Photocatalytic Degradation Mechanism Research Articles

Anchoring gadolinium oxide nanoparticles onto CuInZnS: Efficient photocatalytic tetracycline degradation and mechanism analysis

Photocatalysis technology is one of the potential methods to remit the growing issues of environmental pollution. It is of great significance to rationally design high performance antibiotic wastewater degradation catalysts in the whole pH range. In this experiment, Gd2O3 nanoparticles (GdO NPs) were successfully grown onto CuInZnS (CIZS) by a simple hydrothermal method. The introduction of GdO has obvious effects on the nanosheet thickness of CIZS, which reduces carrier transport distances and improves the active sites number of CIZS. What’s more, the SO4•- absorption and electron transfer ability are also greatly optimized. Under 300 W Xe light, tetracycline can be efficient degraded more than 93 % in the whole pH range, which presents absolute advantage compared to CIZS and GdO. Based on the combination of experimental characterization and density functional theory calculations, the proposed photocatalytic tetracycline degradation pathway and mechanism have been given. Moreover, the results of toxicity analysis proved that the CIZS-GdO catalyst could successfully reduce the toxicity of tetracycline wastewater. This work has reference value for the application of rare earth oxides in the field of photocatalysis at full pH range.

Novel Br-doped Bi2WO6 photocatalyst for high-efficiency removal of norfloxacin: mechanism and photocatalytic activity.

In this work, the bismuth tungstate (Bi2WO6) photocatalyst was successfully prepared, and the pure Bi2WO6 was modified with Br (Br-Bi2WO6). The effects of different experimental conditions on the degradation of norfloxacin (NOR) solution under visible light were investigated. The Br-Bi2WO6 photocatalyst was characterized by FTIR, XRD, SEM, BET, XPS, DRS, EIS, and EPR. The results show that the Br-modified Bi2WO6 photocatalyst can effectively improve the photocatalytic performance. The best photocatalytic performance of Br-Bi2WO6 was observed when the doping amount of Br was 3%. The degradation percentage of norfloxacin can reach 94.67%. The presence of anions and cations (Cl-, SO42-, Ag+, and Cu2+) in the solution significantly inhibited the photocatalytic activity of 3%Br-Bi2WO6. The photocatalytic degradation of norfloxacin by 3%Br-Bi2WO6 was not greatly affected in the presence of HCO3- and NO3-. The characterization analysis showed that Br was successfully doped on the Bi2WO6 photocatalyst, and the original structure of Bi2WO6 was not destroyed by the addition of Br. Br doping increased the specific surface area of Bi2WO6 and decreased the band gap of Bi2WO6 resulting in a broader visible light absorption range. In addition, Br doping promoted the migration rate of photogenerated electron-hole pairs. The ·O2- and h+ played a major role in the photodegradation of norfloxacin, and the mechanism of photocatalytic degradation of norfloxacin by Br-Bi2WO6 was proposed.

Synthesis of leek-based N,S self-doped CQDs/TiO2 and its application in the photocatalytic degradation of organic pollutants

In this work, N,S self-doped CQDs (N,S-CQDs/TiO2) were synthesized from leeks via a microwave method, and a new leek-based N,S-CQDs/TiO2 composite photocatalytic material was prepared by roasting. The structural characteristics, optical properties, and electrical properties of the N,S-CQDs/TiO2 composites were characterized by Scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray powder diffraction (XRD), Solid ultraviolet–visible diffuse reflectance (UV–vis-DRS), Fourier transform infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transient photocurrent response, and Electrochemical impedance spectroscopy (EIS). In addition, the catalytic degradation effect of N,S-CQDs/TiO2 was evaluated by the photocatalytic degradation of Rhodamine B (RhB) and ibuprofen (IBU). The experimental results showed that the photocatalytic degradation effect of leek-based N,S-CQDs/TiO2 was significantly better than that of TiO2, and N,S-CQDs/TiO2 with 1.86 wt% N,S-CQDs (1.86-N,S-CQDs/TiO2), which demonstrated optimal photocatalytic degradation. The photocatalytic degradation rate of RhB (20 mg/L) was 94.65 % within 120 min of high-voltage mercury lamp irradiation, which was 41.15 % higher than that of TiO2(53.50 %), and the degradation rate was 80.10 % after four cycles. After 180 min, the photocatalytic degradation rate of IBU (10 mg/L) was 96.92 %, which was 26.39 % higher than that of TiO2 (70.53 %), and the degradation rate could still reach 78.94 % after four cycles. In this work, the photocatalytic degradation mechanisms of RhB and IBU by N,S-CQDs/TiO2 were explored by free radical capture and ESR free radical detection experiments. This study may serve as an important reference for enhancing the photocatalytic degradation effect by using biomass self-doped CQDs/TiO2 composite photocatalytic materials, and as a reference for the photocatalytic treatment of organic pollutants in water.

Solar-driven remediation of antibiotics in synthetic and real reverse osmosis brine: Addressing lattice oxygen demand and electron transfer for improved purification

This study investigated the significance of integrated advanced oxidation process with reverse osmosis (RO) to ensure the purification and elimination of micropollutants, primarily pharmaceuticals prior to the discharge of brine to the environment. To envisage this, TiO2 based solar driven photocatalysis was employed, highlighting the crucial role of oxygen vacancy formation in the lattice of TiO2 for enhancing the purification of antibiotic contaminants from RO brine. The study elucidated how variations in oxygen environments such as oxygen rich yellow TiO2 (Y-TiO2) and oxygen vacancy black TiO2 (B-TiO2) influence photodegradation reaction kinetics taking ofloxacin (OFX) and tetracycline (TC) as model pollutants. The B-TiO2 exhibited 8.5 times higher photodegradation for OFX compared to Y-TiO2, proving significance in tuning of oxygen environment in lattice. The photodegradation efficiency plot showcases B-TiO2′s efficacy, demonstrating 99.8 % and 99.4 % for OFX and TC, respectively. Additionally, the study investigated the photocatalytic degradation mechanism, identifying predominant charge carriers and reactive species involved, while also assessing the durability of photodegradation processes. The impact of pH on the photocatalytic performance of B-TiO2 in degrading antibiotics explored, spanning pH levels from 2.5 to 10.5. An exploration on band alignment formation in B-TiO2 explains the effectiveness of it over Y-TiO2. Lastly, efficacy of B-TiO2 in degrading antibiotics in real RO brine with high level of salinity (60,200 ppm TDS) is demonstrated, which resulted with photodegradation efficiency of 31.25 % for OFX and 67.8 % for TC, proving applicability of integrated system as a sustainable purification approach. Moreover, the blockage of chloride ions quenching demonstrated improvements in photodegradation emphasizing the influence of chloride ions in high saline conditions.

Investigation of structural, optical, photocatalytic, and antibacterial properties of ZnO doped GO nanoparticles for environment applications.

As a result of their unique and novel properties, nanocomposites have found applications in a wide variety of fields. The purpose of this study is to demonstrate the ability to synthesize nanoparticles consisting of zinc oxide (ZnO) and graphene oxide (GO) via sol-gel techniques. An x-ray diffractometer (XRD) as well as a UV-visible spectrometer were used to determine the crystalline and optical characteristics of the prepared samples. A hexagonal wurtzite crystal structure was observed in both pure ZnO nanoparticles and those that contain GO based on XRD results. It was estimated that the average crystallite size is based on the broadening of x-ray lines. In comparison with pure ZnO, the antimicrobial properties were enhanced when GO was incorporated with ZnO. In addition, experiments on the absorption edge indicated the presence of a red shift as a result of the incorporation of GO. When GO is incorporated in quantitative amounts, the bandgap value of pure ZnO decreased. FTIR spectra exhibit a band of absorption at 486 cm-1, which confirms Zn-O stretching in both samples. SEM images reveal a random pattern of structural features on the surface of the prepared samples. According to the EDX spectrum, pure GO nanoparticles and those doped with ZnO contain 61%-64% zinc and 32%-34% oxygen, respectively. When annealed at a higher temperature, ZnO NPs produced more H2 with a narrower bandgap than before annealing. In addition, methyl blue (MB) was used as an example of an organic compound in order to investigate the potential photocatalytic properties of nanoparticles with ZnO doped GO. In addition to DPPH assays, ZnO nanoparticles and ZnO doped GO nanoparticles were tested for their ability to scavenge free radicals. Comparing ZnO doped GO NPs with pure ZnO, these nanoparticles showed increased antioxidant activity. Based on the increased zone of inhibition observed for pure ZnO and ZnO doped GO (5, 10, 50, and 100 mg/mL), the antibacterial activity of pure ZnO and ZnO doped GO is concentration dependent. A detailed discussion of the results of the study demonstrated that ZnO doped GO and pure ZnO are toxic in different ways depending on how long they survive in degreased Zebrafish embryos and how fast they decompose. RESEARCH HIGHLIGHTS: The scope of the manuscript was under the results of the study confirmed that both nanoparticles exhibited concentration dependent antioxidative activity. Determined that 89% of methyl orange dye can be degraded photocatalytically. ZnO nanoparticles were found to be 74.86% antioxidant at a concentration of 50 g/mL in the present study. At a concentration of 50 g/mL, ZnO doped GO NPs showed 79.1% antioxidant activity. Photocatalytic degradation mechanism scheme is implicit in the photoexcited charge carrier transportation path is observed for all the samples. Survival rate of zebrafish embryos was shown to decrease with increasing concentrations of ZnO and zinc oxide plus GO nanoparticles.

Green synthesis of Bio-CuS quantum dots by sulfate reducing bacteria for solid-phase photocatalytic degradation of polyethylene film

In this study, CuS quantum dots (QDs) synthesized through biological method were used as photocatalysts for the photocatalytic degradation of polyethylene (PE) plastics. Bio-CuS QDs were synthesized through a green process using sulfate reducing bacteria, while Che-CuS QDs were prepared by chemical precipitation for comparison. The crystal structure, surface morphology, microstructure and optical properties of the samples were detected by XRD, SEM, TEM and UV–Vis DRS. The green synthesis mechanism of Bio-CuS was inferred by analyzing changes in amino acid concentration and the three-dimensional fluorescence spectra of extracellular polymeric substances before and after synthesis. The photocatalytic degradation of PE films by Che-CuS and Bio-CuS was investigated. The weight loss rates of PE+Che-CuS and PE+Bio-CuS were 9.1 % and 12.8 % after 14 d irradiation, respectively, while pure PE was only 1.7 %. Furthermore, SEM, UV–Vis DRS, contact angle, TGA, GPC and FTIR were adopted to characterize the PE film. The results revealed that PE+Che-CuS and PE+Bio-CuS underwent major changes in morphology, transparency, hydrophilicity, thermal stability, molecular weight and functional groups compared with PE, with more pronounced changes observed for PE+Bio-CuS. The quenching experiments of active species showed that h+ and·OH were critical to the PE degradation. The intermediate products of PE degradation were analyzed by GC–MS, and a possible degradation pathway was proposed. In addition, the possible mechanism of photocatalytic degradation of PE films by CuS QDs was proposed. This work provides a green remediation approach to addressing the growing plastic pollution in the environment.

Photocatalytic degradation of non-steroidal anti-inflammatory drugs with ketoprofen as model compound. Intermediates and total reaction mechanism

Ketoprofen KET and other non-steroidal anti-inflammatory drugs NSAIDs are extensively used throughout the world to reduce pain, fever, and inflammation. As a result of this, they have been detected in environmental waters and represent a potential health risk. There are several reports about KET photocatalytic degradation but most of them deal with experimental conditions or catalytic materials to perform this process. In this study, the mechanisms and intermediates involved in KET photocatalysis with TiO2 in aqueous media were investigated. First, the mineralization rate was assessed by TOC measurements. The formation and eventual degradation of intermediate organic compounds were investigated by HPLC, UV–Vis, IR, 1H NMR and HPLC-MS studies. TOC analysis indicate that KET is quickly transformed into other compounds that eventually are degradated and 70 % mineralization was achieved after five hours of irradiation. UV–Vis and HPLC studies indicate that KET is transformed into some other aromatic compounds within minutes. IR studies demonstrate the conversion of KET into several aromatic compounds which in turn degradate into low molecular saturated and unsaturated acids. 1H NMR studies indicate KET is transformed into several aromatic compounds such as 3-hydroxy-benzophenone, phenol, 1,4-hydroquinone, 1,2,4-benzenetriol, and catechol. HPLC-MS studies indicate KET is degradated by several photochemical and photocatalytic parallel mechanisms. Based on this and previous studies, a unified and complete mechanism for KET photocatalytic degradation is presented.

Enhanced Photocatalytic Degradation of Methyl Orange by Metal‐Tio2 Nanoparticles

AbstractIn this study, a series of transition metal‐doped TiO2 was prepared by a simple sol‐solvothermal method. Mix an ethanol solution of tetrabutyl titanate and metal nitrate solution to obtain a homogeneous sol, which is then subjected to solvothermal treatment. After calcination, the metal‐TiO2 naoncomposite was obtained. Selected transition metal precursors, including Cu, Fe, Ag, Cr, Co and Zn, were doped into TiO2 nanocatalysts to assess photocatalytic degradation activities. The results show that 1 mol % Ag−TiO2 photocatalyst has a larger specific surface area, a stable anatase phase and the narrowest forbidden band energy (3.00 eV). In photocatalytic degradation of methyl orange (MO) tests, 1 mol % Ag−TiO2 could reach 100 % decolourisation after 70 min and 75.43 % mineralisation after 90 min. ESR analysis confirmed that Ag doping significantly increased the content of ⋅O2− and ⋅OH for the TiO2 catalyst, which are responsible for the oxidation reactions and consequently degradation of pollutants. The photocatalytic degradation mechanism of MO was also proposed. The TOC analyses confirmed the mineralization of MO. The excellent thermal and chemical stability of 1 mol % Ag−TiO2 has also been demonstrated by thermogravimetric analysis and cycling experiments. Electrochemical tests have also demonstrated the excellent electrochemical properties of 1 mol % Ag−TiO2.

Preparation of Fe2O3/g-C3N4 Photocatalysts and the Degradation Mechanism of NOR in Water under Visible Light Irradiation

Fe2O3/g-C3N4 nano-heterostructures for photocatalytic degradation of NOR (norfloxacin) were successfully prepared by combining co-precipitation and calcination methods. The g-C3N4, Fe2O3, and different composite ratios of Fe2O3/g-C3N4 (FeCNs) were characterized by XRD, SEM, XPS, UV-vis DRS, PL, and electrochemical tests, and the mechanism of photocatalytic degradation of NOR was analyzed. The results indicated that the semiconductor was attached to the surface of g-C3N4 in the form of α-Fe2O3 crystal with good crystalline structure. The composite of Fe2O3 with g-C3N4 increased the specific surface area of the material, effectively reduced the band gap, strengthened the photogenerated e−/h+ pair separation, and improved the photocatalytic performance of the composite. The photocatalytic degradation of NOR was consistent with the quasi-primary reaction kinetic model. Among them, FeCN-25wt% showed the optimal photocatalytic degradation of NOR (72.3%) with the largest degradation rate (k = 0.00900 min−1). The Fe2O3/g-C3N4 composite structure is inferred to be a Z-type heterojunction.

Construction dual active sites on SnO2 via Fe doping for effective ciprofloxacin photodegradation

Adjusting the electronic structure via doping and enhancing the active sites of photocatalysts are proven strategies for improving the photodegradation of pollutants. However, the photodegradation mechanism involving doping elements and their impact on pollutant adsorption and activation at active sites remain unclear. In this study, Fe-doped SnO2 photocatalysts were synthesized using the hydrothermal method, featuring small particle sizes and highly active sites. It was found that doping SnO2 with 3 mol% Fe3+ significantly enhances its photocatalytic efficiency in degrading Ciprofloxacin, outperforming pure SnO2 by approximately 18.6 times. Spectroscopy methods, combined with density functional theory calculations, revealed that the presence of Lewis acid sites and oxygen vacancies serve as active sites in the Fe-doped SnO2 samples. Furthermore, a detailed photodegradation mechanism for Fe-doped SnO2 was proposed based on the band energy structure and analysis of free radical results. This research provides new insights into the mechanism of photocatalytic degradation of Ciprofloxacin by elucidating the interactions between the active sites of the photocatalyst and Ciprofloxacin molecules.

Theoretical Analysis of Superior Photodegradation of Methylene Blue by Cerium Oxide/Reduced Graphene Oxide vs. Graphene.

Density functional theory and a semi-empirical quantum chemical approach were used to evaluate the photocatalytic efficiency of ceria (CeO2) combined with reduced graphene oxide (rGO) and graphene (GP) for degrading methylene blue (MB). Two main aspects were examined: the adsorption ability of rGO and GP for MB, and the separation of photogenerated electrons and holes in CeO2/rGO and CeO2/GP. Our results, based on calculations of the adsorption energy, population analysis, bond strength index, and reduced density gradient, show favorable energetics for MB adsorption on both rGO and GP surfaces. The process is driven by weak, non-covalent interactions, with rGO showing better MB adsorption. A detailed analysis involving parameters like fractional occupation density, the centroid distance between molecular orbitals, and the Lewis acid index of the catalysts highlights the effective charge separation in CeO2/rGO compared to CeO2/GP. These findings are crucial for understanding photocatalytic degradation mechanisms of organic dyes and developing efficient photocatalysts.

Construction of CoFe2O4/Fe2O3 S-type heterojunctions on biochar for activating peroxymonosulfate towards simultaneous removal of TC and Cr(VI)

The construction of S-type heterojunctions for restraining the rapid recombination of photogenerated charges is considered an efficient approach to boost redox capacity. Herein, the growth of CoFe2O4/Fe2O3 S-type heterojunctions on biochar (BC) was accomplished by thermal polymerization-hydrothermal. BC/CoFe2O4/Fe2O3 displayed a wide range of light absorption from 200 to 800 nm and enhanced photocurrent (0.41 μA cm−2). Furthermore, BC/CoFe2O4/Fe2O3 can remove tetracycline (TC) (98.84 %) and Cr(VI) (88.43 %) more efficiently compared to the CoFe2O4 (40.32 % of TC, 68.52 % of Cr(VI)) and Fe2O3 (29.81 % of TC, 53.67 % of Cr(VI)) single counterparts upon 45 min visible light irradiation in the presence of peroxymonosulfate (PMS). Free radical capture experiments revealed that •OH, •O2−, and SO4−• are the primary activated species for the removal of TC and e− is the major activated species for the removal of Cr(VI). Meanwhile, the degradation pathway of TC was monitored via LC-MS and Fukui index calculations. Combining density functional calculations (DFT) with UPS and radical capture tests, the possible mechanism of photocatalytic degradation was proposed. The findings demonstrated the remarkable photocatalytic activity and stability of the photocatalyst, evidencing the potential of BC/CoFe2O4/Fe2O3 for practical wastewater treatment.

Construction of NiTiO3/g-C3N4 heterojunction with preferable photocatalytic performance for tetracycline degradation

Tetracycline antibiotics as one of the most widely used antibiotics at present, are difficult to degrade in the environment, which poses a serious threat to the ecosystem and human health. In this work, NiTiO3/g-C3N4 composites were successfully constructed by calcination method using nickel acetate tetrahydrate as nickel source and tetrabutyl titanate as titanium source. The photocatalytic degradation efficiency of the 5 wt% NiTiO3/g-C3N4 composite of TC can reach 88.2 % within 150 min, which was 1.4 and 2.2 times higher than that of pure g-C3N4 (63 %) and NiTiO3 (40 %), respectively. The 5 wt% NiTiO3/g-C3N4 composite can still maintain good stability after four cycles. The experimental results showed that the construction of Z-scheme heterojunction can effectively improve the photocatalytic activity of the catalysts and maintain good redox properties at the same time. Furthermore, a possible mechanism of photocatalytic degradation of NiTiO3/g-C3N4 heterojunction has been suggested.

Co-W18O49/PDI Z-scheme heterojunction photocatalyst for photocatalytic BPA degradation and mechanism

Efficient migration and separation of photogenerated carriers in semiconductors is crucial to the photocatalytic activity, but significant challenges remain. Herein, the Co-W18O49/PDI composite is prepared, and the Z-scheme mechanism is investigated. The Co-W18O49 nanowires are evenly distributed on the PDI nanorods to create closely connected heterojunctions for enhanced interfacial charge-carrier separation and transfer. The photocatalytic activity of Co-W18O49/PDI is monitored by photocatalytic degradation of BPA by visible light irradiation. The degradation rate of BPA by Co-W18O49/PDI composites was 91.2% within 150 minutes of visible light irradiation. Based on the experimental results of LC-MS and ESR, the photocatalytic degradation mechanism is proposed. The synergistic effect not only improve the generation rate of the active species and reduces the activation energy barrier, but also significantly increases O2 adsorption to make activation easier for efficient photocatalytic BPA degradation.

A review on photocatalytic degradation of aromatic organoarsenic compounds in aqueous environment using nanomaterials

AbstractAromatic organoarsenic compounds (AOCs) have proven to be both a boon and a curse by boosting profit maximization in livestock production and at the same time contributing to the pollution of water bodies, the chief cornerstone of the ecosystem. Interestingly, photocatalytic degradation using nanomaterials has emerged as an effective method to mitigate AOC pollution. Thus, this study aims to review and analyze original research works directed toward the photocatalytic degradation of AOC in the aqueous environment. In this study, the photocatalytic degradation efficiency of various nanomaterials is investigated for different aromatic organoarsenic compounds. In addition, an empirical analysis was conducted on the impact of electron trapping and radical scavengers. Furthermore, photocatalytic degradation kinetics and mechanisms were pragmatically discussed. Also, recyclability, stability, and real‐life applicability were empirically evaluated. According to this review, most nanomaterial materials had maximal photocatalytic degradation efficiencies of >75% for most AOCs within an average time of 6–330 min. The radical scavenging study revealed that ●OH and O2● mechanistically play a major role in AOC degradation than electrons and holes. Additionally, it was shown that expended photocatalysts can be eluted mostly with H2O/NaOH and recycled up to 3–6 rounds with a degradation efficiency of >80% in most cases while maintaining their original structural integrity. This indicates that the method has the potential to be both environmentally friendly and industrially scalable. Ultimately, research gaps were highlighted, which can help researchers identify future research hotspots and open doors for technique advancement.

Construction of Z-scheme SbVO4/g-C3N4 heterojunction with efficient photocatalytic degradation performance

As visible light responsive materials, g-C3N4 has become an outstanding research object for photocatalysis due to its facile synthesis, excellent chemical and thermal stability. In this paper, a Z-scheme SbVO4/g-C3N4 heterojunction was successfully constructed by thermal polymerization method. The synthesized SbVO4/g-C3N4 nanocomposite showed efficient photocatalytic activity on tetracycline (TC) degradation. The photocatalytic degradation of TC follows a first-order kinetic model, in which ·O2− and ·OH free radicals play a major role. The formation of Z-scheme heterojunction between SbVO4 and g-C3N4 can effectively promote the separation of photogenerated electron-hole pairs and the generation of ·O2− and ·OH. The photocatalytic removal rate of TC reached 82.3 % within 150 min under visible light. The as-synthesized SbVO4/g-C3N4 heterojunction can still maintain good stability. Furthermore, a photocatalytic degradation mechanism for the SbVO4/g-C3N4 heterojunction is proposed.

Constructing ZnIn2S4@WO3·H2O Z-type heterojunction to boost photocatalytic efficiency under visible-light irradiation

In this paper, hexagonal ZnIn2S4 nanoflowers were grown in situ on tetragonal WO3·H2O nanosheets, yielding a compact ZnIn2S4@WO3·H2O (ZIS@WO) core-shell heterojunction. The formation of the ZIS@WO heterojunction was optimized by meticulously adjusting the quantity of WO3·H2O nanosheets incorporated. The crystal structure and microstructure of ZIS@WO were comprehensively examined using XRD, TEM and EDS analyses. The photocatalytic properties of ZIS@WO heterojunctions were evaluated through the degradation of organic pollutants under visible light irradiation. The results demonstrated a marked enhancement in photocatalytic efficiency for the ZIS@WO heterojunction. Further investigation into the separation and transport of photogenerated carriers were performed using PL spectroscopy and photoelectrochemical measurement. Compared to the individual components of ZnIn2S4 nanoflowers and WO3·H2O nanosheets, the ZIS@WO heterojunction creates an internal electric field at the interface, along with a compact core-shell configuration. This internal electric field, in conjunction with the band structure of the heterojunction, effectively accelerates the separation of photogenerated electrons and holes. Additionally, a comprehensive analysis of the photocatalytic degradation mechanisms were presented, elucidating the intricate processes.

Enhanced photocatalytic degradation of polylactide (PLA) through TiO2-based up-conversion nanoparticles

As a degradable polymer material, the regulation of the degradation rate of polylactide (PLA) under an actual light exposure environment is of significant importance for realizing its multifaceted applications. This study aims to enhance the photodegradation of PLA under irradiation with lower-energy wavelengths by using TiO2-based up-conversion nanoparticles (UCNPs). Two modification methods were employed: doping TiO2 with Yb3+/Er3+/Tm3+ ions integrated within the TiO2 lattice, and creating a composite photocatalyst by adhering Y2O3: Yb3+/Er3+/Tm3+ to the exterior of TiO2 grains. The study investigated the impact of these two different TiO2-based UCNPs on the photocatalytic degradation rate and mechanism of PLA under simulated sunlight irradiation. Research has found that the doped TiO2, due to its narrower bandgap and higher photon utilization efficiency during the up-conversion process, exhibited superior catalytic efficiency in catalyzing the photodegradation reactions of PLA compared to unmodified TiO2 and composite TiO2. This work proposes a novel strategy for preparing PLA composites with enhanced photodegradation speed provided by modified TiO2, efficient light energy utilization offered by the up-conversion process, and potential applications in more advanced packaging and agricultural fields.

Photocatalytic degradation of antibiotics by N-doped carbon nanoflakes-nickel ferrite composite derived from algal biomass

This work reports the synthesis of nickel ferrite (NiFe) nanoparticles, N-doped mesoporous carbon nanoflakes (NCF) and novel nickel ferrite-carbon nanoflakes (NiFe@NCF) nanocomposite using solvothermal method. NCF was derived from a cyanobacterial consortium consisting of Anabaena, Lyngbya and Weistiellopsis, rich in carbon and nitrogen. The synthesized nanoparticles were used as heterogeneous photocatalyst for degradation of two harmful water pollutants, ciprofloxacin (CIP) and levofloxacin (LEV). 99.91% LEV and 98.86% CIP were degraded within 50 and 70 min of visible light irradiation using NiFe@NCF following pseudo first order kinetics. This improved efficiency of the nanocomposite may be attributed to its higher surface area, reduction of band gap (from 2.42 to 2.19 eV), more active sites as well as charge carrier mobility with decreasing agglomeration tendency of the magnetic nickel nanoparticles upon being embedded on NCF. N-doping improves light harvesting property, retards charge recombination and extends as well as delocalises ᴨ-conjugated system resulting in enhanced photocatalytic activity. The scavenging experiments and EPR analysis reveal that O2−• and •OH are the main active species taking part in the degradation process. The material performs well within a wide range of pH and can be effectively used up to 5 repetitive cycles. A feasible photocatalytic degradation mechanism of the antibiotics against NiFe@NCF nanocomposite is also put forwarded along with their possible degradation pathways from LCMS studies.

Photocatalytic degradation of tetracycline hydrochloride and oxytetracycline using novel zinc-based coordination polymers constructed with mixed linkers

In the present work, a new zinc-based coordination polymer was successfully synthesized by mixed-ligand method with the molecular formula of {[Zn(ipa)(Hpap)]·2H2O}n, (abbreviated as Zn-CP), where ipa = isophthalic acid, Hpap = 4-(1H-pyrazol-4-yl)pyridine. Furthermore, reasonable characterization of Zn-CP was carried out by single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and other spectra. During the characterization process, it was found that Zn-CP can have excellent acid-base stability, water stability and thermal stability. In addition, the complex was able to effectively degrade tetracycline hydrochloride (TCH) and oxytetracycline (OTC) within 60 min under visible light irradiation (with degradation efficiencies of 80.2 % and 83.5 %, respectively), and the cycling experiments showed that Zn-CP could still effectively degrade TCH and OTC after three cycles. Finally, in order to propose a rational photocatalytic degradation mechanism, free radical trapping experiments and energy band structure analysis were also carried out.