3.2 Villermaux reaction procedures
All the agents were purchased from Sinopharm Chemical Reagent Co., Ltd of China with a purity level of above 99.0%. The reactor gap was filled with the mixture solution of boric acid (H3BO3, 0.089 mol/L), potassium iodide (KI, 0.0116 mol/L), potassium iodate (KIO3, 0.00233 mol/L), and sodium hydroxide (NaOH) with deionised water. NaOH was used to adjust the pH value around 10.0 in order to prevent the reaction between KI and KIO3 with the presence of H+. Therefore, the pH value should be carefully controlled during solution preparation.
The rotational speed was adjusted within the range of 50 rpm to 1000 rpm, corresponding to the Reynolds Number varying from 2000 to 42000. After the system reached a steady state, H2SO4 solution was injected into the reactor from the bottom inlet. In each run, about 3 mL of sample solution was collected for the UV test from the top outlet after completing the mixing. The absorption intensity test was conducted immediately using the UV spectrophotometer (UNICO SQ4802 UV/VIS Spectrophotometer, U.S.A) at the wavelength of 353 nm to ensure the stability of\(\ I_{3}^{-}\). The experiment and the sample measurement were carried out at the room temperature of 25℃. The operating conditions are summarised in Table 2.
Table 2. Operating conditions.