Activity report 2023

Outcomes

A2.1. Design, development, characterization and testing of the TiO2-gC3N4 VIS-/Solar-active composite photocatalytic beads

Continuing the activity that started in 2022, the influence of the percentage of graphitized carbon nitride (gC3N4) of the thin composite layer on the photocatalytic properties of layers was tested.

  • Thin films with the composition QAS/TiO2-gC3N4(x%) and QAS/TiO2/TiO2-gC3N4(x%), where x is a value of 1, 2, 5 or 10 were obtained. A superior photocatalytic efficiency of the samples that contain an intermediary layer of TiO2 was observed. Also, the most promising results (under UV, UV-VIS radiation, as well as in darkness) were obtained for the sample which contains 5% gC3N4.
  • Stability tests for all 8 samples mentioned above were performed, by submitting them to 3 photocatalytic cycles each, under UV-VIS radiation. In the case of methylene blue (MB), as well as imidacloprid (IMD), the sample QAS/TiO2/TiO2-gC3N4(5%) showed the highest stability.
  • Thin films (composites with GO and gC3N4 filler) deposited on planar substrate, using the same protocol as the films on beaded substrate were analyzed by ellipsometry and Raman.
  • The Raman analysis could point out the presence of GO in the composite thin film, but not that of gC3N4, due to the overlapping structural vibrations of C-N and C-C.
  • The ellipsometric analysis confirmed the small thickness of the layers (approximately 100 nm for the composite layer based on TiO2-GO and 130 nm for the one based on TiO2-gC3N4); bandgap energy values are 3.22 eV and 3.33 eV, respectively.

 

A2.2. Modelling the photocatalytic demonstrator reactor with VIS-/Solar-active composite beads

The demonstrator photoreactor includes:

  • A central device which consists of a vertical quartz tube, perforated lids at the upper and lower sides of the tube, perforated trays that hold the photocatalytic beads and rods that hold everything in place;
  • An aluminum profile support structure;
  • A recirculation vessel for the MB and IMD solutions;
  • A pump and a flow meter, with the electric control panel for both;
  • Hoses for the solution circulation.

The most important (and novel) aspect of the photoreactor is the central device. This was carefully considered and the radiation transmittance through it was modelled using both VIS and UV-A radiation, from a vertical solar simulator.

Three different quartz tubes were considered, with variable interior diameters, wall thickness and quartz crystallinity degree. It was demonstrated that the wall thickness of these tubes can affect their transmittance (which is lost in up to 5% by increasing the wall thickness with just 0.5 mm). However, the quartz crystallinity degree is the deciding factor. Accordingly, a quartz tube with the inner diameter of 66 mm and a wall thickness of 2.5 mm was selected for the photocatalytic demonstrator reactor.

 

A2.3. Design and development of the photocatalytic demonstrator reactor with VIS-/Solar-active composite beads

  • The central device was designed using the CATIA software;
  • The central device was constructed to include the quartz tube previously optimized (transmittance of >90% under UV-A and VIS radiation), 3D printed lids with water canals (made from Acrylonitrile Styrene Acrylate), perforated trays to hold the photocatalytic beads (3D printed, also from Acrylonitrile Styrene Acrylate) and rods (galvanized steel) to hold everything in place.
  • The device was integrated in the photoreactor by positioning it on an aluminum frame. It has been connected using hoses to a recirculating vessel which contains the pollutant solution. The device also requires two pumps which offer a flow of 1 to 2.5 L/min, a flowmeter and an electric control panel.

 

Reactor Components

1 – central device

2 – recirculation vessel

3 – pumps and flow meter

4 – control panel
Tray Beads
The demonstrator photoreactor with photocatalytic beads

 

A2.4. Testing and validating the demonstrator technology with VIS-/Solar-active composite beads

  • The demonstrator photoreactor was tested using distilled water and is in a workable condition.
  • The chemical stability (in darkness, as well as under UV-VIS irradiation, with high irradiation of 1000 W/m2) of all the components was confirmed by comparing conductivity and pH values of the inlet and outlet water;
  • The flow influences the movement of the beads on the surface of the trays, with higher flow leading to overlap of the beads.
  • The process of obtaining the thin composite layers was re-optimized in order to obtain a higher quantity of photocatalytic beads simultaneous.
  • The 2.4 activity will continue in 2024 by testing the photocatalytic technology using MB and IMD, under UV, UV-VIS and no irradiation (controlled irradiance of 200-1000 W/m2), using the solar simulator. The bead amount will be varied between 10 and 40 g for the treatment of 1 to 3 L of pollutant solution. The number and position of the beads trays will also be varied to see the effect on the photocatalytic efficiency.

 

A2.5. Dissemination

The main results of the project were disseminated towards (a) the general public through the update of the project website, (b) the academic community through the publishing of 2 articles in ISI journals, as well as through 9 oral and 1 poster communications at international scientific conferences, (c) interested parties by organizing of 2 workshops.

A. Published papers

• Covei, M.; Bogatu, C.; Gheorghita, S.; Duta, A.; Stroescu, H.; Nicolescu, M.; Calderon-Moreno, J.M.; Atkinson, I.; Bratan, V.; Gartner, M., “Influence of the deposition parameters on the properties of TiO2 thin films on spherical substrates”, Materials (Basel), 2023, 16, 4899. doi:10.3390/ma16144899 (IF=3.748).

• Gartner M., Szekeres A., Stroescu H., Mitrea D., Covei M., “Advanced Nanostructured Coatings Based on Doped TiO2 for Various Applications”, Molecules, 2023, 28 (23), 7828. doi:10.3390/molecules28237828 (IF=4.927).

B. Communications at international conferences

• Covei M., Bogatu C., Perniu D., Gheorghita S., Duta A., Stroescu H., Nicolescu M., Calderon-Moreno J.M., Atkinson I., Bratan V., Gartner M., "Composite TiO₂-gC₃N₄ thin film beads for advanced wastewater treatment", 18th International Conference on Chemistry and the Environment (ICCE 2023), 11-15 June 2023, Venice, Italy;

• Covei M., Bogatu C., Gheorghita S., Duta A., Stroescu H., Nicolescu M., Calderon-Moreno J.M., Atkinson I., Bratan V., Gartner M., "Comparative assessment of TiO2-GO and TiO2-gC3N4 photocatalytic thin films on spherical substrate", 12th International Conference on Environmental Engineering and Management (ICCEM), 13-16 September 2023, Iasi, Romania;

• Bratan V., Covei M., Stroescu H., Carata M., Gartner M., “The use of UV Visible spectroscopy for the characterization of semiconductor oxides”, RomPhysChem, 25-26 September 2023, Bucharest, Romania;

• Covei M., Bogatu C., Gheorghita S., Tismanar I., Duta A., Stroescu H., Nicolescu M., Calderon-Moreno J.M., Atkinson I., Bratan V., Gartner M., “Composite photocatalytic beads based on TiO2 and carbon derivates for wastewater treatment”, RomPhysChem, 25-26 September 2023, Bucharest, Romania;

• Szekeres A., Simeonov S., Gartner M., Covei M., “Influence of sol-gel technological conditions on thin TiO2 films properties”, RomPhysChem, 25-26 September 2023, Bucharest, Romania;

• Stroescu H., Gartner M., Calderon Moreno J.M., Atkinson I., Bratan V., Covei M., Gheorghita S., Bogatu C., Perniu D., Duta A., “Substrate influence on the properties of TiO2 photocatalytic surfaces”, Conference for Sustainable Energy, 26-28 October 2023, Brasov, Romania;

• Gartner M., Stroescu H., Calderon Moreno J.M., Atkinson I., Bratan V., Covei M., Gheorghita S., Bogatu C., Perniu D., Duta A., “VIS-solar active composites based on TiO2 and carbon derivatives (GO and gC3N4)”, Conference for Sustainable Energy, 26-28 October 2023, Brasov, Romania;

• Covei M., „Photocatalytic beads for advanced wastewater treatment”, Conference for Sustainable Energy, 26-28 October 2023, Brasov, Romania;

• Bogatu C., Gheorghita S., Covei M., Duta A., „Photocatalytic thin films based on TiO2-g-C3N4 composites for advanced wastewater treatment”, Conference for Sustainable Energy, 26-28 October 2023, Brasov, Romania;

• Tismanar I., Duta A., „In situ prepared photocatalytic composite of TiO2-gC3N4”, Conference for Sustainable Energy, 26-28 October 2023, Brasov, Romania.

C. Workshops

• A dedicated workshop in the frame of the RomPhysChem-17, International Conference of Physical Chemistry, Bucharest, 26 September 2023. The workshop brought together around 40 participants from universities and research institutes from Romania and abroad, working in the field of advanced materials.

• The “Photocatalytic systems for advanced wastewater treatment” workshop, that took place on the 26th of October 2023, with 32 participants form academic institutions, intercommunity associations and the extended public, which expressed an interest in the results of the PED598/2022 project.