Activity report 2024

Outcomes

A3.1. Testing and validating the demonstrator technology with VIS-/Solar-active composite beads

Continuing the activity that started in 2023, the protocol for depositing the optimized composite thin films based on TiO2 and gC3N4 at larger scale was confirmed to be efficient, through Raman spectroscopy results. The following results were obtained while testing and validating the technology with VIS-/Solar-active composite beads:

  • The mass of the beads that was inserted in the photocatalytic demonstrator reactor has been optimized to ensure the treatment of one liter of pollutant (methylene blue). It has been observed that a mass of 3 grams for each tray (6 grams in total in the reactor) is optimal, as at higher quantities a shielding of the beads has occurred.

  • Tests using the photocatalytic demonstrator reactor were performed, under simulated solar radiation belonging to the UV-VIS and UV domains, as well as in darkness, using two pollutants: methylene blue and imidacloprid. It has been observed that the samples are photoactive under irradiation, registering a higher photocatalytic efficiency under UV-VIS radiation (47% versus 38% for MB and 64% versus 54% for IMD respectively). This confirms the embedding of the graphitate carbon nitrate filling in the matrix TiO2;

  • Test to assess the stability of the samples have been conducted in order to see their reusability. This has been done by subjecting the same samples to 3 consecutive photocatalytic tests under UV-VIS irradiation. The efficiency remains constant for all 3 testing cycles in the case of IMD, however it decreases after the first testing cycle in the case of MB;

  • A complex characterization of the layers before and after photocatalysis as well as before and after regeneration consisting in thermal treatment at 450oC was performed;

  • It was observed that a slight restructuring of the layer surface takes place after the photocatalytic tests, as well as a possible partial washing of the layers, according to SEM;

  • The sample regeneration is efficient in removing the secondary degradation products of the pollutants, which still remained on the surface after photocatalysis, as evidenced by the Raman spectroscopy, XRF and ellipsometry;

  • The crystallinity degree increases following the regeneration treatment, as confirmed by XRD analyses;

  • Photocatalytic tests under natural solar radiation were done, with a promising photocatalytic efficiency (approximatively 50% for both pollutants). The differences from the corresponding tests carried out using the solar simulator can be attributed to the lower irradiance of the natural radiation.

A3.2. Design and testing of the regeneration operation modes

To increase the reusability of the photocatalytic beads, a regeneration stage between two consecutive testing periods is required. In the frame of the project:

  • A regeneration protocol of the photocatalytic beads has been developed and implemented, based on rinsing the photoreactor loaded with beads in distilled water (in two stages), as well as the drying and annealing of the beads in an oven at 450oC.

A3.3. Dissemination

 The main results of the project were disseminated towards (a) the general public through the updated project website, (b) the academic community through the publishing of 1 article in ISI journals, while another is under review, as well as through 4 poster communications at national and international scientific conferences.

A. Published papers

• S. Simeonov, A. Szekeres, M. Covei, H. Stroescu, M. Nicolescu, P. Chesler, C. Hornoiu, M. Gartner, Sol-Gel Multilayered Niobium (Vanadium)-Doped TiO2 for CO Sensing and Photocatalytic Degradation of Methylene Blue, Materials 2024, 17, 1923. https://doi.org/10.3390/ma17081923 FI=3.748.

B. Communications at national / international conferences

• C. Bogatu, M. Covei, I. Tismanar, A. Duta, H. Stroescu, M. Nicolescu, J.M. Calderon-Moreno, I. Atkinson, M. Gartner, TiO2-g-C3N4 „Photocatalytic Composite Beads for Advanced Wastewater Treatment”, SPASEC27-AOT28, 10-14 iun 2024, Limassol, Cyprus;

• M. Covei, I. Tismanar, C. Bogatu, A. Duta, H. Stroescu, M. Nicolescu, J.M. Calderon-Moreno, I. Atkinson, M. Gartner, „Stability of Solar-active Photocatalytic Composite Beads”, SPASEC27-AOT28, 10-14 jun 2024, Limassol, Cyprus;

• M. Covei, C. Bogatu, D. Perniu, I. Tismanar, A. Duta, H. Stroescu, M. Nicolescu, J.M. Calderon Moreno, I. Atkinson, M. Gartner, „VIS-active Photocatalytic Thin Film Beads for Wastewater Treatment”, CHIMIA 2024, 30 may – 1 jun 2024, Constanta, Romania