Photodegradation Of 4-nitrophenol Research Articles

Light driven photodegradation of 4-nitrophenol with novel Co and Cu phthalocyanine in aqueous media

In this work, we have used two different metal centered water soluble phthalocyanines for the degradation of 4-nitrophenol in water media. In the photodegradation reactions that took place in the photoreactor for 1 h without using any oxidant, 4-nitrophenol compound was completed with 95% (for CoPc) and 97% (for CuPc) conversion to toxic and non-harmful species. The hydroquinone compound was identified as the main product and the benzoquinone compound as the by-product. The turnover number for Cu phthalocyanine was 1896 and for Co phthalocyanine was 2101. Finally, recovery studies were carried out for water soluble Cu phthalocyanine used as photocatalyst and the number of cycles was determined as 7.

Green Synthesis of an Activated Carbon-Supported Ag and ZnO Nanocomposite for Photocatalytic Degradation and Its Antibacterial Activities.

In this study Ag nanoparticles (AgNPs), ZnO nanoparticles (ZnONPs), and Ag/ZnO nanocomposites were greenly synthesized and loaded on activated carbon via three different routes: simple impregnation, successive precipitation, and co-precipitation. Neem leaf extract was used as a reducing and stabilizing agent. The morphological and structural properties of the synthesized nanocomposites have been examined using different analytical techniques such as XRD, SEM, FTIR, and UV. The antibacterial and catalytic activity of the synthesized nanocomposites were examined and compared. The results showed that AgNPs loaded on activated carbon (Ag/AC) has the best catalytic activity compared to the other nanocomposites, which is attributed to the good dispersal of AgNPs on the surface of activated carbon. Furthermore, AgNPs showed the best antibacterial effect on eight out of 16 tested pathogens. Results also showed that the order of precipitation is an important factor, as both antibacterial activities and photodegradation activities were higher for ZnO/Ag/AC than Ag/ZnO/AC. Furthermore, the co-precipitation method was shown to be better than the successive precipitation method for 4-nitrophenol photodegradation and 14 out of the 16 antibacterial tests performed.

Fresh versus Photo-recalcitrant Secondary Organic Aerosol: Effects of Organic Mixtures on Aqueous Photodegradation of 4-Nitrophenol

In the atmosphere, brown carbon (BrC) molecules can contribute to photochemistry and to the warming and evaporation of cloud droplets. The lifetimes of BrC molecules in these cloud droplets are not...

Photodegradation of 4-nitrophenol over B-doped TiO2 nanostructure: effect of dopant concentration, kinetics, and mechanism.

The 4-nitrophenol (4-NP) is one of the carcinogenic pollutants listed by US EPA and has been detected in industrial wastewater. This study investigates the photocatalytic degradation of 4-NP with TiO2 and boron (B)-doped TiO2 nanostructures. The degradation on undoped and B-doped TiO2 with various boron loadings (1-7%) was studied to establish a relationship between structure, interface, and photo-catalytic properties. The results of XRD, micro Raman, FTIR, and HRTEM show that the B doping has improved the crystallinity and induces rutile phase along with anatase (major phase). The N2 adsorption-desorption, SEM-EDX, and XPS indicated that the B induced the formation of mesoporous nanostructures in TiO2 and occupies interstitial sites by forming Ti-O-B type linkage. The surface area of pure TiO2 was decreased from 235.4 to 63.3m2/g in B-TiO2. The photo-physical properties were characterized by UV-Vis DRS, which showed decrease in the optical band-gap of pure TiO2 (2.98eV) to B-TiO2 (2.95eV). The degradation results demonstrated that the B doping improved the photocatalytic activity of TiO2; however, this improvement depends on the B concentration in doped TiO2. B-doped TiO2 (> 5% B) showed 90 % degradation of 4-NP, whereas the undoped TiO2 can degrade only 79 % of 4-NP. The degradation followed pseudo-first-order kinetics with rate constant values of 0.006min-1 and 0.0322min-1 for pure TiO2 and B-TiO2 respectively. The existence of a reduced form of Ti3+ on the surface of TiO2 (as evidence from XPS) was found responsible for enhancement in photocatalytic activity.

Preparation of ceric oxide and cobalt sulfide-ceric oxide/cellulose-chitosan nanocomposites as a novel catalyst for efficient photocatalysis and antimicrobial study

In this project, we have prepared a nanostructure of CeO2 nanorods, CoS2-CeO2, and CoS2-CeO2/cellulose-chitosan (CSCS) nanocomposites by ultrasonic method. This nanostructure was characterized using XRD, DLS, field emission scanning microscopy/EDS, DLS, UV–vis DRS, and PL spectrophotometer for determination of crystalline status, morphological, and bandgap data. Both the CeO2 and CoS2 show crystal structure with cubic and pyrite phase. It was found to be the crystal size of CeO2 nanorods, CoS2-CeO2 and CoS2-CeO2/CSCS were 56.19 nm, 62.11 nm, and 65.14 nm, respectively. The photocatalytic activity of CeO2 nanorods, CoS2-CeO2, and CoS2-CeO2/CSCS nanocomposites was evaluated with the photo-degradation of 4-nitrophenol (4NP) as a toxic organic pollutant under UV light irradiation. The 4NP photo-degradation amount reached 95.42% after 60 min UV light irradiation for CoS2-CeO2/CSCS nanocomposites due to the band gap data of CoS2-CeO2/CSCS was lower than other catalyst and photocatalytic modification process. The antimicrobial data indicated the significant properties of CoS2-CeO2/CSCS nanocomposites for this study.

Highly efficient photodegradation of 4-nitrophenol over the nano-TiO2 obtained from chemical bath deposition technique

Herein, we report the collection of TiO2 nanopowder after successful thin film deposition. The obtained TiO2 nanopowder was utilized for photodegradation of 4-nitrophenol (4-NP). The structural, optical, morphological, thermal and photocatalytic properties of TiO2 photocatalyst were systematically studied using XRD, Raman, HR-TEM, FT-IR, FE-SEM, EDS, UV–Vis, DRS, PL, BET and TGA. From XRD, we correlate crystallinity parameters like crystallite domain size, lattice cell parameters, unit cell volume, microstrain, stacking fault and dislocation density. TiO2 nanopowder annealed at 400 °C shows the anatase phase which is confirmed by Raman and XRD analyses. In addition, optical results indicate that the absorption band edge is positioned in the UV region with bandgap energy of 3.03 eV. The FE-SEM and TEM images of TiO2 nanopowder show irregular spherical morphology which results in the aggregation of nanoparticles with a mean diameter of 27 nm. From Brunauer–Emmett–Teller (BET) adsorption isotherm, the surface area was obtained to be 38 m2/g. The TGA curve demonstrates the thermodynamically stable anatase phase of TiO2 photocatalyst appeared in the 350–750 °C. Under UV light irradiation, photodegradation of 4-NP over 1.5 g/dm3 TiO2 photocatalyst dose achieved an excellent degradation efficiency and COD removal efficiency around 99.51 and 82% within 80 min, respectively. From trapping experiments, it indicates that OH· and O2· radicals are major reactive oxygen species involved in the photodegradation of 4-NP.

Engineering of Z-scheme 2D/3D architectures with Bi2MoO6 on TiO2 nanosphere for enhanced photocatalytic 4-nitrophenol degradation

Abstract A novel Z-scheme Bi2MoO6 nanosheets/TiO2 nanosphere (BT) heterojunction in which numerous Bi2MoO6 nanosheets uniformly grow on the surface of TiO2 nanospheres was synthesized through a simple two-step hydrothermal process. The resulting BT heterostructures possess high surface areas and porous structures, providing abundant active sites for photocatalysis. The “line-to-surface” synergistic effect between Bi2MoO6 nanosheets and TiO2 nanospheres endow the Z-scheme heterojunction with high transfer efficiency of photogenerated carriers and increased electron lifetime for photodegradation. As a result, the as-made BT photocatalysts present superier photocatalytic performance and excellent cyclic stability for the photodegradation of 4-nitrophenol in water than pure Bi2MoO6 and TiO2. The smart construction of novel Z-scheme structure in this work would afford a plausible way for designing the promising photocatalysts to address environmental matters.

Zirconia nanoparticle-modified graphitic carbon nitride nanosheets for effective photocatalytic degradation of 4-nitrophenol in water

Zirconia (ZrO2)-modified graphitic carbon nitride (g-C3N4) nanocomposite was used for effective photodegradation of 4-nitrophenol (4-NP) in water. The ZrO2 nanoparticles, g-C3N4 nanosheets, and ZrO2/g-C3N4 nanocomposite were well characterized by including N2 adsorption, X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, UV–Vis diffuse reflectance spectroscopy, photoelectrochemical measurements, and photoluminescence spectroscopy methods. ZrO2/g-C3N4 nanocomposites were formed at room temperature using sonication and used for effective for photodegradation of 4-NP under irradiation with visible light. The nanocomposite samples resulted in a significant increase in photocatalytic activity compared with single-component samples of g-C3N4. In particular, the ZrO2/g-C3N4 nanocomposite exhibited the significant increase in the photocatalytic activity. The ZrO2/g-C3N4 nanocomposite showed an excellent catalytic activity toward the reduction of 4-NP in aqueous medium. Further, ZrO2/g-C3N4 nanocomposite can be reused several times for photocatalytic degradation as well as for 4-NP adsorption.

Photocatalytic Degradation of Dye Pollutant Over FeTPP/NaY Zeolite Nanocomposite

This study aimed to determine the photocatalytic activity of photo-Fenton reagent in the photodegradation of 4-Nitrophenol. For this purpose, Fe(III) tetraphenyl porphyrin encapsulated NaY zeolite (FeTPP/NaY) was successfully synthesised via the zeolite synthesis method. The effects of catalyst amount, H2O2 and UV illumination, concentration of 4-Nitrophenol and pH value on the photodegradation process were examined. Ultraviolet–Visible spectroscopy studies revealed that catechol, benzoquinone, and nitrate as the key intermediate species for photodegradation of 4-Nitrophenol. The chemical oxygen demand analysis indicated mineralisation of pollutant which exhibits 85% conversion of 4-Nitrophenol after 120 min irradiation. Rational design of FeTPP/NaY Nanocomposite as Fenton reagent for efficient photodegradation of 4-Nitrophenol was reported, and the possible reaction pathways of the photocatalytic reaction were proposed.

Enhanced Visible Light Photocatalytic Activity of TiO2 Nanospheres/SnO2 Quantum Dots Composite for Degradation of 4-Nitrophenol

A composite of SnO₂ quantum dots (QDs) decorated on TiO₂ nanospheres was prepared and then used as photocatalyst in photodegradation of 4-nitrophenol. The structure of TiO₂/SnO₂ QD composites revealed that the SnO2 quantum dots are uniformly dispersed on the surface of TiO₂ nanospheres. The effect of various parameters such as pH, concentration of dye, amount of semiconductor and light intensity was observed. The photocatalytic behavior of as-prepared samples shows better activity than pure TiO₂ nanospheres. This study presents a choice for potential applications of quantum dots in water pollution treatment.<div><br></div>

Determination of the crystallinity of TiO2 photocatalysts

This study reports a new simple method to determine the crystallinity of anatase and rutile TiO2 photocatalysts. The crystallinity degree of various anatase and rutile samples was estimated by XRD analysis from the ratio among the full width at half maximum intensities of the main diffraction peaks of anatase or rutile and the (111) peak of CaF2 as internal standard. The photocatalytic activity of selected powders was tested employing the photodegradation of 4-nitrophenol in aqueous solution as probe reaction. The results showed that the photoactivity of the investigated samples increased with increasing crystallinity and crystallite size.

Ultrasonic assisted synthesis with enhanced visible-light photocatalytic activity of NiO/Ag3VO4 nanocomposite and its antibacterial activity

The NiO/Ag3VO4 nanocomposite photocatalysts were developed by ultrasonic assisted preparation method to study the photocatalytic activity under visible light irradiation. The samples were characterized by UV-DRS, XRD, FT-IR, XPS, SEM, EDX, TEM, EIS and BET analysis. The photocatalytic activity of NiO/Ag3VO4 nanocomposite for the photodegradation of 4-Nitro Phenol (4-NP) and Rose Bengal (RB) under visible light irradiation was studied and it is observed that the activity has been much higher than that of the pure Ag3VO4. DRS spectrum shows the absorption edge of NiO-Ag3VO4 in visible region of spectrum. The formation of cubic structured NiO and orthorhombic structured Ag3VO4 was confirmed by powder X-ray diffraction analysis. The results of XPS analysis confirmed the coexistence of NiO and Ag3VO4 in the NiO/Ag3VO4 composite. The specific surface area and pore structure of the prepared samples were measured by BET. Enhanced charge separation efficiency was confirmed by electrochemical impedance spectroscopy (EIS) measurements. The kinetics of the NiO/Ag3VO4 nanocomposite was proposed to investigate the intervened effects of NiO to Ag3VO4 on the promotion of photocatalytic property. NiO/Ag3VO4 was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles. A possible electron-hole transfer mechanism at the NiO/Ag3VO4 interface is proposed. It also showed effective and efficient bactericidal activities against Staphylococcus aureus, Streptococcus, Proteus and Escherichia coli bacteria. Our results provide some new insights on the performance of visible light photocatalysts on environmental remediation.

Low temperature fabrication of Fe2O3 nanorod film coated with ultra-thin g-C3N4 for a direct z-scheme exerting photocatalytic activities.

We engineered high aspect ratio Fe2O3 nanorods (with an aspect ratio of 17 : 1) coated with g-C3N4 using a sequential solvothermal method at very low temperature followed by a thermal evaporation method. Here, the high aspect ratio Fe2O3 nanorods were directly grown onto the FTO substrate under relatively low pressure conditions. The g-C3N4 was coated onto a uniform Fe2O3 nanorod film as the heterostructure, exhibiting rational band conduction and a valence band that engaged in surface photoredox reactions by a direct z-scheme mechanism. The heterostructures, particularly 0.75g-C3N4@Fe2O3 nanorods, exhibited outstanding photocatalytic activities compared to those of bare Fe2O3 nanorods. In terms of 4-nitrophenol degradation, 0.75g-C3N4@Fe2O3 nanorods degraded all of the organic pollutant within 6 h under visible irradiation at a kinetic constant of 12.71 × 10−3 min−1, about 15-fold more rapidly than bare Fe2O3. Further, the hydrogen evolution rate was 37.06 μmol h−1 g−1, 39-fold higher than that of bare Fe2O3. We suggest that electron and hole pairs are efficiently separated in g-C3N4@Fe2O3 nanorods, thus accelerating surface photoreaction via a direct z-scheme under visible illumination.

Synthesis of a novel MOF/CuWO4 heterostructure for efficient photocatalytic degradation and removal of water pollutants

A novel MOF based composite with CuWO4 noted as MOF/CuWO4 successfully prepared via a facile synthesis route. The as prepared MOF/CuWO4 composite was characterized with the aid of various characterization techniques such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray fluorescence analysis (XRF), photoluminescence (PL), Transmission Electron microscopy (TEM) and Brunner-Emmet-Teller (BET) model. The photocatalytic performance of the MOF/CuWO4 composite with different weight ratios have been evaluated for the degradation of methylene blue (MB) and 4-nitrophenol as water pollution. Compared with the different types of composite system the MOF/CuWO4 composite with the weight ratio of (1:1) exhibited superior photocatalytic activity toward the degradation of methylene blue and 4-nitrophenol contaminants under LED light irradiation. Due to the MOF high surface area, efficient separation of electron-hole pairs can be observed.All of the obtained results illustrated that the MOF/CuWO4 composite acts as a highly efficient heterogeneous photocatalyst for the methylene blue and 4-nitrophenol photo degradation compared to pure MOF and CuWO4 structures.

Effects of calcination temperature and heating rate on the photocatalytic properties of ZnO prepared by pyrolysis

A series of ZnO nanorods were prepared by pyrolysis of zinc acetate at different calcination temperatures and heating rates under ambient atmosphere. The as-prepared ZnO nanorods were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of the ZnO nanorods were evaluated by the photodegradation of methyl orange (MO) and 4-nitrophenol (4-NP). The morphology, optical property, surface composition, and photocatalytic performance of the ZnO samples were affected by both calcination temperature and heating rate. The photocatalytic activity of the ZnO sample was obviously decreased with increased heating rate, which might be ascribed to the simultaneous decrease of oxygen vacancies and surface adsorption oxygen species. The ZnO nanorods prepared at 300°C with a heating rate of 1°C/min exhibited good photocatalytic activity and photochemical stability, allowing good potential practical application in environmental remediation.

Fe-doped TiO2/SiO2 nanofibrous membranes with surface molecular imprinted modification for selective photodegradation of 4-nitrophenol

In this study, Fe-doped TiO2/SiO2 (Fe@TS) nanofibrous membranes with molecular imprinted modification, were fabricated by a combination of sol-gel process, electrospinning, calcination and liquid phase deposition techniques. The precursor sol was prepared from one-pot condensation of poly(vinylpyrrolidone), ferric chloride hexahydrate, tetraethyl orthosilicate and titanium n-butoxide in the mixture solvents of N,N-dimethylformamide and ethyl alcohol. Fibrous membrane wasthen fabricated by electrospinning, followed by calcination to form the Fe@TS composite. The physicochemical properties of Fe@TS were characterized. Thereafter, 4-nitrophenol (4NP) was used as the template to deposit onto nanofibrous Fe@TS membranes, with a thin layer of molecular imprinted polymer in liquid phase. The photodegradation capabilities of 4NP and methyl orange wereexamined in both single and binary systems. The results demonstrated that molecular imprinted Fe@TS membranes exhibited excellent selectivity for photodegradation of 4NP.

Fe2O3/3DOM BiVO4: High-performance photocatalysts for the visible light-driven degradation of 4-nitrophenol

The three-dimensionally ordered macroporous (3DOM) BiVO4 and its supported iron oxide (xFe2O3/3DOM BiVO4, x=0.18, 0.97, and 3.40wt%) photocatalysts were prepared using the ascorbic acid-assisted polymethyl methacrylate-templating and incipient wetness impregnation methods, respectively. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their photocatalytic activities were evaluated for the degradation of 4-nitrophenol under visible light illumination. It is found that the BiVO4 possessed a high-quality 3DOM architecture with a monoclinic crystal phase, and the Fe2O3 was highly dispersed on the surface of 3DOM BiVO4. The xFe2O3/3DOM BiVO4 samples much outperformed the 3DOM BiVO4 sample, and 0.97Fe2O3/3DOM BiVO4 showed the best photocatalytic performance (98% 4-nitrophenol was degraded in the presence of 0.6mL H2O2 within 30min of visible light illumination) and excellent photocatalytic stability. The introduction of H2O2 to the reaction system could promote the photodegradation of 4-nitrophenol by providing the active OH species generated via the reaction of photoinduced electrons and H2O2. The pseudo-first-order reaction rate constants (0.0876–0.1295min−1) obtained over xFe2O3/3DOM BiVO4 were much higher than those (0.0033–0.0395min−1) obtained over 3DOM or Bulk BiVO4 and Fe2O3/Bulk BiVO4, with the 0.97Fe2O3/3DOM BiVO4 sample exhibiting the highest rate constant. The enhanced photocatalytic performance of 0.97Fe2O3/3DOM BiVO4 was associated with its unique porous architecture, high surface area, Fe2O3−BiVO4 heterojunction, good light-harvesting ability, high adsorbed oxygen species concentration, and excellent separation efficiency of photogenerated electrons and holes as well as the photo-Fenton degradation process.

The highly efficient and stable Cu, Co, Zn-porphyrin–TiO2 photocatalysts with heterojunction by using fashioned one-step method

A new series of carboxyl porphyrins with different center metals (Cu, Co, Zn) insertion has been successfully synthesized. Their corresponding CuCPp–TiO2, CoCPp–TiO2, and ZnCPp–TiO2 photocatalysts were obtained under a one-pot solvothermal condition. Characterization of these composites can be achieved by both spectroscopic techniques and nitrogen adsorption–desorption measurements. The findings indicate that the MCPp–TiO2 (M(II) = Cu, Co, Zn) composite photocatalysts, formed by the accumulation of disperse spherical nanoparticles, possess heterogeneous structure and large surface area, resulting in the photodegradation of 4-nitrophenol (4-NP) efficiently. The metalloporphyrins with carboxyl group display superior catalytic activities due to the strong interactions between COOH and TiO2. The order for the photocatalytic activities is as follows: CuCPp–TiO2 > CoCPp–TiO2 ≥ ZnCPp–TiO2 > bare TiO2. The reason for the high photocatalytic activity in CuCPp–TiO2 photocatalyst can possibly be explained by the fact that Cu(II) is more readily gaining an electron to reach a steady state, causing the isolation of electrons with holes compare to Co(II) and Zn(II) in MCPp–TiO2 composites. This possible mechanism of photocatalytic efficiencies was proposed based on the multiple tests. The findings of MCPp–TiO2 photocatalysts tests suggested that the metalloporphyrin-based MCPp–TiO2 composite photocatalysts are capable of maintaining superior stability in photocatalysis experiments even after six times cycling.

Absolute crystallinity and photocatalytic activity of brookite TiO2 samples

This study reports a method to determine the absolute crystallinity of partly crystalline brookite TiO2 photocatalysts. A natural, a commercial and various home-prepared brookite powders were characterized by X-ray diffraction analysis, Raman spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy and nitrogen adsorption measurements. The absolute crystallinity was calculated from the ratio between the full width at half maximum intensity of the (121) X-ray diffraction peaks of the brookite samples and the (111) peak of CaF2 as internal standard. The photocatalytic activity of the powders was tested employing the photodegradation of 4-nitrophenol as well as the selective oxidation of 4-methoxybenzyl alcohol to 4-methoxybenzaldehyde (p-anisaldehyde) under UV irradiation. The results indicated that crystallinity positively influenced the photooxidation of 4-nitrophenol and 4-methoxybenzyl alcohol but reduced the selectivity toward the synthesis of p-anisaldehyde.

Host (nanocavity of dealuminated Y zeolite)-guest (Ce(IV) salophen/TiO2) nanocomposite materials as an efficient photocatalyst for degradation of 4-nitrophenol

Ce(IV) salophen encapsulated into dealuminated Y zeolite was prepared by the flexible ligand method. Incorporation of TiO2 into nanocages of dealuminated Y zeolite was performed by the impregnation method. The obtained photocatalyst was characterized by FT-IR, XRD, DRS, SEM, EDS and ICP techniques. The amount of Ce(salophen) in the zeolite supercages was 0.07 mg/g of encapsulated zeolite. This catalytic system was investigated in the photodegradation of 4-nitrophenol. In this work, the effect of dark conditions, and visible and UV illumination was investigated for the degradation of 4-nitrophenol. In addition, the effect of other parameters including catalyst loading, H2O2 and TiO2 was studied in the degradation of 4-nitrophenol. The obtained results reveal that the photocatalyst performance depends on catalyst loading, the presence of H2O2, and UV illumination.