Page 7 - JES202006

jo urna l o f e nviro n mental scie nces 92 (2020) 1 e10 3

Fe 2 O 3 , the final silver deposited hematites were denoted as Ag/
Fe 2 O 3 NPs, Ag/Fe 2 O 3 NSs, and Ag/Fe 2 O 3 NCs, respectively.
1.4. Catalytic activity

The catalytic activity of the as-prepared Ag/Fe 2 O 3 composites
was evaluated by reduction of PNP in the presence of NaBH 4 .
Briefly, 5 mmol of NaBH 4 was mixed with 50 mL PNP solution
(1 mmol/L) by stirring in a beaker, and 5 mg synthesized
catalyst was introduced into the mixture. Once the nano-
composite was added, 0.4 mL of the solution was taken out at
different time intervals, and diluted to measure ultraviolet-
visible (UV-Vis) absorption spectra (UV-Vis 2550, Shimadzu,
Japan) at 400 nm. The UV-Vis absorption could display the
amount of PNP in the solution, and thus monitored the reduc-
tion of PNP.

Fig. 1 e X-ray powder diffraction patterns of Ag/Fe 2 O 3 NPs 1.5. Characterization
(nanoplates), Ag/Fe 2 O 3 NSs (nanospheres), and Ag/Fe 2 O 3
NCs (nanocubes). The crystalline structure and phase of the as-synthesized
samples were characterized by powder X-ray diffraction (XRD,
D8 ADVANCE, Brucker, Germany) patterns with Cu Ka radiation

(the wavelength l ¼ 1.54178 A) at 40 kV and 40 mA. Nitrogen
adsorption-desorption isotherm of the products was deter-
washed with hexamethylene, deionized water and ethanol
mined at 77 K and the Brunauer-Emmett-Teller (BET, ASAP
several times, respectively, and then dried at 40 C for 12 hr.

2460, Micromeritics, USA) surface area was obtained from the
linear part of the BET plot. The morphology and structure im-
1.3. Preparation of Ag/Fe 2 O 3
ages were got by the scanning electron microscope (SEM, JSM-
6700F, JEOL, Japan) and transmission electron microscope
A simple hydrothermal method was applied to synthesize Ag/
(TEM, JEM-2100F, JEOL, Japan). The UV-Vis spectrum was
Fe 2 O 3 . Typically, certain amount of Fe 2 O 3 was ultrasonically
collected by the Shimadzu UV-Vis 2550 spectrophotometer (UV-
dispersed in 60 mL 50% (V/V)ethylene glycolaqueous solution.
Vis 2550, Shimadzu, Japan). X-ray photoelectron spectroscopy
The calculated amount of AgNO 3 was then added rapidly to the
(XPS, EscaLab 250Xi, Thermo, USA) was performed to analyze
above solution, and stirred vigorously for 1 hr. Then, the mixture
the surface composition. The Malvern zetasizer Nano ZS (Mal-
solution was transferred to 100 mL Teflon-lined stainless steel
vern Instruments, UK) was used to measure the zeta potential
autoclave and heated at 140 C for 12 hr. Upon cooling to room

of the samples. Inductively coupled plasma optical emission
temperature, the product was collected, washed with water and
spectrometer (ICP-OES, Avio 500, PerkinElmer, USA) was
ethanol, and dried overnight. According to different shapes of
applied to measure the element content.

Fig. 2 e Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of (a and d) Ag/Fe 2 O 3 NPs,
(b and e) Ag/Fe 2 O 3 NSs, (c and f) Ag/Fe 2 O 3 NCs.