Search

A new electrode was constructed via the anodic electropolymerization of poly-(L-serine) (PLS) on an rGO−Nafion–modified glassy carbon electrode (GCE) for the detection of the emerging organic contaminant naproxen (NPX). The morphology, crystal phase, and surface elements of the electrode were investigated with SEM, TEM, XRD, Raman, ATR-FTIR, zeta potential, C−H−O, and XPS analyses. Results of the surface analysis showed a porous structure resembling graphene sheets inside the Nafion/GCE architecture. Various electrochemical parameters, including scan rate, pH, and NPX concentration, were studied to evaluate the performance of the electrode. The synergistic effect of PLS and rGO−Nafion greatly facilitated the catalytic oxidation of NPX on PLS/rGO−Nafion/GCE. Electrochemical NPX oxidation was a one-electron transfer and adsorption limited process. The optimal working potential was 0.92 V vs. Ag/AgCl. The oxidation current of NPX increased with the increase in the concentration of analyte and scan rate but decreased with pH. The modified electrode exhibited excellent linearity with respect to NPX concentration in the range of 4.3 to 87 μM and limit of detection of 0.23 μM (S/N = 3). The PLS/rGO−Nafion/GCE is a fast, sensitive, reliable, and economical electrode for the detection of NPX in water. [ABSTRACT FROM AUTHOR]

This study evaluated the use of magnetite (Fe3O4), carbon black (CB), and Fe3O4-CB composites activated by persulfate (PS) at circumneutral pH to oxidize polycyclic aromatic hydrocarbons (PAHs) in marine sediments. In addition, the in vitro cytotoxic activity and apoptotic response of the obtained degradation products were investigated. Chemical analyses showed that the total PAH concentration was 26,263 ng/g for sediment samples from an industrial port area. Highly toxic BaP was the main contributor to the TEQ in sediments. Source analyses demonstrated that the PAHs in the sediment were derived from coal combustion. In this study, we found that the PS oxidation processes effectively degrade PAHs at concentration levels of 1.7 × 10−5 M at pH 6.0. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the cytotoxicity of the PAH degradation products before and after Fe3O4/PS, CB/PS, and Fe3O4-CB/PS oxidation treatment using a human hepatoma carcinoma cell line (HepG2) and a zebrafish (Danio rerio) embryonic cell line (ZF4). Each sample extract showed a marked dose-related response, with the cell viability reduced by 82% in the case of HepG2 and 58% in the case of ZF4 at 100 μg/mL after the Fe3O4-CB/PS process. The PAH degradation products had different effects on the cell morphologies of the two cell lines. The results suggested that the ZF4 cell model is more sensitive than HepG2 to the toxicity of the PAH samples. [ABSTRACT FROM AUTHOR]

Phthalate esters (PAEs) can interfere with the endocrine systems of humans and wildlife. The main objective of this study was to evaluate the suitability of a composite for remediating marine sediments contaminated with PAEs. The composite was synthesized with magnetite nanoparticles (Fe3O4) and rice husk biochar (RHB) by using chemical co-precipitation. Fe3O4, RHB, and Fe3O4–RHB substantially activated sodium persulfate (Na2S2O8, PS) oxidation to form SO4−• and thus degrade PAEs in marine sediments in a slurry system. The morphology and structural composition of the magnetic composites were examined using XRD, FTIR, environmental scanning electron microscopy–energy-dispersive X-ray spectrometry, and superconducting quantum interference device. The Fe3O4–RHB composites were confirmed to be prepared successfully. The influences of various parameters, including the PS concentration, composite loading, and initial pH, were investigated. The concentration of high-molecular-weight PAEs (HPAEs) in sediment was much higher than that of low-molecular-weight PAEs (LPAEs); di-(2-ethylhexyl) phthalate (DEHP) was an especially salient marker of PAE contamination in sediments. Furthermore, increasing the PS and Fe3O4–RHB doses accelerated PAE oxidation at pH 3.0; 83% degradation of PAEs was achieved when the PS and Fe3O4–RHB concentrations were increased to 2.3 × 10−2 mM and 1.67 g/L, respectively. LPAEs such as dibutyl phthalate (DnBP) are easier to degrade than HPAEs such as DEHP, diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP). In addition, possible activation mechanisms of the interactions between S2O82− and Fe2+/Fe3+ on the Fe3O4 surface, which involve an efficient electron transfer mediator of the RHB oxygen functional groups promoting the generation of SO4−• in the Fe3O4–RHB/PS system, were clarified. Thus, the Fe3O4–RHB/PS oxidation process is expected to be a viable method for remediating PAE-contaminated marine sediment. [ABSTRACT FROM AUTHOR]

This study evaluated the oxidation of toluene (TOL) by persulfate (PS) in aqueous solution in the presence of a Fe3O4-carbon black (CB) composite oxidant system generating sulfate radicals. The cytotoxic activity and oxidative stress generated by these materials were investigated in rat liver Clone 9 cells. The effects of various operating parameters including the pH and concentrations of PS, Fe3O4-CB, and TOL were evaluated to optimize the oxidation process. The results showed that Fe3O4-CB/PS achieved effective removal of TOL under acidic conditions. The TOL degradation efficiency was strongly pH-dependent, where pH 3.0 > 6.0 > 9.0. Additionally, the viability of Clone 9 cells exposed to 0–400 μg/mL Fe3O4-CB indicated that this material showed low cytotoxicity. A dichlorodihydrofluorescein diacetate assay performed to evaluate the generation of reactive oxygen species indicated that Fe3O4 showed relatively lower toxicity than CB in these cells. Therefore, the cytotoxicity of CB may involve the induction of oxidative stress and physical changes in cell morphology. [ABSTRACT FROM AUTHOR]

The study developed a new and cost-effective method for the remediation of marine sediments contaminated with polycyclic aromatic hydrocarbons (PAHs). Iron oxide (Fe3O4) nanoparticles were synthesized as the active component, supported on carbon black (CB), to form a composite catalyst (Fe3O4–CB) by using a wet chemical method. The oxidation of 16 PAH contaminants present in marine sediments significantly activated sodium persulfate (Na2S2O8) to form sulfate free radicals (SO4−·); this was investigated in a slurry system. In addition, in vitro cytotoxic activity and oxidative stress studies were performed. The synthesized composite catalysts (Fe3O4–CB) were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, a superconducting quantum interference device magnetometry, and environmental scanning electron microscopy. The efficiency of PAH removal was 39–63% for unactivated persulfate (PS) from an initial dose of 1.7 × 10−7–1.7 × 10−2 M. The removal of PAHs was evaluated using Fe3O4/PS, CB/PS, and Fe3O4/PS and found to be 75, 64, and 86%, respectively, at a temperature of 303 K, PS concentration of 1.7 × 10−5 M, and pH of 6.0. An MTT assay was used to assess the cytotoxicity of the composite catalyst at five concentrations (25, 50, 100, 200, and 400 μg/mL) on human hepatoma carcinoma (HepG2) cells for 24 h. This revealed a dose-dependent decrease in cell viability. A dichlorofluorescein diacetate assay was performed to evaluate the generation of reactive oxygen species, which principally originated from the ferrous ions of the composite catalyst. [ABSTRACT FROM AUTHOR]

This work describes the environmentally friendly technology for oxidation of ammonia (NH) to form nitrogen at temperatures range from 423K to 673K by selective catalytic oxidation (SCO) over a nanosized Pt-Rh/γ-AlO catalyst prepared by the incipient wetness impregnation method of hexachloroplatinic acid (HPtCl) and rhodium (III) nitrate (Rh(NO)) with γ-AlO in a tubular fixed-bed flow quartz reactor (TFBR). The characterization of catalysts were thoroughly measured using transmission electron microscopy (TEM), threedimensional excitation-emission fluorescent matrix (EEFM) spectroscopy, UV-Vis absorption, dynamic lightscattering (DLS), zeta potential meter, and cyclic voltammetry (CV). The results demonstrated that at a temperature of 673K and an oxygen content of 4%, approximately 99% of the NH was removed by catalytic oxidation over the nanosized Pt-Rh/γ-AlO catalyst. N was the main product in NH-SCO process. Further, it reveals that the oxidation of NH was proceeds by the over-oxidation of NH into NO, which was conversely reacted with the NH to yield N. Therefore, the application of nanosized Pt-Rh/γ-AlO catalyst can significantly enhance the catalytic activity toward NH oxidation. One fluorescent peak for fresh catalyst was different with that of exhausted catalyst. It indicates that EEFM spectroscopy was proven to be an appropriate and effective method to characterize the Pt clusters in intrinsic emission from nanosized Pt-Rh/γ-AlO catalyst. Results obtained from the CV may explain the significant catalytic activity of the catalysts. [ABSTRACT FROM AUTHOR]