Rapidly regenerated CNC/TiO₂/MnO₂ porous microspheres for high-efficient dye removal

The cellulose nanocrystal (CNC)/transition metal oxide hybrid porous microspheres usually have high adsorption performance and degradability, and show promising applications in the field of wastewater treatment. However, single metal oxides are limited by the forbidden band width and electron-hole complexation, and often fail to achieve good effluent treatment. Herein, a CNC/manganese dioxide/titanium dioxide porous microspheres are prepared by the combination of bubble template and ionic crosslinking between sodium alginate and Ca²⁺ ions as a matrix. Based on the synergistic effect of two kinds of transition metal oxide, the degradation efficiency of CNC/MnO₂/TiO₂ porous microspheres for methylene blue is as high as 97.0%, showing easy recovery process and rapid regeneration of this material. Besides, its maximum removal of dyes reaches up to 310.2 mg/g, which is much higher than most CNC based adsorption materials. The concept of concerted catalysis can to explain the origin for excellent performance of as-prepared hybrid microspheres.