Pharmaceutical compounds in water bodies pose hazards to the ecosystem because of their biotoxicity potency. To eradicate such pharmaceutical compounds, a novel g-CN/BiOBr/Fe3O4 nanocomposites was ...prepared using a simplistic route and appraised for photodegradation of model tetracycline antibiotics. The g-CN/BiOBr/Fe3O4 nanocomposites exhibited complete tetracycline degradation in just 60 min exposure of simulated light irradiation, which is 6 times higher than the g-CN. Under the analogous condition, the tetracycline mineralization ability of the g-CN/BiOBr/Fe3O4 nanocomposites was evaluated to be 78% of total organic carbon removal. The superior photocatalytic performance is ascribed to the extended visible light harvesting ability and enhanced charge carrier separation/transfer with impeded recombination rate in light of effective indirect Z-scheme heterojunction construction. Based on band-edge potential and radical trapping studies indicate that h+ > •O2− > •OH are the active species responsible for photodegradation. Furthermore, the ternary nanocomposites are magnetically retrievable and recyclable while retaining their stable photocatalytic performance. This work endows a new perspective on the rational design and construction of magnetically recoverable ternary nanocomposite for environmental remediation.
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•Magnetically retrievable g-CN/BiOBr/Fe3O4 nanocomposites were successfully prepared.•g-CN/BiOBr/Fe3O4 exhibited superior catalytic activity in TC degradation (ca. 96%).•Z-scheme g-CN/BiOBr/Fe3O4 facilitated the photogenerated charge separation/transfer.
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•Engineered carbon-vacant CN (FCN) using formalin-assisted thermal polymerisation.•FCN achieved complete removal of Tetracycline via sonophotocatalysis within 60 min.•Boosted charge ...separation and extended visible light response over defected FCN.•Adsorption of oxygen molecules on FCN site resulted in abundant reactive species.
Metal-free polymeric graphitic carbon nitride (CN) materials are robust and stable visible-light-driven photocatalysts that have recently piqued interest in photocatalytic applications. Its photocatalytic performance is restricted remarkably due to moderate oxidation ability and fast charge carrier recombination rate. To address these issues, we engineered carbon-vacant CN (FCN) using a facile formalin-assisted thermal polymerization of molten CN precursor in which the carbon vacancies (Cv) were regulated by altering formalin dosage. Consequently, FCN catalysts revealed Cv concentration-dependent sonophotocatalytic degradation of Tetracycline (TC) antibiotics over diverse water matrices. The optimal FCN exhibited complete TC degradation efficiency within 60 min with a synergy index of 1.4, which is approximately 2.6 times higher than that of pristine CN. The enhanced sonophotocatalytic performance was mainly due to the synergistic effect of ultrasound and light irradiation. The Cv formation also resulted in enhanced charge carrier transportation and facilitated oxygen adsorption at the Cv site of FCN - supported by both experimental study and theoretical calculation. Subsequently, FCN generated abundant reactive active oxygen species including, •O2–, as well as indirectly •OH which played a significant role in the degradation pathway and mineralisation of the TC molecules. This study provides insight into understanding the correlation between controllable defects and sonophotocatalytic degradation properties of the self-doped and deficient FCN.
Removal of toxic arsenite As(III) from the contaminated surface and groundwater is essential for human health. However, direct arsenite removal is difficult compared to arsenate As(V). Therefore, the ...peroxidation of arsenite to arsenate is vital for its effective removal from water. Herein, we investigated the removal efficiency of arsenic from groundwater by oxidizing it with UV activated potassium persulfate (KPS) and subsequently adsorbing it on iron oxide impregnated granular activated carbon (FeO/GAC). A batch experiment was carried out to determine the adsorption kinetics and thermodynamics. Further, the effects of the adsorbent mass (FeO/GAC), C/Fe molar ratio, pH, arsenic concentration, competing anions, and humic acid in arsenic adsorption was studied. The characterization of FeO/GAC adsorbent was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and zeta potential measurements. Using the UV activated KPS and FeO/GAC, a ∼100% removal amount was achieved for 10 ppm of the arsenic solution in 1 h. Also, the effect of pH showed the highest removal efficiency in the pH range of 6.0–7.0 and it decreased dramatically at higher and lower pH values. The groundwater collected from Cheongyang in South Korea was spiked with 10 ppm of the arsenic (III) and more than 82% removal of arsenic was achieved in 90 min even in the presence of natural contaminants. Therefore, the results suggest that the UV activated KPS with FeO/GAC provides an effective method for treating highly-arsenic-contaminated water sources and this may be a viable alternative method over the existing methods.
•Efficient oxidation of Arsenic in water using UV activated KPS followed by adsorption on an impregnated FeO/GAC adsorbent.•The arsenic removal efficiency was 100% in artificial water and 82% in groundwater collected from Cheongyang, South Korea.•Adsorption mechanism is associated with electrostatic interaction, ion exchange, surface complexation and coprecipitation.•The thermodynamic studies revealed that the adsorption process was endothermic, spontaneous and feasible.
Extending the absorption to the visible region by tuning the optical band-gap of semiconductors and preventing charge carrier recombination are important parameters to achieve a higher efficiency in ...the field of photocatalysis. The inclusion of reduced graphene oxide (rGO) support in photocatalysts is one of the key strategies to address the above-mentioned issues. In this study, rGO supported AgI-mesoTiO2 photocatalysts were synthesized using a sonochemical approach. The physical effects of ultrasound not only improved the crystallinity of AgI-mesoTiO2 but also increased the surface area and loading of the AgI-mesoTiO2 nanocomposite on rGO sheets. The low intense oxygen functionalities (C-O-C and COOH groups) peak observed in the high resolution C1s spectrum of a hybrid AgI-mesoTiO2-rGO photocatalyst clearly confirmed the successful reduction of graphene oxide (GO) to rGO. The interfacial charge transfer between the rGO and the p-n junction of heterostructured photocatalysts has decreased the band-gap of the photocatalyst from 2.80 to 2.65 eV. Importantly, the integration of rGO into AgI-mesoTiO2 composites serves as a carrier separation centre and provides further insight into the electron transfer pathways of heterostructured nanocomposites. The individual effects of photo-generated electrons and holes over rGO on the photocatalytic degradation efficiency of rhodamine (RhB) and methyl orange (MO) using AgI-mesoTiO2-rGO photocatalysts were also studied. Our experimental results revealed that photo-generated superoxide (O2(-)˙) radicals are the main reactive species for the degradation of MO, whereas photo-generated holes (h(+)) are responsible for the degradation of RhB. As a result, 60% enhancement in MO degradation was observed in the presence of rGO in comparison to that of the pure AgI-mesoTiO2 photocatalyst. This is due to the good electron acceptor and the ultrafast electron transfer properties of rGO that can effectively reduce the molecular oxygen to produce a large amount of reactive O2(-)˙ radicals. However, in the case of RhB degradation, h(+) is the main reactive species which showed a slightly increased photocatalytic activity (12%) in the presence of rGO support where the role of rGO is almost negligible. This study suggests the effective roles of rGO for the degradation of organics, i.e., the rate of photocatalytic degradation also depends on the nature of compound rather than rGO support.
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•Diffused sunlight is firstly used as an effective source for the degradation of organics.•More than 10 fold synergistic effect is achieved by sono-photocatalysis.•rGO enhances the ...degradation efficiency up to 54% as compared with CuO–TiO2 alone.•Plausible mechanism and intermediates formed are supported with experimental studies.
Diffused sunlight is found to be an effective light source for the efficient degradation and mineralization of organic pollutant (methyl orange as a probe) by sono-photocatalytic degradation using reduced graphene oxide (rGO) supported CuO–TiO2 photocatalyst. The prepared catalysts are characterized by XRD, XPS, UV–vis DRS, PL, photoelectrochemical, SEM-EDS and TEM. A 10 fold synergy is achieved for the first time by combining sonochemical and photocatalytic degradation under diffused sunlight. rGO loading augments the activity of bare CuO–TiO2 more than two fold. The ability of rGO in storing, transferring, and shuttling electrons at the heterojunction between TiO2 and CuO facilitates the separation of photogenerated electron–hole pairs, as evidenced by the photoluminescence results. The complete mineralization of MO and the by-products within a short span of time is confirmed by TOC analysis. Further, hydroxyl radical mediated degradation under diffused sunlight is confirmed by LC–MS. This system shows similar activity for the degradation of methylene blue and 4-chlorophenol indicating the versatility of the catalyst for the degradation of various pollutants. This investigation is likely to open new possibilities for the development of highly efficient diffused sunlight driven TiO2 based photocatalysts for the complete mineralization of organic contaminants.
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•Cu-MOF based S-scheme Cu-BTC/ZnWO4heterojunction was fabricated.•Tetracycline was completely removed by Cu-BTC/ZnWO4 within 60 min of sonophotocatalysis.•Photogenerated charge ...carrier separation is accelerated by the S-scheme heterojunction.•High stability and reasonable reuse potential were shown by the catalyst.•Demonstrated unprecedented efficacy in destroying tetracyline from hospital effluent water.
Metal-organic frameworks (MOFs) are a significant class of porous, crystalline materials composed of metal ions (clusters) and organic ligands. The potential use of copper MOF (Cu-BTC) for the sonophotocatalytic degradation of Tetracycline (TC) antibiotic was investigated in this study. To enhance its catalytic efficiency, S-scheme heterojunction was created by combining Cu-BTC with Zinc tungstate (ZnWO4), employing an ultrasound-assisted hydrothermal method. The results demonstrated that the Cu-BTC/ZnWO4 heterojunction exhibited complete removal of TC within 60 min under simultaneous irradiation of visible light and ultrasound. Interestingly, the sonophotocatalytic degradation of TC using the Cu-BTC/ZnWO4 heterojunction showed superior efficiency (with a synergy index of ∼0.70) compared to individual sonocatalytic and photocatalytic degradation processes using the same heterojunction. This enhancement in sonophotocatalytic activity can be attributed to the formation of an S-scheme heterojunction between Cu-BTC and ZnWO4. Within this heterojunction, electrons migrated from Cu-BTC to ZnWO4, facilitated by the interface between the two materials. Under visible light irradiation, the built-in electric field, band edge bending, and coulomb interaction synergistically inhibited the recombination of electron-hole pairs. Consequently, the accumulated electrons in Cu-BTC and holes in ZnWO4 actively participated in the redox reactions, generating free radicals that effectively attacked the TC molecules. This study offers valuable perspectives on the application of a newly developed S-scheme heterojunction photocatalyst, demonstrating its effectiveness in efficiently eliminating diverse recalcitrant pollutants via sonophotocatalytic degradation.
The sonochemical oxidation of As(III) in the presence of peroxydisulfate ion (PDS) has been investigated. Sulfate anion radicals and OH radicals produced during acoustic cavitation readily oxidized ...As(III) to As(V) in an aqueous environment. The rate of oxidation of As(III) was remarkably high (∼10 times) with respect to the concentration of PDS. The As(III) oxidation was found to be independent of the initial pH of the solution in the range 3–8. It was relatively low at pH above 8, however, this could be circumvented by increasing the concentration of PDS. The presence of oxygen in solution played a significant role in the rate of oxidation of As(III). Around 40% oxidation of As(III) was observed in the absence of oxygen compared to 80% oxidation in the presence of dissolved oxygen (10
mg/L) over a sonication time of 5
min. The addition of humic acid (HA) retarded the oxidation rate of As(III), but the effect could be offset by using larger amounts of PDS. The effects of ultrasound intensity, and frequency on the rate of the oxidation of As(III) were also studied. The rate of the oxidation of As(III) was not significantly dependent on the acoustic power applied, for the concentrations of As(III) used in this study. At an ultrasound frequency of 211
kHz, the rate of oxidation of As(III) was lower than that observed at 20
kHz. It is concluded that the sonochemical treatment of As(III) solutions in the presence of PDS is a simple and viable technique for the oxidation of As(III) to As(V).
A series of nanocrystalline mesoporous ZrO2-TiO2 binary oxide photocatalysts with different wt% of ZrO2 and TiO2 were prepared by a sol-gel method. These binary oxide photocatalysts were ...characterized by XRD, N2 adsorption-desorption, DRS, FTIR, Raman spectroscopy, photoluminescence and TEM analyses. Detailed investigations revealed that the ZrO2-TiO2 catalysts are highly micro-crystalline in nature with a larger surface area than that of the pure TiO2 or ZrO2 catalysts since the added ZrO2 plays an important role in promoting the formation of nanoparticles with an anatase structure, high surface area and acidity. The photocatalytic reactivity of the catalysts was investigated for the degradation of 4-chlorophenol in an aqueous phase in which the ZrO2-TiO2 photocatalysts were found to exhibit remarkably higher photocatalytic reactivity than that of pure TiO2 and ZrO2. The catalytic activity of the binary oxide photocatalysts for the degradation of 4-chlorophenol was observed to be gradually enhanced with an increase in the ZrO2 content and reached an optimum at 12wt% of ZrO2 while maintaining the same percentage degradation with further loading of ZrO2 until 50wt%. Such high reactivity is due to the easy transfer of the photo-formed electrons from the conduction band surface trap states of ZrO2 to the conduction band of TiO2 through strong chemical interactions, thereby, preventing the radiative recombination of the photo-formed electrons and holes. The ZrO2-TiO2 catalysts were, thus, found to be highly active for the efficient degradation of 4-chlorophenol and, in fact, exhibited just as efficient activity as the commercial P-25, Degussa TiO2 catalysts, and a new reaction mechanism has, hereby, been proposed.
The density functional theory (DFT) calculations on the chemical functionalization of zigzag graphene nanoribbon (ZGNR) with DNA (Deoxyribonucleic acid) nucleobases were carried out using the local ...density approximation (DFT-LDA). The binding energies, charge transfer, equilibrium geometries and band gap variations of bare ZGNR (b-ZGNR) and nucleobase functionalized ZGNR (nb-ZGNR), were examined at an electron temperature of 300 K. The functionalization of ZGNR with nucleobases adenine (Anb-ZGNR) and cytosine (Cnb-ZGNR) reveals a significant structural deformation compared to bare ZGNR(b-ZGNR).Our findings suggest that functionalization at the edge of ZGNR is effective in tuning its electronic and structural properties through significant enhancement of dipole moment, reduction in %s character and structural asymmetry, thereby suggesting the possibilities of using functionalized ZGNR as nanocarriers in biomedical applications.
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•Effective charge transfer is observed for nucleobases functionalized ZGNR (6,0).•Functionalization induce solubility by creating permanent dipole moments in ZGNR (6,0).•The upward Fermi shift signifies higher chemical reactivity of functionalized system.
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•A NiO/g-C3N4 visible light photocatalyst prepared via wet-impregnation method.•NiO incorporation resulted in a red shift in the bandgap of g-C3N4.•NiO/g-C3N4 exhibited an average H2 ...production rate of 766 μmol/h/g.•A 127 and 109 fold higher H2 production is shown by NiO/g-C3N4 compared to NiO and g-C3N4, respectively.
g-C3N4, a metal-free polymer material is widely used as a photocatalyst because of its visible light bandgap, easy preparation from abundant precursors, and excellent chemical and thermal stability. Herein, NiO/g-C3N4 photocatalysts were prepared using calcination and wet impregnation approaches. X-ray diffraction studies revealed the formation of NiO/g-C3N4 photocatalysts. The p-n junction formation at the interface resulted in redshift in the bandgap of the photocatalysts and further enhancement in visible light absorption as evident from UV–vis diffuse reflectance spectroscopy. The NiO/g-C3N4 produced an average hydrogen evolution rate of 766 μmol/h/g in an aqueous-methanol solution. Compared to bare NiO (6 μmol/h/g) and g-C3N4 (7 μmol/h/g), the NiO/g-C3N4 photocatalysts produced 127 and 109 times higher hydrogen, respectively.
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