the main container and the other pipe is intended to return to the first deposit the
settled sludge accumulated; finally the treated water is conducted from the second
tank through a pipe 10 cm in diameter to the said pipe.
The physicochemical and biological characteristics of the wastewater were
monitored monthly, and these measurements were pH, temperature, sludge volume
index, and total and fecal coliform organisms.
3.2.2 Solar Photocatalysis Disinfection
3.2.2.1 Synthesis and Characterization of the Ag:TiO 2 Catalyst
The synthesis of the TiO 2 substrate was obtained by slowly dissolving the titanium
precursor (titanium isopropoxide, 97 % Aldrich, TTIP) in an organic solvent
(isopropanol, 99.9 %, J.T. Baker). The titanium solution was continuously magnetically stirred for 20 min under nitrogen atmosphere. The hydrolysis process was
then performed by adding water into the flask containing precursor/solvent mixture
and magnetically stirred for 1 h (Esquivel et al. 2013). The molar ratio of the
precursors and solvents are, 0.03:4.2:1 for TTIP:H 2 O:isopropanol, respectively.
For the Ag-modified TiO 2 samples, the precursor was silver nitrate 99.9 %
(Sigma-Aldrich). This precursor was added separately by dissolving it into the
water used for the hydrolysis reaction at different weight percentages (0.005, 0.01,
and 0.1 wt%). The obtained sol was transferred into Teflon-lined vessels and
placed on a turn table for uniform heating using a microwave reaction system
(Synthos 3000, Anton Paar). The change in temperature in the reaction vessel was
monitored automatically by the dual-IR temperature probe and the solutions were
continuously stirred at medium speed (300 rpm). The heating procedures were
conducted for 30 min at 215 °C for 60 min using microwave radiation of 600 W,
and finally the system was cooled down to room temperature. The obtained
powder was filtered and washed with deionized water several times and room
temperature dried for 18 h, and subsequently dried at 80 °C for 20 h in a conventional furnace. A calcination process was carried out at 550 °C for 3 h to
improve the sample crystallinity. The catalyst characterization of the surface
morphology analysis of the materials was carried out by Scanning Electron
Microscopy (SEM) with a microscope JEOL JSM-6060 LV. The accelerating
voltage employed was 15 kV. Elemental analysis was performed by Energy
Dispersive X-ray Spectroscopy (EDS) (EDS Oxford Inca X-Sight coupled to a MT
1000, Hitachi). Also, the morphology analysis was carried out by high-resolution
transmission electronic microscopy (HRTEM) using a JEOL JEM 2000FX
microscope. The catalysts were crushed and dispersed ultrasonically in acetone at
room temperature and then spread onto a perforated carbon–copper microgrid. The
operational accelerating voltage was 200 kV using a filament of LaB 6 . Bandgap
energy (E bg ) values were determined from diffuse reflectance measurements (Cary
5000 UV–Vis-NIR Varian spectrophotometer) by applying the Kubelka–Munk
84
L. Pérez-Sánchez et al.
settled sludge accumulated; finally the treated water is conducted from the second
tank through a pipe 10 cm in diameter to the said pipe.
The physicochemical and biological characteristics of the wastewater were
monitored monthly, and these measurements were pH, temperature, sludge volume
index, and total and fecal coliform organisms.
3.2.2 Solar Photocatalysis Disinfection
3.2.2.1 Synthesis and Characterization of the Ag:TiO 2 Catalyst
The synthesis of the TiO 2 substrate was obtained by slowly dissolving the titanium
precursor (titanium isopropoxide, 97 % Aldrich, TTIP) in an organic solvent
(isopropanol, 99.9 %, J.T. Baker). The titanium solution was continuously magnetically stirred for 20 min under nitrogen atmosphere. The hydrolysis process was
then performed by adding water into the flask containing precursor/solvent mixture
and magnetically stirred for 1 h (Esquivel et al. 2013). The molar ratio of the
precursors and solvents are, 0.03:4.2:1 for TTIP:H 2 O:isopropanol, respectively.
For the Ag-modified TiO 2 samples, the precursor was silver nitrate 99.9 %
(Sigma-Aldrich). This precursor was added separately by dissolving it into the
water used for the hydrolysis reaction at different weight percentages (0.005, 0.01,
and 0.1 wt%). The obtained sol was transferred into Teflon-lined vessels and
placed on a turn table for uniform heating using a microwave reaction system
(Synthos 3000, Anton Paar). The change in temperature in the reaction vessel was
monitored automatically by the dual-IR temperature probe and the solutions were
continuously stirred at medium speed (300 rpm). The heating procedures were
conducted for 30 min at 215 °C for 60 min using microwave radiation of 600 W,
and finally the system was cooled down to room temperature. The obtained
powder was filtered and washed with deionized water several times and room
temperature dried for 18 h, and subsequently dried at 80 °C for 20 h in a conventional furnace. A calcination process was carried out at 550 °C for 3 h to
improve the sample crystallinity. The catalyst characterization of the surface
morphology analysis of the materials was carried out by Scanning Electron
Microscopy (SEM) with a microscope JEOL JSM-6060 LV. The accelerating
voltage employed was 15 kV. Elemental analysis was performed by Energy
Dispersive X-ray Spectroscopy (EDS) (EDS Oxford Inca X-Sight coupled to a MT
1000, Hitachi). Also, the morphology analysis was carried out by high-resolution
transmission electronic microscopy (HRTEM) using a JEOL JEM 2000FX
microscope. The catalysts were crushed and dispersed ultrasonically in acetone at
room temperature and then spread onto a perforated carbon–copper microgrid. The
operational accelerating voltage was 200 kV using a filament of LaB 6 . Bandgap
energy (E bg ) values were determined from diffuse reflectance measurements (Cary
5000 UV–Vis-NIR Varian spectrophotometer) by applying the Kubelka–Munk
84
L. Pérez-Sánchez et al.