CeO
materials have received wide attention given their oxidase-like activity without the need for an unstable oxide substrate in the catalytic process. Nevertheless, their application and mechanism ...in the catalytic oxidation of refractory organic pollutants needs further study. Herein, CeO
hollow microspheres (HMS) with an intrinsic oxidase-like activity were synthesised via a template-free hydrothermal method and their effectiveness in degrading p-nitrophenol(p-NP) was investigated. HMS showed a maximum p-NP degradation rate of 76.5% at a CeO
dosage of 40 mg, 2 h reactive time, at 30°C and pH of 4.8 when the concentration of p-NP was 20 mg L
. The catalytic activity of CeO
HMS also exhibited good thermal stability and reusability. These results provide strong evidence that CeO
HMS can be utilised as an oxidase mimetic for the efficient catalytic degradation of refractory organic pollutants. A possible mechanism for the degradation of p-NP is also discussed.
► Anodic oxidation is an effective method for degrading o-nitrophenol. ► The effect of operating parameters on the degradation was investigated. ► The main intermediate products were determined by ...HPLC technique. ► A plausible degradation pathway of o-nitrophenol was proposed.
The electrochemical oxidation of pesticide, o-nitrophenol (ONP) as one kind of pesticide that is potentially dangerous and biorefractory, was studied by galvanostatic electrolysis using boron-doped diamond (BDD) as anode. The influence of several operating parameters, such as applied current density, supporting electrolyte, and initial pH value, was investigated. The best degradation occurred in the presence of Na2SO4 (0.05M) as conductive electrolyte. After 8h, nearly complete degradation of o-nitrophenol was achieved (92%) using BDD electrodes at pH 3 and at current density equals 60mAcm−2. The decay kinetics of o-nitrophenol follows a pseudo-first-order reaction. Aromatic intermediates such as catechol, resorcinol, 1,2,4-trihydroxybenzene, hydroquinone and benzoquinone and carboxylic acids such as maleic glycolic, malonic, glyoxilic and oxalic, have been identified and followed during the ONP treatment by chromatographic techniques. From these anodic oxidation by-products, a plausible reaction sequence for ONP mineralization on BDD anodes is proposed.
•Chitosan-coated cellulose filter paper was used as support for cobalt nanoparticles preparation.•Cobalt ions were entrapped and reduced by NaBH4 in the chitosan coating layer.•The prepared catalyst ...excellently catalyzed the reductions of toxic 2,6-dinitrophenol and brilliant cresyl blue dyes.•The performance of the catalyst decreased upon using in 4th cycle during re-usability testing.
A facile approach utilizing synthesis of cobalt nanoparticles in green polymers of chitosan (CS) coating layer on high surface area cellulose microfibers of filter paper (CFP) is described for the catalytic reduction of nitrophenol and an organic dye using NaBH4. Simple steps of CFP coating with 1wt% CS aqueous solution followed by Co2+ ions adsorption from 0.2M CoCl2 aqueous solution were carried out to prepare pre-catalytic strips. The Co2+ loaded pre-catalytic strips of CS-CFP were treated with 0.19M NaBH4 aqueous solution to convert the ions into nanoparticles. Successful Co nanoparticles formation was assessed by various characterization techniques of FESEM, EDX and XRD analyzes. TGA analyses were carried out on CFP, CS-CFP, and Co-CS-CFP for the determination of the amount of Co particles formed on the CS-FP, and to track their thermal properties. Furthermore, we demonstrated that the Co-CS-CFP showed an excellent catalytic activity and reusability in the reduction reactions a nitroaromatic compound of 2,6-dintirophenol (2,6-DNP) and brilliant cresyl blue (BCB) dye by NaBH4. The Co-CS-CFP catalyzed the reduction reactions of 2,6-DNP and BCB by NaBH4 with psuedo-first order rate constants of 0.0451 and 0.1987min−1, respectively.
This research investigated the removal mechanisms of p-nitrophenol, p-methoxyphenol, and p-benzoquinone at a porous Ti4O7 reactive electrochemical membrane (REM) under anodic polarization. Cross-flow ...filtration experiments and density functional theory (DFT) calculations indicated that p-benzoquinone removal was primarily due to reaction with electrochemically formed OH•, while the dominant removal mechanism of p-nitrophenol and p-methoxyphenol was a function of the anodic potential. At low anodic potentials (1.7–1.8 V/SHE), p-nitrophenol and p-methoxyphenol were removed primarily by an electrochemical adsorption/polymerization mechanism on the REM. Increasing anodic potentials (1.9–3.2 V/SHE) resulted in the electroassisted adsorption mechanism contributing far less to p-methoxyphenol removal compared to p-nitrophenol. DFT calculations indicated that an increase in anodic potential resulted in a shift in p-methoxyphenol removal from a 1e– direct electron transfer (DET) reaction that resulted in radical formation and significant adsorption/polymerization, to a 2e– DET reaction that formed nonadsorbing products (i.e., p-benzoquinone). However, the anodic potentials were too low for the 2e– DET reaction to be thermodynamically favorable for p-nitrophenol. The decreased COD adsorption for p-nitrophenol at higher anodic potentials was attributed to reaction of soluble/adsorbed organics with OH•. These results provide the first mechanistic explanation for p-substituted phenolic compound removal during advanced electrochemical oxidation processes.
This work attempts to introduce an eco-friendly nano-catalyst PVA/AgNPs portable film for 4-nitrophenol degradation. Silver nanoparticles (AgNPs) doped Polyvinyl Alcohol (PVA) film has been ...synthesized via one-potential pulsed laser ablation in liquids (PLAL) technique. The structural, optical, and morphological studies of the synthesized PVA/AgNPs nanocomposite film have been characterized by different techniques such as; XRD, FT-IR, UV–Vis, PL, FE-SEM, and EDAX. From X-ray diffraction technique (XRD), it is approved that the synthesized PVA/AgNPs film is polycrystalline with cubic structure form. From UV–Visible spectroscopy, the energy band gap was determined by using tauc relation, which was found to be 3.7eV for direct transition. From morphological study, FE-SEM photos of the synthesized PVA/AgNPs film show the homogeneous distributed spherical-like shape of silver nanoparticles in PVA. The qualitative and semi-quantitative elemental analysis of the prepared samples via EDAX technique confirmed the embedding of the silver nanoparticles in the PVA structure. The amazing performance of the prepared PVA/AgNPs film in catalytic degradation activity for 4-nitrophenol reduction has been investigated, which lead to degrade 93% of 4-nitrrophenol in 25 min.
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•The portable film PVA/AgNPs was well prepared by using PLAL process.•XRD diffractograms proved that the embedding of Ag in the chain matrix of PVA is crystalline structure.•FT-IR results confirmed that there is an interaction was happened between AgNPs and PVA.•UV–visible showed the appearing of SPR absorption peak of the embedded AgNPs.•The efficiency percentage amount for degradation of 4-nitrophenol to 4-amiophenl reached 90% in 56 min.
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•Green synthesis of the Pd NPs/Apricot kernel shell using Salvia hydrangea extract.•The catalyst was characterized by FE-SEM, EDS, TEM, XRD, elemental mapping, FT-IR and UV–Vis.•The ...Pd NPs/Apricot kernel shell acted as an effective catalyst in the reduction of CR, RhB, 4-NP, MO and CR.
For the first time the extract of the plant of Salvia hydrangea was used to green synthesis of Pd nanoparticles (NPs) supported on Apricot kernel shell as an environmentally benign support. The Pd NPs/Apricot kernel shell as an effective catalyst was prepared through reduction of Pd2+ ions using Salvia hydrangea extract as the reducing and capping agent and Pd NPs immobilization on Apricot kernel shell surface in the absence of any stabilizer or surfactant. According to FT-IR analysis, the hydroxyl groups of phenolics in Salvia hydrangea extract as bioreductant agents are directly responsible for the reduction of Pd2+ ions and formation of Pd NPs. The as-prepared catalyst was characterized by Fourier transform infrared (FT-IR) and UV–Vis spectroscopy, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive X-ray spectroscopy (EDS), Elemental mapping, X-ray diffraction analysis (XRD) and transmittance electron microscopy (TEM). The synthesized catalyst was used in the reduction of 4-nitrophenol (4-NP), Methyl Orange (MO), Methylene Blue (MB), Rhodamine B (RhB), and Congo Red (CR) at room temperature. The Pd NPs/Apricot kernel shell showed excellent catalytic activity in the reduction of these organic dyes. In addition, it was found that Pd NPs/Apricot kernel shell can be recovered and reused several times without significant loss of catalytic activity.
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► Constructing core–shell structured Fe3O4@SiO2–Ag magnetic nanocomposite. ► Small and highly dispersed Ag nanoparticles with a narrow size distribution. ► An easy magnetically ...separable and recoverable process. ► An excellent catalytic activity toward the reduction of 4-nitrophenol.
In this work, we report a facile method to generate core–shell structured Fe3O4@SiO2–Ag magnetic nanocomposite by an in situ wet chemistry route with the aid of polyvinylpyrrolidone as both reductant and stabilizer. This method can effectively prevent Ag nanoparticles from aggregating on the silica surface, thus resulting highly dispersed and small-sized Ag nanoparticles. The as-prepared nanocomposite is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and numerous highly dispersed Ag nanoparticles with a narrow size distribution. Furthermore, the Fe3O4@SiO2–Ag nanocomposite showed high performance in the catalytic reduction of 4-nitrophenol and could be easily recycled by applying an external magnetic field while maintaining the catalytic activity without significant decrease even after running 15 times.
Transthyretin (TTR) is a plasma homotetrameric protein implicated in fatal systemic amyloidoses. TTR tetramer dissociation precedes pathological TTR aggregation. Native state stabilizers are ...promising drugs to treat TTR amyloidoses. Here we repurpose tolcapone, an FDA-approved molecule for Parkinson's disease, as a potent TTR aggregation inhibitor. Tolcapone binds specifically to TTR in human plasma, stabilizes the native tetramer in vivo in mice and humans and inhibits TTR cytotoxicity. Crystal structures of tolcapone bound to wild-type TTR and to the V122I cardiomyopathy-associated variant show that it docks better into the TTR T4 pocket than tafamidis, so far the only drug on the market to treat TTR amyloidoses. These data indicate that tolcapone, already in clinical trials for familial amyloid polyneuropathy, is a strong candidate for therapeutic intervention in these diseases, including those affecting the central nervous system, for which no small-molecule therapy exists.
A simple and green approach for the synthesis of photoluminescent N,S-carbon dots (N,S-CDs) has been proposed using a single natural source precursor (bamboo leaf) as raw materials. The ...as-synthesized N,S-CDs exhibited a highly stable, excitation wavelength-dependent emission, excellent photobleaching, alkali, and salt tolerance. Here, the mechanism of N,S-CDs luminescence was studied via the UV–vis absorption spectrum and photoluminescence spectroscopy. Based on the quenching properties of nitrophenol compounds on the fluorescence of N,S-CDs, the interaction between N,S-CDs and nitrophenol compounds was investigated on detail in aqueous solution. More importantly, the study on photophysical properties of the N,S-CDs may provide the basis for the development of the N,S-CDs for the fluorescent probe of nitrophenol compounds.
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•High fluorescence N,S-CDs were synthesized with bamboo leaves as carbon source.•The spectral characteristics of N,S-CDs such as absorption and fluorescence were examined in detail.•Different nitrophenols exhibited different fluorescence quenching effects on N, S-CD.•The interaction between nitrophenols and N,S-CDs, and the mechanism of fluorescence quenching are discussed.
Vertical baffled biofilm reactors (VBBR) equipped with Plastic-carriers and Fe-carriers were employed to explore the effect of biofilm carriers on biofilm formation and p-nitrophenol (PNP) ...degradation. The results showed that Fe-carriers enhanced biofilm formation and PNP degradation. The maximum thickness of biofilm grown on the Fe-carriers was 1.5-fold higher than that on the Plastic-carriers. The Fe-VBBR reached a maximum rate of PNP removal at 13.02 μM L−1 h−1 with less sodium acetate addition (3 mM), while the maximum rate of PNP removal was 11.53 μM L−1 h−1 with more sodium acetate addition (6 mM) in the Plastic-based VBBR. High-throughput sequencing suggested that the Fe-VBBR had a higher biodiversity of the bacterial community in evenness, and the Achromobacter genus and Xanthobacteraceae family were as main PNP degraders. Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology analysis suggested more abundances of iron uptake genes were expressed to transport iron into the cytoplasm under an iron-limited condition in two VBBRs, and the metabolic pathway of PNP degradation went through 4-nitrocatechol and 1,2,4-benzenetriol. Our results provide a new insight for iron enhancing biofilm formation and PNP degradation.
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•Fe-carriers can promote biofilm formation and PNP degradation.•More iron uptake genes were expressed under iron-limited conditions.•Plastic-VBBR had a lower community diversity than Fe-VBBR.•Achromobacter genus and Xanthobacteraceae family may be as PNP degraders.
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