Time (min) PHE0d                                                             TiO2=2 mg/La ; TiO2=4 mg/Lb ; TiO2=8 mg/Lc Control                                          Initial phenol metabolites concentrations d 2-PHEd 3-PHEd Catechold 4–methyl catechold Tyrosold Quercetind Caffeic acidd 0 2990 2990 4 9 23 15 42 21 30 Time (min) PHE0d PHERe                                                   Phenol degradation metabolites 2-PHEe 3-PHEe Catechole 4–methyl catechole Tyrosole Quercetine Caffeic acide 150a 299 90 64 68 62 63 61 68 64 150b 90 97 84 83 84 84 83 82 85 150c 179 94 72 69 78 77 79 76 75 Time (min) PHE0d                                                             NiO=4 mg/Lf ; NiO=7 mg/Lg ; NiO=10 mg/Lh PHERe                                                   Phenol degradation metabolites 2-PHEe 3-PHEe Catechole 4–methyl catechole Tyrosole Quercetine Caffeic acide 150f 478 84 61 63 59 60 56 64 61 150g 269 91 81 78 82 81 80 78 82 150h 359 88 69 64 70 73 76 72 71 Time (min) PHE0d                                                             ZnO=1 mg/Lj ; ZnO=3 mg/Lk ; ZnO=5 mg/Lm PHERe                                                   Phenol degradation metabolites 2-PHEe 3-PHEe Catechole 4-methyl catechole Tyrosole Quercetine Caffeic acide 150j 419 86 62 65 60 61 58 65 62 150k 209 93 82 80 83 82 81 80 84 150m 299 90 70 66 72 75 77 74 73 PHE0: Initial total phenol concentration (mg/L), PHER: Total phenol removal efficiency (%), 2-PHE (%): 2-phenyl-phenol removal efficiency (%), 3-PHE (%): 3-phenyl-phenol removal efficiency (%), aTiO2=2 mg/L, bTiO2=4 mg/L, cTiO2=8 mg/L, dConcentration (mg/L), eRemoval efficiency (%), fNiO=4 mg/L, gNiO=7 mg/L, hNiO=10 mg/L, jZnO=1 mg/L, kZnO=3 mg/L, mZnO=5 mg/L.

Table 6: Measurements of phenol metabolites (catechol, 4-methyl catechol, tyrosol, quercetin, caffeic acid, 2-PHE and 3-PHE) in the OMW with the addition of some nano-sized TiO2, NiO and ZnO oxides with HPLC after 150 min ultrasound time at pH=5.4, at an initial total phenol concentration=2990 mg/L, at ultrasound power=640 W, at ultrasound frequency=35 kHz and at 25°C (n=3, mean values).