1：Experimental Design and Method Selection

The study employed a molten salts method to prepare the PTI/ZnO heterojunction. The photocatalytic activity was evaluated through the degradation of tetracycline hydrochloride under visible light irradiation.

2：Sample Selection and Data Sources

Tetracycline hydrochloride was used as the pollutant to evaluate the photocatalytic activity. The samples were characterized using XRD, SEM, TEM, UV–vis DRS, and PL spectroscopy.

3：List of Experimental Equipment and Materials

X-ray diffractometer (Bruker D8 Advance), SEM (FEI Nova NanoSEM 450), TEM (Tecnai G20), UV–vis spectrophotometer (Shimadzu UV-3600), fluorescence spectrophotometer (HORIBA Fluorolog-3), electrochemical workstation (CHI 660D), electron paramagnetic resonance spectrometer (A300-10/12, Bruker).

4：Experimental Procedures and Operational Workflow

The PTI/ZnO heterojunction was prepared by heating a mixture of LiCl, KCl, NaCl, melamine, and ZnO nanoparticles at 550°C for 4 h. The photocatalytic activity was assessed by degrading TC under visible light irradiation, with samples taken at intervals for analysis.

5：Data Analysis Methods

The degradation rate of TC was analyzed using a UV–vis spectrophotometer. The kinetic constant of the degradation reaction was calculated using the equation Ln(C/C0) = kt.