Novel polypyrrole-sensitized hollow TiO2/fly ash cenospheres: Synthesis, characterization, and photocatalytic ability under visible light

► The threshold of PPy-TiO2/FAC can reach 560 nm, and it can take advantage of solar light. ► These fresh photocatalysts can be easily separated from water due to their buoyant property. ► The photocatalysts retained their photocatalytic ability after several reaction cycles. ► A new way of reuse of fly ash is mentioned in this research.