The removal of polycyclic aromatic hydrocarbons (PAHs) from soil is costly and time-consuming. The high hydrophobicity of PAHs makes PAH diffusion from soil particles by hydraulic flow difficult. The phase transfer of PAHs from soil to another available mediator is crucial for PAH removal. This study focuses on the remediation of PAH-contaminated shoal soil, located in Yangtze, China, using three types of laccase-carrying electrospun fibrous membranes (LCEFMs) fabricated via emulsion electrospinning. These LCEFMs were composed of core-shell structural nanofibers (for PAH adsorption), with laccase in the core (for PAH degradation) and pores on the shell (for mass transfer). The LCEFMs with strong adsorptivity extracted the PAHs from the soil particles, resulting in an obvious enhancement of PAH degradation. The removal efficiencies in 6 h for phenanthrene, fluoranthene, benz[a]anthracene and benzo[a]pyrene were greater than 95.1%, 93.2%, 79.1%, and 72.5%, respectively. The removal half-lives were 0.003-1.52 h, much shorter than those by free laccase (17.9-67.9 h) or membrane adsorption (1.25-12.50 h). The third-order reaction kinetics suggested that the superficial adsorption and internal diffusion were the rate-limiting steps of the overall reaction. A synergistic effect between adsorption and degradation was also proposed on the basis of the triple phase distribution and kinetics analyses.
The reductive decomposition of pentachlorophenol (PCP) by photocatalysis with Ti-doped beta-Bi(2)O(3) was investigated under visible light (lambda > 420 nm) irradiation. The results indicated that hydroxyl radical (*OH) and singlet oxygen ((1)O(2)) could not be detected with electron spin resonance (ESR) on the photocatalyst under light irradiation. An electron scavenger weakened the photocatalytic activity of the photocatalyst for the decomposition of PCP; however, scavengers of reactive oxygen species (ROS) enhanced the activity. The decomposition intermediates of PCP detected by liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) suggested the existence of phenol, cyclohexanone, cyclohexanol, glycol, and propylene. All the evidence suggested that reductive dechlorination was the major route in the decomposition of PCP, during which the photogenerated electron under visible light irradiation acted as reductant. The reliability of the proposed reductive mechanism was further verified by comparing the reduction potential (E(re)) of PCP with the conduction band potential (E(cb)) of the photocatalyst. The decomposition pathway of PCP with electron reduction under visible light irradiation was also investigated.
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