Construction of Ag3PO4/TiO2/C with p-n heterojunction using Shiff base-Ti complex as precursor: Preparation, performance and mechanism

Construction of Bi2WO6/g-C3N4 Z-Scheme Heterojunction and Its Enhanced Photocatalytic Degradation of Tetracycline with Persulfate under Solar Light

Z-scheme heterojunction Bi2WO6/g-C3N4 was obtained by a novel hydrothermal process; its photocatalysis-persulfate (PDS) activation for tetracycline (TC) removal was explored under solar light (SL). The structure and photoelectrochemistry behavior of fabricated samples were well characterized by FT-IR, XRD, XPS, SEM-EDS, UV-vis DRS, Mott-Schottky, PL, photocurrent response, EIS and BET. The critical experimental factors in TC decomposition were investigated, including the Bi2WO6 doping ratio, catalyst dosage, TC concentration, PDS dose, pH, co-existing ion and humic acid (HA). The optimum test conditions were as follows: 0.4 g/L Bi2WO6/g-C3N4 (BC-3), 20 mg/L TC, 20 mg/L PDS and pH = 6.49, and the maximum removal efficiency of TC was 98.0% in 60 min. The decomposition rate in BC-3/SL/PDS system (0.0446 min-1) was 3.05 times higher than that of the g-C3N4/SL/PDS system (0.0146 min-1), which might be caused by the high-efficiency electron transfer inside the Z-scheme Bi2WO6/g-C3N4 heterojunction. Furthermore, the photogenerated hole (h+), superoxide (O2•-), sulfate radical (SO4•-) and singlet oxygen (1O2) were confirmed as the key oxidation factors in the BC-3/SL/PDS system for TC degradation by a free radical quenching experiment. Particularly, BC-3 possessed a wide application potential in actual antibiotic wastewater treatment for its superior catalytic performance that emerged in the experiment of co-existing components.

Efficiency of Ag3PO4/TiO2 as a heterogeneous catalyst under solar and visible light for humic acid removal from aqueous solution

Nowadays, the presence of humic acid (HA) in water sources is highly regarded due to the production of extremely harmful byproducts such as trihalomethanes. In this study, the effectiveness of an Ag₃PO₄/TiO₂ catalyst produced by in situ precipitation as a heterogeneous catalyst for the degradation of humic acid in the existence of visible and solar light was evaluated. The Ag₃PO₄/TiO₂ catalyst's structure was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), after which the catalyst dosage, HA concentration, and pH parameters were adjusted. After a 20-min reaction, the highest HA degradation of 88.2% and 85.9% in presence of solar light and visible light were attained at the ideal operating conditions of 0.2 g/L catalyst, 5 mg/L HA, and pH 3, respectively. It was discovered that, based on kinetic models, the degradation of HA matched both Langmuir-Hinshelwood and pseudo-first-order kinetics at concentrations of 5 to 30 mg/L (R² > 0.8). The Langmuir-Hinshelwood model had surface reaction rate constants (K_c) of 0.729 mg/L.min and adsorption equilibrium constants (K_L-H) of 0.036 L/mg. Eventually, a real-water investigation into the process' effectiveness revealed that, under ideal circumstances, the catalyst had a reasonable HA removal efficiency of 56%.

Ag3PO4-anchored La2Ti2O7 nanorod as a Z-Scheme heterostructure composite with boosted photogenerated carrier separation and enhanced photocatalytic performance under natural sunlight

Developing wide spectra-responsive photocatalysts has attracted considerable attention in the photocatalytic technology to achieve excellent catalytic activity. Ag₃PO₄, with strong response to light spectra shorter than 530 nm, shows extremely outstanding photocatalytic oxidation ability. Unfortunately, the photocorrosion of Ag₃PO₄ is still the biggest obstacle to its application. Herein, the La₂Ti₂O₇ nanorod was used to anchor Ag₃PO₄ nanoparticles in this study, and a novel Z-Scheme La₂Ti₂O₇/Ag₃PO₄ heterostructure composite was constructed. Remarkably, the composite showed strong responsive to most of the spectra in natural sunlight. The Ag⁰ formed in-situ acted as the recombination center of photogenerated carriers, which promoted their efficient separation and contributed to the improved photocatalytic performance of the heterostructure. When the mass ratio of Ag₃PO₄ in the La₂Ti₂O₇/Ag₃PO₄ catalyst was 50%, the degradation rate constant of Rhodamine B (RhB), methyl orange (MO), chloroquine phosphate (CQ), tetracycline (TC), and phenol under natural sunlight irradiation were 0.5923, 0.4463, 0.1399, 0.0493, and 0.0096 min^-1, respectively. Furthermore, the photocorrosion of the composite was greatly inhibited, 76.49% of CQ and 83.96% of RhB were still degraded after four cycles. Besides, the holes and O₂^•- played a significant role in RhB degradation, and it included multiple mechanisms of deethylation, deamination, decarboxylation, and cleavage of ring-structures. Moreover, the treated solution can also show safety to the water receiving environment. Overall, the synthesized Z-Scheme La₂Ti₂O₇/Ag₃PO₄ composite exhibited immense potential for removing various organic pollutants through photocatalytic technology under natural sunlight irradiation.

Highly Enhanced Photocatalytic Performances of Composites Consisting of Silver Phosphate and N-Doped Carbon Nanomesh for Oxytetracycline Degradation

Photocatalytic technology based on silver phosphate (Ag₃PO₄) has excellent potential in removing antibiotic pollutants, but the low separation rate of photogenerated hole-electron pairs restricts the application of the photocatalyst. In this study, it was found that the combination of nitrogen-doped carbon (NDC) with carbon defects and Ag₃PO₄ can significantly enhance the photocatalytic ability of Ag₃PO₄. After it was exposed to visible light for 5 min, the photocatalytic degradation efficiency of oxytetracycline (OTC) by the composite photocatalyst Ag₃PO₄@NDC could reach 100%. In addition, the structure of NDC, Ag₃PO_4, and Ag₃PO₄@NDC was systematically characterized by SEM, TEM, XRD, Raman, and EPR. The XPS results revealed intense interface interaction between Ag₃PO₄ and NDC, and electrons would transfer from Ag₃PO₄ to the NDC surface. A possible mechanism for enhancing the photocatalytic reaction of the Ag₃PO₄@NDC composite catalyst was proposed. This study provides a highly efficient visible light catalytic material, which can be a valuable reference for designing and developing a new highly efficient visible light catalyst.

Highly Efficient Bi4Ti3O12/g-C3N4/BiOBr Dual Z-Scheme Heterojunction Photocatalysts with Enhanced Visible Light-Responsive Activity for the Degradation of Antibiotics

A novel Bi₄Ti₃O₁₂/g-C₃N₄/BiOBr(BTO/CN/BOB) composite was synthesized by a solvothermal-mechanical mixed thermal method. The composition, structure, and micromorphology of the samples were analyzed. The BTO/CN/BOB composite photocatalyst shows better photocatalytic performance for tetracycline hydrochloride (TC) degradation compared to Bi₄Ti₃O₁₂ and binary composite photocatalysts. The highest degradation rate of TC can reach 89.84% using the BTO/CN/BOB photocatalyst under the optimal conditions, and BTO/CN/BOB still exhibits good photocatalytic properties after recycling. Moreover, it also shows good photodegradation activity for different kinds of antibiotics, implying its wide application prospect. The photocatalytic performance and reuse stability of BTO/CN/BOB were significantly improved, which may be because of the enhanced spectral absorption range and efficient electron transfer capability by the synergistic effect and interaction among Bi₄Ti₃O₁₂, BiOBr, and g-C₃N₄. Finally, the possible degradation pathway and electron transfer mechanism of the dual Z-scheme heterojunction are proposed.