Screening of factors influencing the photocatalytic activity of TiO2:Ln (Ln = La, Ce, Pr, Nd, Sm, Eu and Gd) in the degradation of dyes

In this work, we analyzed the photocatalytic activity of TiO2:Ln (Ln = La, Ce, Pr, Nd, Sm, Eu and Gd) systems in the degradation of two organic dyes by means of a probabilistic approach to screen the factors influencing their photocatalytic activity. The photocatalytic properties were described by six responses (crystallite size, band gap energy, visible light absorption, specific surface area, zeta potential and photocatalytic conversion) as a function of lanthanide type (seven elements), lanthanide concentration (two), pH level (two) and dye type (methyl orange and crystal violet). We analyzed 140 experiments using the analysis of variance (ANOVA) method. The results show that band gap energy and specific surface area exhibited behavior that depended on the atomic number of the element used. However, visible light absorption was not modified by the type of lanthanide element or its concentration in the range studied (0.1 and 0.3 wt.% lanthanides/TiO2 ratio), and the zeta potential depended mainly on pH. Photocatalytic conversion depended on pH, dye type and doping element. The experimental factorial design of the photocatalytic system allowed us to find the best conditions for enhancing the degradation of these two dyes. (C) 2015 Elsevier B.V. All rights reserved.