Solar driven highly efficient photocatalyst based on Dy2O3 nanorods deposited on reduced graphene oxide nanocomposite for methylene blue dye degradation.

In recent years, the demand for rare earth elements has surged due to their unique characteristics and diverse applications. This investigation focuses on utilizing the rare earth element dysprosium oxide (Dy2O3) for the photocatalytic oxidation of model pollutants under solar light irradiation. A novel RGO-Dy2O3 nanocomposite photocatalyst was developed using a solvothermal approach, Dy2O3 nanorods uniformly deposited onto reduced graphene oxide (RGO) nanosheets. Comprehensive characterization techniques, including Brunner-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, high resolution - transmittance electron microscopy (HR-TEM), field emission-electron scanning microscopy (FE-SEM), atomic force microscopy (AFM), electron paramagnetic resonance spectroscopy (EPR), photoluminescence spectroscopy (PL), and electrochemical impedance spectroscopy EIS techniques. The UV-visible diffusive reflectance spectroscopy (UV-Vis-DRS) studies revealed a band gap energy of 3.18 eV and a specific surface area of 114 m2/g for the fabricated RGO-Dy2O3 nanocomposite. The RGO-Dy2O3 nanocomposite demonstrated a high photocatalytic degradation efficiency of 98.1% at neutral pH for methylene blue (MB) dye for the dye concentration of 10 ppm. The remarkable photocatalytic performance was achieved within 60 min under solar light irradiation. Reusability tests demonstrated stability, maintaining over 90% photocatalytic efficiency after three cycles. The EPR spectra and quenching experiments confirmed that photogenerated hydroxyl radicals significantly influence the photodegradation processes. The RGO-Dy2O3 nanocomposite photocatalyst, with its green, easy preparation process and recycling capabilities, presents an ideal choice for various applications. It offers a viable alternative for the photocatalytic degradation of organic dyes in real wastewater, contributing to sustainable environmental remediation.

Kinetics and thermodynamics studies of nickel manganite nanoparticle as photocatalyst and fuel additive.

In this study, nickel manganite (NiMn2O4) nanoparticles were prepared using a hydrothermal method and examined its potential as a photocatalyst for the Acid Green 25 (AG-25) dye degradation. The nanoparticles were subjected to structural analysis using X-ray diffraction (XRD) and morphological analysis using scanning electron microscopy (SEM). The study examined the kinetics and thermodynamics of degradation processes that are catalyzed by photocatalysis. To ascertain their effect on dye degradation, several parameters, such as catalyst dose, H2O2 concentration, and temperature, were investigated. With a temperature of 315 K in a pseudo-first-order kinetic reaction, a 0.3 M H2O2 concentration, 0.05 mg/mL catalyst dose, and a promising removal efficiency of 96 % was achieved by the NiMn2O4 NPs in 40 min. Thermodynamic analysis revealed the spontaneous and entropy-driven nature of catalytic degradation, progressing favorably at elevated temperatures. Additionally, the NiMn2O4 NPs were applied as a fuel additive to analyze its influence on combustion and the physical characteristics of the modified fuel. The modified fuel demonstrated exceptional catalytic efficiency, emphasizing the potential of the NiMn2O4 NPs as an effective additive.

Synergistic effects of Tin sulfide Nitrogen-doped titania Nanobelt-Modified graphitic carbon nitride nanosheets with outstanding photocatalytic activity.

Designing efficient ternary nanostructures is a feasible approach for energy production under simulated solar irradiation. In this study, excellent photoexcited charge carrier separation and enhanced visible-light response were achieved with nitrogen-doped titania nanobelts (N-TNBs), whose 1D geometry facilitated the fabrication of a heterostructure with SnS2 on the surface of graphitic carbon nitride (g-C3N4). We established the design of SnS2@N-TNB and SnS2@N-TNB/g-C3N4 heterostructures by in situ hydrothermal and ultrasonication processes, and achieved commendable simulated solar light driven photocatalytic H2 generation. UV-vis diffuse reflectance spectroscopy analysis revealed a red shift in the absorption spectra of the SnS2@N-TNB and SnS2@N-TNB/g-C3N4 samples. The H2 produced via SnS2@N-TNB-10/g-C3N4 (6730.8 µmol/g/h) was 2.6 times higher than that produced by SnS2@N-TNB (2515.1 µmol/g/h), and 299 times higher than that produced by N-TNB (22.5 µmol/g/h). The improved photocatalytic H2 production was attributed to the maximum interface contact between SnS2@N-TNB and g-C3N4, and to the improved visible-light absorption and effective charge-carrier separation. Therefore, the present study provides novel insights for combining the advantages of ternary materials to improve the conversion of solar energy to H2 fuel.

Au integrated 2D ZnO heterostructures as robust visible light photocatalysts.

Integration of semiconducting nanostructures with noble metal nanoparticles are turning highly desirable for cost efficient energy and environmental related applications. From this viewpoint, we report on a facile aqueous synthesis of polymer capped gold (Au) nanoparticles on free standing 2D layered structures of zinc oxide (ZnO) to result with ZnO/Au nanocomposites. Concentration of Au nanoparticles were observed to promote the preferential growth of ZnO along the (002) wurtzite plane. The ZnO/Au structures and their morphological dissemination was noted to be of few. This flake like structure was also noted to be greatly influenced by the concentration of Au in the colloidal blend. Optical band edge transformations noted in the absorption spectra across the lower wavelength region and the shift in surface plasmon resonance (SPR) towards the red region of the visible spectrum signify the improved absorptivity of the heterostructures along the visible spectrum. These heterostructures exhibited remarkable visible light driven photocatalytic activity (99% efficiency) on par with pristine ZnO. The findings also attest this new class of composite structures to open up new openings in diversified solar energy conversion related functions.

Plasmonic ZnO/Au/g-C3N4 nanocomposites as solar light active photocatalysts for degradation of organic contaminants in wastewater.

In the present study, novel ZnO/Au/graphitic carbon nitride (g-C3N4) nanocomposites were fabricated via a facile and eco-friendly liquid phase pulsed laser process followed by calcination. Notably, the approach did not necessitate the use of any capping agents or surfactants. The as-prepared photocatalysts were evaluated by various electron microscopy and spectroscopy techniques. The obtained results confirmed good dispersion of the Au nanoparticles (NPs) on the surface of spherical ZnO particles deposited on the g-C3N4 nanosheets. The ZnO/Au/g-C3N4 nanocomposite exhibited substantially enhanced catalytic activity toward the degradation of methylene blue (MB) under simulated solar light irradiation. In particular, the ZnO/Au15/g-C3N4 composite containing 15 wt% Au displayed a rate constant, which was approximately 3 and 5 times greater than those of pristine g-C3N4 and ZnO, respectively. This improved photocatalytic activity of ZnO/Au15/g-C3N4 was attributed to the surface plasmon resonance of Au NPs and the synergistic effects between ZnO and g-C3N4. The boundary between ZnO/Au and g-C3N4 enabled direct migration of the photogenerated electrons from g-C3N4 to ZnO/Au, which hindered the recombination of electron-hole pairs and enhanced the carrier separation efficiency. Additionally, a plausible MB degradation mechanism over the ZnO/Au/g-C3N4 photocatalyst is proposed based on the results of the conducted scavenger study.

Synergistic effect of persulfate and g-C3N4 under simulated solar light irradiation: Implication for the degradation of sulfamethoxazole.

A method combining g-C3N4 and potassium peroxydisulfate (PDS) under simulated sunlight was put forward to effectively degrade sulfamethoxazole (SMX). The SMX removal efficiency was substantially improved compared with the processes involving only g-C3N4 or PDS. The kinetic constants for the g-C3N4, PDS and g-C3N4/PDS systems were 0.0023, 0.0239 and 0.068 min-1, respectively. The g-C3N4/PDS process reached an SMX removal rate of 98.4 % after 60 min of simulated sunlight; in addition, the proposed system showed desirable efficiency for SMX degradation in two different actual water samples as well. The reaction mechanism was illustrated by trapping experiments, which showed that g-C3N4 can promote S2O82- to transfer SO4-, S2O82- favored the generation of O2-, and O2-, SO4- and holes (h+) were the main oxidative species for the SMX degradation in the combined reaction process under simulated sunlight. Then, to further explore this mechanism, the intermediates generated during the combined reaction process were analyzed by LC/MS and possible degradation pathways were proposed. The result showed that the breaking of the SN and C-S bonds, the hydroxylation of the benzene ring and the oxidation of the amino group were identified as the main pathways in the SMX degradation process by the g-C3N4/PDS system under simulated sunlight.

Sono-coprecipitation synthesis of ZnO/CuO nanophotocatalyst for removal of parathion from wastewater.

Semiconductor photocatalysis is an effective method used to degrade organophosphorus compounds. Here, the potential of a commonly mixed oxide semiconductor, ZnO/CuO, has been examined to degrade methyl parathion. Sono-coprecipitation method was used to provide ZnO/CuO nanocomposites, and it was applied to photocatalytic and sono-photocatalytic degradation of methyl parathion under solar light irradiation. Powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), the Brunauer-Emmett-Teller (BET) surface area, field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) were used to characterize the synthesized samples. The optimal experimental conditions such as ZnO/CuO photocatalyst 90:10 M ratios, the initial concentration of 20 mg/L parathion, 1 g/L photocatalyst loading, no compressed air sparging, pH of 8, and ultrasonic power (60 W and 80 kHz) were used to degrade the parathion effectively. The parathion was fully (100% removal) degraded after 60 min sono-photoirradiation in the optimal experimental conditions. A real water sample was used to examine the ability of the ZnO/CuO photocatalyst 90:10 to remove the parathion in the water-soluble ions. Graphical abstract.

Prussian blue-encapsulated Fe3O4 nanoparticles for reusable photothermal sterilization of water.

Waterborne health issues continue to grow despite the large number of available solutions. Current sterilization techniques to fight with waterborne diseases struggle to meet the demands on cost, efficiency and reach. Effective alternatives are pressingly required. Here we introduce Prussian blue coated ferroferric oxide (Fe3O4@PB) composites for water sterilization. The composites exhibit superior photothermal inactivation of bacteria under solar-light irradiation, with nearly complete inactivation of bacterial cells in only 15 min. Even for the mixed bacteria in authentic water matrices, the composites show excellent bacterial inactivation performance. Moreover, the highly magnetized iron core of the Fe3O4@PB enables magnetic separation and recycling. Multiple cycle runs reveal that Fe3O4@PB composites have exceptional stability and reusability. This work demonstrates a scalable, low-cost, high-efficiency and reusable sterilization method to improve water quality and safety.

Rapid Solar-Light Driven Superior Photocatalytic Degradation of Methylene Blue Using MoS2-ZnO Heterostructure Nanorods Photocatalyst.

Herein, MoS2-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS2/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase of MoS2. The synthesized MoS2/ZnO heterostructure nanorods were used as a potent photocatalyst for the decomposition of methylene blue (MB) dye under natural sunlight. The prepared MoS2/ZnO heterostructure nanorods exhibited ~97% removal of MB in the reaction time of 20 min with the catalyst amount of 0.15 g/L. The kinetic study revealed that the photocatalytic removal of MB was found to be in accordance with pseudo first-order reaction kinetics with an obtained rate constant of 0.16262 min-1. The tremendous photocatalytic performance of MoS2-ZnO heterostructure nanorods could be accredited to an effective charge transportation and inhibition in the recombination of photo-excited charge carriers at an interfacial heterojunction. The contribution of active species towards the decomposition of MB using MoS2-ZnO heterostructure nanorods was confirmed from scavenger study and terephthalic acid fluorescence technique.

Reactive Black 5 as electron donor and/or electron acceptor in dual chamber of solar photocatalytic fuel cell.

The role of azo dye Reactive Black 5 (RB5) as an electron donor and/or electron acceptor could be distinguished in dual chamber of photocatalytic fuel cell (PFC). The introduction of RB5 in anode chamber increased the voltage generation in the system since degradation of RB5 might produce electrons which also would transfer through external circuit to the cathode chamber. The removal efficiency of RB5 with open and closed circuit was 8.5% and 13.6%, respectively and removal efficiency for open circuit was low due to the fact that recombination of electron-hole pairs might happen in anode chamber since without connection to the cathode, electron cannot be transferred. The degradation of RB5 in cathode chamber with absence of oxygen showed that electrons from anode chamber was accepted by dye molecules to break its azo bond. The presence of oxygen in cathode chamber would improve the oxygen reduction rate which occurred at Platinum-loaded carbon (Pt/C) cathode electrode. The Voc, Jsc and Pmax for different condition of ultrapure water at cathode chamber also affected their fill factor. The transportation of protons to cathode chamber through Nafion membrane could decrease the pH of ultrapure water in cathode chamber and undergo hydrogen evolution reaction in the absence of oxygen which then increased degradation rate of RB5 as well as its electricity generation.

Photodegradation of novel oral anticoagulants under sunlight irradiation in aqueous matrices.

Kinetics of photodegradation of novel oral anticoagulants dabigatran, rivaroxaban, and apixaban were studied under simulated solar light irradiation in purified, mineral, and river waters. Dabigatran and rivaroxaban underwent direct photolysis with polychromatic quantum yields of 2.2 × 10-4 and 4.4 × 10-2, respectively. The direct photodegradation of apixaban was not observed after 19 h of irradiation. Kinetics of degradation of rivaroxaban was not impacted by the nature of the aqueous matrix while photosensitization from nitrate ions was observed for dabigatran and apixaban dissolved in a mineral water. The photosensitized reactions were limited in the tested river water (Isle River, Périgueux, France) certainly due to the hydroxyl radical scavenging effect of the dissolved organic matter. The study of photoproduct structures allowed to identify two compounds for dabigatran. One of them is the 4-aminobenzamidine while the second one is a cyclization product. In the case of rivaroxaban, as studied by very high field NMR, only one photoproduct was observed i.e. a photoisomer. Finally, seven photoproducts were clearly identified from the degradation of apixaban under simulated solar light.

Solar light irradiation significantly reduced cytotoxicity and disinfection byproducts in chlorinated reclaimed water.

Chlorinated reclaimed water is widely used for landscaping and recreational purposes, resulting in human exposure to toxic disinfection byproducts. Although the quality of chlorinated reclaimed water might be affected by sunlight during storage, the effects of solar light irradiation on the toxicity remain unknown. This study investigated the changes in cytotoxicity and total organic halogen (TOX) of chlorinated reclaimed water exposed to solar light. Irradiation with solar light for 12 h was found to significantly reduce the cytotoxicity of chlorinated reclaimed water by about 75%, with ultraviolet light being responsible for the majority of this reduction. Chlorine residual in reclaimed water tended to increase the cytotoxicity, and the synergy between solar light and free chlorine could not enhance the reduction of cytotoxicity. Adding hydroxyl radical scavengers revealed that the contribution of hydroxyl radical to cytotoxicity reduction was limited. Solar light irradiation concurrently reduced TOX. The low molecular weight (<1 kDa) fraction was the major contributor of cytotoxicity and TOX in chlorinated reclaimed water. Detoxification of the low molecular weight fraction by light irradiation was mainly a result of TOX dehalogenation, while detoxification of the high molecular weight (>1 kDa) fraction was probably caused by photoconversion from high toxic TOX to low toxic TOX.

Transformation of DON in reclaimed water under solar light irradiation leads to decreased haloacetamide formation potential during chloramination.

Reclaimed water is usually stored in rivers or lakes before subsequent use. In storage ecosystems, the natural process of solar light irradiation plays a key role in water quality, altering disinfection byproduct formation potential in later use. This study investigated changes in haloacetamide formation potential (HAcAm FP) during subsequent chloramination when reclaimed water was exposed to solar light irradiation. Significant decreases in HAcAm FP were observed for the solar light irradiated reclaimed water, with reductions of 27%-69% for different haloacetamides. Moreover, transformation of dissolved organic nitrogen (DON) to inorganic nitrogen occurred during irradiation. The application of 15N- labeled monochloramine indicated that the nitrogen source of the decreased HAcAms mainly originated from DON, rather than chloramine. Chloramination of the model compound l-asparagine after irradiation demonstrated that the decreased HAcAms could be attributed to the decrease in DON. After solar light irradiation, the brominated HAcAm FP in the presence of bromide was also reduced, while the bromine incorporation factor remained steady. Overall, this study revealed the contribution of natural processes in controlling HAcAm FP during subsequent chloramination, suggesting solar light irradiation is important to water purification during reclaimed water storage.

A novel P/Ag/Ag2O/Ag3PO4/TiO2 composite film for water purification and antibacterial application under solar light irradiation.

TiO2-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag2O/Ag3PO4/TiO2 composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag2O/Ag3PO4/TiO2 composite films with 3 coating layers, synthesized at 400°C for 2h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag2O/Ag3PO4/TiO2 composite film reached 99.9% after 60min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO2 film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 107CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag2O/Ag3PO4/TiO2 composite films were photo-generated holes and O2- radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag2O/Ag3PO4/TiO2 composite films.

Removal of fluorescence and ultraviolet absorbance of dissolved organic matter in reclaimed water by solar light.

Storing reclaimed water in lakes is a widely used method of accommodating changes in the consumption of reclaimed water during wastewater reclamation and reuse. Solar light serves as an important function in degrading pollutants during storage, and its effect on dissolved organic matter (DOM) was investigated in this study. Solar light significantly decreased the UV254 absorbance and fluorescence (FLU) intensity of reclaimed water. However, its effect on the dissolved organic carbon (DOC) value of reclaimed water was very limited. The decrease in the UV254 absorbance intensity and FLU excitation-emission matrix regional integration volume (FLU volume) of reclaimed water during solar light irradiation was fit with pseudo-first order reaction kinetics. The decrease of UV254 absorbance was much slower than that of the FLU volume. Ultraviolet light in solar light had a key role in decreasing the UV254 absorbance and FLU intensity during solar light irradiation. The light fluence-based removal kinetic constants of the UV254 and FLU intensity were independent of light intensity. The peaks of the UV254 absorbance and FLU intensity with an apparent molecular weight (AMW) of 100Da to 2000Da decreased after solar irradiation, whereas the DOC value of the major peaks did not significantly change.

Elimination of disinfection byproduct formation potential in reclaimed water during solar light irradiation.

Ecological storage of reclaimed water in ponds and lakes is widely applied in water reuse. During reclaimed water storage, solar light can degrade pollutants and improve water quality. This study investigated the effects of solar light irradiation on the disinfection byproduct formation potential in reclaimed water, including haloacetonitriles (HANs), trichloronitromethane (TCNM), trihalomethanes (THMs), haloketones (HKs) and chloral hydrate (CH). Natural solar light significantly decreased the formation potential of HANs, TCNM, and HKs in reclaimed water, but had a limited effect on the formation potential of THMs and CH. Ultraviolet (UV) light in solar radiation played a dominant role in the decrease of the formation potential of HANs, TCNM and HKs. Among the disinfection byproducts, the removal kinetic constant of dichloroacetonitrile (DCAN) with irradiation dose was much larger than those for dichloropropanone (1,1-DCP), trichloropropanone (1,1,1-TCP) and TCNM. During solar irradiation, fluorescence spectra intensities of reclaimed water also decreased significantly. The removal of tyrosine (Tyr)-like and tryptophan (Trp)-like protein fluorescence spectra intensity volumes was correlated to the decrease in DCAN formation potential. Solar irradiation was demonstrated to degrade Trp, Tyr and their DCAN formation potential. The photolysis products of Trp after solar irradiation were detected as kynurenine and tryptamine, which had chloroform, CH and DCAN formation potential lower than those of Trp.