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Ti-doped ZnO sol-composite films were prepared on the glass substrate by the two-step sol-gel technique. X-ray diffraction, Uv-Vis spectrophotometer, and FS spectrum of composite films were used to help make structure characterization and optical performance testing. The results showed that the composite was a mixture of ZnO + Zn sub(2) TiO sub(4) . Because of synergistic effect of both semiconductor oxides, composite films had a wide range of spectral response in the visible region, and the absorption band edge was about 510 nm, and the Green Belt of composite films luminous significantly enhanced. Photocatalytic oxidation experiments showed that using the composite films treatment (16.5 ml, l0 mg/L methyl orange aqueous solution)/cm super(2) , the decolorization rate of methyl-orange was 90% after 3 hours irradiation.

Dye contamination of wastewater has become one of the most critical environmental problems these days. The most critical sources of dyes in wastewater are from industries such as textile factories, food, paper and printing products and vehicles productions. There are various techniques for the removal of dyes from wastewater such as adsorption, oxidation process, photocatalyst, biological decolorization and membrane separation technology. In this paper, the recent advances in the removal of dyes from wastewater by membrane technology as one of the most promising and effective water treatment methods have been reviewed. This review paper covers published articles mostly from 2000 to 2020. It is evident from literature survey articles that nanofiltration (NF) is the most studied type of membrane for the elimination of dyes from wastewater.

Electro-Fenton processes aim at producing oxidizing radicals with fewer added chemicals and residues but are still unable to completely eliminate both. This study demonstrates that a reagent-free electro-Fenton process that runs solely on oxygen and electricity can be achieved by sequential dual-cathode electrocatalysis. H₂O₂ is produced on an electrodeposited PEDOT on carbon cloth (PEDOT/CC) cathode and subsequently converted to hydroxyl radicals on a stainless-steel–mesh cathode. The dual-cathode system demonstrates efficient decolorization and total organic carbon (TOC) removal toward organic dyes at optimized cathodic potentials of −0.9 V for PEDOT/CC and −0.8 V for the stainless-steel mesh. The sequential dual-cathode process also displays high reusability, no iron leaching, high removal efficiency using air instead of oxygen, and low installation and operation costs. This work demonstrates a preeminent and commercially viable example of pollution control rendered by the “catalysis instead of chemical reagent” philosophy of green chemistry.

Congo red is one of the best known and used azo dyes which has two azo bonds (-N=N-) chromophore in its molecular structure. Its structural stability makes it highly toxic and resistant to biodegradation. The objective of this study was to assess the congo red biodegradation and detoxification by Aspergillus niger. The effects of pH, initial dye concentration, temperature, and shaking speed on the decolorization rate and enzymes production were studied. The maximum decolorization was correlated with lignin peroxidase and manganese peroxidase production. Above 97% were obtained when 2 g mycelia were incubated at pH 5, in presence of 200 mg/L of dye during 6 days at 28°C and under 120 to 150 rpm shaking speed. The degraded metabolites were characterized by using LC-MS/MS analyses and the biodegradation mechanism was also studied. Congo red bioconversion formed degradation metabolites mainly by peroxidases activities, i.e., the sodium naphthalene sulfonate (m/z = 227) and the cycloheptadienylium (m/z = 91). Phytotoxicity and microtoxicity tests confirmed that degradation metabolites were less toxic than original dye.

Dye decoloring peroxidases (DyPs) were named after their high efficiency to decolorize and degrade a wide range of dyes. DyPs are a type of heme peroxidase and are quite different from known heme peroxidases in terms of amino acid sequences, protein structure, catalytic residues, and physical and chemical properties. DyPs oxidize polycyclic dyes and phenolic compounds. Thus they find high application potentials in dealing with environmental problems. The structure and catalytic characteristics of DyPs of different families from the amino acid sequence, protein structure, and enzymatic properties, and analyzes the high-efficiency degradation ability of some DyPs in dye and lignin degradation, which vary greatly among DyPs classes. In addition, application prospects of DyPs in biomedicine and other fields are also discussed briefly. At the same time, the research strategy based on genetic engineering and synthetic biology in improving the stability and catalytic activity of DyPs are summarized along with the important industrial applications of DyPs and associated challenges. Moreover, according to the current research findings, bringing DyPs to the industrial level may require improving the catalytic efficiency of DyP, increasing production, and enhancing alkali resistance and toxicity.

Green synthetic method is an important process that can be used for the synthesis of iron nanoparticles in the field of nanotechnology because of its characteristics of low cost and high efficiency for industrial large-scale production. In this study, iron oxide nanoparticles (IONPs) were synthesized by a simple bio-reduction method. Aqueous leaf extract of Daphne mezereum was used as a reducing and stabilizing agent. Ultraviolet–visible (UV–vis) absorption spectroscopy was used to monitor the dye removing ability of IONPs. Also, IONPs were characterized by transmission electron microscopy (TEM), particle size analysis (PSA), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), and thermo gravimetric analysis (TGA). The average diameter of the prepared NPs ranged from 6.5 to 14.9 nm with a mean particle size of 9.2 nm. In addition, the synthesized iron nanoparticles were tested for dye removing activities. The decoloration efficiency of INPs catalyzed reaction was about 81% after 6 h. Thus, it could be concluded that D. mezereum aqueous leaf extract can be used efficiently in the production of iron oxide NPs for commercial applications in environmental fields.

The field of engineered living materials lies at the intersection of materials science and synthetic biology with the aim of developing materials that can sense and respond to the environment. In this study, we use 3D printing to fabricate a cyanobacterial biocomposite material capable of producing multiple functional outputs in response to an external chemical stimulus and demonstrate the advantages of utilizing additive manufacturing techniques in controlling the shape of the fabricated photosynthetic material. As an initial proof-of-concept, a synthetic riboswitch is used to regulate the expression of a yellow fluorescent protein reporter in Synechococcus elongatus PCC 7942 within a hydrogel matrix. Subsequently, a strain of S. elongatus is engineered to produce an oxidative laccase enzyme; when printed within a hydrogel matrix the responsive biomaterial can decolorize a common textile dye pollutant, indigo carmine, potentially serving as a tool in environmental bioremediation. Finally, cells are engineered for inducible cell death to eliminate their presence once their activity is no longer required, which is an important function for biocontainment and minimizing environmental impact. By integrating genetically engineered stimuli-responsive cyanobacteria in volumetric 3D-printed designs, we demonstrate programmable photosynthetic biocomposite materials capable of producing functional outputs including, but not limited to, bioremediation. Engineered living materials (ELMs) are emerging as a field at the intersection of materials science and synthetic biology. Here, the authors describe a photosynthetic ELM composed of genetically engineered cyanobacteria in a hydrogel matrix, capable of bioremediation and inducible cell death.

The textile industry consumes a large volume of organic dyes and water. These organic dyes, which remained in the effluents, are usually persistent and difficult to degrade by conventional wastewater treatment techniques. If the wastewater is not treated properly and is discharged into water system, it will cause environmental pollution and risk to living organisms. To mitigate these impacts, the photo-driven catalysis process using semiconductor materials emerges as a promising approach. The semiconductor photocatalysts are able to remove the organic effluent through their mineralization and decolorization abilities. Besides the commonly used titanium dioxide (TiO 2 ), manganese dioxide (MnO 2 ) is a potential photocatalyst for wastewater treatment. MnO 2 has a narrow bandgap energy of 1~2 eV. Thus, it possesses high possibility to be driven by visible light and infrared light for dye degradation. This paper reviews the MnO 2 -based photocatalysts in various aspects, including its fundamental and photocatalytic mechanisms, recent progress in the synthesis of MnO 2 nanostructures in particle forms and on supporting systems, and regeneration of photocatalysts for repeated use. In addition, the effect of various factors that could affect the photocatalytic performance of MnO 2 nanostructures are discussed, followed by the future prospects of the development of this semiconductor photocatalysts towards commercialization.

Image rescaling is a commonly used bidirectional operation, which first downscales high-resolution images to fit various display screens or to be storage- and bandwidth-friendly, and afterward upscales the corresponding low-resolution images to recover the original resolution or the details in the zoom-in images. However, the non-injective downscaling mapping discards high-frequency contents, leading to the ill-posed problem for the inverse restoration task. This can be abstracted as a general image degradation–restoration problem with information loss. In this work, we propose a novel invertible framework to handle this general problem, which models the bidirectional degradation and restoration from a new perspective, i.e. invertible bijective transformation. The invertibility enables the framework to model the information loss of pre-degradation in the form of distribution, which could mitigate the ill-posed problem during post-restoration. To be specific, we develop invertible models to generate valid degraded images and meanwhile transform the distribution of lost contents to the fixed distribution of a latent variable during the forward degradation. Then restoration is made tractable by applying the inverse transformation on the generated degraded image together with a randomly-drawn latent variable. We start from image rescaling and instantiate the model as Invertible Rescaling Network, which can be easily extended to the similar decolorization–colorization task. We further propose to combine the invertible framework with existing degradation methods such as image compression for wider applications. Experimental results demonstrate the significant improvement of our model over existing methods in terms of both quantitative and qualitative evaluations of upscaling and colorizing reconstruction from downscaled and decolorized images, and rate-distortion of image compression. Code is available at https://github.com/pkuxmq/Invertible-Image-Rescaling.

TiO 2 /ZnO nanocomposites with ratio of Ti/Zn of 1:0, 1:1, 2:1, 3:1 and 0:1 was synthesized by sol–gel and hydrothermal methods. The performance and the photocatalytic of the nanocomposities mechanism were studied by X-ray diffractometer (XRD), Fourier transformed infrared (FT-IR), Brunauer–Emmett–Teller method (BET), Transmission Electron Microscopy (TEM), High-Resolution Transmission Electron Microscope (HRTEM) and UV–visible diffuse reflectance spectra (UV-Vis), respectively. The results showed that TiO 2 /ZnO nanocomposites successfully prepared at different Ti/Zn rations. HRTEM results clearly heterojunction structure, and it can reduce the band gap width of the composite and improve the optical absorption intensity. Besides, the degradation rate of methylene blue (MB) of TiO 2 /ZnO nanocomposites with a Ti/Zn ratio of 2:1 was close to 100% at 80 min, which was better than the other four samples. The photocatalytic degradation reaction confirmed to the first-order kinetic equation. The kinetic constant of TiO 2 /ZnO nanocomposites with a ratio of 2:1 is 0.03748 min −1 , which is 2.8 times of pure ZnO and 4.8 times of pure TiO 2 , respectively. In addition, the major active species of the photocatalytic reaction are •OH and h + through activity capture experiments. The improvement of the catalytic performance of TiO 2 /ZnO nanocomposites is mainly due to the ability to separate holes and electrons. Highlights High efficiency TiO 2 /ZnO photocatalysts are prepared by sol–gel and hydrothermal technology. Increase in catalytic efficiency due to the separation efficiency of electrons and holes. MB decolorization is not directly related to adsorption. The degradation of MB is a first order degradation kinetics. The major reactive species for photodegradation is the •OH.