Immobilisation of ZnO nanoparticles on carbon and on glass fibres for visible light photocatalytic applications

Crystalline zinc oxide (ZnO) nanoparticles (NP) have been used for the evaluation of the effect of manganese doping on the photocatalytic performance towards the degradation of pharmaceutical products and for the preparation of photoactive composite materials based on fibres and ZnO. The presence of manganese effected on the particles size, as obtained by TEM analysis, and the impact on the crystallographic and optical properties was shown by XRD and DRS analysis. The multiple oxidation state of the doping manganese and its impact on the oxygen vacancies of the material, together with possibility of introducing energy levels in the forbidden zone and changes in the bandgap energy could contribute to improve the catalyst properties. However, and contrasting with some reported works, no advantage using the doped particles was observed on the photocatalytic response under UV or visible light irradiation. Later, the ZnO NP were immobilised by in situ hydrothermal approach on carbon and glass fibres and the composites show good nanoparticles coverage on the SEM images and the EDS, FTIR and DRS data are consistent with the presence of NP on the surfaces. Those composites have been successfully used for the degradation of the Diclofenac (DCF) and Carbamazepine (CMZ) pollutants. The complexity of the photodegradation under UV and visible light, due to the production of absorbing degradation products, was unveiled by UV–vis spectroscopy and HPLC analysis, and showed that distinct products may be detected during degradation, depending on the radiation used. The photostability of ZnO nanoparticles and the CF/ZnO composite maintaining 83 % of its initial efficiency after three cycles of reuse highlight the method's success in supporting nanoparticles on substrates and demonstrates promising applicability in fields such as environmental remediation.