Preparation of BiOCl0.9I0.1/β-Bi2O3 composite for degradation of tetracycline hydrochloride under simulated sunlight

Heterojunction Photocatalyst Loaded on Electrospun Nanofibers for Synergistic Enhanced Photocatalysis and Real-Time Temperature Monitoring

Bi2WO6:Ho3+, Yb3+/g-C3N4 (BHY/CN) photocatalysts are successfully loaded on polyacrylonitrile (PAN) nanofibers by electrospinning technology, which combines an upconversion effect and heterojunctions to achieve dual-functional characteristics. Polymer-modified photocatalytic materials offer a large specific surface area of 24.1 m2/g and a pore volume of 0.1 cm3/g, promoting the utility of solar energy. The introduction of rare earth ions and g-C3N4 optimizes the structural band gap, which broadens the light absorption range and promotes electron transfer. Moreover, the heterojunction between Bi2WO6 and g-C3N4 has suppressed the complexation of photoinduced carriers, further improving catalytic performance. The optimized photocatalysts have higher photocatalytic activity with degrading 92.6% tetracycline-hydrochloride (120 min) under simulated sunlight irradiation. The optical thermometry has also been achieved based on the fluorescence intensity ratio technique, where the maximum absolute and relative sensitivity values of BHY/CN-1:6@PAN are 3.322% K-1 and 0.842% K-1, respectively. This dual-functional nanofibers with excellent mechanical properties provide noncontact temperature feedback and efficient catalytic performance for better wastewater treatment and ecological restoration in extreme harsh environments.

Degradation of levofloxacin in wastewater by photoelectric and ultrasonic synergy with TiO2/g-C3N4@AC combined electrode

A novel particle combined electrode named TiO₂/g-C₃N₄@AC (TGCN-AC) was prepared by loading TiO₂ and g-C₃N₄ on activated carbon through gel method, which was used to degrade levofloxacin (LEF) in pharmaceutical wastewater by photoelectric process. The remarkable physicochemical features of particle electrodes were verified by using diverse characterization techniques including SEM-EDS, XRD, FT-IR, BET and pH_ZPC. EIS-CV and photocurrent showed excellent electrocatalysis and photoelectrocatalysis performance of particle electrodes. The photocatalytic characteristics and fluorescence properties of the particle electrode were proved by UV-vis DRS and PL spectra measurements. Combined with Tauc's plot and Mott-Schottky plots curves, the E_CB and E_VB of particle electrodes were determined. The experiments on different influence factors such as pH, ultrasonic, aeration, current density and the concentration of LEF were carried out in the photoelectric reactor. Under the conditions of pH values 3.0, 200 W ultrasonic, 8 L/min aeration, the mass ratio of g-C₃N₄ and TiO₂ is 8%, after 4.0 h of photoelectric process, about 94.76% of LEF (20 mg/L) in water was degraded. TGCN-AC also has excellent reusability. The degradation rate of LEF can still reach 71.17% after repeated use for 6 times. Scavenger studies showed that h⁺ and O^2- were the main active species. By observing the colony size of E. coli, it was proved that the LEF in the effluent had no antibacterial activity. The degradation pathways of LEF was analyzed and drawn by HPLC-MS spectra.

Preparation of floating BiOCl0.6I0.4/ZnO photocatalyst and its inactivation of Microcystis aeruginosa under visible light

Frequent occurrence of harmful algal blooms has already threatened aquatic life and human health. In the present study, floating BiOCl_0.6I_0.4/ZnO photocatalyst was synthesized in situ by water bath method, and and applied in inactivation of Microcystis aeruginosa under visible light. The composition, morphology, chemical states, optical properties of the photocatalyst were also characterized. The results showed that BiOCl_0.6I_0.4 exhibited laminated nanosheet structure with regular shape, and the light response range of the composite BZ/EP-3 (BiOCl_0.6I_0.4/ZnO/EP-3) was tuned from 582 to 638 nm. The results of photocatalytic experiments indicated that BZ/EP-3 composite had stronger photocatalytic activity than a single BiOCl_0.6I_0.4 and ZnO, and the removal rate of chlorophyll a was 89.28% after 6 hr of photocatalytic reaction. The photosynthetic system was destroyed and cell membrane of algae ruptured under photocatalysis, resulting in the decrease of phycobiliprotein components and the release of a large number of ions (K⁺, Ca²⁺ and Mg²⁺). Furthermore, active species trapping experiment determined that holes (h⁺) and superoxide radicals (·O₂^-) were the main active substance for the inactivation of algae, and the p-n mechanism of photocatalyst was proposed. Overall, BZ/EP-3 showed excellent algal removal ability under visible light, providing fundamental theories for practical algae pollution control.

Visible-light driven p-n heterojunction formed between α-Bi2O3 and Bi2O2CO3 for efficient photocatalytic degradation of tetracycline

To improve the efficiency of photocatalytic oxidative degradation of antibiotic pollutants, it is essential to develop an efficient and stable photocatalyst. In this study, a polymer-assisted facile synthesis strategy is proposed for the polymorph-controlled α-Bi₂O₃/Bi₂O₂CO₃ heterojunction retained at elevated calcination temperatures. The p-n heterojunction can effectively separate and migrate electron-hole pairs, which improves visible-light-driven photocatalytic degradation from tetracycline (TC). The BO-400@PAN-140 photocatalyst achieves the highest pollutant removal efficiency of 98.21% for photocatalytic tetracycline degradation in 1 h (λ > 420 nm), and the degradation efficiency was maintained above 95% after 5 cycles. The morphology, crystal structure, and chemical state of the composites were analysed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Ultraviolet-visible diffuse reflection, transient photocurrent response, and electrochemical impedance spectroscopy were adopted to identify the charge transfer and separation efficiency of photogenerated electron-hole pairs. The EPR results verified h⁺ and ˙OH radicals as the primary active species in the photocatalytic oxidation reactions. This observation was also consistent with the results of radical trapping experiments. In addition, the key intermediate products of the photocatalytic degradation of TC over BO-400@PAN-140 were identified via high-performance liquid chromatography-mass spectrometry, which is compatible with two possible photocatalytic reaction pathways. This work provides instructive guidelines for designing heterojunction photocatalysts via a polymer-assisted semiconductor crystallographic transition pathway for TC degradation into cleaner production.

Visible light driven antibiotics degradation using S-scheme Bi2WO6/CoIn2S4 heterojunction: Mechanism, degradation pathways and toxicity assessment

S-scheme heterojunction photocatalysts with strong redox ability and excellent photocatalytic activity are highly desired for photocatalytic degradation of pollutants. Herein, S-scheme Bi₂WO₆/CoIn₂S₄ heterojunctions were synthesized using hydrothermal method. The photo-induced carriers transfer mechanism of the S-scheme Bi₂WO₆/CoIn₂S₄ heterojunction was clarified by band structure analysis, ultraviolet photoelectron spectrometer (UPS), electron spin resonance (ESR) and radical trapping experiments. Significant enhance of light absortion, and more efficient carriers separation were observed from the Bi₂WO₆/CoIn₂S₄ with CoIn₂S₄ nanoclusters growing on the surface of petal-like Bi₂WO₆ nanosheets. TC degradation efficiency of 90% was achieved by Bi₂WO₆/CoIn₂S₄ (15:1) within 3 h of irradiation, and ·O₂^-and ·OH radicals were dominated contributors. Possible decomposition pathways of TC were proposed, and ECOSAR analysis showed that most of the intermediates exhibited lower ecotoxicity than TC. This work provides reference on the constructing ternary-metal-sulfides-based S-scheme heterojunctions for improving photocatalytic performance.

Sun light driven isotropy β-Bi2O3 with high charge-carrier mobility for efficient degradation of bisphenol A and phenol

Nanostructure β-Bi2O3 was synthesized and used for the photocatalytic degradation of bisphenol A and phenol. After 90 minutes of sun light irradiation, the degradation efficiencies of bisphenol A and phenol...

A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h⁺ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

Synergism in TiO2 photocatalytic ozonation for the removal of dichloroacetic acid and thiacloprid

The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst TiO₂ is usually attributed to influences of the physicochemical properties of the catalyst, pollutant type, pH, temperature, O₃ concentration, and other factors. It is also often claimed that good adsorption on the TiO₂ surface is beneficial for the occurrence of synergism. Herein, we tested these assumptions by using five different commercial TiO₂ photocatalysts (P25, PC500, PC100, PC10 and JRC-TiO-6) in three advanced oxidation systems - photocatalysis (O₂/TiO₂/UV), catalytic ozonation (O₃/TiO₂) and PH-OZ (O₃/TiO₂/UV) - for the degradation of two pollutants (dichloroacetic acid - DCAA and thiacloprid) simultaneously present in water. The synergistic effect in PH-OZ was much more pronounced in the case of thiacloprid, a molecule with low adsorption on the surface of the catalyst - in contrast to DCAA with stronger adsorption. The faster kinetics of catalytic ozonation (O₃/TiO₂) correlated with the higher exposed surface area of TiO₂ agglomerates, independent of the (lower) BET surfaces of the primary particles. Nevertheless, DCAA mineralization on the TiO₂ surface was much faster than thiacloprid degradation in solution. Therefore, we propose that a high BET surface area of the photocatalyst is crucial for fast surface reactions (DCAA mineralization), while good dispersion - the high exposed surface area of the (small) agglomerates - and charge separation play an important role in photocatalytic degradation or PH-OZ of less adsorbed organic pollutants (thiacloprid).

A novel PVDF-TiO2@g-C3N4 composite electrospun fiber for efficient photocatalytic degradation of tetracycline under visible light irradiation

A novel composite electrospun fiber with high photocatalytic efficiency, good stability, strong hydrophobicity, good pollution resistance, and easy separation and recovery was synthesized. The TiO₂@g-C₃N₄ (TCN) with special core-shell structure (5-10 nm shell) facilitated the separation of photogenerated electron-holes and had high photocatalytic performance. The poly (vinylidene fluoride) (PVDF) electrospun fiber immobilized with TCN was successfully fabricated (PVDF-TCN) with uniform distribution and size of nanofibers by using electrospinning, which was used for degrading tetracycline under visible-light irradiation (> 400 nm). A special rougher surface of electrospun fiber obtained by washing of sacrificial PVP increased the specific surface area, which became more conducive to the adhesion of the catalyst. The water contact angle and FTIR results demonstrated that the electrospun fiber became extremely hydrophilic after adding TCN catalyst, which could effectively mitigate the fiber pollution. The PVDF-TCN-0.2g electrospun fiber exhibited excellent photocatalytic performance and the degradation efficiency of tetracycline was up to 97% in 300 min under visible-light irradiation. The mechanism of PVDF-TCN electrospun fiber degradation of tetracycline in the photocatalytic process was also proposed. In addition, the PVDF-TCN-0.2g exhibited a stable activity after 4 cycles experiments since the degradation efficiency remained about 90%. Therefore, we believed this study provided a new strategy in catalyst immobilization and wastewater treatment.

The construction of NiFeSx/g-C3N4 composites with high photocatalytic activity towards the degradation of refractory pollutants

In this work, a novel NiFe layered double hydroxide-derived sulfide (NiFeSx)-modified g-C3N4 nanosheet photocatalyst (NiFeSx/g-C3N4) was synthesized, and its morphology, structure and visible light absorption capacity were simultaneously characterized by XRD, SEM, TEM, FT-IR, XPS, UV-Vis DRS, PL techniques and EIS Nyquist plots. Furthermore, it was discovered that at an optimum mass ratio of 3% (NiFeSx to g-C3N4), 3% NiFeSx/g-C3N4 composites exhibited the best degradation efficiency toward tetracycline hydrochloride refractory pollutants. The degradation rate of tetracycline hydrochloride by 3% NiFeSx/g-C3N4 composites was 92.54% under 70 min of visible light illumination, which was about 2.61 times higher than that of pure g-C3N4. The improved degradation activity may be attributed to the synergistic effect between the two constituents of as-synthesized composites, and the formed heterojunction reduced the efficiency of photogenerated carriers. More importantly, this work also gives some inspiration to synthesize some similar photocatalysts for a targeted environmental remediation.