Photochlorination-induced transformation of graphene oxide: Mechanism and environmental fate (original) (raw)
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Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide
arXiv: Materials Science, 2018
Graphene, a two-dimensional (2D) promising emergent photocatalyst consisting of earth-abundant elements. This study evaluated the potential of graphene oxide (GO) towards photocatalytic degradation of a novel organic dye, Methylene Blue (MB). In this work, photocatalytic activity of graphene oxide (GO), graphene oxide (GO) along with hydrogen peroxide (H2O2) were tested by photodegrading Methylene Blue (MB) in aqueous solution. The resulted GO nanoparticles were characterized by X-ray powder diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Ray Spectroscopy. The XRD data confirms the sharp peak centered at 2Theta=10.44 degree corresponding to (002) reflection of GO. Based on our results, it was found that the resulted GO nanoparticles along with H2O2 achieved ~92% photodecolorization of MB compared to ~63% for H2O2 under natural sunlight irradiation at pH~7 in 60 min. The influences of oxygen and hydrogen peroxide (H2O2) on the ...
Chemosphere, 2020
Graphene oxide (GO) is widely used in different applications, however once release into the environment it can change its structure and affect the transport of important contaminants such as arsenic. In this work we show that UV radiation, even in the range of 28-74 µW/cm 2 of irradiance up to 120 h of exposure, can induce important changes in the structure of graphene oxide, by eliminating-OH and C=O functional groups. This reduction affected the stability of graphene oxide in water by decreasing its zeta potential from 41 to 37 mV with the increase of the exposure time. Our results showed that after 24 h of UV exposure, As(III) adsorption capacity decreased from 5 mg/g to 4.7 mg/g, however after 48 h of irradiation the adsorption increased with time, reaching 5.1 mg/g at 120 h under 74 µW/cm 2 of irradiation. Computer modelling showed that even a degraded GO structure can have an interaction energy of 53 kcal/mol with H3AsO3. Furthermore, we observed that despite clear changes in surface composition and particle size, the reduction of graphene oxide maintained a high degree of cytotoxicity since cell viability decreased to 60% with a 50 µg/ml dose; except for the sample irradiated at 74 µW/cm 2 for five days, which showed 20% with the same concentration.
ACS Applied Materials & Interfaces, 2017
This study represents a comprehensive review about the structural features of graphene oxide (GO) and its significance in environmental applications. Two Dimensional (2D) GO is tremendously focused in advanced carbon based nanomaterial for environmental applications due to its tunable physicochemical characteristics. Herein, we report foundational structural models of GO and explore the chemical bonding of oxygen moieties, with graphite basal plane using various characterization tools. Moreover, the impact of these oxygen moieties and the morphology of GO for the environmental applications such as removal of metal ions, catalytic, antibacterial and gas sensing abilities have here been critically reviewed for the first time. Environmental applications of GO are highly significant as in the recent era, the fast progress of industries even in countryside results in air and water pollution. GO has been widely investigated by the researchers to eradicate such environmental issues and for potential industrial and clinical applications due to its 2D structural features, large surface area, presence of oxygen moieties, non-conductive nature, intense mechanical strength, excellent water dispersibility, tunable Optoelectronic properties. Thence, particular emphasis is directed towards the modification of GO by varying the number of its oxygen functional groups and by coupling it with other exotic nanomaterials to induce unique properties in GO for potential environmental remediation purposes.
Insight into the Mechanism of Graphene Oxide Degradation via the Photo-Fenton Reaction
The journal of physical chemistry. C, Nanomaterials and interfaces, 2014
Graphene represents an attractive two-dimensional carbon-based nanomaterial that holds great promise for applications such as electronics, batteries, sensors, and composite materials. Recent work has demonstrated that carbon-based nanomaterials are degradable/biodegradable, but little work has been expended to identify products formed during the degradation process. As these products may have toxicological implications that could leach into the environment or the human body, insight into the mechanism and structural elucidation remain important as carbon-based nanomaterials become commercialized. We provide insight into a potential mechanism of graphene oxide degradation via the photo-Fenton reaction. We have determined that after 1 day of treatment intermediate oxidation products (with MW 150-1000 Da) were generated. Upon longer reaction times (i.e., days 2 and 3), these products were no longer present in high abundance, and the system was dominated by graphene quantum dots (GQDs)....
Photochemical stability and reactivity of graphene oxide
Journal of Materials Science, 2015
The photoreactivity of graphene oxide (GO) suspensions was investigated with a double aim: i) to give insights into the previously reported photo-reduction process, which allows a partial elimination of the oxygen-containing groups from the 2D graphitic structure; ii) to explore the possible use of GO as photo-activator able to promote the photo-transformation/abatement of organic molecules. To reach these goals and clarify some peculiar aspects of the photochemistry of GO till now obscure or confuse, we synthesized and characterized stable GO suspensions which were then subjected to UV-Vis irradiation for prolonged times. GO underwent partial photoreduction with the release of gaseous molecules and soluble organic species (e.g. carboxylic acid). The mechanisms of photo-reduction occurring under air or N 2 are different, as assessed by the release in solution of diverse soluble molecules. In the presence of oxygen, at long irradiation time, a complete solubilization of the graphenic structures was observed. No difference in the nature and amount of released gases (principally CO 2 and CO) was observed in the oxic or anoxic conditions. The possible use of GO as photo-activator was evaluated by using phenol as probe molecule. GO revealed a double role of photo-activator and reagent in phenol degradation, as competition was assessed between GO self-transformation/reduction and phenol degradation. At prolonged irradiation time a marked reactivity of the photoformed species was observed and the complete degradation was achieved for both organic small molecules formed from GO and the phenol added as probe molecule.
Journal of Nanotechnology in Diagnosis and Treatment, 2016
Reduced graphene oxide (RGO)-semiconductor metal oxide nanohybrids at different compositions of RGO and metal oxides (ZnO and/or TiO2) were prepared. The prepared nanohybrids were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and thermogravimetric analysis (TGA). These nanohybrids demonstrated a great improvement in the adsorption of heavy metal ions (As3+ ions) and an enhancement of photocatalytic degradation of an organic pollutant (methylene blue) over the individual nanomaterials in the presence of sunlight. The nanohybrids effectively removed As3+ ions within 60min from the contaminated water. The organic pollutant was efficiently degraded by the studied nanohybrids under solar light as well as direct sunlight. However, among them, RGO-TiO2 demonstrated the best photocatalytic degradation of it under both the conditions. The best-performed nanohybrid was significantly inhibited the growth of both gram negative and p...
Water treatment by new-generation graphene materials: hope for bright future
Environmental science and pollution research international, 2018
Water is the most important and essential component of earth's ecosystem playing a vital role in the proper functioning of flora and fauna. But, our water resources are contaminating continuously. The whole world may be in great water scarcity after few decades. Graphene, a single-atom thick carbon nanosheet, and graphene nanomaterials have bright future in water treatment technologies due to their extraordinary properties. Only few papers describe the use of these materials in water treatment by adsorption, filtration, and photodegradation methods. This article presents a critical evaluation of the contribution of graphene nanomaterials in water treatment. Attempts have been made to discuss the future perspectives of these materials in water treatment. Besides, the efforts are made to discuss the nanotoxicity and hazards of graphene-based materials. The suggestions are given to explore the full potential of these materials along with precautions of nanotoxicity and its hazards....