Visible-light driven of heterostructured LaFeO3/TiO2 photocatalysts for degradation of antibiotics: Ciprofloxacin as case study

TiO2/LaFeO3 Composites for the Efficient Degradation of Benzoic Acid and Hydrogen Production

LaFeO3/TiO2 composites were prepared in the range 0-12.2 wt% of LaFeO3, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal treatment. The composite materials presented agglomerates of LaFeO3 with an average size from 1 to 5 μm, and the TiO2 powder was well dispersed onto the surface of each sample. They showed varying activities for BA degradation depending on composition and light wavelength. The 6.2 wt% and 12.2 wt%-LaFeO3/TiO2 composites exhibited the highest activity under 380-800 nm light and could degrade BA in 300 min at BA concentration 13.4 mg L-1 and catalyst 0.12 g L-1. Using a 450 nm LED light source, all composites degraded less than 10% of BA, but in the presence of H2O2 (1 mM) the photocatalytic activity was as high as 96% in <120 min, 6.2 wt%-LaFeO3/TiO2 composite being the most efficient sample. It was found that in the presence of H2O2, BA degradation followed first order kinetic with a reaction rate constant of 4.8 × 10-4 s-1. The hydrogen production rate followed a classical volcano-like behavior, with the highest reactivity (1600 μmol h-1g-1 at 60 °C) in the presence of 3.86%wt- LaFeO3/TiO2. It was also found that LaFeO3/TiO2 exhibited high stability in four recycled tests without losing activity for hydrogen production. Furthermore, a discussion on photogenerated charge-carrier transfer mechanism is briefly provided, focusing on lacking significant photocatalytic activity under 450 nm light, so p-n heterojunction formation is unlikely.

Efficient tetracycline degradation using carbon quantum dot modified TiO2@LaFeO3 hollow core shell photocatalysts

Efficient harnessing of solar energy presents a significant challenge in environmental cleanup efforts. This study develops a highly effective carbon quantum dots-modified hollow core-shell TiO2-LaFeO3 heterojunction photocatalyst (CDs-TLFO). Structural analysis confirmed that nanosheets are loaded with CQDs, forming a hollow core-shell structure with intimate interconnection. Photocatalytic experiments reveal that CDs-TLFO degrads tetracycline hydrochloride (TC) 2.02 times faster than TLFO alone, and significantly outperformes h-TiO2 and LaFeO3 (11.28 and 2.78 times, respectively). This enhancement is attributed to CQDs acting as electron acceptors with upconversion properties, enhancing the separation of e--h+ pairs and boosting visible light absorption. Integration of CQDs onto the TLFO surface creates numerous active sites and enhances visible light absorption. SEM and TEM tests confirm that the catalyst has a hollow core-shell structure. ESR tests and radical trapping experiments indicate that the high degradation efficiency of the catalyst mainly owns to the synergistic effect of hydroxyl radicals (·OH) and superoxide radicals (·O2-). The reusability and stability of the catalysts are investigated, potential TC degradation pathways are proposed as well as the photocatalytic reaction mechanism is revealed. This research introduces promising avenues for environmental cleanup and offers a straightforward, energy-efficient, and environmentally friendly method for producing CDs-TLFO heterojunction materials with superior photocatalytic capabilities.

Photocatalytic degradation of antibiotic sulfamethizole by visible light activated perovskite LaZnO3

In this work, the perovskite LaZnO3 was synthesized via sol-gel method and applied for photocatalytic treatment of sulfamethizole (SMZ) antibiotics under visible light activation. SMZ was almost completely degraded (99.2% ± 0.3%) within 4 hr by photocatalyst LaZnO3 at the optimal dosage of 1.1 g/L, with a mineralization proportion of 58.7% ± 0.4%. The efficient performance of LaZnO3 can be attributed to its wide-range light absorption and the appropriate energy band edge levels, which facilitate the formation of active agents such as ·O2-, h+, and ·OH. The integration of RP-HPLC/Q-TOF-MS and DFT-based computational techniques revealed three degradation pathways of SMZ, which were initiated by the deamination reaction at the aniline ring, the breakdown of the sulfonamide moieties, and a process known as Smile-type rearrangement and SO2 intrusion. Corresponding toxicity of SMZ and the intermediates were analyzed by quantitative structure activity relationship (QSAR), indicating the effectiveness of LaZnO3-based photocatalysis in preventing secondary pollution of the intermediates to the ecosystem during the degradation process. The visible-light-activated photocatalyst LaZnO3 exhibited efficient performance in the occurrence of inorganic anions and maintained high durability across multiple recycling tests, making it a promising candidate for practical antibiotic treatment.

A Review of Synthesis Methods, Modifications, and Mechanisms of ZnO/TiO2-Based Photocatalysts for Photodegradation of Contaminants

The environment being surrounded by accumulated durable waste organic compounds has become a critical crisis for human societies. Generally, organic effluents of industrial plants released into the water source and air are removed by some physical and chemical processes. Utilizing photocatalysts as cost-effective, accessible, thermally/mechanically stable, nontoxic, reusable, and powerful UV-absorber compounds creates a new gateway toward the removal of dissolved, suspended, and gaseous pollutants even in trace amounts. TiO2 and ZnO are two prevalent photocatalysts in the field of removing contaminants from wastewater and air. Structural modification of the photocatalysts with metals, nonmetals, metal ions, and other semiconductors reduces the band gap energy and agglomeration and increases the affinity toward organic compounds in the composite structures to expand their usability on an industrial scale. This increases the extent of light absorbance and improves the photocatalytic efficiency. Selecting a suitable synthesis method is necessary to prepare a target photocatalyst with distinct properties such as high specific surface area, numerous surface functional groups, and an appropriate crystalline phase. In this Review, significant parameters for the synthesis and modification of TiO2- and ZnO-based photocatalysts are discussed in detail. Several proposed mechanistic routes according to photocatalytic composite structures are provided. Some electrochemical analyses using charge carrier trapping agents and delayed recombination help to plot mechanistic routes according to the direction of photoexcited species (electron-hole pairs) and design more effective photocatalytic processes in terms of cost-effective photocatalysts, saving time and increasing productivity.

Recent progresses in synthesis and modification of g-C3N4 for improving visible-light-driven photocatalytic degradation of antibiotics

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

Synthesis and performance evaluation of S-scheme heterostructured LaFeO3/TiO2 photocatalyst for the efficient degradation of thiamethoxam

The application of perovskite lanthanum ferrite (LaFeO3) as a photocatalyst has shown significant potential in the removal of persistent organic and inorganic contaminants. In the present research, LaFeO3 and various composites consisting of LaFeO3 and TiO2 were prepared. The photocatalytic efficiency of the produced catalysts was assessed by measuring their effectiveness in degrading thiamethoxam, a pesticide belonging to the second generation of neonicotinoids. Experimental investigations were carried out to examine the impact of various factors on the degradation process, including variables like concentration of thiamethoxam, catalyst amount, and pH level. The produced catalysts were characterized by various techniques, including field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). The highest degradation rates were observed when using the synthesized catalyst, 1% LaFeO3/TiO2 (LFTO1), under both UV-C and direct sunlight conditions. This performance outperformed TiO2 and bare LaFeO3. When exposed to ultraviolet (UV-C) radiation at an intensity of 15 W m-2 and under neutral pH conditions, LFTO1 achieved approximately 97% degradation, while under direct sunlight, the LFTO1 photocatalyst exhibited a degradation rate of 79% within a 120-min reaction period. The enhanced activity of LFTO1 could be attributed to its increased surface area, reduced bandgap, and lower electron-hole recombination. The investigation of reaction kinetics showed that the degradation of thiamethoxam followed a pseudo-first-order rate law. Furthermore, LFTO1 can be employed up to 5 times without experiencing any loss in its catalytic activity, thus confirming its long-term utility.

Facile Synthesis of Nano-Flower β-Bi2O3/TiO2 Heterojunction as Photocatalyst for Degradation RhB

Photocatalysis is a hopeful technology to solve various environmental problems, but it is still a technical task to produce large-scale photocatalysts in a simple and sustainable way. Here, nano-flower β-Bi₂O₃/TiO₂ composites were prepared via a facile solvothermal method, and the photocatalytic performances of β-Bi₂O₃/TiO₂ composites with different Bi/Ti molar ratios were studied. The nano-flower Bi₂O₃/TiO₂ composites were studied by SEM, XRD, XPS, BET, and PL. The PL result proved that the construction of staggered heterojunction enhanced the separation efficiency of carriers. The degradation RhB was applied to study the photocatalytic performances of prepared materials. The results showed that the degradation efficiency of RhB increased from 61.2% to 99.6% when the molar ratio of Bi/Ti was 2.1%. It is a mesoporous approach to enhance photocatalytic properties by forming heterojunction in Bi₂O₃/TiO₂ composites, which increases the separation efficiency of the generated carriers and improves photocatalytic properties. The photoactivity of the Bi₂O₃/TiO₂ has no evident changes after the fifth recovery, indicating that the Bi₂O₃/TiO₂ composite has distinguished stability.