Evaluation of Catalytic Conditions for Dye Discoloration Using Nano‐TiO2 Films: A Fractional Factorial Design Approach

In this research, selected catalytic activity conditions of nano Cu-TiO2 films were evaluated through a 2(IV)(4-1) Fractional Factorial Design for methylene blue discoloration. The following conditions were set at two levels: dye concentration (mg/L) (A) at 3.13 and 5.81; aeration (psi) (B) with and without; radiation (nm) (C) at 320 (UV) and 470 (Visible); and nano-TiO2 films (D) without and with Cu-doping. Films were prepared by the Sol-Gel dip-coating method and characterized using X-ray diffraction, revealing an anatase phase in TiO2; and anatase, rutile, and brookite crystalline phases in Cu-doped nano-TiO2, with average band gap energies of 3.82 and 3.77 eV. The catalytic activity of films was significantly affected (p<0.05) by aeration (0.0002), radiation (0.001), and Cu-doped nano-TiO2 (0.004). Dye concentration did not have a significant effect; however, the AC interaction was significant (p=0.015). A discoloration efficiency of 46.23 % was obtained with 5.81 mg/L dye concentration using Cu-doped TiO2, with UV radiation and without aeration, whereas a 52.32 % efficiency was achieved with 3.13 mg/L dye concentration using non Cu-doped TiO2. Using factorial designs allows us to identify the main variables and their interactions to determine the optimal conditions for the catalytic activity of nano-TiO2.