Hierarchically three-dimensional (3D) nanotubular sea urchin-shaped iron oxide and its application in heavy metal removal and solar-induced photocatalytic degradation.

•The 3D- Fe2O3 can be mass-produced by ultrasound irradiation method.•The 3D-Fe2O3 possesses high BET surface area and interconvertible phase.•The 3D-Fe2O3 exhibits rapid adsorption rates for heavy metals.•The 3D-Fe2O3 exhibits excellent photocatalytic activities toward the dyes.