A Ti-doped γ-Fe2O3/SDS nano-photocatalyst as an efficient adsorbent for removal of methylene blue from aqueous solutions.

Synthetic dyes are among the most important environmental pollutants in wastewaters. Consequently, elimination of the synthetic dyes from wastewaters using non-toxic materials and eco-friendly technologies has been of considerable interests. In this study, magnetically separable Ti-doped γ-Fe2O3 photocatalysts were synthesized for the removal of methylene blue (MB) from a dye-contaminated aqueous solution (as a model of dye-polluted wastewaters). Compared to the pristine γ-Fe2O3, the 1.78 v% Ti-doped γ-Fe2O3 significantly increased the adsorption of MB by 57% in the dark condition as a result of the improved BET surface area in this photocatalyst. Moreover, the contact time required for the photocatalytic degradation of MB by the 1.78 v% Ti-doped γ-Fe2O3 decreased due to the higher concentration of charge carriers in this photocatalyst than that of the pristine γ-Fe2O3. The effect of different experimental parameters on the adsorption property and photocatalytic activity of the 1.78 v% Ti-doped γ-Fe2O3 photocatalyst showed that the solution pH had a remarkable influence on the removal performance of this photocatalyst. Surface treatment of the 1.78 v% Ti-doped γ-Fe2O3 with sodium dodecyl sulfate (SDS) resulted in the formation of a negatively charged Ti-doped γ-Fe2O3/SDS photocatalyst, which showed a higher tendency for the adsorption and removal of MB than the untreated photocatalyst. Moreover, the MB removal efficiency of this photocatalyst was among the best performances that have been reported for the γ-Fe2O3-based photocatalysts. The synthesized photocatalysts were characterized by various techniques, and a plausible mechanism for the removal of MB from aqueous solutions by the Ti-doped γ-Fe2O3/SDS photocatalyst was purposed.