Adsorption of phosphate and photodegradation of cationic dyes with BiOI in phosphate-cationic dye binary system

Bismuth oxyiodide (BiOI) with 3D microspheres structure was prepared and used for adsorption of phosphate and photodegradation of dyes in phosphate-dye binary system for the first time. BiOI exhibited excellent adsorption capacity of phosphate up to 55.80 mg P/L and outstanding photocatalytic activities for all the cationic dyes in phosphate-cationic dye binary system. RhB was 100% photodegraded within 50 min, and the photodegradation rates of MB and FB reached 92% and 95% within 100 min, respectively. But in phosphate-anionic/neutral dye binary system, BiOI displayed only good adsorption performance of phosphate but showed no photodegradation performance for anionic or neutral dyes. The mechanism was proposed as that PO43- adsorbed on the surface of BiOI, which changed from being neutral into being negatively charged, and then the cationic dyes were absorbed due to electrostatic attraction for photodegradation. The photodegradation was confirmed that the photogenerated electrons from the conduction band (CB) of BiOI which could reduce O-2 to center dot O-2(-) and associate with h(+) oxidized the cationic dyes. This work established a new approach of photodegrading organic dyes and adsorbing phosphate in waterbodies, and provided a new insight into wastewater treatment with two or more pollutants.