Modified g-C3N4/TiO2/CdS ternary heterojunction nanocomposite as highly visible light active photocatalyst originated from CdS as the electron source of TiO2 to accelerate Z-type heterojunction

A novel ternary composite heterojunction material of K doped g-C3N4 nanosheet -TiO2-CdS with highly visible photocatalytic activity was successfully synthesized by hydrothermal method. K doped g-C3N4 nanosheet -TiO2-CdS showed an excellent ability to catalyze the removal of tetracycline by enhancing the degradation efficiency from 32.1% (the degradation rate of tetracycline by pure g-C3N4) to 94.2% and the mineralization efficiency of about 40.1% under visible light ((λ > 420 nm) within 30 min. In addition, it is also showed excellent optical stability that could degrade tetracycline even after four cycles. The highly visible light photoreactivity is because of CdS acted as an electronic source for TiO2, which could obviously accelerate the separation of electron-hole pairs within the Z-type heterojunction formed by K doped g-C3N4 nanosheet and TiO2. Moreover, the presence of TiO2 provided active sites for tetracycline adsorption. Our work not only provides a promising material for the effective removal of tetracycline in wastewater but also will be useful for design of other heterojunction photocatalyst.