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

Abstract

Evaluation of the photocatalytic activities of TiO 2 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 TiO 2 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 TiO 2 (TD). The COD of all pollutants was completely removed by TD at UV exposure dose B9.36 mWh/cm 2 . 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 TiO 2 samples. TiO 2 samples show different performance abilities toward the various pollutants compared to TD. Based on the obtained data, TiO 2 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.

Analysis of Toxic Chemical Substance Present in Wastewater Samples Around the Urban Area of Tirupati, Andhra Pradesh

“…There was no significant difference (P<0.05) among the study areas. The volatile organic compound (VOC) values range from 1.2-2.8 mg/l S 1 and S 4 respectively [19]. The values significant difference (P<0.05) among study.…”

A Review on Eco-Restoration of Rivers with Special Focus on Industrial Wastewater Treatment

“…Decomposition of organic pollutants occurs in two ways-direct oxidative destruction at the holes or indirect oxidative destruction via (OH-) radicals. Various organic pollutants like dyes, pesticides, organic compounds containing halogens, Polychlorinated Biphenyls (PCB), detergents and phenols have been removed (EL-Mekkawi et al, 2016;Zhang et al, 2014):…”

“…TiO2 catalyst is bound to the polymeric sheets inside the CPC reactor through silicon based adhesives. The reactor is mounted on a platform and a centrifugal pump circulates wastewater inside the reactor (El-Mekkawi et al, 2016) (Fig. 3).…”

Photocatalytic Degradation of Aqueous Rhodamine 6G Using Supported TiO2 Catalysts. A Model for the Removal of Organic Contaminants From Aqueous Samples

“…The determination of the COD of the photocatalytic process can provide useful information in these type of complex oxidative systems where parallel and sequential reactions might take place, systems in which common first order kinetics or initial rate kinetic methods might be somewhat limited to describe the overall process, particularly when spectrophotometric methods are used and the oxidative bleaching of the target molecule may not fully correspond with the whole oxidative pathway of said molecule (Mills et al, 2012). Similarly, COD has been successfully used in comparative studies involving semiconductor photocatalysts (El-Mekkawi et al, 2016). Data in Table 5 shows COD values and Rh6D photodegradation percentages for the studied photocatalysts.…”