1：Experimental Design and Method Selection:

A hydrothermal method was used to synthesize Fe-doped CdWO4 nanoparticles, with variations in Fe/Cd atomic ratios. The rationale was to enhance photocatalytic activity through metal ion doping.

2：Sample Selection and Data Sources:

Samples were synthesized with Fe/Cd ratios of 0,

3：05, 10, and Methyl orange dye was used as the pollutant for photocatalytic testing. List of Experimental Equipment and Materials:

Chemicals included sodium tungstate dihydrate, cadmium nitrate tetrahydrate, iron sulfate heptahydrate, sodium hydroxide, sulfuric acid, ethyl alcohol, and methyl orange from Sinopharm Chemical Reagent Limited Company. Equipment included a scanning electron microscope (SEM, FEI Quanta 200FEG), x-ray diffractometer (XRD, Empyrean XRD-Panalytical), surface area and porosity analyzer (TriStar II 3020, Micromeritics Instrument Corporation), UV lamp (100 W, Model SB-100 P/F, Spectronics Corporation), and UV-visible spectrophotometer (UV-6100, Metash).

4：Experimental Procedures and Operational Workflow:

Solutions were prepared, mixed, pH-adjusted to

5：62, subjected to hydrothermal treatment at 180°C for 24 hours, washed, dried, and characterized. Photocatalytic activity was tested by irradiating catalyst-dye mixtures with UV light and measuring degradation over time. Data Analysis Methods:

XRD for crystal structure, SEM for morphology, BET for surface area, UV-Vis spectroscopy for dye concentration, and pseudo-first-order kinetics for degradation rates.