Steel sludge was used as a source of technical zinc oxide (ZnO
L
) for the preparation of ZnO–graphene oxide (ZnO
L
–GO) composite with photocatalytic effects. The specific surface of the ...manufactured product was determined by
S
BET
method, and structural analysis was performed by FTIR spectroscopy. The photocatalytic efficiency of the ZnO
L
–GO composite was studied using optical methods (UV–Vis spectroscopy, photoluminescence). The obtained results were confronted with a model composite prepared from pure components. It was found that the prepared ZnO
L
–GO composite showed excellent photodegradation activities against the azo dye Acid Orange 7 in comparison with the model composite. The presence of other metal oxides in ZnO
L
in conjunction with GO causes a significant increase in the photocatalytic efficiency of the prepared composite material, which can be explained by the modification of the electronic structure and more efficient separation of charge carriers. The obtained results show new possibilities in the field of processing and further use of metallurgical waste.
Graphitic carbon nitride (CN) was synthesized from guanidine hydrochloride (G), melamine (M) and dicyandiamide (DCDA). The CN materials synthetized from the pure precursors and their mixtures were ...characterized by common methods, including thermal analysis, and their photocatalytic activities were tested by the degradation of selected organic pollutants, such as amoxicillin, phenol, Rhodamine B (RhB). Remarkable changes in their texture properties in terms of particle sizes, specific surface areas (SSA) and consequently their photocatalytic activity were explained by the role of guanidine hydrochloride in their synthesis. The SSA increased due to the release of NH
and HCl and its complex reactions with melamine and DCDA forming structure imperfections and disruptions. The photocatalytic activity of the CN materials was found to be dependent on their SSA.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Graphitic carbon nitride (g-C
N
, hereafter abbreviated as CN) was prepared by the heating of melamine (CN-M) and melamine-cyanurate complex (CN-MCA), respectively, in air at 550 °C for 4 h. The ...specific surface area (SSA) of CN-M and CN-MCA was 12 m
g
and 225 m
g
and the content of oxygen was 0.62 wt.% and 1.88 wt.%, respectively. The band gap energy (E
) of CN-M was 2.64 eV and E
of CN-MCA was 2.73 eV. The photocatalytic activity of the CN materials was tested by means of the decomposition of antibiotics ofloxacin and ampicillin under LED irradiation of 420 nm. The activity of CN-MCA was higher due to its high SSA, which was determined based on the physisorption of nitrogen. Ofloxacin was decomposed more efficiently than ampicillin in the presence of both photocatalysts.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A novel analysis was conducted on the friction and wear properties of a commercial friction material formulation with the addition of bulk (named: gCN) and exfoliated (named: TEX6) graphitic carbon ...nitride in varying quantities: 4.5, 9, 13.5, and 18 wt%. The analysis was two-fold. In the first part, the samples were tested in the form of pins on a pin on disc testing equipment. The typical trend was that the friction coefficient magnitude increased with the addition of gCN. On the other hand, the friction coefficient decreased with the TEX6 addition. The pin wear reduced with the addition of gCN until 9 wt%. Beyond this amount, an increase in pin wear was observed. The TEX6 samples generally noted a decrease in pin wear with the increase in its content. An improvement in the characteristics of the secondary plateaus was seen with the increase in both gCN and TEX6 content. Through this study, the 13.5 wt% addition of both gCN and TEX6 was considered to display permissible friction and wear magnitude, and desirable extension and compaction of secondary contact plateaus. In the second part of the study, the formulation with 13.5 wt% of gCN and TEX6 was tested on a subscale dynamometer to replicate a real-life braking scenario. The friction and wear magnitudes were similar to the pin on disc study and the extension of the secondary contact plateaus was better than the virgin formulation. This study provides a complete analysis of the feasibility of the inclusion of g-C3N4 variations in automotive braking applications.
•Wear analysis on two kinds of gCN in a friction material formulation was conducted.•Bulk gCN behaved as an abrasive and exfoliated gCN behaved as a lubricant.•The most feasible gCN and TEX6 addition was 13.5 wt% in the CFM formulation.•The pin on disc and subscale dynamometer tests fetched similar, desirable results.
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GEOZS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study compares the effect of the addition of two types of lubricants on the dry sliding behavior of a simplified Cu-free phenolic resin-based composite material. The lubricants were commercial ...graphite and exfoliated graphitic carbon nitride (codenamed: TEX6). The graphite particles were rounded and of ‘flaky’ character. The TEX6 particles were not only flaky, but also irregular in shape, and ‘fluffy’. Both lubricants were added individually in the basic formulation and subjected to dry sliding tests on pin-on-disc testing equipment in mild conditions and against a grey cast-iron counterface. The tests with TEX6 observed a stable steady state in the friction coefficient (CoF) with lower scatter and lower average friction coefficient and pin wear magnitude when compared to samples containing graphite. Additionally, the worn surfaces of the TEX6-containing samples had extremely smooth, compact, and continuous secondary plateau coverage when compared to the graphite-containing samples. The counterface paired with the TEX6-containing samples observed much lower abrasive action compared to the graphite-containing samples. Through the wear testing and further evaluation of the secondary plateaus, the possible addition of TEX6 as a lubricant in friction material composition was explained, making it a promising component for automotive braking applications.
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•Acetate leachate of steel sludge used as precursor for GO/ZnO and gCN/ZnO composites.•Significantly better photocatalytic properties of GO/ZnO-L and gCN/ZnO-L composites.•Effect of ...adsorption on the degradation efficiency of GO/ZnO-based composites.
Acid leachate from steel sludge was used as a source of zinc oxide (ZnO-L) for the preparation of photocatalytically active composites based on GO/ZnO-L and g-C3N4/ZnO-L (further denoted as gCN/ZnO-L). The prepared composites were characterized using UV–Vis spectrophotometry, SBET, XRD, FTIR and DRS. The photocatalytic efficiency was tested using the photodegradation of azo dye Acid Orange 7. The obtained results were confronted with model composites prepared from pure components. For GO/ZnO-L and gCN/ZnO-L samples, the degradation efficiency was found to be 60.2 % and 51.5 %, respectively. While in the case of gCN/ZnO-L composites, it was purely photochemical degradation, in the case of GO/ZnO-L composites adsorption was significantly co-applied. For both composites containing ZnO-L, a higher photo-degradation activity against azo dye was found compared to the model composites. The reason is the modification of the electronic structure and the emergence of new quantum levels between the valence band and the conduction band of ZnO and gCN due to the presence of other metal oxides in ZnO-L, which leads to a more efficient separation of photo-generated charge carriers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Bare and oxygen doped graphitic carbon nitride were synthetized by the thermal polymerization of melamine (CN-M) and the mechanical mixtures of melamine and cyanuric acid, respectively, at 550 °C for ...4 h. The ratios of melamine and cyanuric acid were 1:0.5, 1:1 and 1:2 (CN-MCA1, CN-MCA2 and CN-MCA3). The content of oxygen increased from 1.88 wt% (CN-M) to 3.93 wt% (CN-MCA3) and the specific surface area increased from 14 to 41 m2 g−1. The prepared CN materials were characterized by the elemental analysis, UV-Vis diffuse reflectance, X-ray diffraction, Fourier transform infrared spectrometry, the physisorption of nitrogen, scanning electron and high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, the determination of zeta potentials, and the Mott-Schottky method.
The addition of cyanuric acid led to partial changes in the CN morphology, as documented by occurrence of CN tubes, increase in the specific surface area and was a source of additional -O- and -OH moieties which modified the CN surface in addition to the spontaneous oxygenation observed in CN-M. The above effects positively influenced photocatalytic activity of the CN materials as demonstrated using Rhodamine B (RhB) and the Ofloxacin antibiotics. The photocatalytic decomposition of Ofloxacin was more efficient than that of RhB and differed in kinetics (first-order vs. zero-order reaction). The reusability and stability of the CN materials was verified by repeating batch photocatalytic decompositions of Ofloxacin experiments for five times.
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•Oxygen doped g-C3N4 (OCN) was synthetized from melamine and cyanuric acid.•Cyanuric acid was used to control the content of oxygen in the OCN materials.•Surface properties of g-C3N4 were modified by its doping with oxygen.•OCN improved the photocatalytic decomposition of Rhodamine B and Ofloxacin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Graphitic carbon nitride and soot (g-C3N4/soot) metal-free nanocomposites were synthesized by a simple one-pot thermal synthesis from mixtures of dicyandiamide with different volumes of xylene. The ...soot nanoparticles of 17.7 ± 1.7 nm in size were observed on the g-C3N4 surface.
The band gap energies of the synthesized nanocomposites decreased from 2.65 eV to 2.53 eV with the increasing content of soot nanoparticles. The photocatalytic activity of the g-C3N4/soot nanocomposites to degrade phenol, ofloxacin, and ampicillin under the LED irradiation of 420 nm was investigated. Time-resolved photoluminescence measurements, electrochemical impedance spectroscopy, and trapping experiments indicated that photoinduced electrons were accumulated in the soot particles, reacted with oxygen forming superoxide radicals, which decomposed the organic compounds. The degradation efficiency decreased in the sequence ofloxacin > ampicillin > phenol. The g-C3N4/soot nanocomposites were investigated for the photocatalytic degradation of organic compounds for the first time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•P-doped g-C3N4 was prepared using melamine and hexachlorocyclotriphosphazene (HCCP).•Initial HCCP concentration determined the nature of P in the g-C3N4 structure.•The doping ...mechanism of g-C3N4 with P using melamine and HCCP was proposed.•The optimum amount of HCCP regarding to the photodegradation activity was found.
The synthesis of P-doped graphitic carbon nitride (PCN) by in situ doping via co-pyrolysis of melamine and hexachlorocyclotriphosphazene (HCCP) is being investigated. The amount of HCCP varies between 2 and 40 wt% and the results show continuous enrichment of graphitic carbon nitride (CN) by phosphorus. The detailed characterization of prepared samples leads to the proposition of the occurrence of phosphorus in synthesized samples as well as to the proposition of a P-doping mechanism. The results of the characterization techniques used indicate that with up to 1.2 wt% of phosphorus in final PCN, phosphorus predominantly substitutes carbon in the structure. An increase of the phosphorus content to 2.44 wt% causes its incorporation into substitutional positions and part of the phosphorus occurs in other forms. PCN with 2.44 wt% of phosphorus obtained from the mixture of melamine with 20 wt% of HCCP thermally treated at 525 °C shows the highest photodegradation activity under VIS irradiation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Exfoliated graphitic carbon nitride (g-C3N4) and two commercially available nanomaterials from titanium dioxide (P25 and CG300) were tested for the photocatalytic degradation of paracetamol (PAR), ...ibuprofen (IBU), and diclofenac (DIC). Prior to photocatalytic experiments, the nanomaterials were characterized by common methods, such as X-ray diffraction (XRD), UV–VIS diffuse reflectance spectroscopy (DRS), Fourier transformed infrared spectroscopy in attenuated total reflection mode (FTIR–ATR), transmission electron microscopy (TEM), physisorption of nitrogen, and dynamic vapor adsorption (DVS) of water. The sizes and specific surface area (SSA) of the TiO2 nanoparticles were 6 nm and 300 m2·g−1 for CG300 and 21 nm and 50 m2·g−1 for P25. The SSA of g-C3N4 was 140 m2·g−1. All photocatalytic experiments were performed under UV (368 nm), as well as VIS (446 nm) irradiation. TiO2 P25 was the most active photocatalyst under UV irradiation and g-C3N4 was the most active one under VIS irradiation. Photodegradation yields were evaluated by means of high performance liquid chromatography (HPLC) and reaction intermediates were identified using gas chromatography with mass detection (GC–MS). Paracetamol and ibuprofen were totally removed but the intermediates of diclofenac were observed even after 6 h of irradiation. Some intermediates, such as carbazole-1-acetic acid, 2,6-dichloraniline, and hydroxylated derivates of diclofenac were identified. This study showed that g-C3N4 is a promising photocatalyst for the degradation of pharmaceuticals in an aqueous environment, under visible light.
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