**3.2. Analytical methods**

This technique presents operational and capital costs 2.5 times lower than those of wet air oxidation (WAO) and 4.1 times lower than those of electric plasma oxidation (EPO) [27].

**Figure 1** show a schematic representation of the pilot plant used in the experiments that was

The phenol solution was prepared in Tank 1. The operation of the system was stabilized by heating the water to almost 70°C for an hour and a half; phenol was subsequently added to Tank 1, and the synthetic effluent was transferred from Tank 1 to Tank 2. The reactor had an internal helical groove with a rectangular shape, in the axial direction, through which the liquid effluent flowed. Wastewater polluted with phenol was injected into the reactor

composed of a vertical, stainless-steel reactor and a gas-liquid separator.

330 Phenolic Compounds - Natural Sources, Importance and Applications

**Figure 1.** Pilot plant using the DiCTT process.

For the experiments, a phenol solution of analytical grade and oxygenated water 35% PA were employed. For the chromatographic analysis, methanol UV/HPLC grade and for TOC analysis phosphoric acid 25% PA were used.

The concentrations of phenol, catechol and hydroquinone were monitored using an HPLC instrument (Shimadzu, model LC-20AT, with integrated data acquisition using a UV detector and a CLC-ODS column (M)/(C-18) that was 250 mm in length and 4.6 mm in diameter, also from Shimadzu). An isocratic elution mode was used under the following conditions: oven temperature of 35°C; flow rate of 0.75 mL min−1 for the mobile phase; injection volume of 20 μL; mobile phase consisting of 10% methanol and 90% phosphoric acid/deionised water with pH adjusted to 2.2; and operation of the UV detector at a wavelength of 270 nm to detect phenol, catechol and hydroquinone [4].

The TOC content was measured using a TOC analyser (TOC-Vcsh model, Shimadzu) to analyse phenolic mineralisation quantitatively [28].
