**2.3.2.2 Photocatalytic degradation of paracetamol using solar photocatalysis**

Conditions were evaluated to promote the mineralization of paracetamol (or acetaminophen), a known emerging contaminant (Daughton, C. G. & Ternes, T. A., 1999; Bound, J. P. & Voulvoulis, N., 2004; Jones, O. A. H., Voulvoulis, N. et al. , 2007; Nikolaou, A., Meric, S. et al., 2007; Zhang, X. *et al.*, 2008; Bartha, B. *et al.*, 2010), employing heterogeneous photocatalysis mediated by TiO2/ZnPc 2.5% m/m, under the action of solar radiation. The results were compared with process under similar conditions, using TiO2 P25 as photocatalyst.

Firstly, to find the best experimental conditions, the influence of hydrogen peroxide concentration and pH was evaluated in the photocatalytic reactions mediated by 100 mg L-1 of photocatalyst, on a laboratory scale using an experimental setup already described (Machado et al., 2003a; Oliveira et al., 2012). The best conditions for the reactions in laboratory scale were obtained at pH 6.80 using 33.00 mg L-1 of hydrogen peroxide for the degradation and mineralization of aqueous solutions containing 10 mg L-1 of paracetamol (França, 2011). Under these conditions, the substrate was completely oxidized after 40 minutes of reaction using TiO2 P25, while 78% of mineralization with this same photocatalyst was reached after 120 minutes of reaction. Using the TiO2/ZnPc composite, the substrate was completely oxidized after 60 minutes of reaction, and 63% was mineralized after 2 hours of reaction.

In the photocatalytic tests using a CPC reactor and solar radiation (**Fig. 8**), the experiments were done preferentially at pH 3.00 (França, 2011), using 50 L of an aqueous solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. Hydrogen peroxide, used as additional radical source (Machado et al., 2003a), was employed at the same concentration as defined in studies on laboratory scale.

Although the mineralization of paracetamol under the action of solar radiation has been equivalent in both cases (56%), after the accumulation of an UVA dose equal to 700 kJ m-2, comparing the results obtained on laboratory scale and induced by solar radiation, it was observed that the increase in mineralization obtained with the use of the composite, 33%, was higher than that obtained using the commercial photocatalyst, equal to 25%, suggesting a better utilization of solar radiation by TiO2/ZnPc composite.

In terms of degradation, monitored by high performance liquid chromatography (HPLC), the commercial photocatalyst required the accumulation of less UVA radiation (200 kJ m-2) to oxidize 96% of paracetamol, whereas for the composite this level of degradation was achieved when the dose reached 350 kJ m-2 (**Fig. 9**).

The results obtained by Zhang et al (2010) indicated that TiO2 photocatalytic degradation is an effective way to remove paracetamol from wastewater and drinking water without any generation of more toxic products. Although we have not analyzed the intermediates and products obtained, our results also point to the efficiency of heterogeneous photocatalysis in the treatment of acetaminophen, even if present in high concentrations in wastewater and drinking water.

Despite the fact that part of ZnPc adsorbed to the surface of TiO2 P25 may have been degraded during the photocatalytic process, surprisingly, the photocatalytic efficiency of the composite did not decrease when reused. Results suggest that the composite can be reused

Conditions were evaluated to promote the mineralization of paracetamol (or acetaminophen), a known emerging contaminant (Daughton, C. G. & Ternes, T. A., 1999; Bound, J. P. & Voulvoulis, N., 2004; Jones, O. A. H., Voulvoulis, N. et al. , 2007; Nikolaou, A., Meric, S. et al., 2007; Zhang, X. *et al.*, 2008; Bartha, B. *et al.*, 2010), employing heterogeneous photocatalysis mediated by TiO2/ZnPc 2.5% m/m, under the action of solar radiation. The results were compared with process under similar conditions, using TiO2 P25 as

Firstly, to find the best experimental conditions, the influence of hydrogen peroxide concentration and pH was evaluated in the photocatalytic reactions mediated by 100 mg L-1 of photocatalyst, on a laboratory scale using an experimental setup already described (Machado et al., 2003a; Oliveira et al., 2012). The best conditions for the reactions in laboratory scale were obtained at pH 6.80 using 33.00 mg L-1 of hydrogen peroxide for the degradation and mineralization of aqueous solutions containing 10 mg L-1 of paracetamol (França, 2011). Under these conditions, the substrate was completely oxidized after 40 minutes of reaction using TiO2 P25, while 78% of mineralization with this same photocatalyst was reached after 120 minutes of reaction. Using the TiO2/ZnPc composite, the substrate was completely oxidized after 60 minutes of reaction, and 63% was

In the photocatalytic tests using a CPC reactor and solar radiation (**Fig. 8**), the experiments were done preferentially at pH 3.00 (França, 2011), using 50 L of an aqueous solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. Hydrogen peroxide, used as additional radical source (Machado et al., 2003a), was employed at the same

Although the mineralization of paracetamol under the action of solar radiation has been equivalent in both cases (56%), after the accumulation of an UVA dose equal to 700 kJ m-2, comparing the results obtained on laboratory scale and induced by solar radiation, it was observed that the increase in mineralization obtained with the use of the composite, 33%, was higher than that obtained using the commercial photocatalyst, equal to 25%, suggesting

In terms of degradation, monitored by high performance liquid chromatography (HPLC), the commercial photocatalyst required the accumulation of less UVA radiation (200 kJ m-2) to oxidize 96% of paracetamol, whereas for the composite this level of degradation was

The results obtained by Zhang et al (2010) indicated that TiO2 photocatalytic degradation is an effective way to remove paracetamol from wastewater and drinking water without any generation of more toxic products. Although we have not analyzed the intermediates and products obtained, our results also point to the efficiency of heterogeneous photocatalysis in the treatment of acetaminophen, even if present in high concentrations in wastewater and

at least five times before making any significant loss of photocatalytic efficiency. **2.3.2.2 Photocatalytic degradation of paracetamol using solar photocatalysis** 

photocatalyst.

drinking water.

mineralized after 2 hours of reaction.

concentration as defined in studies on laboratory scale.

achieved when the dose reached 350 kJ m-2 (**Fig. 9**).

a better utilization of solar radiation by TiO2/ZnPc composite.

Fig. 8. Variation of dissolved organic carbon (DOC) as a function of cumulative dose of UVA, during the photocatalytic degradation of paracetamol mediated by solar radiation: TiO2/ZnPc 2.5% m/m (●);TiO2 P25 (■).

Fig. 9. Variation in the concentration of paracetamol measured by HPLC during photodegradation experiments mediated by TiO2 P25 (■) and TiO2/ZnPc 2.5% m/m (▲) and induced by solar radiation.
