In this study, hierarchical MnO2-coated magnetic nanocomposite (Fe3O4/MnO2) was synthesized by a mild hydrothermal process, and its application for removing heavy metal ions from contaminated water systems was examined. Structural characterization showed that the Fe3O4 nanoparticle core was coated with amorphous MnO2 shell with flowerlike morphology. The as-prepared nanocomposite had a large surface area and high magnetic saturation value, which ensured its good sorption ability and convenience of separation. Fe3O4/MnO2 exhibited a greatly improved removal capacity toward four different heavy metals (Cd(II), Cu(II), Pb(II), and Zn(II)) compared to unmodified Fe3O4 nanoparticles. The adsorption property of Fe3O4/MnO2 was studied with Cd(II) in more detail. The sorption equilibrium data were well fitted to the Langmuir model, and the maximum adsorption capacity toward Cd(II) was 53.2 mg g(-1). Fe3O4/MnO2 retained over 80% of its adsorption capacity under various solution conditions that are typically encountered in natural waters. This nanocomposite was easily recovered and reused through consecutive adsorption-desorption experiments with the assistance of an external magnetic field. Overall, the findings propose that Fe3O4/MnO2 could be used as an effective recyclable adsorbent for heavy metal ions.

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In this study, we synthesized a novel perovskite nanomaterial consisting of AgBiO nanoparticles (NPs) via an ion-exchange method for remediation of polluted environments. The AgBiO NPs could self-produce significant amounts of reactive oxygen species (ROS) without light illumination or any other additional oxidant due to the controllable release of lattice oxygen from the crystalline AgBiO, resulting in the formation of ROS somehow. The self-produced O, O, and OH were confirmed by electron spin resonance spectroscopy using a spin trap technique. We found that the AgBiO NPs could be reused for the mineraliztion of most recalcitrant organic compounds alone, including Rhodamine B (RhB), phenol, 4-chlorophenol, 2,4-dichlorophenol, and bisphenol A. After the repeated eight cycles of continious treatment of RhB, AgBiO NPs still achieved 79% of degradation after 30 min of treatment. Characterization results revealved that the lattice oxygen inside AgBiO was activated to form active oxygen (O*), which resulted in consecutive formation of ROS. This study provides new insight on the lattice oxygen activation mechanism of silver bismuthate and its application to the remediation of polluted waters.

Multifunctional zerovalent-iron/platinum (ZVI/Pt) Janus bubble-propelled micromotors with high decontamination efficiency and efficient self-propulsion properties were fabricated by the asymmetric deposition of catalytic platinum (Pt) in one hemisphere of ZVI microspheres. In the ZVI/Pt micromotors−hydrogen peroxide (H 2 O 2 ) system, ZVI acts as a heterogeneous Fenton-like catalyst for the degradation of organic pollutants, while simultaneously the hemispheric Pt layer catalytically decomposes H 2 O 2 into water and oxygen, thereby resulting in an oxygen-bubble propulsion system. The ZVI/Pt Janus micromotors were bubble-propelled at a high speed of over 200 μm/ s in the presence of 5% H 2 O 2 . In addition, complete oxidative degradation of methylene blue (MB) occurred in the presence of 5% H 2 O 2 after 60 min of treatment, whereas ZVI microspheres removed only 12% of MB in 60 min. The magnetic controllable and reusable properties of the ZVI/Pt micromotors make the water purification process more attractive and feasible. Therefore, the application of ZVI with unique redox chemistry to a micromotor system could hold great promise for the development of innovative water purification and remediation technologies in the future.

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