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A magnetic core–shell Pr 6 O 11 /SiO 2 @Fe 3 O 4 catalyst using chemical precipitation was prepared. Its structure was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectrum. The catalytic activity was evaluated by the catalytic ozonation of acetochlor. The results showed that the catalyst could effectively improve the acetochlor removal and mineralization. The total organic carbon removal reached 37.3% with the catalyst at 120 min, whereas the removal was 14.1% with ozonation alone. The catalyst was proved to be stable and recyclable by determining the concentration of the leaching praseodymium ions and the catalyst’s activity after repeated use. The effect of the radical scavengers indicated that the catalytic ozonation process followed an OH reaction mechanism. In addition, we employed Chlorella and zebrafish as model organisms to investigate the aquatic toxicity of the treated solution and the dissolved praseodymium ions. We found that the aquatic toxicity of the reaction solution decreased with an increase in the degradation time, and no obvious toxicity was found for the dissolved praseodymium ions. [ABSTRACT FROM AUTHOR]

Catalytic oxidation with nano magnetic catalysts has the advantages of easy recovery, good stability and high activity. In this study, three nano magnetic lanthanide catalysts with a core–shell structure of Ce/SiO 2 @Fe 3 O 4 , La/SiO 2 @Fe 3 O 4 and Pr/SiO 2 @Fe 3 O 4 were prepared and characterized by Brunauer–Emmet–Teller, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectrum and vibrating sample magnetometer analysis. All catalysts have Fe 3 O 4 nanoparticles as cores, SiO 2 as the mid-layer, and CeO 2 , La 2 O 3, or Pr 6 O 11 as the outer layer, and have a good magnetic property. The catalyst activities followed the descending order of Pr/SiO 2 @Fe 3 O 4 > La/SiO 2 @Fe 3 O 4 > Ce/SiO 2 @Fe 3 O 4 upon the degradation of diethyl phthalate (DEP), and the catalytic ozonation process followed an OH reaction mechanism. The removal rate of DEP was small effected because of the presence of Cl − , and addition of sodium carbonate had no obviously influence. The initial mineralization rate had a positive relation with the hydroxyl groups and pH value at the zero charge point (pH pzc ) of the catalysts, but had no significant relation with the surface area of the catalysts. The catalysts were relatively effective and stable after 3 repeated uses, and the leaching out concentrations of Ce, La and Pr were 1.33 mg/L, 0.138 mg/L and 0.115 mg/L after a 90 min reaction. [ABSTRACT FROM AUTHOR]

• Catalytic oxidation of o -ClA and nitrogen transformation in HCW were investigated. • A flexible micro-reactor platform consist of FQTR and Raman spectroscopy was developed. • Mn 2 O 3 improved the degradtion of ammonia-N and inhibited the production of nitrate-N. • o -Chlorophenol was the main intermediate product of o -ClA in HCWO process. • The potential degradation pathway of o -ClA was proposed. Catalytic oxidation of o -chloroaniline (o- ClA) in hot compressed water (HCW) was investigated in a fused quartz tube reactor (FQTR) to determine the effects of catalyst, temperature, oxygen stoichiometric ratio (OSR) and reaction time on o- ClA mineralization, total nitrogen (TN) removal rate and nitrogen-containing products distribution. The results showed that o -ClA can be effectively degraded in HCW. With the increased of OSR, retention time and temperature or added of Mn 2 O 3 as catalyst, the mineralization rate of o -ClA and the removal rate of TN increased. Ammonia-N was the main nitrogen-containing intermediate product of o -ClA degradation, however, when the oxidant was excessive, ammonia-N was oxidized to form nitrate-N. Althought the catalytic effect of Mn 2 O 3 on the mineralization of o -ClA was not outstanding, it promoted the removal of ammonia-N from the benzene ring, improved the degradtion of ammonia-N, and inhibited the production of nitrate-N. GC–MS analyzed results indicated that o -chlorophenol was the main degradation intermediate product of o -ClA in HCWO process. Meanwhile, the potential degradation pathway of o -ClA was proposed. This work thus provides basic knowledge about o -ClA catalytic oxidation removal in HCW process. [ABSTRACT FROM AUTHOR]