S1
SUPPLEMENTAL DATA
ADSORPTION OF PHENANTHRENE, 2-NAPHTHOL, AND
1-NAPHTHYLAMINE TO COLLOIDAL OXIDIZED MULTI-WALLED
CARBON NANOTUBES: EFFECTS OF HUMIC ACID AND SURFACTANT
MODIFICATION
LEI HOU,† DONGQIANG ZHU,‡ XIMENG WANG,† LILIN WANG,†
CHENGDONG ZHANG,† WEI CHEN*†
† College of Environmental Science and Engineering, Ministry of Education Key
Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of
Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071,
China
‡ State Key Laboratory of Pollution Control and Resource Reuse, School of the
Environment, Nanjing University, Jiangsu 210093, China
Number of pages: 6
Number of tables: 1
Number of figures: 1
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Detailed procedures used to prepare HA- and SDS-modified O-MWNT suspensions
Stable suspensions of humic acid (HA) and surfactant (sodium dodecyl sulfate, SDS)
modified O-MWNT were prepared using following procedures.
A stock solution of HA
was prepared by dissolving approximately 300 mg as-received HA powder in 5 mL 0.1 M
NaOH solution, and was filtered through a 0.45-μm Millipore membrane filter. Then, it
was diluted to approximately 1 g/L using the 0.001 M NaCl background solution, and the
pH of the solution was adjusted to neutral.
The exact concentration of HA was
determined with total organic carbon (TOC) analysis using a high sensitivity TOC
analyzer (Shimadzu Scientific Instruments), based on the carbon content provided by the
IHSS. This HA solution was further diluted with the background solution to obtain a 60
mg/L working solution of HA, and was used to prepare the HA-modified O-MWNT
suspension. A 300 mg/L SDS solution was obtained by dissolving SDS powder in the
0.001 M NaCl background solution. To prepare the HA- or SDS-modified O-MWNT
suspension, 200 mg O-MWNT was added to 1 L of 60 mg/L HA solution or 1 L of 300
mg/L SDS solution, and was sonicated at 100 W (Vibra-Cell VCX800, Sonics & Material)
for 30 min. Afterward, the suspension was centrifuged at 10000 rpm for 15 min. Then,
the upper 75 to 80% of the supernatant was carefully withdrawn and stored.
Then, the
collected supernatant was dialyzed using a dialysis bag of 6000 to 8000 molecular weight
cutoff to remove the freely dissolved HA or SDS from the colloidal O-MWNT
suspension, following the procedures of Li et al. [1].
The molecular weight of HA is
roughly in the range of 1-5 kDa [2,3]. The molecular weight of SDS is 288, and the
total concentration of SDS (300 mg/L) was significantly below the critical micelle
concentration (2382 mg/L). Thus, freely dissolved HA or SDS should have been
S3
sufficiently removed by repeated dialysis, and essentially all the HA or SDS retained in
the dialysis bag was that adsorbed to O-MWNT.
X-ray photoelectron spectroscopy (XPS) analysis
Surface elemental contents (C, O, N, and S) of the O-MWNT and the three colloidal
O-MWNTs were analyzed by X-ray photoelectron spectroscopy (XPS) with an
ion-pumped Physical Electronics PHI-1600 ESCA system equipped with a
Circumferential analyzer.
An Mg Kα anode, operated at 15 kV and 250 W with a
photon energy of hν = 1254.6 eV, was used.
The base chamber pressure after a bakeout
was approximately 5 × 10-10 Torr, and the typical working pressure was approximately 1
× 10-8 Torr.
The samples were mounted onto a sample probe with double-sided tape and
loaded into the main analysis chamber via a turbo-pumped antechamber. The C 1s core
level at 284.6 eV, corresponding to the O-MWNT oxidation state, was used to
charge-reference the XP spectra.
The XPS data were analyzed using Multipak 8.2
(Copyright © ulvac-PHI Inc, 1994-2006).
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Table S1.
Summary of fitted Freundlich model coefficients (KF and n) obtained from
adsorption results.
Adsorbate
phenanthrene
2-naphthol
1-naphthylamine
a
KF
(L ·mmol1-n·kg-1) a
na
R2
530±40
0.25±0.01
0.992
O-MWNT-colloid
1400±400
0.38±0.03
0.960
O-MWNT/HA-colloid
920±100
0.44±0.02
0.984
O-MWNT/SDS-colloid
1000±100
0.40±0.01
0.993
O-MWNT
400±30
0.22±0.02
0.942
O-MWNT-colloid
180±20
0.12±0.03
0.762
O-MWNT/HA-colloid
640±200
0.70±0.10
0.937
O-MWNT/SDS-colloid
330±200
0.45±0.20
0.761
O-MWNT
3200±400
0.32±0.05
0.904
O-MWNT-colloid
2900±60
0.22±0.01
0.996
O-MWNT/HA-colloid
800±30
0.22±0.03
0.907
O-MWNT/SDS-colloid
560±50
0.14±0.02
0.820
Adsorbent
O-MWNT
n
Values after  sign indicate relative standard deviation.
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103
phenanthrene
q (mmol/kg)
q (mmol/kg)
103
102
101
100
10-6
-5
10
10
-4
-3
10
-2
10
-1
10
2-naphthol
102
101
100
10-4
10-3
C (mmol/L)
10-2
10-1
100
101
C (mmol/L)
4
q (mmol/kg)
10
1-naphthylamine
O-MWNT
O-MWNT-colloid
O-MWNT/HA-colloid
O-MWNT/SDS-colloid
103
102
101
10-5
10-4
10-3
10-2
10-1
100
C (mmol/L)
Figure S1.
Adsorption isotherms of phenanthrene, 2-naphthol, and 1-naphthylamine to
the non-colloidal O-MWNT, and colloidal O-MWNTs (O-MWNT-colloid,
O-MWNT/HA-colloid, and O-MWNT/SDS-colloid).
The lines were plotted by
curve-fitting the adsorption data with the Freundlich model.
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2.
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3.
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