Enhanced photo Fenton-like activity by effective and stable Al–Sm M-hexaferrite heterogenous catalyst magnetically detachable for methylene blue degradation

Article abstract of DOI:10.1016/j.jallcom.2019.153410

Nano-compositing technologies are getting enhanced attention due to unique catalytic and separation activity with advanced characteristics for dye wastewater treatment. In this study, novel easily separable Ba–Sr based Al–Sm substituted M-hexaferrites (BASF-NPs) were fabricated as a highly effective heterogenous photo-Fenton-like catalysts via sol-gel route. The analytical techniques were applied to investigate BASF-NPs characteristics such as TGA, XRD, FTIR, XPS, SEM/TEM/EDS, UV–Vis, BET and VSM analysis. The results revealed that all fabricated BASF-NPs showed excellent photo-Fenton-like catalytic performance towards Methylene Blue (MB) degradation. Virtually complete degradation of an initial 10 mg/L MB was achieved under optimal conditions (i.e. 16 mM H₂O₂ and 0.25 g/L BASF-NPs) within 140 min of UV-irradiated reaction time and followed pseudo-first order reaction kinetic at the rate of 6.514 × 10^?2 min^?1. Similar degradation trend was noticed at various pH levels (pH 3–12), signifying the efficiency of the NPs at wide pH range. Due to the intrinsic magnetic nature of BASF-NPs, it was readily recoverable by external magnetic field and exposed strong capacity for dye removal treatment. The photo-catalysts retained its performance after four consecutive cycles, indicating robust reusability and excellent stability.

Full text of DOI:10.1016/j.jallcom.2019.153410

Journal of Alloys and Compounds 821 (2020) 153410
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
Enhanced photo Fenton-like activity by effective and stable AleSm M-
hexaferrite heterogenous catalyst magnetically detachable for
methylene blue degradation
Ghulam Abbas Ashraf , Raqiqa Tur Rasool , Muhammad Hassan , Lanting Zhang a
a
b
c
,
*
, **
a
School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
School of Chemistry and Chemical Engineering (SCCE), Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 August 2019
Received in revised form
Nano-compositing technologies are getting enhanced attention due to unique catalytic and separation
activity with advanced characteristics for dye wastewater treatment. In this study, novel easily separable
BaeSr based AleSm substituted M-hexaferrites (BASF-NPs) were fabricated as a highly effective heter-
ogenous photo-Fenton-like catalysts via sol-gel route. The analytical techniques were applied to inves-
tigate BASF-NPs characteristics such as TGA, XRD, FTIR, XPS, SEM/TEM/EDS, UVeVis, BET and VSM
analysis. The results revealed that all fabricated BASF-NPs showed excellent photo-Fenton-like catalytic
performance towards Methylene Blue (MB) degradation. Virtually complete degradation of an initial
18 November 2019
Accepted 15 December 2019
Available online 16 December 2019
Keywords:
Ba-Sr M-hexaferrites
Methylene blue
Photo-Fenton-like system
Heterogeneous photo-catalysts
Degradation pathway
10 mg/L MB was achieved under optimal conditions (i.e. 16 mM H
2 2
O and 0.25 g/L BASF-NPs) within
1
40 min of UV-irradiated reaction time and followed pseudo-first order reaction kinetic at the rate of
ꢁ
2
ꢁ1
6.514 ꢀ 10 min . Similar degradation trend was noticed at various pH levels (pH 3e12), signifying the
efficiency of the NPs at wide pH range. Due to the intrinsic magnetic nature of BASF-NPs, it was readily
recoverable by external magnetic field and exposed strong capacity for dye removal treatment. The
photo-catalysts retained its performance after four consecutive cycles, indicating robust reusability and
excellent stability.
©
2019 Elsevier B.V. All rights reserved.
1
. Introduction
potential for industrial waste water treatment among the various
water treatment methods tested so far because hydroxyl radicals
are extremely reactive species having 2.80 eV redox potential by
The primary source of dye wastewater at large scale is
manufacturing include industries of textile, paper, leather,
cosmetic, food and paper that is highly dangerous for humans and
environment, as it includes elevated dyes and a range of recalci-
trant. For illustration, annually more than 100,000 commercially
accessible dyes are manufactured worldwide at an approximate
adding H
2 2
O [3]. The produced hydroxyl radicals reacted with
recalcitrant organic compounds as a consequence degradation of
2
þ
2 2
pollutants. The economical Fenton scheme (Fe and H O ) has
ꢂ
substantial owing to generation of hydroxyl radicals ( OH) [4].
However, this traditional Fenton system has significant constrains,
5
rate of over 7 ꢀ 10 tons. Due to the toxicity and carcinogenic na-
such as narrow pH < 3 range, high consumption of H
sludge produced as a binary pollution in treated waste water [5].
The heterogeneous (e.g. Fe -Fe and -FeOOH) Fenton
catalysts typically have lesser activity in H , due to the potential
2 2
O and iron
ture character that eventually damage the human health and nat-
ural environment so the degradation of dyes in wastewater is a
burning issue. The effective dye degradation methods like chemical
oxidation, physical separation and biological degradation [1,2].
Advanced oxidation processes (AOPs) have presented excellent
3
O
4
,
g
2
O
3
a-b-g
2 2
O
dissemination resistance of the reactants on the catalyst surface
than the homogeneous counterpart. Additionally, in oxidation cir-
cumstances some catalysts possessed poor stability or durability
due to metal leaching [6]. It is still necessary to develop efficient,
stable, durable heterogenous catalysts to achieve a challenge.
Heterogeneous (HC) photo-Fenton-like systems are currently
being researched as a more practical and effective alternative
*
Corresponding author.
*
* Corresponding author.
E-mail addresses: m.hassan@sjtu.edu.cn (M. Hassan), lantingzh@sjtu.edu.cn
(
L. Zhang).
https://doi.org/10.1016/j.jallcom.2019.153410
925-8388/© 2019 Elsevier B.V. All rights reserved.
0

2
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
procedure for degrading recalcitrant organic pollutants. The mag-
netic materials required the characteristic like stability, reusability
and high reactivity; can be functional in an extensive range of
photo-decomposition of toxic and organic pollutants in wastewater
nitrate: Ba(NO
Aldrich), aluminum nitrate: Al(NO
ammonium hydroxide: NH
3
)
2
(99%, Merck), samarium (III) oxide: Sm (99%,
2
O
3
3
)
2
, citric acid: C H O and
6 8 7
4
OH (99%, Aldrich) were utilized. All
chemicals were of analytical grade and applied without further
[
7]. In significance, various studies have been explored on HC
purification.
photo-Fenton-like system using ferrites owing to their potential
characteristics in the photo-degradation of different dyes. Andrei
2.2. Synthesis of BASF-NPs
2
þ
2þ
2þ
et al. [8] explored metal ions doped such as Co , Mn , Cu and
2
þ
Ni , MgFe
2
O
4
nano-particles were applied as photo-Fenton-like
BASF-NPs were fabricated via sol-gel method. First, a distinct
catalysts for MB degradation in aqueous medium. Wang et al. [9]
studied mesoporous copper substituted spinel ferrite HC Fenton-
like system for imidacloprid degradation in existence of H O .
2 2
3 3 2 3 2 3 2
aqueous solution of FeCl , Sr(NO ) , Ba(NO ) and Al(NO ) of
analytical grade according to stoichiometric calculation were
equipped in deionized water for all metal ions precursors. For pure
Xing et al. [10] studied Mg doped spinel ferrite with spherical nano-
particles as HC Fenton-like system for dye removal. Strontium
sample preparation the aqueous solution of FeCl
Ba(NO were poured into baker and kept on stirring for 3 h at
room temperature. In the meantime, C was steadily decanted
down into the solution. C to metal nitrates were engaged
with 1:1 ratio, whereas NH OH solution was used to maintain the
pH value ~ 7e8 for pure sample and others. For AleSm based
samples fabrication, the aqueous of Sr(NO , Ba(NO and
Al(NO , FeCl and the measured quantity of Sm was liquefied
in concentrated HNO with constantly stirring at 80 C to produce
3 3 2
, Sr(NO ) ,
3 2
)
based M-hexaferrite (SrFe12
catalytic removal of toludine blue dye. Luna et al. [12] synthe-
sized barium M-hexaferrite (BaFe12 19) with an application of HC
O
19) [11] was applied for the photo-
6 8 7
H O
6 8 7
H O
O
4
photo-Fenton-like system for decolorization and mineralization of
MB. Li et al. [13] used manganese substituted spinel ferrite HC
catalysts with sphere-like particles as Fenton system for the dye
degradation. Fatemeh et al. [14] fabricated with core shell structure
3
)
2
3 2
)
3
)
2
3
2 3
O
ꢃ
3
Sr-M-hexaferrite@SiO
2
@TiO
2
composites with low degradation rate
Sm(NO
3
)
3
then gradually transferred into solution. As the temper-
ꢃ
of MB under UV-irradiation. Guo et al. [15] prepared nickel
substituted spinel ferrite with hollow sphere nano-particles which
was applied as HC photo-Fenton catalysts for dye degradation. Rare
ature steadily reached up to 120 C, the solution was more
concentrated like a gel and obtained gel burned out, which was
ground and further heated at 800 C for 3 h and 1100 C for 1 h to
attain stable M-hexaferrite structure.
ꢃ
ꢃ
earth cations like La and Ce substituted CoFe
Rimi [16] for photo-Fenton activity. Similarly, Fe-based catalysts,
such as Fe [17], Fe [18], -FeOOH [19] and CuFe [20] have
been used to stimulate H into reactive radicals for degradation
of organic contaminants in water. Lili et al. [21] characterized
copper doped AlPO catalyst as a Fenton-like degradation in the
existence of H at neutral pH.
2 4
O were explored by
2
O
3
3
O
4
a
2
O
4
2.3. Characterization of BASF-NPs
2 2
O
In the ambient atmosphere, thermo gravimetry (TGA: NETZSCH
STA 449) was performed with heating rate of 10 C per minute.
BASF-NPs structure were recognized at room temperature by X-ray
ꢃ
4
2
O
2
However, AleSm substituted M-hexaferrite were rarely re-
ported yet because of the key concern to improve catalytic activity
diffraction (D8 ADVANCE Da Vinci) with CuKa as the radiation
ꢃ
ꢃ
source. The XRD pattern was recorded in the range of (20 e85 )
ꢃ
of Ba0.4Sr0.6Al0.4-xSm
based M-hexaferrite nano-particles henceforth named as BASF-
x
Fe11.60
O
19 (Pure, x ¼ 0.0, 0.2, and 0.4) BaeSr
with scan rate 5 per minute. The FTIR spectra (Nicolet 6700) was
ꢁ
1
recorded from 4000 to 350 cm using the weight ratio of BASF-
NPs and KBr (0.1:0.45), then mixed and ground in stainless steel
die to make thin layer pellets at 27 C and 10 T. X-ray photoelectron
3
þ
2ꢁ
NPs. Whereas, in M-hexaferrite, 24 Fe
ions, 38 O ions and
2
þ
3þ
ꢃ
2
M
ions are contained in unit cell, but Fe ions are located at
five locations (4f
three sites octahedral (4f
(
2
, 4f
1
, 2b, 12k and 2a), one site tetrahedral (4f
,12k, 2a) and one site trigonal bipyramidal
2b). The sites of Fe ions (2a, 2k and 2b) and 4f and 4f are
positioned with spin up and spin down direction, respectively.
1
),
spectroscopy (XPS; AXIS UltraDLD) was conducted using Al Ka as an
2
exciting X-rays energy of 30 eV. Scanning electron microscope
(SEM) and transmission electron microscopy (TEM) (Hitachi JEM)
was employed to observe the size and morphology of BASF-NPs and
elemental composition was detected by energy dispersive X-ray
spectroscopy (EDS) (INCA X-Act/). Before carrying out the SEM/EDS
analysis, BASF-NPs were coated with gold particles. TEM study was
equipped through carbon film copper grid method. UVevis spectra
were attained by UV-VIS, Lambda 750S spectrometer and from
Kubelka-Munk method band gap was estimated. For the surface
area and porosity assessment, Brunauer-Emmett-Teler (BET) sur-
3
þ
2
1
3
þ
3þ
Fe eOeFe are connected by aforementioned sites by super ex-
change interaction leading to ferromagnetic structure [22]. AleSm
substituted having hexagonal structure shape, narrow energy band
g
gap (E ) and magnetic nature have turned out to be suitable ma-
terial for environmental remediation. The synthesized hexaferrites
catalysts have excellent diffusion efficiency and can be effectively
and simply recovered by an external applied magnetic field for their
ultimate reusability. As a result, the sustainability of superior active
hexaferrite fulfills the green chemistry standards.
In this work, novel AleSm substituted M-hexaferrites (BASF-
NPs) were fabricated by sol-gel method. This idea presents the
application of BASF-NPs to elucidate as a HC photo-Fenton-like
catalysts for MB degradation as a model bio-recalcitrant dye
2
face analyzer (24/Autosorb-IQ3) was applied. At 77 K, nitrogen (N )
isotherm gas adsorption was obtained. Before the test, BASF-NPs
were outgassed at 424 K under vacuum. Magnetic performance
was explored by applying the magnetometer (VSM, Quantum
Design PPMS-9T EC-II) at room temperature within range ꢁ15 kOe
to 15 kOe.
2 2
pollutant. The effects of BASF-NPs dosage, H O concentration, and
pH were evaluated. Reaction pathway was proposed based on the
production of active intermediates during MB degradation process.
2.4. Photo degradation experiments
A 10 mg/L MB dye was used in a desired amount of distilled
water solvent under photo irradiation sourced by low pressure
mercury lamp (UV; 10 W) and inserted into the lab designed photo-
reactor with displacement volume of 1 L (Fig. 1). To prevent from
the surround light intact, the reactor was coated with tinfoil.
2
. Experimental procedure
2.1. Chemicals
Methylene blue (MB, C16
H
18ClN
3
S$3H
2
O) (Macklin), ferric chlo-
, barium (II)
Various BASF-NPs doses and H
ranging from 0.00 to 1.00 g/L and 4e16 mM, respectively for
2 2
O concentrations were applied
ride (FeCl .6H O), strontium (II) nitrate: Sr(NO )
3
2
3 2

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
3
Fig. 1. Experimental assembly.
optimization during 140 min reaction time. The sample was taken
every 20 min interval from photo-reactor. BASF-NPs were sepa-
rated by applying external magnetic effect and then filtered the
Fig. 2. TGA/DSC analysis of BASF-NPs (x ¼ 0.1).
BASF-NPs crystal structure is composed in between oxygen ions
solution through 0.2 mm syringe filters. The filtered solution was
ꢁ
3þ
3þ
(
O2 ) and metal ions such as Fe and Me as metal substituted
examined using double-beam UVeVis spectrophotometers (UV-
VIS, Lambda 750 S) within wavelength of 400e700 nm. The ach-
ieved optimal condition such as such as 0.25 g/L BASF-NPs and
ions. XRD patterns were evaluated for M-hexaferrites to examine
the hexagonal phase as presented in Fig. 3. There is a strong indi-
cation of hexagonal M-type structure with space group P63/mmc
16 mM H
2 2
O were further used to explore the impact of various pH
(
194) and having standard JCPDS file no. 51e1879 which is inserted
in Fig. 3 for comparison. It appears that XRD pattern demonstrate
minor -Fe secondary phase having JCPDS file number 00-033-
(
3, 7 and 12 with HCl or NaOH) and also changing the primary MB
concentration (10, 20 and 30 mg/L) on MB degradation. The
degradation percentage of MB was achieved by:
a
2 3
O
3
þ
0
664. In addition, Sm substitution (0.2 ꢄ x ꢄ 0.4) caused another
ðC
o
ꢁ C
t
Þ
minor phase FeSmO
well as minor -Fe
3
having JCPDS file number 00-039-1490 as
secondary phase. While pure M-hexaferrite
MB Degradation ¼
ꢀ 100%
(1)
C
o
a
2
O
3
(
Ba0.4Sr0.6Fe12O19) depicted obviously identical results as described
whereas, C
o
¼ initial and C
t
¼ after t time concentration of MB. Total
by Iqbal et al. [26]. The lattice parameters a (5.885 to 5.891 Å) and c
(23.085 to 23.106 Å) depicted the slight variation in the crystal
structure due to the AleSm substitution at Fe site [27,28]. By using
the Debye-Scherer eq. (2), the crystallite size (Dxrd) was evaluated:
organic carbon (TOC) (TOC-5050, Shimazdu, Japan) tracked the
degree of MB mineralization. The level of metallic ions leaching was
evaluated with inductive coupled plasma optical (ICAP7600). For
ꢂ
the detection of hydroxyl radicals ( OH) fluorescence spectropho-
tometer (RF-5301-PC-Shimadzu) was employed. Liquid chroma-
tography attached with tandem mass spectrometer (UPLC-MS)
evaluated the photo-degraded intermediates of MB. The study of
recyclability and stability were explored as the recovered photo-
catalyst from solution by a bar-magnet, washed with water, dried
then spread over in the next cycles with same conditions.
0:9l
Dxrd ¼ b
(2)
1
2
cos q
whereas, Dxrd ¼ average crystallite size, Ɵ ¼ Bragg angle (degree),
l
¼ 1.5406 Å and
b
¼ full wave at half maximum (FWHM). Hence,
D
xrd of BASF-NPs is within range (39.47e45.49 nm) which is well
matched [29].
3
. Results and discussions
The FTIR spectra of the synthesized BASF-NPs is shown in Fig. 4.
ꢁ1
The wavenumber range extended from 4000 to 350 (cm ). The
ꢁ1
3.1. Characteristics of BASF-NPs
existence of two absorption band around 452.74 and 596.58 (cm
)
are attributed to the stretching vibration of M-O bond (metal-ox-
ꢁ
1
As shown in Fig. 2 the clear hexaferrite structure formation
ygen) [30]. No absorption in the range of 1000e3500 cm could be
occurred through TGA/DSC curves from room temperature to
1
attributed to the absence of residual (metal carbonate), nitrates and
ꢃ ꢃ
200 C. At 150 C the endothermic (TGA) curve was observed due
to the weight loss of hydrated water from dried sample. In the
ꢃ
second portion of temperature range from 200 to 850 C was
associated with the decomposition of metal hydroxides in their
respective metal oxide and loss of NH gas [23]. In addition, the
3
larger weight loss in the second portion of exothermic peaks tend
to show the response of nitrates and citric acid that eventually
ꢃ
formed metal oxides. The endothermic peaks from 300 to 850 C
display that the decomposition of unreacted citric acid. Indeed,
growth of grain and nucleation can be achieved from amorphous to
hexagonal where the weight loss can be stable. For the achieve-
ment of hexagonal phase, the dried gel was calcinated for 3 h at
ꢃ
ꢃ
8
00 C and 1 h at 1100 C [24,25].
Fig. 3. XRD pattern of BASF-NPs. (pure sample; Ba0.4Sr0.6Fe12
O
19, x ¼ 0.0, 0.2 and 0.4).

4
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
UVeVis spectra were employed to investigate BASF-NPs optical
absorption properties. Optical band gaps (E ) in semiconductor
type materials are significant consideration during photo-
degradation. As the narrow E leads to elevated solar photon ab-
sorption effectiveness. The absorption band is linked to electron
excitation from valance to conduction band, that determines E
g
g
g
2
features. The absorption spectra and (
ahn) vs hn (eV) of BASF-NPs
were calculated, as shown in Fig. 8 (a) and (b) respectively. In a Taue
equation (3), energy of the incident photon (h
n) and absorption
coefficient a:
À
Á
1
=2
ahn
¼ A h
n
ꢁ E
g
(3)
whereas, A ¼ constant value and E
g
¼ energy band gap. BASF-NPs’
Tauc graph with measured E
g
values as presented in Fig. 8 (b). For E
g
values a tangent line was calculated to bisect the horizontal x-axis
which crossed the absorption curve at the point of inflection, and
the values were found to be 1.65 eV, 1.68 eV, 1.74 eV and 1.85 eV for
pure sample, BASF-NPs (x ¼ 0.0, 0.2 and 0.4), respectively. It was
g
seen from Fig. 8 (b) that E values increase by AleSm substitution,
suggesting the role of substituents in altering the basic lattice
structure. It can be attributed to the quantum confinement effect
which is corroborated with shape and size of the grains [39,40].
Fig. 4. FTIR spectra of BASF-NPs.
residual water stretching vibration, signifying that water residues,
carbon and nitrates were totally burned off by self-ignition. The
g
Luna and Wang et al. [12,37] reported E ; 1.77 eV and 1.70 eV for
barium hexaferrite, correspondingly. Furthermore, the narrowband
gap of substituted M-hexaferrites enhanced the visible-light
absorption.
The porous behavior of BASF-NPs are evaluated by adsorption
desorption isotherms analysis as shown in Fig. 9. The catalyst’s
activity primarily depends on the surface area. It is ascribed to
larger surface area of nano-particles that provides more active
surface for photo-catalytic response. BET surface analyzer was
ꢁ
1
appearance of absorption in 434e443 cm
ascribed to FeeO bending vibrations of FeeO
brations of FeeO , while the FeeO stretching vibrations of FeeO
ascribes in range 580e597 cm
bands ( 1 and
and decrease in Al contents (x).
(
n
2) band range
4
and stretching vi-
6
4
ꢁ
1
(n
1) [31]. Moreover, a slight shift of
3
þ
n2) to low frequency occurred with increasing Sm
n
3
þ
XPS was used for the oxidation states of elements in BASF-NPs.
As shown Fig. 5 (a), from the XPS spectrum (from 1200 to 10 eV) of
BASF-NPs (x ¼ 0.2) surface consists of Ba, Sr, Al, Sm, Fe and O ele-
applied to explore the surface area of pure sample at 77 K. Sample
ꢃ
testing was initially performed with N
2
gas stream at 150 C for 2 h.
2
þ
ments. As illustrated in Fig. 5 (b) Ba 3d XPS spectra possessed
binding energies of Ba 3d5/2 (780.4 eV) and Ba 3d3/2 (795.7 eV). The
Fig. 9 (a) illustrates the specific curves of adsorption-desorption
with relatively pore sizes of BASF-NPs. The surface area of pure,
strontium Sr2 3d two positioned around 134.4 eV (Sr 3d5/2) and
þ
2
x ¼ 0.0, 0.2 and 0.4 were noted as 5.85, 5.44, 8.26, 5.90 m /g; its
1
[
36.2 (Sr 3d3/2) eV agreeing to the photo-electron peaks (Fig. 5 (c))
pore volume was approximately 0.007, 0.014, 0.059, 0.025 cc/g,
respectively as shown in Fig. 9 (b), according to BJH desorption
summary. During photo Fenton-like catalysis, the well-grown
porosity and larger surface area of the catalyst allow contami-
nants to boost catalytic efficiency [41].
3
þ
2þ
32,33]. The spectra of Fe 2p 1/2 (720 eV) and Fe 2p 3/2 (711.6 eV)
is presented in Fig. 5 (d), Al binding energy located around
3.9e74.9 eV which is well matched [34]. The Sm 3d3/2 binding
energy was 1083.8 eV [35,46] which is depicted Fig. 5 (e).
SEM observed the surface and microstructure of BASF-NPs as
depicted in Fig. 6. By implementing line intersection method on
each SEM image, the grain size of BASF-NPs was deliberated. It is
3
þ
7
M-H loops of BASF-NPs were calculated at room temperature
within applied magnetic field ꢁ15 kOe to 15 kOe (Fig. 10 (a)). The
magnetic features are measured as summarized in Table S1 from M-
H loops. The varying saturation magnetization (Ms) values are
linked to different cationic position in unit cell of M-hexagonal
found that the average grain was within range of 1.20e0.50 mm. The
observed morphology of grains shape is seemed to be irregular
platelet-like hexagonal [36,37]. The size of grain is increased up to
x ¼ 0.4 as the Sm contents increased and the grain shape is
appeared spherical. The increasing grain size might be associated
with substituted Sm3 ions in hexaferrite system having lager
atomic size which repositioned on grain boundaries [38]. EDS was
used to acquire BASF-NPs from a quantitative energy dispersive
spectrum. It is obviously disclosed in a possible error range about
ferrite. The declining trend of M
s
is correlated to the substituted
non-magnetic ions. Non-magnetic having large sized substituted
ions prefer octahedral sites like 4f
system [42]. Al ions are preferred at following sites 4f
2
, 2a and 12k in M-hexaferrites
, 4f and
þ
3þ
2
1
1
2k which decreased the M
s
at x ¼ 0.0. As the substitution contents
3þ
of Sm ions increased up to x ¼ 0.2 and increase of M
s
might be
3þ
ascribed to occupancy at A-site. The Sm ions have lesser magnetic
1
(
0% for all related peaks of BASF-NPs elements like as strontium
Sr), barium (Ba), iron (Fe), samarium (Sm), aluminum (Al) and
3þ
3þ
moment than Fe ions [43] whereas, the maximum Sm ions
substitution at x ¼ 0.4 caused in declining of M because of the
s
oxygen (O). Sr, Ba Sm, Al, Fe and O are elemental mapping of all
noticed elements in EDX spectroscopy, which clearly specify the
homogeneous elemental distributions as presented in Fig. S1. TEM
explored the morphology in order to get clearer perspective of
BASF-NPs for pure and x ¼ 0.2) samples. The 3D grain shape is
presented in Fig. 7 (c). As observed in Fig. 7 BASF-NPs are platelet-
like hexagonal structure. The results of XRD and TEM confirmed
that BASF-NPs composites was successfully fabricated.
3þ
reduction of magnetization of B sub lattice by Sm ions [43].
The coercivity (H ) is an intrinsic and extrinsic feature that is
reliant on shape and size of crystalline, microstructure and cations
distribution. The significant decreasing trend of H due to magneto
c
c
crystalline anisotropy was observed by the substituted AleSm ions
at Fe site as presented in Table S1. Hc is proportionally dependent
on anisotropy field H
significant role whereas, Sm ions have larger ionic radii than Fe
a
. The substituent and host ionic radii play a
3þ
3þ

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
5
Fig. 5. XPS spectrum of BASF-NPs (x ¼ 0.2).
ions. H
the grain size was observed larger with substitution (x) as shown in
Table S1. The existence of impurity phases such as Fe and
FeSmO impacted so, Hc (Oe) is decreased while M (emu/g)
increased at x ¼ 0.2 and then decreases as the amount of Sm
increased as reported in literature [44,45]. M-hexaferrite catalyst
was effectively isolated after MB degradation with an external
applied magnetic field as presented in Fig. 10 (b).
c
is inversely proportional to grain size of M-hexaferrites as
3.2. Photo-catalytic activity of MB
3.2.1. Photo-catalyst dosage
The selected dosage of BASF-NPs (x ¼ 0.0) are consumed from
0.00 g/L to 1 g/L with constant concentration of dye 10 mg/L (MB) in
photo-degradation system. MB degradation performance of the
photo-catalyst without hexaferrite (0.00 g/L) showed a slight shift
in MB concentration. It is ascribed to photolysis degradation. The
2 3
O
3
s

6
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
Fig. 6. SEM micrographs of BASF-NPs (pure sample: Ba0.4Sr0.6Fe12
O19, x ¼ 0.0, 0.2 and 0.4).
Fig. 7. TEM micrographs of BASF-NPs (pure sample: Ba0.4Sr0.6Fe12
O
19 and x ¼ 0.2) and (c) 3D view of particles.

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
7
Fig. 8. (a) UVeVis spectra of BASF-NPs (b) Tauc’s plots of (
ah
n
)2 versus photon energy for band gap energy of pure sample, x ¼ 0.0, 0.2 and 0.4 (BASF-NPs).
concentration of BASF-NPs was increased from 0.50 to 1 g/L as a
result degradation of MB was decreased which is due to the filter
blocking effect by passage of light in reaction with reaction rate
alternative was declined the production rate of active species [47].
M-hexaferrite (BASF-NPs) exhibited optimum catalyst concentra-
tion of 0.25 g/L about 39% degradation of MB after 140 min by
photolysis. Thus, the optimal concentration of BASF-NPs was
determined 0.25 g/L at natural pH (7) as revealed in Fig. 11. (a).
ꢁ2
ꢁ1
constant k from 0.0356 to 0.0292 ꢀ 10 min . However, the more
catalyst was created to reduce light transmittance in solution, the

8
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
Fig. 10. (a) The variation trend in M ꢁ H loops of BASF-NPs and (b) the diagram shows
the degradation of MB to water.
experiment i.e. 4, 8, 12 and 16 mM as shown in Fig. 12. Upon
employing 16 mM H
2 2
O concentration, complete MB degradation
Fig. 9. (a) Isotherms of adsorption-desorption nitrogen (N2) and (b) pore volume of
pure sample, x ¼ 0.0, 0.2 and 0.4 (BASF-NPs).
occurred after 140 min in photo-Fenton-like system. It might be
attributed to the production of hydroxyl radicals ( OH) as a result of
activation by BASF-NPs catalyst. Furthermore, photo decom-
position on BASF-NPs (x ¼ 0.0) surface by forming electron-hole
ꢂ
2 2
H O
The closely-fitted lines in Fig. 11. (b) revealing a high linearity
2
ꢁ
þ
(
R ¼ 0.99) indicated that MB degradation followed pseudo-first-
pair (e /h ), or electrons generated in reaction mixture that are
3
þ
2þ
order kinetics during photolysis, which can be stated in Eq. (4) [48];
immediately trapped by Fe and react with H
which can react with H
2
O
2
to form Fe
ꢂ
ꢀ
ꢁ
2
O
2
to generate OH. But, MB degradation
C
C0
t
ꢁln
¼ kt
(4)
efficacy was reduced by using 4, 8 and 12 mM concentration of
H O and significantly affect the generation of the secondary
2
2
ꢁ
ꢂꢁ
ꢁ
ꢂ
2
causing a contest
reactive species, like HO , O
among all reactive species existing in reaction mixture. The
6 mM H concentration accelerated the production of oxidizing
2
, OH
2
and OH
where, C
0
¼ initial concentration, C
t
¼ after time (t) concentration
ꢁ
1
of MB, t ¼ irradiation time (min) and k (min ) is the rate constant
of first order reaction. The rate constant (k value) for various con-
centration of hexaferrite are presented in Fig. 11. (c). The maximum
1
2 2
O
intermediates which were accountable for MB oxidation. On the
other hand, negligible MB degradation was observed in the pres-
ence of only H O and without BASF-NPs.
2 2
ꢁ
2
ꢁ1
k value of 0.0292 ꢀ 10 min was obtained at 0.25 g/L M-hex-
aferrite dosage removing 39% of MB concentration. Therefore,
Fig. 12. (b) Demonstrates the reaction behavior corresponding to
pseudo first order reaction. At neutral pH, the complete degrada-
tion was seemed using 0.25 g/L of BASF-NPs (x ¼ 0.0) and 16 mM of
0
.25 g/L BASF-NPs dosage was chosen for further studies.
2 2
H O after 140 min reaction. This reflects a substantial enhance-
3
.2.2. Concentration effect of H
concentration is crucial for the Fenton and photo-Fenton-
like system. Several H concentrations were used in this
2 2
O
ment in MB degradation with regard to photo-catalytic system. As
shown in Fig. 12. (b) The result of MB degradation data fitting by
2 2
H O
2 2
O

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
9
Fig. 11. (a) Effect of different concentration of BASF-NPs (x ¼ 0.0) for MB photo degradation (b) pseudo first order linear transformation (c) The rate of reaction constant of BASF-NPs
x ¼ 0.0) loading at room temperature.
(
means of pseudo-first-order kinetic with R2 value of 0.99. The
pseudo-first order kinetic rate constants were k ¼ 2.66, 3.164, 3.218
shaped particle size ~ 6e7 mm. It showed that the substitution
played a significant part for the present study for degradation of MB
as well as size and shape of the particles. The best performance was
attained at pure sample and x ¼ 0.2 with photo-catalyst concen-
ꢁ2
ꢁ1
and 6.514 ꢀ 10 min with respect to 4, 8, 12 and 16 mM H
2 2
O
concentration, respectively as revealed in Fig. 12. (c).
The photo-Fenton-like catalytic performances of BASF-NPs
2 2
tration 0.25 g/L, 10 mg/L of MB, 16 mM of H O and under UV
(
Pure, x ¼ 0.0, 0.2, and 0.4) for MB degradation are revealed in
irradiation about ~100 and 99% degradation, respectively after
140 min at neutral pH (7) as shown in Table 1.
2 2
Fig. 13. In the presence of UV irradiation and H O 9.99% MB
degradation was achieved without catalyst. MB degradation was
attained ~100% for pure sample (Ba0.4Sr0.6Fe12
19) and x ¼ 0.2 after
40 min. Such results specified that, relative to x ¼ 0.0 and 0.4
Fig.13 (b) demonstrates the pseudo first order reaction behavior.
This significantly enhances MB degradation efficiency substituted
M-hexaferrite photo-catalytic system. As illustrated in Fig. 13 (b),
pseudo-first-order kinetic model with R value of 0.99 of MB
degradation data. The pseudo-first order kinetic rate constants are
O
1
2
nanoparticles, the pure sample and x ¼ 0.2 displayed the highest
photo Fenton-like activity. TEM micrographs, UVeVis spectra and
BET analysis can explain the higher catalytic activity of the pure and
x ¼ 0.2. In Fig. 7, TEM micrographs are displayed and the platelet-
like hexagonal structure of the pure sample and x ¼ 0.2 are
observed with larger particle size as shown in Table S1. The
comparatively narrow energy band gap was achieved as presented
ꢁ
2
ꢁ1
k ¼ 6.52, 3.16, 5.09 and 3.22 ꢀ 10 min with respect to (Pure,
x ¼ 0.0, 0.2 and 0.4) BASF-NPs as revealed in Fig. 13 (c).
The comparative study of dyes degradation is presented in
Table 1 by using various ferrite nanoparticles. The degradation of
dye is associated on type of nano-particles, size and morphology. In
the present study, BASF-NPs were used for the first time and
removed ~100% MB with an optimum 0.25 g/L photo-catalyst. Diao
2
2
in Fig. 8. The pure samples (5.85 m /g) and x ¼ 0.2 (8.26 m /g)
displayed a larger area than the remaining samples as revealed in
Fig. 9. While under optimal condition, MB degradation was ach-
2 4
et al. [50] explored MgFe O magnetic NPs for dye degradation
ieved about 45% in the dark (without UV light/H
2
O
2
/BASF-NPs)
efficiency of about 96.8% having spherical shaped particles of size
93 nm under UV light within 180 min. Valero et al. [12] synthesized
ꢁ
þ
which is due to lack of the electron-hole pairs (eCB þ hVB) were not
produced on BASF-NPs surface [49]. Valero et al. [12] reported pure
photo-catalyst BaFe12
in the existence of H
[10] reported MgFe
of dye at given circumstances such as pH 6.44, dosage of catalyst
O
19 M-hexaferrite for dye degradation (70.8%)
and vis irradiation in 360 min. Xing et al.
2 4
O as a catalyst and achieved 97.8% degradation
barium M-hexaferrite BaFe12
O
19/H
2
O
2
/vis-light can decompose
2 2
O
about 70.8% degradation and without vis-light dye degradation is
quite lower. Wang et al. [37] attained 95.8% degradation in 100 min
ꢁ
1
with 16.8 wt% BaFe12
O
19/g-C
3
N
4
composites having lamellar
0.625 g L
2 2
and 1.0 vol% H O in 300 min. Fatemeh and co-

10
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
Fig. 12. (a) Effect of different concentration of H
formation (c) The reaction rate constant.
2
O
2
(4e16 mM) and 0.25 g/L of BASF-NPs (x ¼ 0.0) for photo-Fenton-like degradation of MB (b) pseudo first order linear trans-
researchers synthesized SrFe12
O
19@SiO
2
@TiO
2
having sporadic
concentration required. This finding verified Ba0.4Sr0.6Fe12O19 and
hexagonal shape and their particles estimated size 122 nm and
applied photo-catalysts which exposed 80% degradation of MB
x ¼ 0.2 photo-catalyst endured stable over a wide pH range. Further
the extra change of pH esteems by acidification of treated waters
could be sidestepped.
within 180 min [14]. Wang et al. [37] fabricated 16.8 wt% BaFe12
g-C (polymeric) nanocomposites for dye degradation in pres-
ence of UV light/H . The degradation was attained about 95.80%
under UV irradiation and 56.60% without light irradiation in
00 min. Debesh et al. [51] introduced SrFe12 19 having plate-like
19
O /
3 4
N
2 2
O
3.2.4. MB concentration
The different primary MB concentrations such as 10, 20 and
0 mg/L was selected to measure MB degradation with this optimal
1
O
3
particles shape and energy band gap 1.70 eV for MB degradation
in the presence of visible light, MB degradation was achieved 95%
with 270 min.
condition (0.25 g/L of pure sample; Ba0.4Sr0.6Fe12
under UV irradiation). At MB concentrations of 10, 20 and
0 mg/L, 99%, 75% and 50% degradation were attained, respectively
Fig. 15). The degradation efficiency slows down at higher con-
O19 and 16 mM of
2 2
H O
3
(
centration of MB due to MB adsorption on photo-catalyst surface
may reach saturation level. The transferred electrons to photo-
catalyst surface was intervened by adsorbed MB [54]. Addition-
ally, on the photo-catalyst surface the produced intermediates and
MB could compete with each other for limited reactive sites, hence
inhibiting the overall degradation of MB. It is accepted that increase
of MB concentration influences light infiltration throughout the
solution. The level of light infiltration at high beginning concen-
trations is diminished which will result the reaching of fewer
photons at the surface of catalyst [55].
3
.2.3. Impact of pH
Mostly, pH range adjustment assumes a significant job in HC
Fenton reaction since this parameter determines the generation
rate of hydroxyl radicals. Fig. 14 displays that after 140 min, ~100%
degradation of MB dye by pure sample (Ba0.4Sr0.6Fe12O19) photo-
catalyst was optimally achieved at pH 7. The oxidative volume of
hydroxyl radicals was inclined to decline due to a decrease in the
oxidation potential of hydroxyl radicals, which resulted in degra-
dation efficacy up to 91.96% at pH 12 [52]. While at lower pH 3
about 95.61% degradation was achieved which may be ascribed
protonating H
icals [53]. It can be clearly observed that Ba0.4Sr0.6Fe12
2
O
2
and disfavoring the formation of hydroxyls rad-
19 photo-
O
3.2.5. Proposed degradation pathway of MB
catalyst is relatively comparable to further reported photo-
catalysts whether catalyst concentration and reaction time
The accumulation, generation and degradation of MB molecules
by photo-Fenton-like process in pure sample/H O /UV system were
2 2
[
12,14,37]. Hence, Ba0.4Sr0.6Fe12
O
19 and x ¼ 0.2 are potential photo-
monitored by UPLC-MS analysis. The chromatograms of generated
intermediates as a function of reaction-time are presented in
Fig.16. It can be clearly observed that generated intermediates were
catalysts in the photo-Fenton-like system which establishes the
excellent degradation of MB within less time and catalyst

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
11
Fig. 13. (a) Effect of BASF-NPs (pure sample, x ¼ 0.0, 0.2 and 0.4) having concentration 0.25 g/L, 16 mM H
2 2
O for photo-Fenton-like degradation of MB (b) pseudo first order linear
transformation (c) The reaction rate constant.
Table 1
Comparative analysis of photo-degradation of MB for various BASF-NPs photo-catalysts, Present work: PW.
Oxidation system
Ba0.4Sr0.6Fe12 19 (pure)/H
Reaction parameters
Degradation efficiency (%) Ref.
O
2
O
2
/UV Light
10 mg/L of MB; Hexaferrite (0.25 g/L); H
2
O
2
(16 mM); reaction time (140 min)
~100
PW
x ¼ 0.0/H
x ¼ 0.2/H
x ¼ 0.4/H
2
2
2
O
O
O
2
2
2
/UV light
/UV light
/UV light
98.8
99
98
96.8%
70.8
80
PW
PW
PW
MgFe
2
O
4
/H
19/H
19@SiO
6.8 wt% BaFe12
BaFe /UV light
NiFe2ꢁxAl /Visible light
19/Ag PO
19/Visible light
2
O
2
/Vis light
/Vis light
@TiO /UV light
19/g-C /H
RhB (10 mg/L); catalyst (1 g/L); 1% of H
MB (10 mg/L); catalyst (0.75 g/L); 12 mM of H
MB (50 mg/L); catalyst (0.03 g/L); reaction time (180 min)
2
O
2
; reaction time (180 min)
; reaction time (360 min)
[50]
[12]
[14]
[37]
[64]
[65]
[66]
[51]
BaFe12
O
2
O
2
2
O
2
SrFe12
O
2
2
1
O
3
N
4
2
O
2
/Vis light Tetracycline and RhB (10 mg/L); catalyst (1 g/L); 0.5 mL of H
2
O
2
reaction time (100 min) 95.8
2
O
4
Methyl orange (20 mg/L); catalyst (5 g/L); reaction time (120 min)
MB (5 ppm/100 mL); catalyst (40 mg/100 mL); reaction time (120 min)
BPA (20 mg/L); 70 mg of catalyst; Xe arc lamp; reaction time (120 min)
MB (10.0 ppm); catalyst (1 g/L); reaction time (270 min)
90
x
O
4
82.58
79.8
95
10% BaFe12
O
3
4
SrFe12
O
transformed further and degraded in 140 min. The proposed
mechanism of degradation is presented in Fig. 16 following two
paths.
which generate different intermediates at m/z ¼ 226, 198, 230, 203.
The peak at m/z ¼ 203 indicates the breakdown of thionine ring by
releasing sulfur dioxide which boost the opening of phenothiazine
heterocyclic structure. The peak at m/z ¼ 94 specified the removal
For the MB only, a strong signal appeared at m/z ¼ 284 which
2
ꢁ
links to dye solution. Based on the generation of sulfate ion SO
4
2
of NO from relative parent molecule. The phenolic group further
and nitrate ion NO3 , the predominant suggested mechanism fol-
ꢁ
degraded and transformed into inorganic molecules, such as H
and CO which represents a comprehensive photocatalytic degra-
dation of MB accelerated by OH radicals.
O
2
þ
lowed by the oxidation of CeS ¼C group thionine ring into two
2
ꢂ
paths. Path A followed by the oxidation of dimethylamino group

12
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
Fig. 14. The influence of pH (3, 7 and 12) on MB degradation with conditions: UV,
.25 g/L of pure sample; Ba0.4Sr0.6Fe12 19, 16 mM H and 10 mg/L of MB after
40 min.
0
O
2 2
O
1
Fig. 16. Proposed degradation reaction mechanism of MB by using pure sample;
Ba0.4Sr0.6Fe12 19 (0.25 g/L), 16 mM of H under UV irradiation.
O
2 2
O
3.2.6. Total organic carbon (TOC)
To explore the mineralization of MB catalyzed by utilizing TOC
analyzer. The maximum mineralization of MB (10 mg/L) was
attained about 89.85% by using pure sample (0.25 g/L), 16 mM of
2 2
H O under UV irradiation which exhibited a high catalytic activity
as shown in Fig. 17. Conversely, less mineralization of MB was
seemed with similar comparable amounts of further catalysts un-
der optimum condition. Such as, 79.71, 77.09 and 88.5% minerali-
zation efficiencies were found in the cases of x ¼ 0.0, 0.2, and 0.4,
respectively. The possible accumulation of dead-end metabolites or
intermediate products of MB might be responsible for the partial
mineralization of MB as compared to their total degradation.
Fig. 15. Impact of initial MB concentration (10, 20 and 30 mg/L) on MB degradation
under optimum condition at pH 7 after 140 min.
For instance, the demethylation reaction proved the maximum
absorption peaks from parent MB molecules by the blue-shifts
accompanying the many intermediated peaks at m/z ¼ 348, 189,
125, 109 as resented in mechanism scheme by path B. The formation
of different intermediates indicates the variation in the concentra-
tion and composition of degradation products. The peak appeared at
m/z ¼ 348 is because of the hydroxylation of parent MB molecule by
replacement of dimethylamino groups. The scission of central ring
lead to generate peaks at m/z ¼ 189, 124 accordingly. Furthermore,
the desulphonenation reaction of scission products produced diols
and then phenol. Fig. S2 presented to intermediate fragments
generated during degradation reaction. After 60, and 120 min
appearance of sharp signals represent the presence of oxidative
byproducts. The small low intensity peaks show the generation of
3
.2.7. Recyclability and leaching of BASF-NPs
A persistent issue of photo-catalysts is its reusability. BASF-NPs
stability is attributed in the real implementation with long-term
reusability. Four cycles of MB degradation were performed to
explore pure sample photo-catalyst effect at optimal conditions.
Photo-catalyst was removed easily by applying external magnet,
ꢃ
washed five time with fresh water and then dried in oven at 150 C
after completing each cycle. For each next cycle recovered photo-
catalyst concentration was added in water under same optimal
conditions. As presented in Fig. 18, after 140 min, the removal of MB
for four cycles were 99%, 98.96%, 98.94 and 98.90%, respectively.
Hexaferrite photo-catalyst was not showed any significant least
inorganic fragments having low molecular weight like CO
2 2
and H O,
which reveal the MB was degraded completely over time [56].

G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
13
hydroxyl radicals triggered the decomposition of H
HC photo-catalyst.
2
O
2
catalyzed by
3
.2.8. Photocatalytic mechanism in BASF-NPs system
To explore the reactive species contribution to MB degradation
mechanism in BASF-NPs/H /UV irradiation system. The hydroxyl
2 2
O
radical’s production was assessed by fluorescence technique and
terephtalic acid (TA) was used as a probe during the degradation
phase. The fluorescence spectra were generated between 340 and
550 nm. From Fig. S4, the active photo-generated hydroxyl radicals
were in HC photo-Fenton-like system. At 460 nm the fluorescence
signal enhanced by increasing the time which clearly show TA re-
ꢂ
action with OH and formed 2-hydroxylterepthalic acid. The
maximum intensity of fluorescence is associated directly with the
ꢂ
amount of OH radicals [57,58]. BASF-NPs as a HC photocatalyst
ꢂ
show that generated OH species play a significant role in this
system.
MB degradation mechanism by (x ¼ 0.2) BASF-NPs/H
2 2
O /UV
irradiation system at neutral pH (7) as shown in Fig. 19. Normally,
HC catalyst system require mass transfer of pollutants to the surface
of the catalyst [59]. Without light the MB was adsorbed on hex-
aferrites surface. While in the presence of UV light, the absorbance
Fig. 17. TOC analysis for BASF-NPs (pure sample; Ba0.4Sr0.6Fe12
photo-catalysts after 140 min.
O
19, x ¼ 0.0, 0.2 and 0.4)
ꢁ
þ
of photo energy from UV light, the electron-hole pairs (eCB þ hVB
)
were produced on (x ¼ 0.2) BASF-NPs surface (Eq. (5)) [49]. The
BASF-NPs (x ¼ 0.2) photo Fenton-like reaction enhancement could
be due to AleSm substitution being able to accelerate electron
transfer production by enhancing the interface between H O , and
performance after four cycles, which revealed the elevated strength
and endorsing their commitment for water pollution treatment.
The FTIR examination of used NPs after four cycles, also revealed
that there were no apparent structural and chemical changes in
both fresh and used samples. This investigates an excellent stability
of presented photocatalyst (Fig. S3).
During the implementation of HC photo-catalysts, major
concern must be paid to the issue of ion leaching. The leaching of
Ba, Sr, Al, Sm and Fe ions from the surface of the photo-catalyst was
explored after 140 min of MB treated solution after first cycle under
optimal condition. In present study, the level of leached Ba, Sr, Al,
Sm and Fe ions in the solution approximately was obtained 0.001,
2
2
3
þ
ꢂ
Fe resulting in more OH radical ensuing from a high rate of H O
2
2
decomposition [60]. XPS valance band spectra of sample (x ¼ 0.2)
was depicted in Fig. S5 for the determination of the valance band
energy (VB). The measured VB energy is positioned at 3.10 eV, while
the band gap (E ¼ 1.74 eV) was calculated in Fig. 8 (x ¼ 0.2). As
g
stated by this given equation (E ¼ E - E ), the conduction band
CB
VB
g
energy (ECB ¼ 1.36 eV) was measured [61]. Definitely, BASF-NPs
would easily have excited in the presence of UV light due to nar-
ꢁ
þ
row band gap ultimately the photo electron-hole pairs (e þ h
CB
VB
)
0
.003, 0.00, 0.00 and 0.001 mg/L, respectively. There was a very
were generated. The photo-electrons at CB could respond with
oxygen molecule and reduce it to superoxide radical anion. Also,
minor leaching in BASF-NPs photo-catalyst. The catalytic impact of
such a minor leached ions concentration that further demonstrates
HC catalytic reaction happens on BASF-NPs photo-catalyst surface.
Similarly Xiao et al. [57] reported that the degradation of MB by
ꢁ
ꢂ
photo-electrons were produced OH ions and OH radical in the
þ
ꢁ
presence of H O . The holes (h ) react with H O and OH ions in
2
2
VB
2
ꢂ
the presence of hexaferrites to generate OH radical (Eq. (6)) or
ꢁ
ꢂ
þ
direct oxidation. These active species like (O
liable for MB molecule degradation having some other products,
CO and water [62,63]. The suggested photocatalytic degradation
2
, OH and hVB) are
2
mechanism for BASF-NPs may be presented as follows;
Fig. 18. Operational life of pure sample; Ba0.4Sr0.6Fe12O19 photo-catalyst (0.25 g/L),
1
6 mM of H under UV irradiation system at neutral pH.
2
O
2
Fig. 19. The MB degradation mechanism by BASF-NPs under UV light.

14
G.A. Ashraf et al. / Journal of Alloys and Compounds 821 (2020) 153410
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2
ꢂ
ꢂ
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ꢁ
2
2
2
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ꢁ
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2 2
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[
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ꢀ
Author contribution
Ghulam Abbas Ashraf: Major experiments have been carried out
in the manufacture of nanoparticles and experimental application
and writing. Raqiqa Tur Rasool: The chromatograms of the gener-
ated intermediates as a function of the reaction time have been
completed. Muhammad Hassan: The work’s novelty is established
and directed. Lanting Zhang: The work’s novelty is established,
directed and supported financially.
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Declaration of competing interest
The authors declare that there are no conflicts of interest.
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