Summary for April-December 2022
In the first phase of the project AutoMATiO, 9 photocatalysts were prepared by the chemical reduction of TiO2 with NaBH4 in air atmosphere. We obtained materials with varying colours from light gray to black by changing the time and the temperature of reduction.
For quantifying and understanding the influence of time and reduction temperature, these materials were characterized by N2 sorption and Diffuse Reflectance UV-vis Spectroscopy. We observed a 2-fold increase of specific surface area and a decrease of the band-gap energy from 3.2 eV to 1.4 eV.
The photocatalytic activity of the materials was preliminary tested in degradation of two organic pollutants, phenol and imidacloprid (pesticide) in batch under the irradiation of a conventional light source with broad emission (290 nm-750 nm) and pseudo-monochromatic emission obtained using LEDs. Two LED light sources were designed and constructed and were characterized by emission in the UV (394 nm) and in the visible domain (467 nm, 520 nm, 635 nm). The batch photoreactor was designed considering the thermal management of the LED light sources, so that the temperature in the photoreactor did not exceed 26°C.
Next, the photocatalysts were deposited as thin films with uniform distribution and with controllable mass of the photocatalyst using a reproducible deposition procedure. The films were characterized by UV-Vis spectroscopy and tested for phenol degradation in flow.
The flow reactor was made using the 3D printing technique in collaboration with Assoc. Prof. Dr. Eng. Razvan Udroiu (Faculty of Technological Engineering and Industrial Management, Transilvania University of Brasov) and allows the replacement of the deposited photocatalytic film. The performance of the flow reactor was tested with success for phenol degradation under LED light source, showing reproducibility and stability of the photocatalyst activity after 160 min of operation.
Summary for January – December 2023
In the second phase of the project, a new series of photocatalysts were prepared by chemical reduction of P25 with NaBH4, by varying the reduction temperature between 275 and 400°C and reduction time between 0.5 and 3 h. The synthesized materials were characterized by N2 sorption, DR UV-Vis spectroscopy, XPS, Raman and XRD. The powder photocatalysts were immobilized on glass plates as thin films. It was observed that the distribution of the material and the thermal treatment duration influence the mechanical stability of the films when operated in the photo microreactor. Moreover, a microfluidic platform was developed by integrating a syringe pump, a 3D-printed microreactor, a rotating LED light source with emission at 395, 413, and 443 nm, and a flow cell connected to a spectrometer for online measurement of the imidacloprid concentration. Moreover, an automation methodology for the microfluidic platform was developed which was implemented in python.
The degradation efficiency of imidacloprid was screened in batch and in flow at 395/400, 413, and 443 nm. In flow, the influence of irradiating wavelength and of the presence of air gas was investigated by performing multiple test during 405 min on the same immobilized photocatalyst. It was observed that the screening in flow captured well the observations acquired in batch. The stability of the photocatalyst in flow was verified by performing the same test at multiple moments during operation, and it was found that the photocatalysts showed a good stability for different periods depending on the catalyst, between 160 and 402 min. Finally, by comparing the screening parameters (number of tested conditions, type of gained information, screening period, materials and energy consumption) for the automated microfluidic platform with the flow and batch photoreactor, it was found the online measurement of imidacloprid will lead to the reduction of screening time and of materials and energy consumption.
Summary for January – May 2024
The final configuration of the microfluidic screening platform consists of a syringe pump, in-house built valve for liquid distribution towards the four 3D-printed microreactors, photoreactor assembly, in-house built valve for selecting the pathway of the liquid exiting the microreactors (i.e. analysis or waste), in-line flow cell connected to UV-Vis spectrometer, a stepper motor for rotating the LED light source, a water cooling system, power supply for LEDs and Arduino hardware. The 3D-printing of the platform components was performed in collaboration with Assoc. Prof. Dr. Eng. Razvan Udroiu (Manufacturing Engineering Department, Transilvania University of Brasov). The equipment was controlled and automated using python in collaboration with Lect. Dr. Eng. Alexandru Dinu (Electronics and Computers Department, Transilvania University of Brasov). The microfluidic platform was tested for degradation of imidacloprid using 4 immobilized photocatalytic films of TiO2 P25, during 12 h of operation, the degradation efficiency of each film being investigated at 6 conditions (dark, 395 nm, 409 nm, 413 nm, and 443 nm, and at the initial illumination wavelength).
Overview of project results
In this project a series of photocatalysts were prepared by chemical reduction of commercial titania (P25) by varying the reduction temperature between 275 and 400°C and reduction time between 0.5 and 3 h. We obtained materials with varying colors from light gray to black which means they absorb light not only in ultraviolet range, but also in the visible and infrared ranges. These materials were tested in in-house built batch and flow photoreactors which offer radiation at 395-400 nm, 413 nm and 443 nm. TiO2 P25 presented higher photocatalytic activity than the reduced materials at 400 and 413 nm. However, at 443 nm, the material reduced at 400°C exhibited the highest degradation efficiency of 16.8 % compared to 4.2 % as found for P25. Selected photocatalysts were then immobilized as thin films and tested in a 3D-printed flow photoreactor using a new methodology which mainly reduced wasted polluted water and the required amount of photocatalytic material. The new methodology was validated as the wavelength and photocatalyst’s impact on imidacloprid degradation in flow mode aligned with batch mode observations, even though the investigation in flow consisted in testing all the conditions on a single immobilized photocatalytic film. The design of the 3D-printed microreactor and the screening methodology were used for the design and construction of a novel screening microfluidic platform described in the patent application 138050 (A0). The control of the integrated equipment was automated using python, and various automation flows were developed to allows different type of experiments such as dynamic water pumping and dynamic irradiation. The microfluidic platform was tested for degradation of imidacloprid using 4 immobilized photocatalytic films of TiO2 P25, during 12 h of operation, the degradation efficiency of each film being investigated at 6 conditions (dark, 395 nm, 409 nm, 413 nm, and 443 nm, and at the initial illumination wavelength).