Cuprous oxide created on sepiolite: Preparation, characterization, and photocatalytic activity in treatment of red water from 2,4,6-trinitrotoluene manufacturing

► Cu2O crystals were firstly created on the natural sepiolite fibers. ► The structures of the sepiolite are altered when acidized, benefiting the immobility of cuprous oxide crystals. ► The carrier sepiolite improves efficiently the photocatalytic activity of cuprous oxide crystals. ► Cu2O/sepiolite composites show superior photocatalytic activity for the degradation of red water.