**5. Conclusions**

as well as the final look (color changes) of the porous medium in the following four distinct

after saturation (OTC adsorption)

but in the column filter with the coated quartz, the adsorption is function of the feed flow rate. With a flow rate of 6 L/h, the equilibrium concentration was reached within 90 minutes, and

Moreover, it was also observed a high regeneration ability by the photocatalytic porous medium, which can completely recover its oxidative properties after a simple solar radiation exposure of about 4 hours [15]. **Figure 10** presents the time evolution of saturation and regen-

As reported on item 3.3, the toxicity of the oxytetracycline both before and after the photocatalytic degradation (performed in each reactor – PR1 and PR2) was evaluated by using *L. sativa*

The results of these toxicity tests toward lettuce seed growth showed a toxicity decrease after the photocatalytic OTC degradation, enabling the adoption of this emerging water treatment

technique as an apparently safe alternative for the antibiotics removal challenge.

) has a negligible OTC adsorption,

after OTC adoption test.

**Figure 9.** Results of the OTC adsorption tests and final look (color changes) of the porous medium.

for 4L/h, the equilibrium concentration was only reached after 120 minutes.

In darkness and after 120 minutes, the quartz (without TiO<sup>2</sup>

eration processes observed in this photocatalytic filter.

seeds germination as a bioindicator.

situations:

**a.** Quartz without TiO<sup>2</sup>

140 Application of Titanium Dioxide

**d.** Quartz without TiO<sup>2</sup>

**b.** Quartz coated with TiO<sup>2</sup> **c.** Quartz coated with TiO<sup>2</sup> The chemical structure of OTC was effectively degraded by in both lab-scale photo-oxidation reactors, achieving very high OTC removal efficiencies for photocatalytic experiments (96–98%), even with small amounts of suspended and coated TiO<sup>2</sup> nanoparticles.

The results obtained in the photo-oxidation experiments using suspended TiO<sup>2</sup> indicate that:


The results obtained in the photocatalytic filtration experiments performed by a porous media coated with TiO<sup>2</sup> nanoparticles indicate that:


The *Langmuir-Hinshelwood* model was adequately adapted to the kinetic behavior observed in the OTC photo-oxidation processes in all of the analyzed scenarios, and for both used photocatalytic reactors.

The toxicity tests carried out showed that the use of heterogeneous photocatalysis with suspended TiO<sup>2</sup> does not induce the appearance of toxic by-products in the water, since the seeds of lettuce *L. sativa* always showed inhibition percentages lower than 22% after treatment.
