Preparation of Z-type heterojunction ammonium phosphotungstate/CdS composite photocatalyst and photocatalytic degradation of tetracycline

Ammonium phosphotungstate (PW 12 NH 4 ) nanoparticles were prepared via the hydrothermal method, and CdS nanocrystals were deposited on the PW 12 NH 4 to construct the PW 12 NH 4 /CdS composite photocatalytic materials. The characterisation of the photocatalytic materials was conducted using a range of analytical techniques, including XRD, SEM, TEM, DRS, XPS and FTIR, thereby confirming the successful preparation of the composite photocatalytic materials. The degradation effect of the prepared photocatalytic materials on tetracycline was investigated, along with the mechanism of photocatalysis. The findings demonstrated that the PW 12 NH 4 /CdS (1:2) composite material exhibited the optimal degradation efficiency for tetracycline under visible light conditions, with a complete degradation rate of 99.7 % achieved within 60 min. The photocatalytic mechanism was explored by conducting free radical capture experiments, which confirmed that superoxide radicals (·O 2 − ) and holes (h VB + ) were the main active substances in the photocatalytic process. The valence band and conduction band positions of PW 12 NH 4 and CdS were calculated based on various tests, indicating that the PW 12 NH 4 /CdS composite photocatalytic material formed a Z-type heterojunction. This resulted in a broadened visible light absorption range, high redox ability, reduced recombination rate of photogenerated electrons and holes, and improved photocatalytic activity. • A series of PW 12 NH 4 /CdS photocatalytic materials were synthesized by a simple hydrothermal method. • Under light irradiation, the degradation rate of tetracycline by the PW 12 NH 4 /CdS photocatalytic material reached 99.7 % within 60 min. • The photocatalytic degradation process of tetracycline by the PW 12 NH 4 /CdS photocatalytic material conforms to the Z-scheme heterojunction mechanism.