Abstract
The purpose of this investigation was to construct amended mesoporous Mn
3
O
4
/g-C
3
N
4
photocatalysts of various loadings of mesoporous Mn
3
O
4
nanoparticles (1,2,3 and 4 wt%) for reinforced remediation of mercury ions (Hg
2+
)
under visible light illumination. It was performed via decorating g-C
3
N
4
nanosheets with finite portions of the prepared mesoporous Mn
3
O
4
NPs by employing hard and soft templates. The optimized 3 wt% Mn
3
O
4
/g-C
3
N
4
heterojunction gained confined bandgap (2.24 eV) as well as great surface area (140 m
2
g
-1
) that support the application of such heterojunction for efficacious removal of Hg
2+
under visible light. Morphological examination elucidated that the dispersed Mn
3
O
4
NPs over g-C
3
N
4
nanosheets were of spherical shape with particle dimension of 10-15 nm. Hg
2+
was removed significantly over the formed Mn
3
O
4
/g-C
3
N
4
nanocomposites when related to the pure materials (Mn
3
O
4
NPs and g-C
3
N
4
). It was confirmed that Mn
3
O
4
content, incorporated to g-C
3
N
4
nanosheets, largely influenced the efficiency corresponding to the Hg
2+
photoreduction such that appropriating 3 wt% Mn
3
O
4
was capable of accomplishing complete removal of Hg
2+
whereas, pure g-C
3
N
4
was able to accomplish the same process by the efficiency of 15% after illumination for 60 min. Similarly, fast rate of Hg
2+
photoreduction was accessed when 3% Mn
3
O
4
/g-C
3
N
4
nanocomposite (485
µ
mol g
–1
h
–1
) was administered while the photoreduction reaction was very slow with smaller rate magnitudes when pure g-C
3
N
4
(82
µ
mol g
-1
h
-1
) or pure Mn
3
O
4
NPs (120
µ
mol g
-1
h
-1
) were adopted. The powerful Hg
2+
removal over the established heterojunctions can basically be associated with the larger attained surface area as well as the declined bandgap. Besides, the great dispersion of the small-sized
Mn
3
O
4
NPs and the mesoporous structure of the formed heterojunctions participated significantly in efficient Hg
2+
removal. The improved characteristics of the prepared heterojunctions led to strong absorption of visible light and fast transference of reactant
species, leading to enhanced photocatalytic efficiency. Recyclability experiments demonstrated that neither the photocatalytic performance nor the structure of the mesoporous Mn
3
O
4
/g-C
3
N
4
heterojunction was altered after being reused for Hg
2+
removal from aqueous solutions.