Photocatalytic Degradation of Diclofenac Using Al(2)O(3)-Nd(2)O(3) Binary Oxides Prepared by the Sol-Gel Method

This paper reports the sol-gel synthesis of Al(2)O(3)-Nd(2)O(3) (Al-Nd-x; x = 5%, 10%, 15% and 25% of Nd(2)O(3)) binary oxides and the photodegradation of diclofenac activated by UV light. Al-Nd-based catalysts were analyzed by N(2) physisorption, XRD, TEM, SEM, UV-Vis and PL spectroscopies. The inclusion of Nd(2)O(3) in the aluminum oxide matrix in the 10–25% range reduced the band gap energies from 3.35 eV for the γ-Al(2)O(3) to values as low as 3.13–3.20 eV, which are typical of semiconductor materials absorbing in the UV region. γ-Al(2)O(3) 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-x with Nd(2)O(3) contents in the range 10–25% was improved with respect to that of γ-Al(2)O(3) at short reaction times. The diclofenac photoconversion using γ-Al(2)O(3) 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 Nd(2)O(3,) and these compounds presented the lowest band gap energies. The experimental results also demonstrated that Nd(2)O(3) acts as a separator of charges favoring the decrease in the recombination rate of electron-hole pairs.