The role of TiO2 NPs catalyst and packing material in removal of phenol from wastewater using an ozonized bubble column reactor

Abstract

Phenol is present as a highly toxic pollutant in wastewater, and it has a dangerous impact on the environment. In the present research, the phenol removal from wastewater has been achieved using four treatment methods in a bubble column reactor (treatment by ozone only, using packed bubble column reactor with ozone, utilizing ozone with TiO2 NPs catalyst in the reactor without packing, and employing ozone with TiO2 NPs in the presence of packing). The effects of phenol concentration, ozone dosage, TiO2 NPs additions, and contact time on the phenol removal efficiency were determined. It was found that at a contact time of 30 min, the phenol removal was 60.4, 74.9, 86.0, and 100% for the first, second, third, and fourth methods, respectively. The results indicated that the phenol degradation method using catalytic ozonation in a packed bubble column with TiO2 NPs is the best treatment method. This study demonstrated the advantages of using packing materials in a bubble column reactor to enhance the mass transfer process in an ozonation reaction and then increase the phenol removal efficiency. Also, the presence of TiO2 NPs as a catalyst improves the ozonation process via the production of hydroxyl routs. Additionally, the reaction kinetics of ozonation reaction manifested that the first order model is more applicable for the reaction. Eventually, the packed bubble column reactor in the presence of TiO2 NPs catalyst provided a highperformance removal of phenol with a high economic feasibility.

Enhancement of Ozonation Reaction for Efficient Removal of Phenol from Wastewater Using a Packed Bubble Column Reactor

“…Additionally, it was observed that the phenol dosage is a significant variable in the ozonation process performance in the presence or absence of packing in a bubble column reactor. These results agree with the reported trends [10,22,27].…”

“…After that, o-benzoquinone and pbenzoquinone undergo decomposition, which results in the formation of oxalic acid, propionic acid, formic acid, and acetic acid. Finally, these acids undergo an oxidation process to produce CO 2 and H 2 O [10,18,36].…”

“…Phenol and its derivatives are usually produced in petroleum refineries as a result of operating unit activities. These materials are regarded as highly toxic compounds in the petroleum industry because they cause pollution in water supplies [9][10][11][12].…”

“…The ozonation process is one of the most advanced oxidation techniques employed to remove organic pollutants from wastewater [10,13]. In the ozonation technique, the hydroxyl group and other radicals are generated during the oxidation reaction, which provides a high removal percentage of organic materials [14][15][16][17][18].…”

“…This low solubility leads to low mass transfer of ozone from the gas to the liquid phase and the high ozone demand for contaminants decomposition during ozonation. Then, adding packing material to the reactors is an efficient method for increasing the residence time, which causes the enhancing decomposition of ozone gas in an aqueous solution to improve ozone utilization and increase the removal efficiency of phenol degradation [10,43]. In comparison with other multiphase reactors, the bubble column reactor is characterized by having no moving parts, low maintenance, and simple operation [44] and can be applied in the ozone oxidation process with high performance [32,45].…”