Photocatalytic Degradation of Diclofenac Using AlO-NdO Binary Oxides Prepared by the Sol-Gel Method.

This paper reports the sol-gel synthesis of AlO-NdO (Al-Nd-; = 5%, 10%, 15% and 25% of NdO) binary oxides and the photodegradation of diclofenac activated by UV light. Al-Nd-based catalysts were analyzed by N physisorption, XRD, TEM, SEM, UV-Vis and PL spectroscopies. The inclusion of NdO in the aluminum oxide matrix in the 10-25% range reduced the band gap energies from 3.35 eV for the γ-AlO to values as low as 3.13-3.20 eV, which are typical of semiconductor materials absorbing in the UV region. γ-AlO and Al-Nd-x binary oxides reached more than 92.0% of photoconverted diclofenac after 40 min of reaction. However, the photocatalytic activity in the diclofenac degradation using Al-Nd- with NdO contents in the range 10-25% was improved with respect to that of γ-AlO at short reaction times. The diclofenac photoconversion using γ-AlO was 63.0% at 10 min of UV light exposure, whereas Al-Nd-15 binary oxide reached 82.0% at this reaction time. The rate constants determined from the kinetic experiments revealed that the highest activities in the aqueous medium were reached with the catalysts with 15% and 25% of NdO and these compounds presented the lowest band gap energies. The experimental results also demonstrated that NdO acts as a separator of charges favoring the decrease in the recombination rate of electron-hole pairs.