironment Protection (Chengdu
University of Technology), Chengdu 610059, PR China. Tel. /fax: +86
(0) 28 8407 3253; E-mail: [email protected];
[email protected]]
1State Key Laboratory of Geohazard Prevention and Geoenvironment
Protection (Chengdu University of Technology), Dongsanlu,
Erxianqiao, Chengdu 610059, Sichuan, P.R.China;
2State Key Laboratory of Environmental Criteria and Risk
Assessment, Chinese Research Academy of Environmental Sciences,
Beijing 100012, China;
3Department of Plant and Environmental Sciences, University of
Copenhagen, Thorvaldsensvej 401871 Frederiksberg, Denmark
4 School of Chemical Engineering, Chonnam National University,
Gwangju 61186, South Korea
5School of Environment, Tsinghua University, Beijing 100084,
China
Supplementary materials
1. Characterizations techniques
All the material characterization and analysis were carried out
by using sophisticated instruments. The Zeta Potential (ZP) of the
biochar’s, soil and nZVI was determined by Malvern ZETA SIZER Nano
series 3600 (Malvern Instruments, UK). The pH measurement at
different intervals of experiments was monitored by Sartorius PB10,
Goettingen, Germany. The total iron concentration is measured by
using TU-1901 UV-vis spectrophotometer (Beijing Purkinje General
Instrument Co., Ltd, China). The crystallography of nZVI, GTBC and
nZVI@GTBC was characterized by XRD (Ultima IV, Japan) employing Cu
Kα radiation (λ = 0.154 nm, 40 KV) in the range of 10° to 65°. The
morphology and micrographs of nZVI and nZVI@GTBC were studied by
using FE-SEM & TEM, which was performed on SIGMA 300 (Germany)
instrument equipped at an accelerating voltage of 20 kV and TEM
(JEM2100, Japan) operated at 200 kV respectively. XPS measurements
were performed by a K-alpha Probe (Thermo Scientific, USA) with
monochromatic Al-K radiation (300W). The BET surface area was
measured at 77 K using F-Sorb 2400 N2 adsorption analysis (Gold APP
Instruments, China). The different functional groups of biochar’s
and nZVI incorporated biochar were analyzed by using FTIR
(Nicolet-1170 SX, USA) in wavenumber range from 4000 cm-1 to 400.
Raman spectroscopy was measured at room temperature using a Bruker
FRA 106/S spectrometer. The radiation from an Nd-YAG laser was used
as the excitation source. The magnetic properties of the magnetic
samples were measured by using a VSM (MPMS SQUID, USA) at 25 ± 2°C
in the range of - 4 T to 4 T. The Instruments TGA (STA6000, USA)
was used to understand the decomposition and stability of nZVI and
nZVI incorporated biochar’s. The studies were carried out under an
N2 atmosphere (40 cc/min) heated at a rate of 5 oC/min, over a
temperature range from 25C to 800C. Careful procedures were carried
out for sample preparation for analysis. The TOC of soil and as
prepared GTBC and nZVI@GTBC samples were measured by using solid
sample combustion unit SSM-5000A and TOC-L (Shimadzu), Japan. The
carbon (C), nitrogen (N), hydrogen sulfur (S) and oxygen (O) were
measured by using CHNSO elemental analyzer.
2. Physiochemical characteristics study of nZVI@GTBC and soil
samples
(i). Mass yield and Ash content
The mass yield and ash content for biochars produced at
different temperatures were determined gravimetrically, according
to methods reported in Weber et al. (2018) [1]
(ii). pH, Electrical conductivity and pHPZC measurement’s
Initially, the samples (soil, biochars, etc.) were air-dried and
pH of air-dried samples was determined using a glass electrode
meter (Sartorius Professional pH Meter PP-50) in a suspension of
1:5 soil/water ratios (w/v). The measurement of conductivity is
followed accordingly. The pHPZC of biochar prepared at different
temperatures was measured using 0.01 M CO2 free KNO3 solution at a
given value in the range between 2 to 8. Each washed and air-dried
biochar was added to 15 mL tubes containing these KNO3 solutions at
a ratio of 200:1 (liquid-solid). After agitation at 30 oC for 24 h,
the pH of each sample was measured. The pHPZC was obtained from a
plot of initial pH against the supernatant pH after 24 h.
(iii). Cation exchange capacity
The cation exchange capacity (CEC) was determined by
hexamminecobalt trichloride solution-spectrophotometric method and
according to the Chinese standard method (HJ 889-2017)[2–5]
(iv). Soil organic carbon (SOM in %)
The soil organic matter (SOM) was calculated by multiplying SOC
(obtained from TOC measurements by using TOC analyzer) by a
coefficient (1.72)[6–8].
(v). Total phosphorus
The total phosphorus (TP) was measured by using a UV-vis
spectrophotometer (Beijing Purkinje General Instrument Co., Ltd,
China) after wet digestion with ethanol and NaOH [9].
(vi). Acidic functional group matters
The acid functional group contents of green tea biochar and
nZVI@GTBC were measured using the method of Boehm titration
[10,11], an acid-base titration. Specifically, base having a
concentration (i.e., 0.01/0.1 M NaOH solution, 0.1 M NaHCO3
solution, and 0.1 M NaCO3) and acids (0.1/0.5 HCl solution) were
prepared carefully by using deionized water. The dried GTBC and
nZVI@GTBC, precisely about 0.1 g was added to 50 mL of alkaline
solution (0.05 M NaOH solution/0.1 M NaHCO3 solution/0.1 M NaCO3),
the mixtures were shaken at room temperature by using automatic and
reciprocate shaker for 12 h and filtered with a 0.25 μm membrane.
Then, 10 mL of each filtrate was pipetted to 100 mL Erlenmeyer
flask, containing a required volume of HCl solution. The solution
mixture is back-titrated with 0.01/0.1M NaOH solution to the
endpoint using the phenolphthalein indicator. To avoid the effect
of carbon dioxide from the air on titration results, all the
solutions in the titration experiment should be freshly prepared
and standardized. The resultant observations of back titration were
used for quantifying the acid functional groups. The NaOH consumed
titrant acidity was considered as the total acidic surface
functional groups, the NaHCO3 consumed titrant acidity as R-COOH
groups; the difference between the two acidity groups (NaOH-NaHCO3)
was regarded as phenol groups, and the difference between Na2CO3
and NaHCO3 acidity was assumed to lactone groups.
3. Colloidal stability and mobility studies of magnetic
nZVI@GTBC biochar
The prepared nZVI@GTBC and bare nZVI suspension (constant Iron
content) and sonicated for 5 minutes in de-ionized water, while the
absorbance was studied at 508 nm with a UV-Vis spectrophotometer,
respectively. To evaluate the mobility of bare-nZVI and magnetic
nZVI@GTBC, their transference activities were studied in
water-saturated silica sands that were packed in a vertical glass
column. A similar study was also reported in the literature
[12,13]. The column was 2 cm in diameter and 20.0 cm in length, and
was fitted with a nylon sieve (80 mesh) at the bottom to prevent
loss of silica sand 15 pore volumes (PVs) of deionized water was
initially pumped through the column to ensure uniform packing and a
steady-state flow (6 mL/ min). Next, 100 mL of magnetic nZVI@GTBC
suspension was introduced into the column at the same state flow.
To prevent sedimentation of samples, the suspension was
continuously sonicated prior to injection at room temperature.
After the above suspension was entirely pumped through the column,
the deionized water was used to elute the materials in the column.
The effluent was collected at selected time intervals and then was
digested with 1 M HCl for 2 h. The total iron concentration in the
outflow was determined by a UV/Vis spectrophotometer at a
wavelength of 580 nm [14]. For comparison, the transport behavior
studies of the following samples were examined accordingly.
Fig.S1. (a) nZVI Particle size at different weight ratio of
nZVI@GTBC (b) Influence of pH (pH 1.5 to 11) on nZVI (c) influence
of temperature on nZVI particle size {nZVI@GTBC (2%), temperature
(150 to 650 oC)}
Fig. S2. Raman spectrum of nZVI, GTBC, and nZVI@GTBC
Fig. S3. TG-DSC curves of (a) GT; (b) nZVI; (c) GTBC; and (d)
nZVI@GTBC
Fig. S4. Colloidal stability experiments (a) Pristine nZVI, (b)
nZVI@GTBC; mobility experiments (c) Pristine nZVI, (d)
nZVI@GTBC
Fig S5. Wide scan comparative XPS survey spectra of (a) nZVI,
(b) nZVI@GTBC and (c) nZVI@GTBC + soil (30 days).
Table S1: Mass yield (%), ash content (%), for GTBC and
nZVI@GTBC prepared at different temperatures.
Pyrolysis Temperature
GTBC
nZVI@GTBC
Mass Yield%
Ash content%
Surface area (m2/g)
Mass Yield%
Ash content%
Surface area
(m2/g)
150
92.33±0.61
7.80±0.10
12.34
98.07±0.25
1.91±0.03
7.84
250
82.43±1.21
18.53±0.35
21.70
97.17±0.42
3.40±0.10
18.57
350
78.10±0.90
22.57±0.61
28.41
92.77±0.65
8.13±0.21
26.30
450
61.40±0.66
39.20±0.66
47.52
89.00±0.62
11.87±0.40
38.08
550
54.87±0.15
46.00±0.75
40.17
82.37±1.20
18.83±0.35
25.41
650
32.27±1.10
67.87±0.65
28.15
74.60±0.53
26.12±0.83
11.47
3
Table S2. pH, conductivity, SOM and iron viability in soil
(after treatments from 1st day to 30th day)
Samples
Initial Conditions
Observed pH variations
Conductivity
(mS cm-1)
SOM (%)
Available Iron content (mg/kg of soil)
E0
E1
E2
E3
E4
1ST day
6.8 ± 0.5
6.8 ± 0.5
0.31 ± 0.01
1.94 ± 0.04
32.52 ± 1.14
28.29 ± 0.79
252.43 ± 0.49
3.39 ± 0.02
98.23 ± 0.89
4.0 ± 0.5
4.0 ± 0.5
0.48 ± 0.01
0.86 ± 0.15
29.64 ± 1.16
28.41 ± 0.86
279.27 ± 0.35
3.44 ± 0.03
132.38 ± 1.05
8.0 ± 0.5
8.2 ± 0.5
0.41 ± 0.03
0.67 ± 0.02
31.94 ± 1.45
30.36 ± 0.80
295.15 ± 0.60
3.57 ± 0.03
156.07 ± 2.67
15th day
6.8 ± 0.5
6.7 ± 0.5
0.47 ± 0.02
2.87 ± 0.03
31.82 ± 0.75
28.34 ± 0.93
297.84 ± 0.35
2.59 ± 0.08
68.48 ± 1.11
4.0 ± 0.5
4.5 ± 0.5
0.61 ± 0.01
0.82 ± 0.05
30.64 ± 0.74
27.86 ± 0.85
315.37 ± 0.54
3.14 ± 0.03
123.29 ± 2.30
8.0 ± 0.5
7.9 ± 0.5
1.34 ± 0.03
0.96 ± 0.03
34.60 ± 1.17
29.24 ± 1.74
323.85 ± 0.57
3.03 ± 0.03
140.82 ± 1.04
30th day
6.8 ± 0.5
6.8 ± 0.5
0.61 ± 0.01
3.35 ± 0.10
33.60 ± 0.89
28.38 ± 1.22
304.60 ± 0.79
2.28 ± 0.12
42.09 ± 0.90
4.0 ± 0.5
4.9 ± 0.5
0.83 ± 0.01
1.31 ± 0.27
31.29 ± 1.27
26.56 ± 0.95
321.49 ± 0.39
2.75 ± 0.03
91.30 ± 0.47
8.0 ± 0.5
7.8 ± 0.5
1.56 ± 0.03
1.37 ± 0.05
34.53 ± 1.24
28.46 ± 1.52
340.03 ± 1.20
2.55 ± 0.03
115.01 ± 1.63
References:
[1]K. Weber, P. Quicker, Properties of biochar, Fuel. 217 (2018)
240–261. doi:10.1016/j.fuel.2017.12.054.
[2]D. Ross, Q. Kettering, Recommended methods for determining
soil cation exchange capacity., Recomm. Soil Test. Proced.
Northeast. United States. Coop. Bull. No. 493. (2011).
[3]A. Sharma, D.C. Weindorf, D.D. Wang, S. Chakraborty,
Characterizing soils via portable X-ray fluorescence spectrometer:
4. Cation exchange capacity (CEC), Geoderma. (2015).
doi:10.1016/j.geoderma.2014.10.001.
[4]D.S. Ross, Chapter 9 Soil Cation Exchange Capacity, in:
Recomm. Soil Test. Proced. Northeast. United States, 2011.
[5]M. Csuros, Cation Exchange Capacity, in: Environ. Sampl.
Anal., 2018. doi:10.1201/9780203756881-28.
[6]S.J. Hall, W.L. Silver, V.I. Timokhin, K.E. Hammel, Iron
addition to soil specifically stabilized lignin, Soil Biol.
Biochem. 98 (2016) 95–98. doi:10.1016/j.soilbio.2016.04.010.
[7]E.K. Bünemann, G. Bongiorno, Z. Bai, R.E. Creamer, G. De
Deyn, R. de Goede, L. Fleskens, V. Geissen, T.W. Kuyper, P. Mäder,
M. Pulleman, W. Sukkel, J.W. van Groenigen, L. Brussaard, Soil
quality – A critical review, Soil Biol. Biochem. 120 (2018)
105–125. doi:10.1016/j.soilbio.2018.01.030.
[8]X. Wang, K. Yoo, A.A. Wackett, J. Gutknecht, R. Amundson, A.
Heimsath, Soil organic carbon and mineral interactions on
climatically different hillslopes, Geoderma. 322 (2018) 71–80.
doi:10.1016/j.geoderma.2018.02.021.
[9]F. Ii, 3 . Methods for Sampling / Analysis of Mercury in
Water and Solids, Aquat. Sci. (2000) 1–13.
[10]T.T. Qian, P. Wu, Q.Y. Qin, Y.N. Huang, Y.J. Wang, D.M.
Zhou, Screening of wheat straw biochars for the remediation of
soils polluted with Zn (II) and Cd (II), J. Hazard. Mater. 362
(2019) 311–317. doi:10.1016/j.jhazmat.2018.09.034.
[11]V.K. Gupta, A. Rastogi, Sorption and desorption studies of
chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass,
J. Hazard. Mater. 154 (2008) 347–354.
doi:10.1016/j.jhazmat.2007.10.032.
[12]H. Su, Z. Fang, P.E. Tsang, J. Fang, D. Zhao, Stabilisation
of nanoscale zero-valent iron with biochar for enhanced transport
and in-situ remediation of hexavalent chromium in soil, Environ.
Pollut. 214 (2016) 94–100. doi:10.1016/j.envpol.2016.03.072.
[13]S. Wang, B. Gao, Y. Li, A.E. Creamer, F. He, Adsorptive
removal of arsenate from aqueous solutions by biochar supported
zero-valent iron nanocomposite: Batch and continuous flow tests, J.
Hazard. Mater. 322 (2017) 172–181.
doi:10.1016/j.jhazmat.2016.01.052.
[14]A.E. Harvey, J.A. Smart, E.S. Amis, Simultaneous
Spectrophotometric Determination of Iron(ll) and Total Iron with
1,10-Phenanthroline, Anal. Chem. (1955).
doi:10.1021/ac60097a009.
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