Dredged-Sediment-Promoted Synthesis of Boron-Nitride-Based Floating Photocatalyst with Photodegradation of Neutral Red under Ultraviolet-Light Irradiation

A novel floating photocatalyst (BN-DS-7) has been successfully synthesized by calcining the mixture of boron nitride (BN) and dredged sediment (DS) with a specific mass ratio (3:7) at 1100 °C for a half hour. BN is synthesized for the first time using an oxygen-limited method, which consists of a nanoplate ∼30 nm in size and has a bandgap at 3.94 eV. The as-synthesized BN can degrade NR under ultraviolet (UV) light irradiation. For BN-DS-7, X-ray photoelectron spectroscopy analysis suggests that BN mainly interacts with DS through the strong coordination between these N atoms in BN and these Si and Al atoms in DS. This leads to BN-DS-7 having good compression strength (∼9 MPa). Thermogravimetric analysis for BN shows that a few BN (∼13%) synthesized via an oxygen-limited method will pyrolyze at 1100 °C and the released gas can be sealed in the inside of DS at 1100 °C, resulting in that BN-DS-7 can float on the water surface. Photodegradation results show that BN-DS-7 can degrade 84% of NR (20 mg/L) under UV-light irradiation for 5 h, and the active species are •OH and photoinduced hole. Total organic carbon analysis for NR solution before and after photodegradation show that ∼70% of NR has been mineralized into inorganic carbons. This work is helpful to develop a new type of BN-based floating material and enlarge the application field of DS.