Photoassisted Degradation of 4-Chlorophenol and p-Cresol Using MgAl Hydrotalcites

• DOI: 10.1021/ie1006883
• Publication Date: 2010-08-09T19:58:05Z
• Authors: Angeles Mantilla; Gabriela Jácome-A...; Getsemaní Morales...; Francisco Tzompantzi; Ricardo Gómez
• Keywords: 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 3. Good health; 0104 chemical sciences

MgAl hydrotalcites, or layered double hydroxides (LDHs), with different Mg/Al molar ratios were synthesized by the coprecipitation method. The structure of the solids was collapsed by thermal treatment at 723 K obtaining MgAl mixed oxides with high specific surface areas (264-318 m 2 /g). When these oxides were put in contact with aqueous solutions containing 4-chlorophenol and para-cresol (80 ppm:0.62 and 0.73 mmol, respectively) the layered structure was recovered by rehydration of the material showing the named "memory effect" of LDH materials. Mg/Al LDHs were active for chlorophenol and p-cresol degradation under UV irradiation, being more active and selective to the mineralization of the pollutants than TiO 2 P-25 photocatalysts. Since Mg/Al hydrotalcites are not semiconductors their high photoassisted activity was surprising; this activity was explained by a photo excitation which produces mobility of charges in the lamellar structure, inducing the formation of photoactive defects.