Characterization and high pollutant removal ability of buoyant (C, N)–TiO2/PTFE flakes prepared by high-energy ball-milling

Abstract

Buoyant photocatalysts which are able to remove organic pollutants under all lighting and weather conditions are in demand for the treatment of large volumes of organic wastewater. Buoyant carbon and nitrogen co-doped TiO₂/polytetrafluoroethylene (NCT/PTFE) flakes which meet these requirements were prepared by the high-energy ball-milling of NCT powder and PTFE. The physicochemical properties of the as-prepared composite flakes were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflection spectroscopy (UV-vis DRS), Brunauer–Emmett–Teller (BET) surface area determination, and X-ray photoelectron spectroscopy (XPS), as well as electrical conductivity and density measurements. The density of the composite flakes was 0.93 g cm⁻³, slightly lower than that of water, rendering them buoyant. And the used-and- regenerated (by UV-vis irradiation for 8 h) flakes are also buoyant. Adsorption in the dark and photodegradation experiments indicated that the as-prepared flakes have high dark adsorption and high photocatalytic properties. The 6 h photodegradation ratio of methylene orange (20 mg L⁻¹, 100 mL, as a model dye) is 96.6%, and a close degradation ratio of 97% can be obtained by three-cycle dark adsorption with minor stirring (1 cycle includes 8 h dark adsorption followed by 8 h regeneration by UV-vis irradiation per cycle). The high adsorption and good photocatalytic properties can be mainly attributed to the large BET surface area resulting from the small NCT particle size. The as-prepared flakes have the potential for use in organic pollutant adsorption at any time and can be regenerated through light irradiation when sunlight is available. This kind of environmental protection material has great practical significance due to its low cost, simple preparation, thermal durability, highly efficient organic pollutant removal, large-volume treatment capacity, recyclability, and the possibility of working at any time.