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Inthis study, double-shelled C/SiO2hollow sphereswith an outer hydrophilic silica shell and an inner hydrophobic carbonshell were initially prepared by activating a solid silica layer ofC/SiO2aerosol particles. This low-cost preparation technique,which can easily be scaled up, includes a rapid aerosol process anda subsequent dissolution–regrowth process. The large surfacearea (226.3 m2/g), high pore volume (0.51 cm3/g), and high mechanical stability of the spheres benefit their highadsorption capacities for methylene blue (MB) and metal ions. Thenovel spheres show a high adsorption capacity of 171.2 mg/g for MB,which is higher than the adsorption capacity of single-shelled silicahollow spheres (150.0 mg/g). The adsorption efficiency of the hollowspheres remains higher than 95% after five cycles of regeneration.The saturation adsorption values of Pb2+and Ag+ions on the hollow spheres were found to be 216.5 and 283.1 mg/g,respectively, which are higher than the corresponding values of 189.8and 213.4 mg/g on the single-shelled SiO2spheres. Moreover,the adsorption capacities of the five-times-recycled spheres for Pb2+and Ag+ions reached as high as ∼180 and∼245 mg/g, respectively. These results reveal that the outerporous silica layer with a ζ-potential of −37.4 mV makesthe main contribution to the excellent adsorption performance of thespheres. In addition to the contribution to the adsorption capacityof the double-shelled hollow spheres, the inner carbon layer playsa crucial role in supporting the outer silica shell and in improvingthe adsorption efficiency, mechanical stability, and recycling propertiesof the hollow spheres. [ABSTRACT FROM AUTHOR]

Magneticmicrospheres with an Fe3O4coreand a SiO2–TiO2hybrid shell were preparedby a surfactant-assisted aerosol process and subsequent etching treatment.The core–shell spheres with robust and chemically stable Ti–O–Sishells exhibit excellent adsorption performance toward basic dyes.The maximum adsorption capacities were obtained at 147 mg/g for methyleneblue (MB) and 124.6 mg/g for basic fuchsin. MB with an initial concentrationof 20 mg/L can be completely removed in 5 min at a dosage of 0.5 mg/L,and the equilibrium time is 90 min in the MB concentration range 20–250mg/L. The adsorption kinetics follows the pseudo-second-order model.Furthermore, the dye saturated microspheres can be easily recycledby an external magnetic field and regenerated using 1–3 wt% NaOH aqueous solution. After six recycle runs, 98% of the adsorptioncapacity was still retained. The low-cost magnetic hollow sphereswith good adsorption capacity are a promising candidate for watertreatment. [ABSTRACT FROM AUTHOR]