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In this work, nanocomposites based on titanium dioxide and reduced graphene oxide (TiO2@rGO) with different weight percentages of rGO (4, 8, and 16 wt%) were prepared by the hydrothermal/solvothermal synthesis method and thermally treated at 300 °C. The prepared nanocomposites were explored for the removal of methylene blue dye (MB) in the presence of simulated solar illumination as well as natural sunlight. The structural, morphological, chemical, and optical properties of the as-synthesized TiO2@rGO nanocomposites were characterized. The obtained results of the graphene-based nanocomposite materials indicated the existence of interactions between TiO2 and rGO, i.e., the Ti–O–C bond, which confirmed the successful integration of both components to form the TiO2@rGO nanocomposites. The addition of rGO increased the specific surface area, decreased the band gap energy, and increased the photocatalytic degradation efficiency of MB from water compared to TiO2 nanoparticles. The results of photocatalytic activity indicated that the amount of rGO in the prepared TiO2@rGO nanocomposites played a significant role in the application of different photocatalytic parameters, including the initial dye concentration, catalyst concentration, water environment, and illumination source. Our studies show that the reinforcement of the nanocomposite with 8 wt% of rGO allowed us to obtain the maximum photocatalytic decomposition performance of MB (10 mg·L−1) with a removal percentage of 99.20 after 2 h. Additionally, the obtained results show that the prepared TiO2@rGO_8 wt% nanocomposite can be used in three consecutive cycles while maintaining photocatalytic activity over 90%. [ABSTRACT FROM AUTHOR]

Textile industries significantly impact the contamination of wastewater. Conventional wastewater treatment methods consider the most common pollutants; however, they are very expensive and commonly produce toxic by-products. In the scientific community, advanced oxidation processes appear to be the most appealing, and a majority of the published work considers heterogeneous photocatalysis for the degradation of various toxic chemicals. For convenience, the reaction is performed directly in the water environment. In this work, a metal-free graphitic carbon nitride (g-C3N4) was prepared through a simple thermal method using urea as a precursor. Prepared g-C3N4 was deposited on the surface of the alumina ceramic ring by the dip-coating method using ethylene glycol as binder. The alumina ceramic ring, as substrate, was prepared by the slip casting method. Photocatalytic properties of immobilised graphitic carbon nitride were used for degradation of methylene blue as a model pollutant under simulated solar light irradiation. The photocatalyst was characterised by XRD, FTIR, UV-Vis DRS, TGA, BET and SEM/EDX analyses. The photocatalytic degradation of MB from an aqueous solution was found to increase with increasing irradiation time. It was found that the graphitic carbon nitride immobilised on alumina ceramic is convenient for largescale environmental applications because the whole setup is cheap, nontoxic, easy to operate and offers reusability with a high removal rate of MB after three consecutive cycles. [ABSTRACT FROM AUTHOR]

This work presents the immobilisation of titanium dioxide (TiO2) nanoparticles (NPs) and reduced graphene oxide (rGO)-TiO2 nanocomposite on glass sheets for photocatalytic degradation of methylene blue (MB) under different radiation sources such as ultraviolet and simulated solar radiation. The TiO2 NPs and rGO-TiO2 nanocomposite were synthesised through a simple hydrothermal method of titanium isopropoxide precursor followed by calcination treatment. Deposition of prepared photocatalysts was performed by spin-coating method. Additionally, ethylene glycol was mixed with the prepared TiO2 NPs and rGO-TiO2 nanocomposite to enhance film adhesion on the glass surface. The photocatalytic activity under ultraviolet and simulated solar irradiation was examined. Further, the influence of different water matrices (milli-Q, river, lake, and seawater) and reactive species (h+, •OH, and e−) on the photocatalytic efficiency of the immobilised rGO/TiO2 nanocomposite was careful assessed. MB dye photocatalytic degradation was found to increase with increasing irradiation time for both irradiation sources. The immobilisation of prepared photocatalysts is very convenient for environment applications, due to easy separation and reusability, and the investigated rGO/TiO2-coated glass sheets demonstrated high efficiency in removing MB dye from an aqueous medium during five consecutive cycles. [ABSTRACT FROM AUTHOR]

This study presents a novel method for the development of TiO2/reduced graphene oxide (rGO) nanocomposites for photocatalytic degradation of dyes in an aqueous solution. The synergistic integration of rGO and TiO2, through the formation of Ti–O–C bonds, offers an interesting opportunity to design photocatalyst nanocomposite materials with the maximum absorption shift to the visible region of the spectra, where photodegradation can be activated not only with UV but also with the visible part of natural solar irradiation. TiO2@rGO nanocomposites with different content of rGO have been self-assembled by the hydrothermal method followed by calcination treatment. The morphological and structural analysis of the synthesized photocatalysts was performed by FTIR, XRD, XPS, UV-Vis DRS, SEM/EDX, and Raman spectroscopy. The effectiveness of the synthesized nanocomposites as photocatalysts was examined through the photodegradation of methylene blue (MB) and rhodamine B (RhB) dye under artificial solar-like radiation. The influence of rGO concentration (5 and 15 wt.%) on TiO2 performance for photodegradation of the different dyes was monitored by UV-Vis spectroscopy. The obtained results showed that the synthesized TiO2@rGO nanocomposites significantly increased the decomposition of RhB and MB compared to the synthesized TiO2 photocatalyst. Furthermore, TiO2@rGO nanocomposite with high contents of rGO (15 wt.%) presented an improved performance in photodegradation of MB (98.1%) and RhB (99.8%) after 120 min of exposition to solar-like radiation. These results could be mainly attributed to the decrease of the bandgap of synthesized TiO2@rGO nanocomposites with the increased contents of rGO. Energy gap (Eg) values of nanocomposites are 2.71 eV and 3.03 eV, when pure TiO2 particles have 3.15 eV. These results show the potential of graphene-based TiO2 nanocomposite to be explored as a highly efficient solar light-driven photocatalyst for water purification. [ABSTRACT FROM AUTHOR]

Numerous studies expose the catastrophic impact of plastic pollution on a daily basis. The research conducted to assess its impact on global ecology and human health suggests an immediate need for action. In particular, aquatic systems are full off toxic chemicals and small man-made organic debris that irreversibly break down into even smaller fragments through biotic or abiotic processes. Among these are microfibers from synthetic textiles. Within the work, we explored the degradation of polyethylene terephthalate (PET), polypropylene (PP), and polyamide (PA) fibers for the purpose of remediation of wastewater from washing machines. By mimicking natural processes, we investigate the benefits of photodegradation enhanced by the use of a photocatalyst and biodegradation by fungi. In the study, photocatalysis was conducted for 48 hours in a covered quartz beaker. The beaker contained fibers, Milli-Q water, and photocatalyst; we tested TiO2 and ZnO. Reactor systems were irradiated while stirring using a UV-vis simulated sun spectrum (Ultra Vitalux, 300 W, Osram). Biodegradation was performed by two selected species of fungi, Pleurostoma richardsiae and Coniochaeta hoffmannii. Sterilized plastic fibers were transferred to tubes with sterile M9 liquid medium. A cell suspension of each selected strain was added to the tube and incubated at 24°C for 2 and 6 months. Microscopy analysis after the photocatalysis showed that the surface of individual fibers became rough with clear signs of partial degradation, which could not be observed on pristine fibers. We also observed a successful growth of fungi, indicating that their main food source came from fibers. Cross-sectional FIB-SEM analysis revealed details of the damage, and Raman analysis showed structural changes in the plastic material. The kinetics of both degradation processes are relatively slow; however, repetition and proper reactor design could potentially increase the dynamics of microplastics degradation. [ABSTRACT FROM AUTHOR]

Plastic, which was not so long ago considered the material of the future, is today one of the biggest environmental problems. The most common type of primary microplastics that enters the aquatic environment in large numbers are fibers released during the washing of synthetic textiles. Due to their small size, they do not enter the ecosystem only through wastewater, but also through sewage treatment plants. In the present work, we tested a method for the degradation of microplastics from the wastewater of a washing machine, which is based on photocatalysis. In our study, the photocatalytic degradation of polyethylene terephthalate (PET) and polyamide (PA) fibers was carried out for 48 hours in a coved quartz beaker. The beaker contained fibers, 5 mg of TiO2 as a photocatalyst, 5 mL of Milli-Q water and a stirrer. In a photocatalytic reactor, quartz beakers were placed on a magnetic stirrer and irradiated with simulated sunlight (lamp: ULTRA-VITALUX, 230 V, 300 W, Osram). After photocatalysis, plastic samples were taken from the suspension and air-dried in a dust-free chamber. SEM analysis after photocatalytic degradation showed that the surface of the fibers became rough with clear signs of degradation, which could not be observed in the original ones. Cross-sectional FIB-SEM analysis revealed details of the damage. Changes in the chemical structure was analyzed by Raman spectroscopy, and ICP-MS analysis was used to analyze the amount of finer microplastic fiber fragments released into the suspension. In the future work, the presented degradation process will also be tested on real samples, which consist of different types of microplastic (PET, PA) and cotton fibers. [ABSTRACT FROM AUTHOR]

The presence of organic pollutants in the environment and their alarming negative effects on the environment and human health have been described in numerous studies [1]. Various methods have been developed to reduce and degrade organic pollutants with varying effectiveness [1]. Synthetic, heterogeneous, semiconducting, and multidimensional ZnO is utilized in various fields [1,2]. ZnO can act as a photocatalyst in the oxidation of organic pollutants, both in powder and thin film form [3]. The main advantages of ZnO thin films are easier and more efficient reusability and the possibility of using them in continuous processes [3]. Several methods are known for the synthesis of ZnO, among which hydrothermal synthesis is widely used due to its advantages such as low process temperature, low cost, and environmental friendliness [2]. It enables the deposition of ZnO on the substrate and offers the possibility to control and optimize the size and morphology of the resulting ZnO crystals. In this study, the ZnO nanorod arrays were synthesized in two parts. First, a solution of zinc acetate dihydrate (0.50 and 0.25 M) was spin-coated onto glass substrates and annealed at 360 °C for 5 hours. In the second part, the hydrothermal growth method was performed at 90 °C for 3 and 6 hours. The morphology and size of the synthesized particles were characterized by SEM. The photocatalytic activity of the ZnO nanorod arrays was evaluated by studying the degradation of a 5 ppm caffeine solution under simulated solar irradiation using UV-Vis spectrophotometry. The results show that ZnO films are photocatalytically active and that their catalytic performance is affected by the synthesis conditions. The ZnO films can be reused since their photocatalytic efficiency does not change significantly during the cycle. Since the stability of the catalysts is important from both an environmental and economic point of view and the results obtained are promising, it would be useful to further improve the ZnO films (e.g., by doping) and to test the photocatalytic degradation of other pollutants. [ABSTRACT FROM AUTHOR]

The three-component hybrid (rGO/TiO2/CN) nanocomposite was prepared in order to enhance the photocatalytic properties of anatase TiO2 nanoparticles (NPs) under solar-like irradiation. The rGO/TiO2/CN was prepared in a mixture of the reduced graphene oxide (rGO, 8 wt%), anatase TiO2 nanoparticles (NPs), and graphitic carbon nitride (g-C3N4, 16 wt%). It was self-assembled through the one-step hydrothermal method, followed by an annealing process. The photocatalyst was thoroughly characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET) nitrogen adsorption/desorption technique and UV-Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the TiO2, TiO2/rGO, TiO2/CN and hybrid rGO/TiO2/CN nanocomposite was studied through the degradation of a rhodamine B (RhB) aqueous solution under solar-like irradiation. The results showed that the highest photocatalytic activity was achieved by the rGO/TiO2/CN mixture, which can be attributed to the synergistic effect of the incorporation of both rGO and g-C3N4 with TiO2. Further, the influence of the pH value of the RhB dye aqueous solution and different water matrix (Milli-Q, tap, and alkaline water) on the photocatalytic efficiency of the rGO/TiO2/CN nanocomposite was examined. In addition, a recycle test was performed for hybrid rGO@TiO2/CN to investigate the effectiveness of the photodegradation of RhB dye in three successive cycles. The conducted results indicate that the pH value of RhB dye aqueous solution and water matrices play an important role in the photocatalytic degradation rate. [ABSTRACT FROM AUTHOR]