Photocatalytic and magnetic porous cellulose macrospheres for water purification

In this work, we report the preparation of photocatalytically active and easy to recycle porous cellulose-based spheres from polymer solutions in ionic liquid/dimethylsulfoxide mixtures by using the dropping cum phase separation technique. The factors affecting the sphere structure formation in relation to their efficiency as photocatalysts have been studied in detail. It was found that the increase of the nanoparticulate dopant fraction (TiO₂ and/or Fe₃O₄) in the casting solution led to the formation of nanocomposites with a higher specific surface area as well as with enhanced photocatalytic activity. The embedment of the TiO₂ nanoparticles in the polymeric matrix did not change the bandgap of the photocatalyst. Furthermore, the co-doping with Fe₃O₄ had no negative impact on the photocatalytic activity of the TiO₂ doped porous cellulose spheres. The addition of a moderate amount of dimethylsulfoxide led to an improvement of the photocatalytic activity of the formed nanocomposites, due to an increase of the matrix porosity without an agglomeration of the active nanoparticles. However, higher fractions of dimethylsulfoxide led to the agglomeration of the photocatalytic nanoparticles and therefore a decrease of the photocatalytic activity of the hybrid materials. The obtained porous spheres could be successfully recycled and reused in at least five consecutive cycles for the photocatalytic degradation of the model organic pollutant Rhodamine B in aqueous solution. Additionally, the prepared porous spheres also exhibited good adsorber properties toward Cu²⁺ ions which were used in this study as model metal ion pollutant in water.