Fabrication of Ti-PDA nanoparticles with enhanced absorption and photocatalytic activities for hexavalent chromium Cr(VI) removal

This article prepared a nanoparticle (NP) Ti-PDA made from bis (2-hydroxy propionic acid) diammonium titanium hydroxide (Ti-BALDH) chelating dopamine (DA), as a photocatalyst to absorb and reduce hexavalent chromium (Cr(VI)) under visible light with recycling ability from waste water. Ti-PDA NPs with part of TiO 2 -like structure can perform some function of TiO 2 , while participation of PDA will not only broaden absorption spectrum from UV to visible light, but offer the ability to absorb Cr(VI). Compared with TiO 2 Ti-PDA NPs would make full use of sunlight, increasing the photocatalytic efficiency. The adsorption results of Ti-PDA NPs for Cr(VI) showed that the adsorption capacity of Ti-PDA NPs can reach 500.24 mg/g when the concentration of Cr(VI) was 300 mg/L, and the adsorption data matched well with the Langmuir isotherm model, and confirmed to a quasi-second-order dynamics. Under visible light irradiation, Ti-PDA NPs could reduce Cr(VI) to Cr(III) within 30 min, and can almost completely reduce Cr(VI) within 15 min even at pH = 4. After three cycles, photocatalytic reduction efficiency was still 95.02%. Thereby the toxic Cr(VI) can be effectively eliminated by Ti-PDA NPs from sewage. As a result, Ti-PDA will be a promising green photocatalyst to remove Cr(VI) in disposal of water pollution.