ZnO shell on mesoporous silica by atomic layer deposition: Removal of organic dye in water by an adsorbent and its photocatalytic regeneration

•ZnO/SiO2 shell/core structure was prepared by atomic layer deposition.•Due to unique property of ZnO shell, ZnO/SiO2 shows superior adsorption capacity.•ZnO/SiO2 adsorbent can be reused by its ‘self-regenerating process’ with UV exposure.•ZnO/SiO2 particles can be easily separated from water and recycled. We fabricated a ZnO shell on mesoporous SiO2 (ZnO/SiO2) particles with diameters of 250–500μm using atomic layer deposition. This structure showed a higher adsorption capacity for methylene blue than bare mesoporous SiO2. Moreover, the ZnO/SiO2 saturated by methylene blue could be easily separated from the aqueous solution and regenerated upon UV exposure by the photocatalytic activity of ZnO for decomposing adsorbed methylene blue. This system can be used for efficiently removing organic pollutants from water by adsorption under dark conditions and photocatalytic regeneration, i.e., organic pollutants in water can steadily be removed under alternating dark-light conditions.