Facile synthesis of Z-scheme g-C3N4@MIL-100 (Fe) and the efficient photocatalytic degradation on doxycycline and disinfection by-products by coupling with persulfate: Mechanism and pathway

Construction of p-n-p nano heterojunction through coupling La2O3, (BiO)2CO3 and Ag3PO4 for effective photocatalytic degradation of doxycycline: Insights into mechanism, pathway and intermediate toxicity evaluation

The present work is centred around the development of La2O3/(BiO)2CO3/Ag3PO4 (LBA), a p-n-p nano-heterojunction to photodegrade doxycycline under visible light irradiation. Here, ultrasonication assisted co-precipitation method was employed to synthesize the photocatalyst. The photocatalyst was characterized using different analysis such as SEM, TEM, elemental mapping, XRD, XPS, FTIR, Raman, BET, DRS, PL and EIS which confirmed the successful fabrication of LBA and their excellent ability to refrain the e-/h+ recombination owing to the construction of the heterojunction. LBA was found to degrade DOX by 91.75 % with the high mineralization of 87.23%. The impact of the reaction parameters influencing the photodegradation process including the concentration of the NCs and DOX, pH and the influence of the commonly present anions were studied. The stability and reusability of the LBA was assessed through subjecting it to four cycles of photodegradation of DOX. In addition, the recovered LBA was characterized through XPS and XRD analysis to confirm the particles stability and reusability. The active participation of the photogenerated charges and the reactive oxygen species were identified through the scavenging assay and ESR analysis. Further, GC-MS/MS analysis was performed to put forward a plausible photodegradation pathway. The toxicity of the end products as well as the intermediates was predicted through ECOSAR software.

Phyto-assisted synthesis of CuO/industrial waste derived biochar composite for adsorptive removal of doxycycline hydrochloride and recycling of spent biochar as green energy storage device

The highest exposure of Endocrine disrupting compounds (EDC) into the water bodies as a result of extensive production and application of Covid-19 related drugs is a growing concern now a days. Herein, a novel nanocomposite material was developed by impregnating green synthesized copper oxide nanoparticles on the porous surface of fabric waste derived biochar to eliminate the concerned EDCs along with a sustainable disposal strategy for the spent adsorbent. Morphological characterizations by Field emission scanning electron microscopy confirmed the formation of hierarchical porous structured material. X-ray analysis revealed presence of both amorphous nature of biochar matrix as well as the crystalline nature attributed from monodispersion of copper oxide nanoparticles onto biochar surface. Batch sorption study showed removal of doxycycline hydrochloride (DOX) of >97% after 2 h at pH 7, 30 mg L-1 initial concentration of DOX and 2 g L-1 of adsorbent dose at room temperature after a two-step optimization process. Spectroscopic study and Raman shift suggested that pore filling, strong complexation and electrostatic interactions maximise the adsorption of DOX in the CuO/biochar composite as compared to the pristine biochar. However disposal of spent adsorbent is a crucial aspect for the environment and therefore, a sustainable recycling strategy for DOX loaded adsorbent as electrode material has been proposed for the first time in this study. Maximum specific capacitance value was observed in the range of 221.9-297.3 F g-1 for the DOX loaded nanocomposite at 1 mV s-1 comparable with other reported heteroatom-doped carbonaceous material as electrode. Therefore the excellent adsorption capacity of green synthesized CuO/biochar composite and its recycling after DOX adsorption can be recommended as a sustainable solution for mitigation of pharmaceuticals from wastewater. A detail study on degradation of DOX into eco-friendly products and its cost-effectiveness would be beneficial to suggest appropriate mitigation strategy for such compounds.

Activation persulfate for efficient tetrabromobisphenol A degradation via carbon-based materials: Synergistic mechanism of doped N and Fe

In this study, a novel carbon-based material (Fe-N-PGWBC) utilizing the garden waste, melamine and FeSO₄ as the precursor was successfully synthesized, efficiently activating peroxydisulfate (PDS) to degrade tetrabromobisphenol A (TBBPA). Under typical conditions (Fe-N-PGWBC dose of 100 mg·L^-1, PDS of 0.2 mM and TBBPA of 10 mg·L^-1), Fe-N-PGWBC/PDS system could achieve over 99% TBBPA removal (including adsorption and degradation) within 60 min, and the corresponding rate constant k_s was 0.0724 min^-1, which was almost 40.2 times higher than that of the pristine biochar. The extraction experiments implied that the excellent adsorption performance of Fe-N-PGWBC did not hinder the degradation of TBBPA. Abundant active sites (rich oxygen-containing functional groups, Fe-O and Fe₃C) of Fe-N-PGWBC could effectively promote PDS decomposition to produce reactive oxygen species. The probe-based kinetic modelling methods verified that approximately 87.6% TBBPA was degraded by SO₄^·-, 12.2% TBBPA was degraded by ¹O₂, and 0.2% TBBPA was degraded by ^·OH. Furthermore, based on the calculation of density functional theory and identification of products, TBBPA was mainly involved in three transformation pathways including hydroxylation, debromination and β-scission process. The study proposed a facile resource approach of garden waste and provided deeper understanding for the TBBPA degradation mechanisms in heterogeneous system.

The MIL100(Fe)/BaTi0.85Zr0.15O3 nanocomposite with the photocatalytic capability for study of tetracycline photodegradation kinetics

The visible light-active nanocomposite with the photocatalytic capability was facile one-pot solvothermal method successfully synthesized. X-ray diffraction (XRD), Thermogravimetry and Derivative Thermogravimetry (TG-DTG), Scanning Electron Microscopy with Energy Dispersive X-ray Analysis (SEM-EDX), Diffuse Reflectance Spectroscopy (UV-Vis DRS), and Fourier Transform Infra-Red (FT-IR) analysis were employed to characterize the synthetized BaTi_0.85Zr_0.15O3, MIL-100(Fe), and the MIL-100(Fe)/BaTi_0.85Zr_0.15O₃ samples. As a result of the Scherrer equations, the size of grains for MIL-100(Fe), BaTi_0.85Zr_0.15O₃, and MIL-100(Fe)/BaTi_0.85Zr_0.15O₃ was estimated to be 40.81, 12.00, and 22.70 nm, respectively. MIL-100(Fe), BaTi_0.85Zr_0.15O₃, and MIL-100(Fe)/BaTi_0.85Zr_0.15O₃ samples showed bandgap values of 1.77, 3.02, and 2.56 determined from their absorption edge wavelengths. In the photodegraded solutions, chemical oxygen demand (COD) data and tetracycline (TC) absorbencies were used to obtain the rate constants of 0.032 min^-1 and 0.030 min^-1, respectively. This corresponds to t_1/2-values of 27.7 min and 21.7 min, respectively, for the degradation and mineralization of TC molecules during photodegradation process.

Enhanced photocatalytic degradation performance of In2O3/g-C3N4 composites by coupling with H2O2

Environmental pollution by organic pollutants poses a great threat to the ecosystem and human development. Solar-powered catalytic oxidation technology can solve the existing energy and pollution crisis. Hence, in this work, cubic nano-In₂O₃ modified g-C₃N₄ composite was synthesized by in situ calcination, then it was coupled with hydrogen peroxide for the degradation of antibiotic under visible light. The results of SEM and XPS showed that In₂O₃ and g-C₃N₄ were closely combined. The catalytic oxidation efficiency of the antibiotic doxycycline was greatly improved when the as-prepared compound was coupled with hydrogen peroxide, and 88.2% of doxycycline was degraded within 80 min. By designing the active species inhibition test, it was found that a large number of hydroxyl radicals were generated in the system after adding hydrogen peroxide, which accelerated the degradation of the target. Hydrogen peroxide not only acts as a source of hydroxyl radical, but also as an active electron acceptor, which promotes the separation of photogenerated electron-hole pairs in the composite photocatalyst. Therefore, the double oxidation system formed by In₂O₃/g-C₃N₄ coupled with hydrogen peroxide can degrade the target at a higher rate. This work provided a research basis for the synthesis of In₂O₃ with regular morphology and simplified synthesis of In₂O₃/g-C₃N₄, and explored the practicability of the coupling method of double advanced oxidation for pollutant degradation.

Modulation of Z-scheme photocatalysts for pharmaceuticals remediation and pathogen inactivation: Design devotion, concept examination, and developments

The recent outbreak of Covid-19 guarantees overconsumption of different drugs as a necessity to reduce the symptoms caused by this pandemic. This triggers the proliferation of pharmaceuticals into drinking water systems. Is there any hope for access to safe drinking water? Photocatalytic degradation using artificial Z-scheme photocatalysts that has been employed for over a decade conveys a prospect for sustainable clean water supply. It is compelling to comprehensively summarise the state-of-the-art effects of Z-scheme photocatalytic systems towards the removal of pharmaceuticals in water. The principle of Z-scheme and the techniques used to validate the Z-scheme interfacial charge transfer are explored in detail. The application of the Z-scheme photocatalysts towards the degradation of antibiotics, NSAIDs, and bacterial/viral inactivation is deliberated. Conclusions and stimulating standpoints on the challenges of this emergent research direction are presented. The insights and up-to-date information will prompt the up-scaling of Z- scheme photocatalytic systems for commercialization.

Green synthesis of two-electron centre based ZnO/NiCo2S4 QDs-OVs using Punica granatum fruit peel extract for an exceptional visible light photocatalytic degradation of doxycycline and ciprofloxacin

Biosynthesis of nanomaterials using plant extract makes them attractive in the field of photocatalysis as they are environmental friendly. The current study focused on the biosynthesis of ZnO/NiCo₂S₄ QDs (NCs) using Punica granatum fruit peel extract as the reducing agent. The nanomaterials were characterized with XRD, FTIR, Raman, SEM, TEM, UV-vis DRS, BET, PL, EIS, and ESR analysis and were used for photocatalytic degradation of doxycycline (DOX) and ciprofloxacin (CIP). The bandgap of ZnO is 3.2 eV, and the decoration of NiCo₂S₄ QDs aids in narrowing the bandgap (2.8 eV), making the NCs visible light active. The fabricated NCs achieved 99 and 89% degradation of DOX and CIP respectively. The photocatalytic efficiency of ZnO/NiCo₂S₄ QDs was much higher compared to individual ZnO and NiCo₂S₄ QDs. The half-life period of DOX and CIP were evaluated to be 58 and 152 min respectively. The percentage of TOC removal in the photodegraded product of DOX and CIP was estimated to be 99 and 89% respectively, indicating the mineralization of the compounds. The enhanced photocatalytic efficiency of the NCs was attributed to the narrowed visible light active bandgap, synergistic charge transfer across the interface, and lower charge recombination. The intermediates formed during the photocatalytic degradation of DOX and CIP were analyzed using GC-MS/MS analysis, and the photodegradation pathway was elucidated. Also, the toxicity of the intermediates was computationally analyzed using ECOSAR software. The fabricated ZnO/NiCo₂S₄ QDs have excellent stability and reusability, confirmed by XRD and XPS analysis. The reusable efficiency of the NCs for the photocatalytic degradation of DOX and CIP were 98.93, and 99.4% respectively. Thus, the biologically fabricated NCs are shown to be an excellent photocatalyst and have wide applications in environmental remediation.