Natural sunlight driven degradation of tetracycline in wastewater by dual Z − scheme photocatalyst of hollow nanospherical β–In2S3 decorated g − C3N4/WO3: performance, mechanism and products toxicity

The dual Z–scheme photocatalysts of β–In2S3/g − C3N4/WO3 (ISCNWO) were synthesized with improved light adsorption, carrier separation and specific surface area for tetracycline (TC) degradation by sunlight irradiation. The ISCNWO2 exhibited superior solar photodegradation performance of TC, and the kinetic constant was 2.2, 5.6 and 2.3 times that of g–C3N4, WO3 and In2S3, respectively. According to response surface methodology, the optimum TC removal was 96.4 ± 0.37 % at pH = 3.4 for 140 min irradiation without electrolyte. Even in river, municipal, hospital, frog farming field and tail wastewater, TC degradation efficiencies under solar irradiation for 300 min were > 74 %. As the lower work function of WO3 than that of In2S3 and g–C3N4 calculated by density functional theory (DFT), the electrons migrated from WO3 to In2S3 and g–C3N4 driven by built–in electric field. Under destruction of O2− and OH radicals, TC progressively transformed into 22 intermediates by addition, aromatic ring opening, etc. The toxicity prediction and in vivo experiments towards D. magna, V. fisheri and E. coil suggested that some intermediate products had relative high acute and bioaccumulation toxicity, so it was necessary to control ecological risks. Besides, as the satisfactory reusability of ISCNWO2 with 82.9 % TC removal after 5 cycles, the ISCNWO might had great application prospects in the treatment and remediation of antibiotic contaminated wastewater/natural water.