Potential of Scenedesmus-fabricated ZnO nanorods in photocatalytic reduction of methylene blue under direct sunlight: kinetics and mechanism.
02 Feb 2021-Environmental Science and Pollution Research (Springer Science and Business Media LLC)-Vol. 28, Iss: 22, pp 28234-28250
TL;DR: In this article, a green synthesis of ZnO nanorod was achieved in a fast, environment-friendly, and safe microwave process employing algal extract, which showed strong catalytic activity in photoreduction of a model organic dye methylene blue (MB) under direct sunlight irradiation.
Abstract: Organic synthetic dyes are widely used in several industries; however, their inherent resistance to biodegradation necessitates to investigate alternative methods for the remediation of this class of hazardous substances. In the present study, a green synthesis of ZnO nanorods was achieved in a fast, environment-friendly, and safe microwave process employing algal extract. Different metabolites like sugars, proteins, fatty acids, amino acids, and vitamins present in the algal extract reduced the Zn2+ into ZnO. The XRD analysis showed that the nanostructure was a crystalline hexagonal nanorod having a crystalline size of 27.37 nm. The XPS spectra of ZnO nanorod showed characteristic peaks at binding energy 1043, 1020, 496, 137, 87, and 8 eV corresponding to Zn2p1/2, Zn2p3/2, ZnLMM, Zn3s, Zn3p, Zn3d, respectively. The synthesized ZnO nanorods were in-situ functionalized and showed strong catalytic activity in photoreduction of a model organic dye methylene blue (MB) under direct sunlight irradiation. Synthesized ZnO nanorods showed a complete (100%) reduction of model dye MB from its 10 mg/L aqueous solution. The photocatalytic degradation of MB followed the Michaelis-Menten kinetics. The rate of ZnO-catalyzed photocatalytic degradation depends on the concentrations of ZnO, pH, and sunlight irradiation. The ZnO nanorod-catalyzed photoreduction of MB involves hydroxyl radicals. Algal-mediated and microwave-assisted synthesis provides a scalable source of metal oxide nanoparticles for the remediation of dye-containing wastewaters under natural sunlight. Apart from application in the removal of dyes, ZnO nanorods are excellent material for applications in semiconductors, electronics, optics, bio-imaging, and drug delivery.
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TL;DR: In this article, the TiO2/UV photocatalytic degradation of methylene blue (MB) has been investigated in aqueous heterogeneous suspensions, and it has been shown that the degradation pathway can be determined by a careful identification of intermediate products, in particular aromatics, whose successive hydroxylations lead to the aromatic ring opening.
Abstract: The TiO2/UV photocatalytic degradation of methylene blue (MB) has been investigated in aqueous heterogeneous suspensions. In addition to a prompt removal of the color, TiO2/UV-based photocatalysis was simultaneously able to oxidize the dye, with an almost complete mineralization of carbon and of nitrogen and sulfur heteroatoms into CO2 ,N H4 + ,N O3 − and SO4 2− , respectively. A detailed degradation pathway has been determined by a careful identification of intermediate products, in particular aromatics, whose successive hydroxylations lead to the aromatic ring opening. These results suggest that TiO2/UV photocatalysis may be envisaged as a method for treatment of diluted waste waters in textile industries. © 2001 Elsevier Science B.V. All rights reserved.
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TL;DR: In this article, a review of existing research papers on various biological, chemical and physical dye removal methods to find its efficiency through percentage of dye removal is presented, which highlights enzyme degradation and adsorption (physical) dye removal as these are known as one of the most efficient dye removal techniques these days.
Abstract: Dye effluents released from numerous dye-utilizing industries are harmful towards the environment and living things. Consequently, existence of dye effluent in environmental water bodies is becoming a growing concern to environmentalists and civilians. A long term sustainable and efficient dye effluent treatment method should be established to eliminate this issue. Dye wastewater should be treated first before release to minimize its negative impacts towards the environment and living things. However, due to lack of information on efficient dye removal methods, it is difficult to decide on a single technique that resolves the prevailing dye effluent issue. Therefore, this paper reviews existing research papers on various biological, chemical and physical dye removal methods to find its efficiency through percentage of dye removal. Although there are numerous existing tried and tested methods to accomplish dye removal, most of them have a common disadvantage which is the generation of secondary pollution to the environment. This paper highlights enzyme degradation (biological) and adsorption (physical) dye removal as these are known as one of the most efficient dye removal techniques these days. This paper also suggests the usage of a combined adsorbent as it is envisioned that this technique has better efficiency and is able to remove dyes at a faster rate.
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