Ozone was generated with dried air by a WH-S-B10 ozone generator
(Wohuan Science and Technology Industrial Co., LTD in Nanjing,
China, 600 L/h) and its concentration was measured using the
iodometric method. Ozonation was performed in a 7.5 L working
cylindrical glass column (1000 mm in total length and 100 mm
inner diameter) with continuously bubbling ozone into the solution
through a porous diffuser fixed at the bottom of the column,
and the ceramic media approximately 4–6 mm in diameter was
packed in order to enhance the proportion of microozone bubble.
The coking wastewater effluent was continuously introduced by
a peristaltic pump in a lateral at the bottom of the column
(Fig. 1). The emission from the reactor flowed into two wash bottles,
which were placed in series and contained 1000 and 500 mL
potassium iodide (KI) solution, respectively, to trap unconsumed
ozone from the column. A port was mounted to the first wash bottle
considering sampling from the KI solution and analyzing the
amount of ozone consumed in the column. The second one guaranteed
complete capture of ozone from the outlet gas before released
to the environment. Hydrochloric acid was used to adjust the pH of
the wastewater when experiments were conducted under acidic
condition. The ozone consumption was calculated according to
the literature [30]. Ozone dose was represented by O3(applied)/
COD0. The O3(applied) yield corresponded to the ratio between consumed
ozone and supplied ozone.