Several candidate floating support materials, including two varieties of perlite and five varieties of hollow glass microspheres (HGM) with different crush strength, particle diameter, and density were screened for floatation and durability, and iM30k (3M Company; 18 µm average particle diameter) was selected for all experiments going forward as it had the highest percent floatation following washing procedures (Table , ESI). In addition to CNx, P25 TiO2 and nitrogen-doped graphitic carbon dots were screened as potential PR photocatalysts anchored to the HGMs using a sodium metasilicate-based binder, however neither was selected for further study due to poor composite stability and co-catalyst incompatibility (See ESI for additional details; "alternative composite compositions").