Magnetic, Fluorescence and Transition Metal Ion Response Properties of 2,6-Diaminopyridine Modified Silica-Coated Fe3O4 Nanoparticles

Multi-functional nanoparticles possessing magnetic, fluorescence and transition metal ion response properties were prepared and characterized. The particles have a core/shell structure that consists of silica-coated magnetic Fe3O4 and 2,6-diaminopyridine anchored on the silica surface via organic linker molecules. The resultant nanoparticles were found by transmission electron microscopy to be well-dispersed spherical particles with an average diameter of 10–12 nm. X-ray diffraction analysis suggested the existence of Fe3O4 and silica in/on the particle. Fourier transform infrared spectra revealed that 2,6-diaminopyridine molecules were successfully covalently bonded to the surface of magnetic composite nanoparticles. The prepared particles possessed an emission peak at 364 nm with an excitation wavelength of 307 nm and have a strong reversible response property for some transition metal ions such as Cu2+ and Zn2+. This new material holds considerable promise in selective magneto separation and optical determination applications

Removal of the UV Filter Benzophenone-2 in Aqueous Solution by Ozonation: Kinetics, Intermediates, Pathways and Toxicity

<p>Benzophenone-2 (BP-2) is an important type of UV filter that has been widely used and detected in the aquatic environment with greater estrogenic toxicity. In our work, the removal of BP-2 with the initial concentration of 25 mg L⁻¹ was first carried out by ozone at different pH (ranging from pH 3.0 to 11.0), and we found a positive correlation between the pH values and the degradation efficiency of BP-2, among which the more rapid removal of BP-2 in alkaline condition was observed than acidic and neutral conditions. For the influence of aqueous humic acid (HA, the concentration ranged from 0 ppm to 100 ppm), the degradation rate of BP-2 by ozonation was first increased with the growth of humic acid concentration (from 0 ppm to 5 ppm), reaching to maximum at 5 ppm of HA and subsequently decreased with the growth of HA concentration (from 5 ppm to 100 ppm). Fourteen intermediate products in the ozonation process were distinguished by an electrospray time-of-flight mass spectrometer and then two degradation pathways were proposed. Through the theoretical calculation, we found the carbanyl group of BP-2 has the most reactivity to be easily attacked by ozone, providing us guides and theoretical basis on the supposed intermediate products. Furthermore, the <i>P. phosphoreum</i> acute toxicity test was conducted to evaluate the potential toxicity during the ozonation process.</p

Photodegradation of Polyfluorinated Dibenzo‑<i>p</i>‑Dioxins in Organic Solvents: Experimental and Theoretical Studies

Eighteen polyfluorinated dibenzo-<i>p</i>-dioxins (PFDDs) were synthesized by pyrolysis of fluorophenols. Using a 500 W Xe lamp as the light source, the PFDDs photodegradation kinetics in <i>n</i>-hexane were investigated. The photolysis reactions obeyed the pseudo-first-order rate equation, and higher fluorinated PFDDs tended to photolyze more slowly. Theoretically calculated parameters reflecting the molecular structural properties were used to develop a new model of PFDDs photolysis rates. The results indicated that the substitution pattern for fluorine atoms and the C–O bond length were major factors in the photolysis of PFDDs. We selected octafluorinated dibenzo-<i>p</i>-dioxin (OFDD) as a representative PFDDs to explore the influence of solvent on the photolysis rate of PFDDs, and the results indicated that neither the polarity nor donor hydrogen of organic solvents are independent influencing factors. Mechanistic pathways for the photolysis of OFDD in <i>n</i>-hexane were first studied. The results indicated that photodegradation of OFDD produces octafluorinated dihydroxybiphenyls, octafluorinated phenoxyphenols, and fluorinated phenols. The major pathway for photodegradation of OFDD was C–O bond cleavage. Defluorination reactions did not occur during the photolysis process

Rapid Removal of Tetrabromobisphenol A by Ozonation in Water: Oxidation Products, Reaction Pathways and Toxicity Assessment

<div><p>Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and has attracted more and more attention. In this work, the parent TBBPA with an initial concentration of 100 mg/L was completely removed after 6 min of ozonation at pH 8.0, and alkaline conditions favored a more rapid removal than acidic and neutral conditions. The presence of typical anions and humic acid did not significantly affect the degradation of TBBPA. The quenching test using isopropanol indicated that direct ozone oxidation played a dominant role during this process. Seventeen reaction intermediates and products were identified using an electrospray time-of-flight mass spectrometer. Notably, the generation of 2,4,6-tribromophenol was first observed in the degradation process of TBBPA. The evolution of reaction products showed that ozonation is an efficient treatment for removal of both TBBPA and intermediates. Sequential transformation of organic bromine to bromide and bromate was confirmed by ion chromatography analysis. Two primary reaction pathways that involve cleavage of central carbon atom and benzene ring cleavage concomitant with debromination were thus proposed and further justified by calculations of frontier electron densities. Furthermore, the total organic carbon data suggested a low mineralization rate, even after the complete removal of TBBPA. Meanwhile, the acute aqueous toxicity of reaction solutions to <i>Photobacterium Phosphoreum</i> and <i>Daphnia magna</i> was rapidly decreased during ozonation. In addition, no obvious difference in the attenuation of TBBPA was found by ozone oxidation using different water matrices, and the effectiveness in natural waters further demonstrates that ozonation can be adopted as a promising technique to treat TBBPA-contaminated waters.</p></div

A comprehensive comparative study of CO2-resistance and oxygen permeability of 60 wt % Ce0.8M0.2O2– (M = la, Pr, Nd, Sm, Gd) - 40 wt % La0.5Sr0.5Fe0.8Cu0.2O3– dual-phase membranes

In this study, dual-phase membranes 60 wt % Ce0.8M0.2O2–δ (M = La, Pr, Nd, Sm, Gd) - 40 wt % La0.5Sr0.5Fe0.8Cu0.2O3–δ (CMO-LSFCO) were prepared via a combination of EDTA-citric acid complexing sol-gel and mechanical mixture method. Their chemical compatibility, CO2 tolerance, oxygen permeability, conductivity, and long-term regenerative durability regarding the phase structure and composition were systematically studied. Among the studied CMO-LSCFO dual-phase membranes, CGO-LSFCO shows the highest oxygen permeability under air/He and air/CO2 gradients, which can be associated with the small particle size and high electronic conductivity of the CGO phase resulting in a good percolation with different transfer paths based on the correlations between membrane material characterization and oxygen permeability. The comprehensive comparative study presented in this work identifies the critical factors influencing the oxygen permeability, which may provide guidelines for designing further high performance dual-phase oxygen transport membranes