Scalable Preparation of Sub-Millimeter Double-Shelled AlO Hollow Spheres and Their Rapid Separation from Wastewater after Adsorption of Congo Red.

Porous double-shelled ceramic hollow spheres (PDSs) have attracted extensive attention due to their high specific surface areas and multifunctional designs. When used in wastewater treatment, millimeter or sub-millimeter spheres can be quickly separated from water by commercial sieves. However, the simple, scalable, and low-cost preparation of sub-millimeter PDSs in the solid phase remains a challenge.