Synthesis of Hydroxide–TiO 2 Compounds with Photocatalytic Activity for Degradation of Phenol J.C. CONTRERAS-RUIZ, 1 S. MARTI ´ NEZ-GALLEGOS , 1,3 E. ORDON ˜ EZ, 2 J.C. GONZA ´ LEZ-JUA ´ REZ, 1 and J.L. GARCI ´ A-RIVAS 1 1.—Instituto Tecnolo ´ gico de Toluca, Av. Instituto Tecnolo ´ gico s/n, Colonia Agrı ´cola Bellavista, C.P. 52149 Toluca, Edo. de Me ´xico, Mexico. 2.—Departamento de Quı ´mica, Instituto Nacional de Investigaciones Nucleares, A.P. 17-1027. Col. Escando ´n. Delegacio ´n Miguel Hidalgo, C.P. 11801 Mexico, D.F., Mexico. 3.—e-mail: soniazteca@hotmail.com Photocatalytic degradation of phenol using titanium dioxide (TiO 2 ), either alone or in combination with other materials, has been tested. Mg/Al hydro- talcites prepared by two methods using inorganic (HC) or organic (HS) chemical reagents, along with mixed oxides produced by calcination of these products (HCC and HSC), were mixed with titanium isopropoxide to obtain hydroxide–TiO 2 compounds (HCC–TiO 2 and HSC–TiO 2 ) and their photocat- alytic activity tested in solutions of 10 mg/L phenol at 120 min under illumi- nation at k UV = 254 nm with power of 4 W or 8 W. The obtained materials were characterized by various techniques, revealing that TiO 2 was incorpo- rated into the mixed oxides of the calcined hydrotalcite to form the above- mentioned compounds. The photocatalytic test results indicate that the activity of HCC–TiO 2 can be attributed to increased phenol adsorption by hydrotalcite for transfer to the active photocatalytic phase of the impregnated TiO 2 particles, while the better results obtained for HSC–TiO 2 are due to greater catalyst impregnation on the surface of the calcined hydrotalcite, reducing the screening phenomenon and achieving HSC–TiO 2 degradation of up to 21.0% at 8 W. Reuse of both compounds indicated tight combination of HCC or HSC with TiO 2 , since in four successive separation cycles there was little reduction of activity, being associated primarily with material loss dur- ing recovery. Key words: Calcined hydrotalcite, hydroxide, TiO 2 , composites, photocatalysis, phenol INTRODUCTION Presence of phenol in water is mainly associated with anthropogenic activities, including application of pesticides and/or agrochemical aids that result in runoff, emissions during manufacturing processes (paper industry, paints, fertilizers, pharmaceutical), as well as energy production. 1 Presence of phenol in water is a serious environmental problem due to its toxicity at even low concentrations. Various meth- ods have been used for its elimination from aqueous media, but conventional techniques only transfer the pollutant from one medium to another without removing it; such is the case for separation by distillation, 2 extraction, 3 adsorption, 4 evaporation, 5 and membrane techniques. 6 Other processes have the capacity to destroy phenol, in particular hetero- geneous photocatalysis, which consists of ultraviolet (UV) light irradiation (k £ 380 nm) of a catalyst, in this case titanium dioxide (TiO 2 ), to generate elec- tron–hole pairs and create hydroxyl ( Æ OH) radicals which have the capacity to degrade organic mole- cules such as phenol. Despite the good photocat- alytic performance of TiO 2 , its use is limited due to its low adsorption rates. In addition, recombination of photogenerated electron–hole pairs results in low catalytic efficiency and also a tendency for it to (Received September 2, 2016; accepted December 2, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-5209-7 Ó 2017 The Minerals, Metals & Materials Society