**2.4. Evaluation of the extent of mineralization**

of 14.5 mW cm−2 at 15 cm distance. Pyrex glass bottles with a capacity of 250 mL were employed as photoreactors, containing the pesticide solutions and placed in the center of the photolysis construction. Substrates were dissolved in distilled water at ppm (mg L−1) levels, under their solubility levels by spiking the appropriate volume of a stock solution in methanol, so as to have a methanol content <0.05% [13]. Fortified aqueous solutions containing each tested insecticide individually (optimum pesticide's final concentration, 10 mg L−1, unless otherwise stated), in the presence and absence of the photocatalyst, were prepared by dissolving the appropriate quantities of each one of the substances in water.

**Compound [IUPAC name] Chemical structure Physicochemical properties**

N N

N

CH2 S

P <sup>S</sup> <sup>O</sup>

O

O

O P <sup>S</sup> <sup>O</sup>

O

P <sup>S</sup> <sup>O</sup>

O

CH2

CH2

N

S CH3

CH3

CH3

CH3

Melting point, 73°C; boiling point, >200°C at 0.01 mmHg; vapor pressure, <0.18 mPa (at 20°C; water solubility, 28 mg L−1 (at 20°C); log Kow, 2.96;

Melting point, 50°C; boiling point, 147°C (at 1.3 Pa); vapor pressure, <0.32 mPa (at 20°C); water solubility, 4–5 mg L−1 (at 20°C); log Kow, 3.18; and

point, 117°C (at 0.1 mmHg); vapor pressure, 0.29 mPa (at 20°C); water solubility, 23 g L−1 (at 20°C and pH = 5); log

Melting point, <−25°C; boiling point, 128°C (at 1 mmHg); vapor pressure, 24 mPa (at 20°C); water solubility, 25 mg L−1 (at 20°C and pH = 7); log

Melting point, 7°C; boiling point, 90°C (at 1 Pa); vapor pressure, 0.74 mPa (at 20°C); water solubility, 55 mg L−1 (at 20°C and pH = 7); log Kow,

, 278.33

, 229.28

, 274.4

CH3

CH3

CH3

CH3

and M<sup>r</sup>

Mr , 345.4

<sup>H</sup> Melting point, 49°C; boiling

Kow, 0.704; and M<sup>r</sup>

Kow, 3.95; and M<sup>r</sup>

4.84; and M<sup>r</sup>

, 317.3

O

N

CH2 S

O

O P

O

P S S

S

S

N N

O <sup>O</sup> H3C H3C

H3C

H3C

H3C

H3C

**Table 1.** Chemical names, chemical formulas, and physicochemical properties of selected pesticides.

the mixtures were magnetically stirred to obtain homogenization and a good dispersion of the catalyst and equilibrated in the dark for 30 min prior to illumination. Samples of 250 mL of the above-fortified solutions (in the absence of the photocatalyst) or suspensions (in the presence of the photocatalyst) were added to Pyrex bottles covered air tightly

concentration, 100 mg L−1, unless otherwise stated),

When TiO<sup>2</sup>

**Azinphos methyl**

dithiophosphate]

**Azinphos ethyl**

dithiophosphate]

**Dimethoate** [*O,O*-dimethyl

**Disulfoton**

**Fenthion**

phosphorodithioate]

[O,O-dimethyl S-[(4-oxo-1,2,3 benzotriazin-3(4H)-yl)methyl]

244 Titanium Dioxide - Material for a Sustainable Environment

[O,O-diethyl S-[(4-oxo-1,2,3 benzotriazin-3(4H)-yl)methyl]

*S*-methylcarbamoylmethyl phosphorodithioate]

[O,O-diethyl S-[2-(ethylthio)ethyl]

[*O,O*-dimethyl *O*-4-methylthio-*m*-tolyl phosphorothioate] <sup>S</sup>

was used (optimum TiO<sup>2</sup>

Total organic carbon (TOC) measurements were performed with a Teledyne Instruments Tekmar TOC Combustion Analyzer (model Apollo 9000, Ohio, USA) calibrated with standard solutions of potassium phthalate [6]. Additionally, the release of inorganic anions containing the heteroatoms of the organophosphorus pesticides was monitored, such as phosphate (PO4 3−), nitrate (NO3 − ), ammonium (NH4 + ), and sulfate (SO4 2−) ions, as a function of irradiation time was performed spectrophotometrically by using UV/Vis spectrophotometer (Varian, model **C**ary 50, Australia) and by following the appropriate method of the American **S**tandard **T**est **M**ethod (ASTM). Specifically, nitrate ion determination was performed according to the ASTM 4500-NO3 − -E cadmium reduction method and ammonium ions according to ASTM 4500-NH3 -F phenate method, whereas **sulfate** and phosphate ions according to ASTM 4500-SO4 2−-E turbidimetric and ASTM 4500-P− -E ascorbic acid methods, respectively [16].
