To heighten the absorption to visible light and improve photocatalytic degradation to organic pollutants, a novel photocatalyst of m-Bi2O4/Bi2O2CO3 was constructed through a facile hydrothermal method. The crystal structure, optical properties, morphology, composition and photocatalytic ability of the photocatalysts were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscope (TEM), high resolution TEM, selected-area electron diffraction and X-ray photoelectron spectroscopy technologies. The as-prepared photocatalysts could efficiently degrade rhodamine B and mixed dye under visible light. The removal rate was up to 95.3% within 50 min. The results demonstrated that m-Bi2O4/Bi2O2CO3 photocatalysts showed outstanding photocatalytic degradation ability compared to the single photocatalyst with the narrow band gap. In addition, photocurrent response tests certified that the heterostructure of the photocatalysts effectively accelerated the separation and migration of photo-induced electrons and holes. Active species trapping experiments indicated that holes (h+) and superoxide radical (•O2−) were major species rather than hydroxyl radicals (•OH) during the degradation process of organics. According to the test results, a probable photocatalytic mechanism was proposed. This work provided a new and efficient photocatalyst for environmental remediation and water treatment.

A novel p-n heterostructure photocatalyst m-Bi2O4/BiOCl was successfully synthetized through a facile ion-etching method. Via adjusting the added volume of HCl solution, a series of different ratios of composite photocatalysts were obtained. The as-prepared samples of physical, chemical and optical characteristics were examined by X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscopy, selected-area electron diffraction, Fourier transform infrared absorption, Raman microscope, N2 adsorption-desorption, X-ray photoelectron spectroscopy and UV-vis spectrum technologies. The photocatalysts showed high degradation rate and complete mineralization ability for methyl orange and tetracycline solution under visible light. The reaction rate constant of m-Bi2O4/BiOCl for methyl orange was 52.28 times higher than that of BiOCl. The characterization presented a good stability of materials. Furthermore, the photocurrent response test certified that the heterostructure effectively accelerated the separation and migration of photo-generated carries. The scavenger experiments evidenced that hole (h+) and superoxide radical (•O2—) were the primary active radicals. A possible photocatalytic mechanism was proposed. This work provided an alternative photocatalyst applied to water environmental remediation.

The Fe3O4 magnetic polypyrrole–graphene (PPy–GO) has a Langmuir adsorption capacities of 400.0 mg g−1 for Hg(ii). And it has a favorable saturation magnetization of 19.0 emu g−1, easily separated from solutions via additional exterior magnets.