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![Band gap potential diagram of the most common semiconductors, used as photocatalysts at NHE scale [22]; reproduced from [22] with permission from the Springer Nature.](publication/353639269/figure/fig4/AS:1052344036892673@1627909778760/Band-gap-potential-diagram-of-the-most-common-semiconductors-used-as-photocatalysts-at.jpg)
Band gap potential diagram of the most common semiconductors, used as photocatalysts at NHE scale [22]; reproduced from [22] with permission from the Springer Nature.
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Plastic waste becomes an immediate threat to our society with ever-increasing negative impacts on our environment and health by entering our food chain. Sunlight is known to be the natural energy source that degrades plastic waste at a very slow rate. Mimicking the role of sunlight, the photocatalytic degradation process could significantly acceler...
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... potentials. As illustrated in Figure 4, using water splitting redox potentials as the reference, TiO2 has a more positive electrochemical potential with respect to the normal hydrogen electrode (NHE) potential. Having the valance band maximum (VBM) more positive than 1.23 eV, showing that the oxidation ability is sufficient in oxidizing water. ...
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Chlorazol yellow (CY) is a commonly used anionic, toxic, mutagenic, and potentially carcinogenic azo dye, which is menacing to the environment, aquatic system, food chain, and human health as well. To remove CY dye molecules from an aqueous medium, a series of Ce, Bi, and N co-doped TiO2 photocatalysts were prepared by varying the composition of th...
Citations
... The ability to enzymatically degrade microplastic has been thought to be limited to a few fungal species, therefore, biodegradation is not yet a viable remediation or recycling strategy [8]. Photocatalytic degradation proves to be a potential method in this direction due to its promisingly environment friendly nature [9,10]. This method is advantageous due to the use of clean energy sources, high degradation efficiency, and more importantly, the generation of harmless end-products. ...
The waste effluents, such as microplastics, present in the drinking water led to health-related issues for humans and animals. Among various plastic materials, low-density polyethylene (LDPE) in the form of microplastic is one of the major sources of environmental pollution. Thus, there is an urgent need to control pollution due to microplastics for environmental sustainability and the human life cycle. Here, we propose an approach to the degradation of LDPE by using the photocatalysis reaction process. We have used In2O3-rGO nanocomposite-based metal oxide that exhibited effective photocatalytic degradation of polyethylene films when illuminated under visible light with different time durations of 0, 10, 20, 30, 40, and 50 h. A substantial variation in surface morphology with pattern formation supports the degradation behavior of visible light-treated films. The XRD results confirm the purity and orthorhombic crystal structure. The Raman measurement results show characteristic modes and reveal the semi-crystalline nature of the films; however, the crystallinity of the films first increases with an increase in illumination time up to 30 h and then decreases. FTIR results indicate variation in the stretching and bending of C–C and CH2 modes in the films, justifying the degradation of LDPE. The thermogravimetric analysis shows a maximum weight loss (99.47%) of the film exposed to visible light for 50 h. The possible mechanism of polyethylene degradation by In2O3–rGO under visible light illumination is also explained.
... A TiO 2 photocatalyst is an attractive material because of its physical and chemical stability, safety, resistance to photocorrosion, low cost, non-toxicity, large specific surface area and oxidation strength [7][8][9][10][11][12][13][14][15][16][17][18][19]. However, its insignificant activity under visible light requires improvements. ...
A mixed metal oxide W-TiO2 nanopowder photocatalyst was prepared by using the sol–gel method with a broad range of elemental compositions x = CW/(CW + CTi), including TiO2 and WO3. The material was structurally characterized and evaluated in adsorption and photocatalytic processes by testing its removal capacity of a representative pollutant methylene blue (MB) in aqueous solutions and under UV-A and sunlight illuminations. The nanopowders appeared to be more effective adsorbents than pure TiO2 and WO3 materials, showing a maximum at 15 mol% W, which was set as the tungsten solubility limit in anatase titania. At the same time, the photocatalytic decomposition of MB peaked at 2 mol% W. The examination of different compositions showed that the most effective MB removal took place at 15 mol% W, which was attributed to the combined action of adsorption and heterogeneous photocatalysis. Moreover, MB decomposition under sunlight was stronger than under UV-A, suggesting photocatalyst activation by visible light. The pollutant removal efficiency of the material with 15 mol% W was enhanced by a factor of ~10 compared to pure TiO2 at the beginning of the process, which shows its high potential for use in depollution processes in emergency cases of a great pollutant leak. As a result, a Wx=0.15-TiO2 catalyst could be of high interest for wastewater purification in industrial plants.
... An alternative mechanism to photodegrade MPs is through oxidizing singlet oxygen, which can be generated through photochemical, thermal, chemical, and enzymatic reactions [102,103]. In this mechanism, singlet oxygen-a highly reactive form of molecular oxygen-directly reacts with and oxidize plastics, causing subsequent chain scission [104]. ...
... The singlet oxygen formed is also capable of reacting with the vinyl group produced by a Norrish reaction [102]. This interaction prompts further decomposition of the molecule, culminating in chain scission and the emergence of the hydroperoxides functional group (ROOH), as illustrated in Figure 9. ...
Microplastics (MPs) are a critical environmental issue, with impacts ranging from ecosystem contamination to health risks through bioaccumulation. This review addresses the inefficacy of traditional water treatments in removing MPs and proposes photodegradation, particularly via nanomaterial-enhanced photocatalysts, as a solution. Utilizing their unique properties like large surface area and tunable bandgap, nanomaterials significantly improve degradation efficiency. Different strategies for photocatalysts modification to improve photocatalytic performance are thoroughly summarized, with the particular emphasis on element doping and heterojunction construction. Furthermore, this review thoroughly summarizes the possible fundamental mechanisms driving photodegradation of microplastics facilitated by nanomaterials, with a focus on processes like free radical formation and singlet oxygen oxidation. By clearly elucidating these strategies and mechanisms, this review aims to provide valuable insights and inspire further progress in microplastic photodegradation.
... La efectividad de un fotocatalizador depende de su potencial de óxido-reducción, en este sentido se muestran a continuación los potenciales de óxido reducción de diversos compuestos usados como fotocatalizadores en la degradación de plásticos. Los valores del potencial normal de oxidación están referenciados al potencial de oxidación normal del hidrogeno [36]. ...
... Por el contrario, si el semiconductor exhibe una banda de conducción mínima más negativa que el potencial normal de reducción de hidrógeno, significa que ese fotocatalizador será capaz entonces de promover la reducción del agua, y cuanto mayor sea la el valor de esa banda de conducción, el foto-catalizador tendrá una mayor capacidad de reducción (ZnS -CdS -CdSe > ZnO > TiO2 -Si) [36]. ...
... Por otra parte, el óxido de zinc (ZnO) posee una separación de bandas semejante a la del TiO2 y a menudo es usado como alternativa al TiO2. Otros semiconductores empleados como fotocatalizadores en la degradación de plásticos son: óxido de hierro (Fe2O3), Sulfuro de cadmio (CdS), sulfuro de zinc (ZnS), oxido de tungsteno (WO3), oxido de estaño (SnO), vanadato de bismuto (BiVO4), y nitruros de carbono no metálicos (N3C4) [36]. A continuación, la tabla 5 muestra un resumen de los distintos sistemas foto-catalíticos heterogéneos que se han estudiado en la degradación de diversos tipos de plásticos. ...
Se describen los procesos de degradación ambiental que sufren los plásticos en el medio ambiente generando así fragmentos de menor tamaño, conocidos como microplásticos. Se describirán los diversos mecanismos químicos mediante los cuales éstos microplásticos se pueden descomponer por efecto de la luz y el oxígeno ambiental (foto-oxidación de polímeros). Se hace énfasis en el rol de la fotoquímica en los procesos de degradación de los microplásticos hasta transtornarlos en compuestos inofensivos para el ambiente, es decir, hasta llevarlos a su mineralización (HCO3, CO2, etc.). Se presentan además algunos avances en el desarrollo de foto-catalizadores heterogéneos basados en metales de transición, empleados en la degradación de los microplásticos, incluyendo un particular e interesante sistema de foto-catalizador microrobot autómata basado en BiVO4/Fe3O4, el cual ha demostrado ser efectivo en la degradación de microplásticos de poliácido láctico (PLA), policaprolactona (PCL), ereftalato de polietileno t (PET) y polipropileno (PP) a escala de laboratorio.
... The photocatalytic degradation of waste microplastic materials have been studied for the last few years, e.g. [34][35][36][37][38][39][40][41][42][43]. However, the photocatalytic degradation can be also connected with the formation of useful chemical substances and it is called photoreforming [44][45][46][47][48][49][50][51][52][53]. ...
Microplastics in the environment are a serious global problem for our society and there is a strong need to develop technologies for their removal and recycling. Photoreforming based on photocatalysis is a novel approach to convert microplastics to useful chemical compounds. In this work, the literature related to the photoreforming of microplastics was reviewed. The main product of the photoreforming was hydrogen obtained from polyethylene terephthalate (PET) and polylactic acid (PLA) with the highest yields of 113 mmol g−1 h−1 and 95.6 mmol g−1 h−1, respectively. The hydrogen yields were processed by the non-parametric Mann-Whitney, Kolmogorov-Smirnov, Mood´s median, and Kruskal-Wallis tests. The pre-treatment of microplastics before the photoreforming was not found to be a critical factor for the photoreforming. In addition, the photoreforming of PET and PLA was statistically proved to provide similar hydrogen yields. The selection of suitable photocatalysts was identified as the most important factor in the photoreforming process due to the effective separation of photoinduced electrons and holes. The reaction conditions should be optimized, especially in terms of the concentration of photocatalysts in the reaction suspensions of highly concentrated KOH or NaOH. The advantages of the photoreforming, such as reactions at ambient temperature and pressure, and the use of visible (solar) irradiation, are a challenge for further research mainly concerning the hydrogen production. More experimental data are necessary to evaluate and optimize some key parameters of this photoreforming process.
... Among the identified polymers, polyethylene (PE) emerges as the most dominant type recorded. In the atmosphere, the presence of ozone, oxides, and various pollutants can accelerate plastic degradation (Lee & Li, 2021). Exposure to sunlight in the presence of oxygen and other pollutants facilitates the cross-linking of polymer chains in PE and PP (Crawford & Quinn, 2017). ...
Microplastics (MPs) pose a threat to ecosystems due to their capacity to bind with toxic chemicals. While the occurrence of MPs in aquatic environmental matrices like water, sediments, and biota is well studied, their presence in the atmosphere remains less understood. This study aimed to determine the presence of airborne MPs and their characteristics through ground-based sampling in the coastal city of Kuala Nerus, Terengganu, Malaysia. Airborne MP samples were collected using passive sampling technique in December 2019. MPs were manually counted and identified using a stereomicroscope based on their colour and shape. The average deposition rate of airborne MPs during the sampling period was 5476 ± 3796 particles/m²/day, ranging from 576 to 15,562 particles/m²/day. Various colours such as transparent (38%), blue (25%), black (20%), red (13%), and others (4%) were observed. The predominant shape of airborne MPs was fibres (> 99%). The morphology structure of MPs observed using a scanning electron microscope (SEM) showed a cracked surface on MPs, suggesting weathering and irregular fragmentation. Further elemental analysis using energy dispersive X-ray spectroscopy (EDS) showed the presence of heavy metals such as aluminium (Al) and cadmium (Cd) on the surface of MPs, attributed to the adsorption capacities of MPs. Polymer types of airborne MPs were analysed using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), which revealed particles composed of polyester (PES), polyethylene (PE), and polypropylene (PP). The preliminary findings could provide additional information for further investigations of MPs, especially in the atmosphere, to better understand their sources and potential human exposure.
... For the photocatalytic degradation of PET, TiO 2 is used because of its versatile properties such as level of oxidation-reduction ability, high-temperature stability, chemical stability, eco-friendly, and cost-effectiveness. ZnO, is also used as photocatalyst with high degradation potential (Lee and Li, 2021). Even though, the photocatalyst plays the major role in photodegradation, the degradation rate highly influenced by the experimental setup, polymeric structure, and photocatalyst mass loading. ...
... Since the 1950 s, plastic, as a synthetic polymer, has been extensively utilized in a wide range of industries and daily life due to its numerous advantages, including low cost, lightweight, convenience, durability, and excellent stability [1][2][3][4]. Based on data from Plastics Europe, global plastic production was around 2 million tons in 1950 and has since surged to 335 million tons in 2016 and 367 million tons in 2020 [5,6]. Moreover, it is projected that the total global plastic production will reach an alarming 330 billion tons by 2050 [7,8]. ...
... In the nine cycles, the photocurrent response remains essentially unchanged, demonstrating the stability and reproducibility of the red QDs. Furthermore, the maximum photocurrent and the speed at which it reaches the maximum value of red QDs capped with SCNexceed those of red QDs capped with PF - 6 . The results confirm that the photogenerated electron-hole separation ability of red QDs capped with SCNis superior to that of red QDs capped with PF -6 . ...
... There are many methods used to overcome the textile waste problem. For example, using active mud [4][5][6] or anaerobic with bioremediation processes [7][8][9], the most common method is photodegradation, utilizing photocatalyst [10][11][12]. Nanostructures used for photocatalyst are ZnO. ZnO nanostructures are beneficial for photocatalysis since Zn has a lower negative standard reduction potential compared to any [13]. ...
ZnO nanostructures were successfully synthesized using the sol-gel method with pineapple extract ( Ananas comosus (L.) ) as a chelating agent. ZnO nanostructures using cayenne pineapple ( Ananas comosus var.cayenne ) chelate were calcined at temperatures ranging from 500 ˚C to 900 ˚C, while queen pineapple ( Ananas comosus var.queen ) was calcined at 700 ˚C and 800 ˚C. ZnO nanostructures synthesized with cayenne pineapple chelate and calcinated at 800 ˚C showed an average particle size of 1.858 μm and an average crystallite size of 35.10 nm, while at 700 ˚C, it was 30.90 nm. The diffraction peaks can be indexed as a hexagonal wurtzite structure (a = 3.25x10 ⁻¹⁰ m, c = 5.21x10 ⁻¹⁰ m). The photocatalytic activity of ZnO was evaluated for the photodegradation of methylene blue under UV light radiation. The most effective degradation was achieved with ZnO nanostructures synthesized with cayenne pineapple chelate at a calcination temperature of 700 ˚C under UV light irradiation for 240 minutes. The degradation rate was 55.87% at a concentration of 10 ppm MB solution.
... It has high chemical stability, hightemperature stability and is not detrimental to the environment. The energy bandgap of TiO2 is small, so when a VB (valence band) electron absorbs energy from light in the UV spectrum, it becomes more excited and jumps to the CB (conduction band) [4]. In another words, when a UV A light shines on a material, it can cause electrons to move from the lower energy level to the higher energy level, creating new possibilities for energy transfer and utilization, forming positively and negatively charged particles (as shown in Figure 2) [5]. ...
Contemporary society has witnessed a large variety of hazard plastic made. Plastic waste has become a major concern for individuals, governments, and organizations all over the world. The extensive use of plastics in producing consumer goods has resulted in huge amounts of plastic waste that has to be managed appropriately. Plastic waste is hazardous to the environment because it takes a long time to decompose. This article starts with a range of explanation techniques and outlines their principles and origins, for examples of common practices in today's culture include photocatalytic degradation, thermal degradation, biodegradation, etc. In the hope that they might effectively decompose these toxic compounds, many people are now pursuing study in these areas in order to offer a quick analysis of the current major explanation methods. A rise in future deteriorating methods can alleviate the negative effects on both human and animals’ life, and thus a healthier ecological environment can be achieved.
