ABSTRACT
The construction of novel efficient catalysts for the treatment of organic pollutants in the aqueous environment is essential. The lamellar-like Cu-Al layered double hydroxides (CuAl-LDHs) with various mole ratios were synthesized by a simple route of co-precipitation, and the corresponding degradation characteristic was tested for the removal of tetracycline (TC) using PMS activation. The degradation efficiency of TC over CuAl-LDHs increased up to 93% within 10 min for the Cu/Al mole ratio of 3:1 and almost not changed at a higher mole ratio. For further calcining the optimal catalyst at 300 â, the degradation efficiency of TC was found to be increased to 96%. Sulfuric radicals and singlet oxygen were analyzed to be the main reason for the change in degradation characteristics, which was proved by radical quenching experiments and electron paramagnetic resonance technique. The parameters including PMS concentration, catalyst dosage, and reaction temperature on the TC degradation as well as the degradation mechanism for PMS activation were elaborated. The best proportion of CuAl-LDHs owned splendid stability and catalytic activity after reusing, which showed enormous potential in practical application.
Subject(s)
Hydroxides , Tetracycline , Anti-Bacterial Agents , Water , Catalysis , PeroxidesABSTRACT
Several activated fly ash cenosphere (AFAC) supporting TiO2 coated ZnFe2O4 (TiO2/ZnFe2O4/AFAC) photocatalysts were prepared by sol-gel and hydrothermal methods. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-DRS) and nitrogen adsorption analyses for Brunauer-Emmett-Teller (BET) specific surface area measurements. We found that the main components of spherical AFAC were mullite (Al6Si2O13) and SiO2; the crystallite size of the TiO2/ZnFe2O4 nanocomposite was less than 10 nm and its specific surface area was 162.18 m2 g-1. The TiO2/ZnFe2O4 nanocomposite had a band-gap of 2.56 eV, which would photodegrade 95% of rhodamine B (RhB) under visible light within 75 min. When hybridized with 0.02 g AFAC, the TiO2/ZnFe2O4/0.02 g AFAC photocatalyst with a band-gap of 2.50 eV could remove 97.1% of RhB and be reused three consecutive times with minor decrease in photocatalytic performance. However, the photocatalytic performance decreased to 91.0% on increasing the dosage of AFAC to 0.30 g. The mesoporous structure of all the photocatalysts and the strong adsorption ability of AFAC accounted for the notable performance.
ABSTRACT
Molybdenum disulfide (MoS2) nanopetals were successfully synthesized by hydrothermal method (sample without sintering) and then sintered at different temperature (sintered samples). The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen (N2) adsorption analyses for Brunauer-Emmett-Teller (BET) specific surface area measurements, X-ray photoelectron spectrum (XPS) and Raman spectrum. XRD pattern indicated that the samples can be indexed to hexagonal phase 2H-MoS2. SEM and TEM images showed that the sintered MoS2 nanopetals had sizes ranging from 150 to 300 nm with almost the same morphology. The pore structure and surface area were nearly the same for the three sintered MoS2 nanopetals. Interestingly, XPS and Raman spectra implied that there was a few 1T-phase in the MoS2 nanopetals which enhanced the photocatalytic performance greatly when sintered at low temperature.
ABSTRACT
The structural stability, magnetic properties and electronic structure of tetragonal BiCoO(3) under pressure have been studied by first-principles density functional calculations. The calculated results reveal that no tetragonal-to-cubic and ferroelectric-to-paraelectric phase transitions occur up to 30 GPa with a volume compression of about 25%. An electronic spin crossover transition of the Co(3+) ion from the high-spin to nonmagnetic low-spin configuration (magnetic moment collapse) occurs at 4 GPa by about 4.87% volume compression, which is concomitant with a first-order isosymmetric transition and an insulator-to-semimetal transition. The metallization in BiCoO(3) is driven by the spin-state transition at high pressure. Coexistence of the structural, spin-state and insulator-to-semimetal transitions implies that there is a strong coupling among the lattice, spin and charge degrees of freedom in BiCoO(3).
