TiO2/MgAl layered double hydroxides mechanical mixtures as efficient photocatalysts in phenol degradation

MgAl layered double hydroxides (MgAl LDH) were synthesized by the sol–gel method using ultrasound irradiation in the crystallization step. The interlayer anions were nitrate and acetylacetonate-ethoxide. The solids were characterized by XRD, N2-physisorption and TEM. TiO2/MgAl LDH mixtures were prepared by mixing the MgAl LDH (as prepared) or the calcined sample with TiO2 (Aldrich, 99.9% anatase) in different weight ratios. Photocatalytic activities of the TiO2/MgAl LDH mixtures were evaluated through the degradation of phenol as model pollutant. TiO2/MgAl LDH mixture (1:1) was more photocatalytically active for the degradation of phenol than pure TiO2. The synergy effect was attributed to a higher production of •OH radicals, which were formed from the structural hydroxides. Also, the hydrotalcite phase enhanced the phenol adsorption and transfer to the TiO2 sites where the phenol was photocatalytically degradated.

Graphical abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The study presents a novel system, which integrates titanium dioxide with Mg–Al layered double hydroxides (LDH) mechanical mixtures for the photocatalytic degradation of phenol. ► TiO2/MgAl LDH mixtures were more active than the TiO2 anatase alone, however a significant dependence of the weight ratio of TiO2/MgAl LDH was observed. ► It is suggested that LDH particles in contact with TiO2 may act as a barrier layer for charge recombination and electron trap sites leading to a better charge separation.