Abstract
Photocatalysis is of high interest for the treatment of wastewater containing non-biodegradable organic components. In this work, the photocatalytic degradation of phenol by TiO2 photocatalysis was assessed, the influence of ultrasound (US) treatment was evaluated, and the mechanisms behind it were elucidated. It was shown that the TiO2 concentration (in suspension) has a large influence on the degradation kinetics. At high TiO2 concentrations, a reduced efficiency was observed due to the shielding of the UV light by TiO2 particles. US treatment effectively increased phenol degradation by improving the mass transfer while it was shown by the experimental data that particle deagglomeration did not play a significant role. The degradation mainly occurred through indirect phenol oxidation by hydroxyl (OH*) radicals, which were formed in situ at the surface of the photocatalyst. Finally, based on the partial least squares (PLS) methodology, a mathematical model was developed, representing phenol degradation as a function of the selected process conditions.
Highlights
Phenol is one of the most widespread industrial wastewater contaminants
The aim of the present research is to study the degradation of phenol in synthetic wastewater using the combination of UV/TiO2, with the main goal being the evaluation of the synergistic effect of US application at 24 kHz
It was seen that the remaining phenol concentration after 60 min reaction time decreased from 32% of its initial value in the absence of US to 26.0% and 11.3% of the initial value at an US power of 50 W and 100 W, respectively
Summary
Phenol is one of the most widespread industrial wastewater contaminants. It normally exists in high concentrations in the effluent of various industrial sectors, including the chemical, petrochemical and pharmaceutical industry, refineries and oil field activities, coal processing, and olive oil production [1]. Various techniques have been developed for its removal from the effluents [2], including (i) classical separation techniques (e.g., distillation, liquid–liquid extraction, adsorption, membrane separation) [3,4], (ii) biochemical treatments (aerobic and anaerobic) [5], and (iii) advanced oxidation processes (e.g., wet air oxidation, ozonation, peroxide wet oxidation, electrochemical and photocatalytic oxidation) [6,7,8,9]. Apart from its industrial relevance, phenol is frequently described in the literature as a model component to assess the effectiveness of various advanced oxidation processes (AOP) to remove low biodegradable or toxic organic components from wastewater. Enables a comparative evaluation of the treatments reported in different literature sources
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