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The heterostructure Ag@WO3–x(x=0.1 or 1) composites with high selectivity for breaking azo-bond were obtained by in situreduction of Ag2WO4. The crystal structure and morphology of Ag@WO3–xwere characterized by X-ray powder diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM). The residue solution of methyl orange(MO) after degradation was tested by gas chromatograph mass spectrometer (GCMS) to analyze the exact components. The results indicate that the products after degradation are N,N-dimethylaniline, N,N-dimethyl-p-phenylenediamine and sulfanilic acid. This is caused by specific breaking of azo-bond in MO. The azo-bond breaking of MO by Ag@WO3–xcould occur in dark without any light illumination. Therefore, we proposed a possible mechanism for this azo-bond breaking reaction based on the reaction condition and results.

Magnetic Fe3O4nanospheres with a average diameter of (201±0.5) nm were synthesized at 200 °C viaa solvothermal method. The as-synthesized Fe3O4nanospheres performed an efficiency in the Fenton degradation of xylenol orange with a degradation rate of 90%—95%. Additionally, the catalyst was easily recyclable and the recovery rate was greater than 90%. Moreover, the catalyst could be regenerated under an ultrasonic treatment, and the degradation performance remained essentially the same. More importantly, the degradation rate varied with respect to the amount of H2O2and the pH of the best reaction process. And the reaction efficiency was achieved with 1.5 mL of H2O2in an acidic environment.