New and effective photocatalysts for removal of mordant black 17 and Congo red pollutants: In3+ and Sb5+ doped and codoped TiO2 semiconductor

Abstract

The incorporation of trivalent (In3+) and pentavalent (Sb5+) ions into nano-sized TiO2 structure critically improved the visible light absorption and the photodegradation characteristics toward mordant black 17 and Congo red (CR) dyes as model organic pollutants. The X-ray diffraction (XRD) proved that pure TiO2 and Ti0·97In0·03O2 powders have a single tetragonal anatase phase structure while Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 compositions possess mixed phases of anatase and brookite. The sacnning electron microscope (SEM) images displays that Ti0·94In0·03Sb0·03O2 powder has fine and homogenous particles. The transmission electron microscope (TEM) images confirmed that Ti0.94In0·03Sb0·03O2 powder hasthe lowest mean particles size of 20 nm. The visible light response of TiO2 is significantly enhanced owing to addition of Sb5+ and In3/Sb5+ions. The calculated band gap energies of TiO2, Ti0·97In0·03O2, Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 samples are 3.35, 3.21, 2.97 and 2.91 eV, respectively. The engineering of the optical characteristics powerfully boosted the photocatalytic charcteristics of Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 catalysts under natural sunlight irradiation. Both samples exhibit photocatalytic efficiencies of 89 and 97% toward 30 ppm mordant black 17 solution under sunlight irradation in 60 min, respectively. As well, Ti0·97Sb0·03O2 and Ti0·94In0·03Sb0·03O2 catalysts show high photo-degradation efficiencies of 81 and 86% toward 15 ppm CR after sunlight irradation for 80 min. The enhanced degradation properties of the nanocrystalline Ti0·94In0·03Sb0·03O2 catalyst may be related to high separation of charge carriers, oxygen vacancies generation and good visible light response. For three cycles, Ti0·94In0·03Sb0·03O2 catalyst reveals high photodegradation activity within 89–97% for 30 ppm mordant black 17 dye under the same circumstances, demonstrating good photostability.