Topics in Current Chemistry (2020) 378:3
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may represent an important source of waste-derived sulfur. Physical–mechanical
separation by flotation, chemical modification by sulfide addition, and extraction
via supercritical H 2 O or CO 2 are some of the most common processes for removing
this element from the residue [65]. However, further purification steps must be optimized to be able to consider the obtained materials suitable for producing sulfide
catalysts. A very interesting case is the use of waste pig bristles as S (and C) source
for the production of metallic sulfides, considering that 225,000 tons are produced
per year [66, 67]. Figure 4a, b presents some results for microwave-assisted valorization of pig bristles to produce Cu 2 S, employed in the photodegradation of methyl
red under light-emitting diode (LED) irradiation conditions. Figure 4a shows the
X-ray diffraction (XRD) patterns for three samples which were prepared by varying the amount of sodium hydroxide (employed to accelerate the degradation of pig
bristles) during microwave-assisted synthesis [67]. The coral-like homogeneous
Cu 2 O structure obtained showed activity under all experimental conditions tested.
The study was performed with an LED lamp (6A) of 465 nm (blue), 515 nm (green),
and 630 nm (red), as well as white light (as simultaneous illumination of the three
LEDs). As shown in Fig. 4b, a higher degradation of methyl red was obtained using
white illumination conditions, which outperformed the photocatalytic response of
the P25 titania reference [67]. The authors expanded the idea of using pig bristles
as raw materials for the synthesis of two additional compounds, ZnS and Ag/Ag 2 S,
as recently reported, both with potential photocatalytic applications [66, 68]. As a
representative example, Fig. 4c shows the XPS analysis of a series of ZnS materials.
The Zn and S XPS regions confirmed the presence of the ZnS structure, while some
differences were recorded in the C1s XPS region. XPS deconvolution analysis indicated that a strong interaction could occur between C and Zn which must be considered during the production of this type of material [68].
5 Carbon Quantum Dots: Biomass‑derived
Carbon quantum dots (CQDs) have gained increasing attention in recent years as an
attractive alternative to other types of multicolor emissive materials such as quantum dots (QDs). QDs possess inherent disadvantages associated mainly with their
high toxicity, while CQDs have been well recognized for their low/nontoxic characteristics and biocompatible features, being good candidates for use for in vivo
applications including cell imaging, drug delivery, visible light bactericidal activity,
and chemical sensing. In addition to biological applications, the use of CQDs as
photocatalytic materials for pollutant degradation, solar devices, and in photo/electrochemical water splitting has steadily increased, taking advantage of their high solubility and aqueous affinity, chemical/photo and colloidal stability, notable optical
Fig. 4 a X-ray diffraction spectra of Cu 2 S samples prepared using pig bristles as S and C source [67]. b
Photodegradation results of methyl red using synthesized samples and P25 reference. c XPS deconvolution analysis of C, Zn, and O elements [68]
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Reprinted from the journal
1 3
may represent an important source of waste-derived sulfur. Physical–mechanical
separation by flotation, chemical modification by sulfide addition, and extraction
via supercritical H 2 O or CO 2 are some of the most common processes for removing
this element from the residue [65]. However, further purification steps must be optimized to be able to consider the obtained materials suitable for producing sulfide
catalysts. A very interesting case is the use of waste pig bristles as S (and C) source
for the production of metallic sulfides, considering that 225,000 tons are produced
per year [66, 67]. Figure 4a, b presents some results for microwave-assisted valorization of pig bristles to produce Cu 2 S, employed in the photodegradation of methyl
red under light-emitting diode (LED) irradiation conditions. Figure 4a shows the
X-ray diffraction (XRD) patterns for three samples which were prepared by varying the amount of sodium hydroxide (employed to accelerate the degradation of pig
bristles) during microwave-assisted synthesis [67]. The coral-like homogeneous
Cu 2 O structure obtained showed activity under all experimental conditions tested.
The study was performed with an LED lamp (6A) of 465 nm (blue), 515 nm (green),
and 630 nm (red), as well as white light (as simultaneous illumination of the three
LEDs). As shown in Fig. 4b, a higher degradation of methyl red was obtained using
white illumination conditions, which outperformed the photocatalytic response of
the P25 titania reference [67]. The authors expanded the idea of using pig bristles
as raw materials for the synthesis of two additional compounds, ZnS and Ag/Ag 2 S,
as recently reported, both with potential photocatalytic applications [66, 68]. As a
representative example, Fig. 4c shows the XPS analysis of a series of ZnS materials.
The Zn and S XPS regions confirmed the presence of the ZnS structure, while some
differences were recorded in the C1s XPS region. XPS deconvolution analysis indicated that a strong interaction could occur between C and Zn which must be considered during the production of this type of material [68].
5 Carbon Quantum Dots: Biomass‑derived
Carbon quantum dots (CQDs) have gained increasing attention in recent years as an
attractive alternative to other types of multicolor emissive materials such as quantum dots (QDs). QDs possess inherent disadvantages associated mainly with their
high toxicity, while CQDs have been well recognized for their low/nontoxic characteristics and biocompatible features, being good candidates for use for in vivo
applications including cell imaging, drug delivery, visible light bactericidal activity,
and chemical sensing. In addition to biological applications, the use of CQDs as
photocatalytic materials for pollutant degradation, solar devices, and in photo/electrochemical water splitting has steadily increased, taking advantage of their high solubility and aqueous affinity, chemical/photo and colloidal stability, notable optical
Fig. 4 a X-ray diffraction spectra of Cu 2 S samples prepared using pig bristles as S and C source [67]. b
Photodegradation results of methyl red using synthesized samples and P25 reference. c XPS deconvolution analysis of C, Zn, and O elements [68]
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8
Reprinted from the journal