Photocatalytic Activity Of TiO2 Nanoparticles Research Articles

TiO2 nanotubes immobilized on polyurethane foam as a floating photocatalyst for water treatment

We investigated the photocatalytic activity of TiO2 nanoparticles (TiO2-NPs) and TiO2 nanotubes (TiO2-NTs) supported on a floating polyurethane (PU) foam for removing Bisphenol A (BPA) as a model pollutant. We fabricated TiO2-NPs by the sol-gel method and TiO2-NTs by the ultrasound-assisted hydrothermal method. Subsequently, the photocatalysts were immobilized onto the PU foam through the wet chemical deposition process. The synthesized photocatalysts were characterized by contact angle, SEM-EDS, TEM, XRD, DRS, and BET analyses. TiO2-NPs and TiO2-NTs were successfully deposited onto the PU foam, creating floating photocatalysts denoted as TiO2-NPs@PU and TiO2-NTs@PU. Our findings indicated that the nanotubular structure of floating TiO2 photocatalysts enhanced the removal efficiency of BPA relative to the nanoparticles, resulting in the complete removal of the pollutant over 180 min of simulated sunlight irradiation. TiO2-NTs@PU was also stable after five reuse cycles. Moreover, h+ was the main scavenging reactive species during the photocatalysis of BPA with TiO2-NTs@PU.

Vitamin B5 copper conjugated triazine dendrimer improved the visible-light photocatalytic activity of TiO2 nanoparticles for aerobic homocoupling reactions

In this work, Cu-vitamin B5 (pantothenic acid) bonded to 2,4,6-trichloro-1,3,5-triazine produced a bioconjugated dendrimer giving rise to the visible-light photocatalytic activity of nanocrystalline TiO2. XPS spectra uncovered the coexistence of Cu(II)/Cu(I) oxidation states with a predominant contribution of Cu(I). The new heterogeneous bio-relevant Cu-photocatalyst (Cu(I) Cu(II) [PTAPA G2-B5] @TiO2) revealed a band gap value [Eg = (2.8 eV)] less than those of Cu free components [PTAPA G1-B5]@TiO2 (3.04) and [PTAPA G2-B5]@TiO2 (3.06) and particularly the bare TiO2 (3.15 eV). The reactions showed to be light-dependent with the best performance under room light bulbs. The photocatalytic efficiency of the as-prepared heterojunction photocatalyst was exploited in the aerobic Csp2–Csp2 homocoupling of phenylboronic acid and Csp–Csp homocoupling of phenyl acetylenes under visible-light irradiation to prepare structurally and electronically different biaryls. A radical pathway relying on the photogenerated e− and h+ and involving the Cu(I)–Cu(II) synergistic cooperation was postulated. The reusability and stability of the catalyst were verified by the recycling test, FT-IR spectra, and ICP-OES analysis.

Enhanced Photocatalytic Activity of Metal‐Metal‐Nonmetal Multidoped TiO2 Nanoparticles towards Visible Light

AbstractTiO2 is the most important and remarkable material in photocatalytic applications. In the present work, pure and doped TiO2 nanoparticles were fabricated by the sol‐gel synthesis route. The impact of the metal and nonmetal dopants on the performance of the photocatalysts was examined systematically. X‐ray diffraction (XRD) analysis affirmed the existence of anatase and rutile phases in the fabricated nanoparticles. The diffuse reflectance spectroscopy (DRS) analysis confirmed that all doped TiO2 nanoparticles have a lower bandgap than undoped TiO2, and (N, Cu, Ag)‐doped TiO2 nanoparticles having the lowest bandgap (2.38 eV), demonstrating that metal‐metal‐nonmetal multidoping improves TiO2′s sensitivity towards visible light. In comparison to pure and other doped TiO2 nanoparticles, methylene blue (MB) photodegrades at a faster rate (rate constant of 0.04878 min−1) with the highest photocatalytic activity (99.61 % MB degradation) on the surface of (N, Cu, Ag)‐doped TiO2. The photocatalytic activities of TiO2 nanoparticles have been improved by multidoping in the following sequence: TiO2<N‐doped TiO2<(N, Cu)‐doped TiO2<(N, Ag)‐doped TiO2<(N, Cu, Ag)‐doped TiO2.

A facile strategy for fabrication of nanocomposite ultrafiltration membrane: oily wastewater treatment and photocatalytic self-cleaning

Understanding the importance of reclaiming water from a huge oily wastewater stream generated during the drilling of oil in the petroleum industry and mitigating membrane fouling, a polymeric-inorganic nanocomposite membrane was fabricated with self-cleaning properties. The photocatalytic TiO2 nanoparticles were embedded in the polyvinylidene fluoride (PVDF) matrix during wet phase inversion. To enhance the separation potential and photocatalytic activity of TiO2 nanoparticles, a conjugated polypyrrole (PPy) was grown on the membrane through oxidative polymerization leading to an active layer composed of PPy@TiO2 nano-photocatalyst. The study of membrane wettability revealed the hydrophilic and underwater superoleophobic nature of the PPy@TiO2/PVDF membrane. The PPy@TiO2/PVDF membrane was applied for treating water-containing emulsified oily feed. Different types of feeds contaminated by different oils such as motor oil, diesel oil, and crude oil were studied. The separation efficiency of the PPy@TiO2/PVDF membrane stayed above 99% as the membrane allowed only water to permeate while oil was rejected. The permeate pure water flux was found to be dependent upon feed pressure and the nature of oil in the feed. While keeping the separation efficiency constant at 99%, the flux was decreased with increasing concentration of oil in the feed which is attributed to the fouling of the membrane. The fouled membrane was photo-catalytically cleaned by exposing the fouled PPy@TiO2/PVDF membrane to solar-simulated visible light as the surface features of the cleaned membrane completely resembled that of the pristine PPy@TiO2/PVDF membrane.

Novel gamma-ray enhanced TiO2 nanoparticles photoanode for efficient photoelectrochemical (PEC) water splitting

The photocatalytic activity of TiO2 nanoparticles (TiO2NPs) for Hydrogen Evolution Reduction (HER) was significantly enhanced through a multi-step process involving oxygen-doping with γ-ray irradiation treatment (ranging from 10 kGy to 100 kGy), methanolic dispersion, and post-annealing temperatures. Remarkably, γ rays induced oxygen-doping, leading to improved electronic properties and chemical bonding, as demonstrated in the XPS section, which ultimately contributed to the exceptional stability of the photoanode. The resulting higher crystallinity and larger crystallite sizes, evident in Raman and XRD spectra, further enhanced the structure of the TiO2NPs. Upon γ irradiation, the deposited TiO2NPs exhibited enlargement and agglomeration, which promoted enhanced surface area, catalytic sites, and light absorption when used as a photoanode in PEC cells. The post-irradiation conditions caused a reduction in the energy band gap, resulting in a quenching effect from 3.25 eV to 3.18 eV. Intriguingly, PL analysis showed that the radiated photoanode displayed a remarkable reduction in the energetic separation of photo-generated electron-hole pairs, accompanied by a simultaneous decrease in carrier recombination. Overall, the 70 kGy TiO2NP photoanode demonstrated exceptional photostability and significantly outperformed the pure TiO2NP counterpart by increasing the photocurrent density by over 300%, reaching approximately 100.12 μA cm−2 at 1.23 vs. RHE, compared to 36.42 μA cm−2 for the pure TiO2NP. These findings underscore the significance of gamma irradiation in the field of nanomaterials and its promising potential for photoelectrochemical (PEC) solar water splitting applications.

Visible-Light-Driven Photodegradation of Methylene Blue Dye and Pathogenic Escherichia Coli By Mn-Doped TiO2 Nanoparticles

A sol–gel method was used to synthesize TiO2 nanoparticles doped with varying amounts of Mn. The physico-chemical properties of the synthesized nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and diffuse reflection spectroscopy (DRS). The XRD results indicated that the anatase phase was the major phase of TiO2, while a minor rutile phase was observed in the Mn-doped TiO2 0.2 wt.% and 0.3 wt.% samples. The TEM analysis showed that the Mn atoms existed in different oxidation states, including Mn[Formula: see text], Mn[Formula: see text], Mn[Formula: see text] and Mn[Formula: see text], and that the nanoparticles had a spherical-like morphology with a size ranging from 10[Formula: see text]nm. The narrowest band gap of 2.80[Formula: see text]eV was observed in the Mn-doped TiO2 0.2 wt.% sample. The photocatalytic activity of the synthesized nanoparticles was evaluated for methylene blue (MB) photodegradation and Escherichia coli (E. coli) photokilling under visible light irradiation. The MB degradation efficiency was found to be the highest in the Mn-doped TiO2 0.2 wt.% sample, with a removal efficiency of 96% and a degradation rate constant of 0.08 1/min. The degradation efficiency decreased in the following order: Mn-doped TiO2 0.1 wt.%, 0.3 wt.% and undoped TiO2. Similarly, complete E. coli photokilling was achieved only in the Mn-doped TiO2 0.2 wt.% sample, while some residual E. coli was observed in the other doping nanoparticles and undoped TiO2. In summary, the results suggest that Mn doping significantly improved the photocatalytic activity of TiO2 nanoparticles, and the Mn-doped TiO2 0.2 wt.% sample exhibited the highest efficiency in both MB photodegradation and E. coli photokilling under visible light irradiation.

Photocatalytic performance evaluation of flame‐sprayed and polymeric suspension coatings from TiO2 nanoparticles

AbstractBACKGROUNDHeterogeneous photocatalysis offers an interesting alternative to mitigate air pollution by using materials capable of reacting with toxic gases under ultraviolet light. One of these materials is titanium dioxide (TiO2), and thus it is necessary to analyze and improve its photocatalytic response for air depollution, in order to facilitate its use in surface applications.RESULTSThe photocatalytic ability of the synthesized TiO2 particles to remove nitric oxide (NO) was tested, and it was found that both the anatase and rutile phases present in the samples led to a NO abatement capacity of ≈60% η NO. Two different methods to coat surfaces with TiO2 particles were evaluated: thermal spray by oxyacetylene flame and dripping of polymeric suspensions of TiO2. A more detrimental effect on photocatalytic efficiencies was found using polymeric suspension rather than flame‐spraying as coating method. This was despite the anatase transformation to rutile and Ti7O13 that TiO2 particles undergo using the latter process as a consequence of heat transfer from the flame to the particles during the coating formation.CONCLUSIONResults obtained in this research demonstrate that polymeric suspensions inhibit the photocatalytic activity of TiO2 nanoparticles, probably due to the formation of a polymeric matrix on samples that constrains the action of pollutant and testing factors on samples. However, the thermal method can help retain part of the photocatalytic capability to abate NOx, despite depletion in the anatase content resulting from the heat transfer to the TiO2 raw particles sprayed to form coatings. © 2023 Society of Chemical Industry (SCI).

Effect of Iron-Doping on the Structure and Photocatalytic Activity of TiO2 Nanoparticles

This research reports a simple, innovative, and low-cost doping method of TiO2 nanoparticles presenting the effects of calcination and the weight ratio of TiO2:FeCl3 (1:0.33–1:4.5). The photocatalytic activity of the nanomaterials was investigated by decolorizing Rhodamine B (RhB) dye in an aqueous solution. The main results showed that there is anatase-to-rutile transformation after the calcination process. The Fe-doped process modified the TiO2 spectrum and showed a connection in the Ti–O–Fe vibration. The particle size is within the nanometer range, between 20–51 nm, except for calcined TiO2. The inclusion of Fe in TiO2 decreased the band gap energy from 3.16 (reference) up to 2.06 eV (1:3). Additionally, after the calcination, there was a decrease in this value from 3.03 eV (reference) up to 1.95 eV (1:1.6). The TiO2, with a ratio of (1:1.6), showed the highest activity in the photocatalytic degradation of RhB with an efficiency of 93.8% after 3 h of irradiation.

Photocatalytic Activity of Defective TiO2-x for Water Treatment/Methyl Orange Dye Degradation

This study is designed to highlight photocatalytic activity of TiO2 nanoparticles in methyl orange (MO) dye degradation. Titanium dioxide TiO2 nanopowder was synthesized by conventional sol-gel method and calcined in air atmosphere at different temperatures 350C, 550C and 850C. The prepared TiO2 nanoparticles then were subjected to a solid state reaction with calcium hydride (CaH2) at the same temperatures but calcined in argon atmosphere. X-Ray Diffraction (XRD) measurements used for phase and crystalline size identification showed that the obtained samples have the same TiO2 anatase phase, but the crystalline size decreased after reduction treatment. The electronic properties obtained via UV spectroscopy showed the decrease in calculated energy gap from 3.3 eV for prepared TiO2-550 to 2.65 eV for reduced TiO2-CaH2-550, which extend the absorption spectra toward visible light region. Energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) measurements revealed that the particle size decreased after reduction treatment similar to the XRD crystalline size. EDS results indicated that the deficient in oxygen content relates to formation oxygen vacancies responsible for nonstoichiometric TiO2-x oxides formation. The synthesized reduced TiO2 showed an excellent photo-catalytic activity in methyl orange dye degradation under optimum condition: pH 4.5, 40 mg catalyst loading and 10 ppm initial dye concentration.

Photocatalytic activities of TiO2 nanoparticles modified by nanoclusters of copper oxides prepared by atomic layer deposition

We employed atomic layer deposition to deposit nanoclusters of Cu2O on TiO2 nanoparticles to produce TiO2/Cu2O photocatalysts with the Cu concentration in the range of 0.4 - 4.6%. By annealing the TiO2/Cu2O photocatalysts in the air at 400 °C for 4 h, the oxidation of Cu2O resulted in the formation of TiO2/CuO photocatalysts having the same Cu concentration. Transmission electron microscopy and X-ray diffraction characterizations demonstrated the successful deposition of Cu2O nanoclusters with an average diameter in the range of 1.3 - 2.0 nm and a face-centered cubic crystalline structure, whereas a weak signal of the monoclinic structure of CuO was detected for the TiO2/Cu2O catalysts. The photocatalytic activity of the TiO2/Cu2O and the TiO2/CuO photocatalysts was investigated by the degradation of RhB under UV radiation. The results show that the presence of Cu2O and CuO nanoclusters could improve the photocatalytic activity of TiO2, and for the same Cu concentration, the TiO2/Cu2O photocatalyst provided higher catalytic activity than the TiO2/CuO counterpart.

Exposure to low levels of photocatalytic TiO2 nanoparticles enhances seed germination and seedling growth of amaranth and cruciferous vegetables

Titanium dioxide (TiO2) is one of the most common compounds on Earth, and it is used in natural forms or engineered bulks or nanoparticles (NPs) with increasing rates. However, the effect of TiO2 NPs on plants remains controversial. Previous studies demonstrated that TiO2 NPs are toxic to plants, because the photocatalytic property of TiO2 produces biohazardous reactive oxygen species. In contrast, another line of evidence suggested that TiO2 NPs are beneficial to plant growth. To verify this argument, in this study, we used seed germination of amaranth and cruciferous vegetables as a model system. Intriguingly, our data suggested that the controversy was due to the dosage effect. The photocatalytic activity of TiO2 NPs positively affected seed germination and growth through gibberellins in a plant-tolerable range (0.1 and 0.2 mg/cm2), whereas overdosing (1 mg/cm2) induced tissue damage. Given that plants are the foundations of the ecosystem; these findings are useful for agricultural application, sustainable development and maintenance of healthy environments.

Pyrolysis mechanism of aliphatic amines bound to titania nanoparticles after H2O2 oxidation

Organic compounds bound to peroxotitanates can influence the photocatalytic activity of TiO2 nanoparticles (NPs) obtained by subsequent annealing. Knowledge of how this influence plays out is fundamental for the development of NPs with desirable catalytic behavior, which can be used for several applications. Thermoanalytical techniques can be used to simulate the annealing process on a small scale, but there is a lack of literature on this topic. This is especially true for nitrogen-containing organic compounds, which are not often used as organic modifiers in NP synthesis. Here, we present a multianalytical study of the pyrolytic behavior of the organic fraction of amine-functionalized titania NPs after peroxide treatment (namely peroxotitanate nanoparticles modified with aliphatic amines). The study was carried out by TGA-MS, evolved gas analysis-mass spectrometry (EGA-MS) and double-shot analytical pyrolysis-GC-MS. The most abundant peaks in the GC-MS profiles obtained after thermal desorption were ascribed to nitriles, unsaturated hydrocarbons, and oxygenated compounds, whose total relative areas accounted for almost 100% for DPA and up to 70% for the other amines. This indicated that the presence of an N-Ti bond modulated the oxidating effect of hydrogen peroxide. Pyrolysis of the residual organic fraction on oxidized NPs underwent coupling reactions that led to the formation of aromatic species and, most interestingly, heteroaromatic compounds.

Characterization and photocatalytic activity of TiO2 nanoparticles on cotton fabrics, for antibacterial masks.

The in-situ impregnation of two commercial cotton fabrics (lab coat and Indiolino) with TiO2 nanoparticles (TiO2-NPs) was carried out. For this, two commercial cotton fabrics were dipped in titanium isopropoxide, titanium butoxide and titanium tetrachloride solutions to the TiO2-NPs formation and in-situ TiO2-NPs impregnation on the cotton fabric surface by the sonochemical, hydrothermal and solvothermal methods, respectively. The impregnated fabrics were characterized by ATR-FTIR, SEM–EDS, Raman, UV–Vis, DRS and tension tests. The results showed the successful formation and impregnation of TiO2-NPs on both cotton fabrics. The leaching of TiO2-NPs from cotton fabrics was negligible after several washing cycles. The self-cleaning properties and antibacterial activity of TiO2-NPs functionalized cotton fabrics were assessed by photocatalytic and antibacterial tests. The photocatalytic activity was determined by the degradation of methylene blue dye under UV and solar irradiation. The materials showed good photoactivity, since MB was degraded up to 99% under solar and UV irradiations in 60 min. The bactericidal capacity of the TiO2-NPs on fabrics, evaluated in-situ by SEM, showed that Indiolino presented the best antibacterial properties against Escherichia coli and Bacillus pumilus.

Semi-automated EPR system for direct monitoring the photocatalytic activity of TiO2 suspension using TEMPOL model compound.

The photocatalytic activity of TiO2 nanoparticles in aqueous solutions is commonly evaluated by monitoring the rate of methylene blue bleaching and phenols degradation, but both substrates suffer from many drawbacks, e.g., the high capacity of dark adsorption, self-degradation, and photosensitization. Besides, filtration is always required to separate the particulate photocatalyst before the analysis. Herein, we investigated the potential use of electron paramagnetic resonance(EPR) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) to directly monitor the photocatalytic activity of TiO2 suspensions without the need for filtration. The results showed that TEMPOL aqueous solution is in the dark and under UV-A illumination, does not absorb UV-A and visible light, and has negligible dark adsorption. The influence of TEMPOL concentration, light intensity, and TiO2 loading on the photocatalytic deactivation rate has been investigated. The mechanisms of TEMPOL deactivation in the presence and absence of oxygen as well as in the presence of methanol •OH radicals' scavenger have been discussed. The photocatalytic deactivation products have been analyzed using EPR, 1H-NMR, and 13C-NMR spectroscopies. It is found that the deactivation of TEMPOL is initiated by •OH radicals and α-H abstraction from the 4-piperidine position followed by the formation of TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) and 4-oxo-2,2,6,6-tetramethylpiperidine). In the presence of methanol, the formed α-hydroxyl radicals (•CH2OH) attack the nitroxide side of TEMPOL and produce 4-hydroxy-tetramethylpiperidine. Same activity trends have been observed for the photocatalytic methanol oxidation and TEMPOL deactivation over different types of TiO2 photocatalysts evincing that the proposed method has a potential for direct monitoring of the activities of photocatalyst suspensions.

Enhanced Photocatalytic Activity of TiO2 Nanoparticles Immobilized on Porous-Sulfonated Polystyrene Microspheres through Multiple Scattering Process

Enhanced Photocatalytic Activity of TiO2 Nanoparticles Immobilized on Porous-Sulfonated Polystyrene Microspheres through Multiple Scattering Process

Photocatalytic activity of anatase-brookite TiO2 nanoparticles synthesized by sol gel method at low temperature

TiO2 photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution, and photoelectrochemical conversion. In this paper TiO2 nanoparticle was investigated for the degradation of Rhodamine B (RhB) under UV light. Nanocrystalline Anatase-Brookite TiO2 catalyst was synthesized via sol-gel method using the Titanium tetraisopropoxide (TTIP) at a temperature of 50 °C under mild conditions. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO2 powder has been obtained with diameter <30 nm at 500 °C using an acid. The photocatalytic activity of TiO2 nanoparticle show that the degradation of Rhodamine B under UV light have removal of 95% dye was degraded in 60min.

Antibacterial, antifungal, antiviral, and photocatalytic activities of TiO2nanoparticles, nanocomposites, and bio-nanocomposites: Recent advances and challenges

The applications of nanomaterials specifically metal and metal nanoparticles in various medical and industrial fields have been due to their unique properties compared to bulk materials. A combination of pharmacology and nanotechnology has helped the production of novel antimicrobial agents to control resistant microorganisms of bacteria and fungi. The properties of metal nanoparticles and metal oxides such as titanium dioxide (TiO2), zinc oxide (ZnO), silver (Ag), and copper (Cu) are well known as efficient antimicrobial agents. In particular, TiO2nanoparticles have been considered as an attractive antimicrobial compound due to their photocatalytic intrinsic and their stable, non-toxic, inexpensive, and safe physicochemical properties. Therefore, in this review, recent advances and challenges of antibacterial, antifungal, antiviral, and photocatalytic activities of TiO2nanoparticles, nanocomposites, and bio-nanocomposites are presented to help future studies.

Eco-friendly mechanochemical synthesis of titania-graphene nanocomposites for pesticide photodegradation

Titania graphene hybrid nanocomposites (TiO2-FLG) synthesized from graphite and TiO2 precursors, in a simple and sustainable approach via a three-step method, including the mechanochemical treatment of pre-synthesized FLG and TiO2 NPs are efficient has led to the preparation of TiO2-FLG as efficient nano-catalysts for photocatalytic degradation of a complex mixing of pesticides (isoproturon, pyrimethanil, alachlor and methomyl). The effect of few layer graphene (FLG) loading (0–1.0%) was analyzed to define the optimal ratio of FLG to TiO2 and compared with the corresponding physical mixtures. X-ray Powder Diffraction (XRD) patterns of all these hybrid photocatalysts have presented the same crystal structure, with anatase as the main crystalline phase and brookite as secondary phase. An interaction between the graphene structure and the TiO2 nanoparticles has been observed from Energy Dispersive X-Ray (EDX), X-ray photoelectron (XPS) and Raman spectroscopy studies, indicating that FLG is mainly deposited on the surface wrapping the TiO2 nanoparticles. The presence of FLG in low concentrations and the mechanochemical activation are the key steps to improve the photocatalytic activity of TiO2 nanoparticles on these hybrid nanocomposites. The TiO2-FLG-0.5% hybrid nanocomposite, with circa 1.9 % content of graphitic carbon in surface, has showed the best photocatalytic performance in the degradation of pesticides. Pesticides were completely removed at 350 min, and around 82 % of total organic carbon (TOC) conversion was achieved at 540 min of irradiation time.

Simultaneous adsorption-photocatalytic treatment with TiO2-Sep nanocomposites for in situ remediation of sodium pentachlorophenol contaminated aqueous and soil

Sodium pentachlorophenol (NaPCP) is a highly toxic and persistent organic pollutant. With sepiolite as the support, a series of TiO2-Sep nanocomposites (NCs) with different Ti/Sep ratios were developed. The objective was to understand the effect of Ti/Sep ratio on the structure and activity of the NCs in aqueous and soil systems and to evaluate the feasibility of the NCs for in situ soil remediation. The prepared NCs were characterized with XRD, SEM, TEM, and N2 adsorption-desorption, respectively. The results showed that high surface area and good dispersion of TiO2 on sepiolite surface were obtained. The photocatalytic activities in aqueous and soil of the as-developed NCs were examined using NaPCP as a model pollutant. Compared with bare sepiolite and TiO2, the heterogeneous NCs showed significantly higher photocatalytic performance in decomposing NaPCP, and the photocatalytic activities varied with the content of TiO2 in the NCs. In aqueous media, treatment with TiO2-S-30 showed excellent degradation efficiency with about 90% NaPCP decomposed in 140min. Nevertheless, the sample TiO2-S-20 promotes maximum rate reduction of NaPCP with above 90% within 20-h irradiation in soil. The results indicate that an appropriate Ti/Sep ratio could significantly enhance the activities of NCs on NaPCP remediation and the role of carrier sepiolite is more important in soil media than that in aqueous phase. The excellent performance of the TiO2-Sep in wastewater degradation and soil remediation can be attributed to the synergistic effects between the high photocatalytic activity of TiO2 nanoparticles and the strong adsorption capacity of sepiolite nanofibers. This work revealed that sepiolite adsorption coupled with TiO2 photocatalysis can be one promising technique for in situ remediation of NaPCP-contaminated soil.

Effects of nitrogen/bismuth-doping on the photocatalyst composite of carbon dots/titanium dioxide nanoparticles (CDs/TNP) for enhanced visible light-driven removal of diclofenac

The present work demonstrates the coupling of titanium dioxide, TiO2 nanoparticles (TNP) with N-doped, Bi-doped, and N–Bi co-doped rice husk-derived carbon dots (CDs) via a facile dispersion method, forming respective photocatalyst composites of CDs/TNP, N-CDs/TNP, Bi-CDs/TNP and N–Bi-CDs/TNP. Characterization analyzes verified the successful incorporation of respective CDs samples into TNP, forming photocatalyst composite with narrowed band gap and quenched photoluminescence intensity. Photocatalytic activity of TNP and the respective composites was investigated for photodegradation of diclofenac (DCF) under both simulated sunlight and natural sunlight irradiation. The as-prepared N–Bi-CDs/TNP composite showed the best photocatalytic performance among all composites, able to completely degrade 5 ppm of DCF within 60 min and 180 min under both types of visible light irradiation, respectively. The N–Bi-CDs/TNP composite also showed a TOC removal efficiency up to 87.63%. N–Bi-CDs, worked as photosensitizer and electron reservoir, contributed to the outstanding photocatalytic activity of N–Bi-CDs/TNP, whereby the recombination was prolonged and light absorption was shifted towards the visible light region. Furthermore, the composite of N–Bi-CDs/TNP also demonstrated good stability and reusability over repeated degradation cycles. The photodegradation of DCF resulted into several intermediates, which were identified from LC-MS analysis. The present work could provide an insight on the application of heteroatoms doped and co-doped carbon dots in semiconductor oxide as high performance photocatalysts.