Removal of rhodamine 6G dye contaminant by visible light driven immobilized Ca1⿿Ln MnO3 (Ln = Sm, Ho; 0.1 ⿤x⿤ 0.4) photocatalysts

Abstract Visible-light-driven Ca 1⿿ x Ln x MnO 3 (Ln = Sm, Ho; 0.1 ⿤ x ⿤ 0.4) films were grown by RF-magnetron sputtering onto fused silica substrates. The effects of Ca 2+ substitution for Ho 3+ or Sm 3+ in Ca 1⿿ x Ln x MnO 3 on the structural, morphological and photocatalytic properties for rhodamine 6G dye degradation under visible light irradiation were investigated. XRD showed a pure typical perovskite phase for all the prepared films, except for Ca 0.9 Ho 0.1 MnO 3 and a decrease of the crystallite size with the increase of the amount of ion substituted. SEM and AFM revealed that the films surface is dense, with low roughness. UV⿿vis spectroscopy indicated for the two series band gaps in the range of 1.6⿿2.8 eV, being lower for the films containing holmium. The results showed that some Ca 1⿿ x Ho x MnO 3 and Ca 1⿿ x Sm x MnO 3 films present higher photocatalytic activity for Rh6G degradation in comparison with TiO 2 films and for the same x value the Ho-films exhibited higher photocatalytic activity. For both films series the maximal degradation rate was obtained for x = 0.2; above this content the degradation percentage exhibits a decreasing trend with the increase of Ho or Sm substitution, except for x = 0.4 in the case of Ho system, which is observed again an increase in the degradation rate. The Rh6G photocatalytic degradation followed a pseudo first-order reaction kinetics. XRD and SEM of the used photocatalysts evidenced high photochemical stability.