Molecularly imprinted TiO₂ photocatalysts for degradation of diclofenac in water

In order to improve the selectivity in photocatalytic process, molecularly imprinted photocatalysts containing a low loading of TiO₂ (from 6.6 to 16.6% of total mass) were prepared for photocatalytic degradation of an organic pollutant, diclofenac (DIC). The photocatalytic component TiO₂ (P25), with and without being doped with Cu₂O, was embedded in diclofenac-imprinted polymers. The molecularly imprinted polymers (MIPs) and the composite photocatalysts exhibited a superior specific target recognition for selective degradation of DIC over non-target reference molecules, fluoxetine (FLU) and paracetamol (PARA). In contrast to the non-selective commercial sample of TiO₂, the average value of selectivity of the imprinted catalysts for photocatalytic degradation of DIC was estimated to be 2.8, which suggests that the specific binding sites created by the molecular imprinting are essential for gaining high catalytic selectivity and efficiency. After 6 cycles of testing under UV-light, the imprinted catalysts maintained almost the same efficiency for photo degradation of DIC. In addition, the morphology and the structure of the imprinted catalysts remained after repeated uses. The results suggest that it is feasible to use MIPs to control the selectivity of photocatalytic degradation of organic pollutants.