**4. Conclusions**

**Figure 11.** Time evolution of As(III) concentration during sorption and photocatalysis using PAC-TiO<sup>2</sup>

water [29]. The comparative results regarding As(III) removal in the presence of HA showed a

(c), and natural zeolite (d).

<sup>−</sup> concentration during photolysis (a), photocatalysis using Z-TiO<sup>2</sup>

Another common problem of groundwater source used for drinking water supply is given by the presence of ammonium, nitrite, and nitrate. Nitrate could not be removed from water on

good efficiency for both sorption and photocatalysis using *supported TiO2*

**Figure 12.** Time evolution of NO<sup>2</sup>

110 Photocatalysts - Applications and Attributes

concentration during photocatalysis using Z-TiO<sup>2</sup>

these tested materials, while ammonium and nitrate were removed from Z-TiO<sup>2</sup>

and GAC-TiO<sup>2</sup>

material (**Figure 11**).

(**Figure 12**).

(b), of NH<sup>4</sup>

+

.

In this chapter, two types of composites obtained by two different methods and applied in the drinking water treatment were studied:


The sorption and photocatalysis studies showed that for HA removal, the sorption capacity of tested materials increased in order, PAC-TiO<sup>2</sup> > Z-TiO<sup>2</sup> > GAC-TiO<sup>2</sup> > CNT-TiO<sup>2</sup> -Epoxy>CNF-TiO2 -Epoxy, and for the photocatalytic activity, GAC-TiO<sup>2</sup> > Z-TiO<sup>2</sup> > PAC-TiO<sup>2</sup> > CNT-TiO<sup>2</sup> - Epoxy> CNF-TiO<sup>2</sup> -Epoxy.

The removal of pollutants/impurities dissolved in water is based, on the one hand, on the sorption capacity of activated carbon and/or zeolite, which exhibited selectivity for certain impurities dissolved under the lamp-off conditions. On the other hand, but taking into account the sorption phase, by starting the lamp, TiO2 on the active carbon surface and the zeolite acted by photocatalytic activity generating oxidation and reduction processes that cause the degradation and mineralization of the dissolved organic compounds and the transformation of the inorganic contaminants into the compounds that can be retained on the surface material or compounds that do not affect the quality of the water. Also, the oxidation and reduction processes under irradiation conditions allow the destruction of the contaminants and, implicitly, the cleaning of the sorbent surface. A mixture of zeolite and activated carbon as support for TiO2 could exhibit bifunctionality, depending on the water features. Thus, for low loading of water with contaminants that can be adsorbed on the filter material, the lamp is not switched on during system operation but only in the washing/ regeneration stage, and for a water loaded with contaminants that cannot be adsorbed on the filter material, the system works with the lamp on, ensuring water decontamination and self-cleaning during operation.
