Influence of the Textural Parameters of LDH-TiO₂ Composites on Phenol Adsorption and Photodegradation Capacities

Abstract

Layered double hydroxides (LDH) M 2+ M 3+ CO 3 2− were synthesized following the sol-gel methodology using Mg-Al, Mg-Fe, and Zn-Al as cation pairs for subsequent use in the preparation of TiO 2 /LDH materials. The samples were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), and the Brunauer–Emmett–Teller (BET) technique to determine the surface area (SA); the results of which were used to determine the roughness of the samples in terms of surface fractal dimension (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>D</mml:mi></mml:math>). The prepared materials exhibited both adsorption and photocatalytic properties in the removal of phenol in aqueous solution under ultraviolet irradiation. This work studies the relationship between the textural parameters of the materials obtained in relation to their photocatalytic efficiency and adsorption capacity, finding that the surface of the solids, their structural heterogeneity, and roughness condition the photodegradation and adsorption processes, using phenol as reference organic pollutant. The results show that different cation in LDH influences in photocatalytic capacity; the TiO 2 /ZnAl was the best material in one test, but after 10 times of test, the TiO 2 /MgFe gave the better photodegradation material. In adsorption capacity, TiO 2 /ZnAl and TiO 2 /MgFe have a close rate for phenol adsorption and both were better than TiO 2 /MgAl. The differences in textural characteristics (surface area, surface roughness, and pore-size distribution) affected phenol adsorption and photodegradation efficiency.