Photocatalytic activity evaluation of TiO2 nanoparticles based on COD analyses for water treatment applications: a standardization attempt

• Published in: International journal of environmental science and technology (Tehran) Vol. 13; no. 4
• Main Authors: Mekkawi, D. M. EL, Galal, H. R, Abd EL Wahab, R. M, Mohamed, W. A. A
• Format: Journal Article
• Language: English
• Published: Center for Environment and Energy Research and Studies (CEERS) 04-07-2017
• Subjects: Chemical oxygen demand (COD); Nanosized TiO2; Organic pollutants; Photocatalytic activity; Standard test method; Water treatment
• ISSN: 1735-1472

Evaluation of the photocatalytic activities of TiO2 nanomaterials based
on the chemical oxygen demand (COD) analyses under identical
experimental conditions was not previously reported. In this work, COD
has been selected as an adequate industrial water quality measure
toward the establishment of a representative standard test method. The
initial COD values of six organic pollutants representing dye,
surfactants, phenols and alcohol were set at 30 ± 2 mg/L. Ten of
different commercial and synthesized TiO2 samples representing anatase,
rutile and mixed phases were used and characterized. The data of
photocatalytic processes were compared to that obtained using the
commonly widespread Degussa-P25 TiO2 (TD). The COD of all pollutants
was completely removed by TD at UV exposure dose ≤9.36 mWh/cm2.
Consequently, the maximum irradiation dose was set at this value in all
experiments. The percentages of COD removal as well as the values of
the accumulated UV doses required for complete removal of pollutants
were measured using the different TiO2 samples. TiO2 samples show
different performance abilities toward the various pollutants compared
to TD. Based on the obtained data, TiO2 photocatalysts were divided
into two categories according to the hydroxyl radical formation rates.
Comparison with previous studies reveals that the photocatalytic
efficiency evaluation depends on the method of measurement. COD is
recommended to be used as an adequate technique of analysis that meets
the purpose of water treatment applications.