TEXTILE LIGHT FOR WATER TREATMENT BY PHOTOCATALYSIS – AQUAPHOTEX*

The aim of the modelling part is to design a suitable reactor in order to maximize treated volume by optimizing the contact time between pollutant and the photocatalytic textile.
The modelling will be based on the study of tangential flow and flow through the textile, and on the development of a pollutant transport model in order to predict the decontamination in aqueous solution in representative volume element. Several phenomena were modelled in this study:
• The flow near the textile.
• The flow in the porous media.
• The transport by convection-diffusion of the pollutant in the fluid and in the porous media.
• Adsorption - desorption and photocatalytic reaction on textile surface.
The first step is to represent both tangential flow and flow through the textile, then a numerical model at the optical fiber scale is proposed to perform numerical simulations in a geometrical domain consisting of a Representative Volume Element (RVE) of the photocatalytic textile with periodic boundary conditions.
The second step is to integrate kinetic constants calculated from experimental test using the cylindrical reactor at IRCELYON.
The last step is to determine photocatalytic performance of the textile using the plan reactor designed after the modelling.

At first, a hydrodynamic model is built by coupling a free flow and a flow in porous media on a representative elementary motive for the textile. This study allows to distinguish 3 flow types inside RVE. The fluid can pass freely in the space inter-textile and must be forced to pass by in the porous media: between optical fibers and in the fibrous media.
In the frontal case, the flow depends of the permeability of textile, whereas in tangential, it is the space inter-fabric which plays a role on the flow of the fluid.
Secondly, a model of transport of molecules by this flow is coupled with a reaction of surface. The equation of dimensional convection-diffusion is used to calculate the transport of pollutant.
An experimental pilot was designed in order to collect experimental data for tangential flow and flow through the textile. The confrontation between the experimental measures and the numeric simulations will allow to determine the tensor of permeability of the fabric.
Photocatalytic performances were evaluated in the designed reactor on pollutant models: formic acid and phenol, and on siloxane solution representing a real industrial effluent.

As perspectives, there is many applications especially in the domain of effluent treatment in process output of chemical, pharmaceutical and agriculture industries.
However, in order to scale up the reactor for lab scale to the industrial one, it seems necessary to develop a lab reactor at intermediate scale to predict performance at high flow rate.
For these reasons, the three partners decided to continue in a new collaboration by predicting to submit FUI project to realize the scale up. A new partner will be integrated to the consortium of the new project having the role of end user.

LISBP : publication on the modelling of the woven optical fiber textile.
Degrave, R; Moreau J; Cockx A; Schmitz P; Multiscale analysis and modelling of fluid flow within a photocatalytic textile Chemical Engineering Science, 2015, 130, 264-274.

IRCELYON : publication on optical fibre ageing under UV.
Indermühle C., Puzenat E., Simonet F., Peruchon L., Brochier C., Guillard C. Modelling of UV optical ageing of optical fibre fabric coated with TiO2 Applied Catalysis B: Environmental, Volume 182, March 2016, Pages 229-235.

The AQUAPHOTEX project proposes to develop a light side-emitting textile applied to the treatment of water by photocatalysis. This Advanced Oxidation Process (AOP) might get place in complement to other treatment, either at the end of string, because the photocatalysis can degrade organic molecules, including pollutants such as pesticides and other targets refractory compounds, either at the beginning of string to make biodegradable products.

Technological innovation focuses on the design of a photocatalytic lighting textile adapted to the aqueous environment based on work during project PHOTEX (ANR 2007-2010) which was involved in air purification.

One of the main lock in photocatalysis is the relationship between volume and irradiated surface of the photocatalyst.

The proposed photocatalytic system differs significantly from existing systems which use photocatalytic media receiving the irradiation of an outer point source. In this project, the textile with “side-emitting optical fibre" connected to UV LED - UVtex ® - developed by the Brochier Technologies company, is both source of UV irradiation and support of the photocatalyst, which creates a contact surface maximum between these two elements.

Others scientific locks remain the selection and adaptation of photocatalytic light textile in the aqueous medium and its arrangement in a reactor to maximize meeting and contact time of pollutant-UV-Photocatalyst.

The research work planned will therefore focus on:

(i) the design and the realization of the photocatalytic light textile structure for an aqueous medium,
(ii) the study of the flow of the liquid and reactive transport of target molecules in the system on a microscopic scale (unit cell) and macroscopic scale (fabric panel),
(iii) the characterization of photocatalytic performance of innovative material on two models pollutants (formic acid and a pesticide, the imidacloprid).

The ambition of the project is to propose an innovative solution for the treatment of industrial effluents by photocatalysis. The final success of the project would for example propose a compact and field prototype for testing on actual water loaded in phytosanitary products.