Abstract
The study investigated that the change in the pH ranged from 5 to 7 affects the adsorption degree of selected organic micropollutants such as: polycyclic aromatic hydrocarbons (anthracene, benzo[a]pyrene), pharmaceutical compounds (diclofenac) and industrial additives (octylphenol and pentachlorophenol) on the photocatalyst surface (100 mg TiO 2 /dm 3 ). For example, in suspension of pH 5 a 12% reduction in the concentration of octylphenol was noted, while in the suspension of pH 7 the concentration of this compound was reduced by 64%. In the case of anthracene an inverse relationship was observed. The concentration of this micropollutant decreased by 94% for pH 5 and only by 61% for pH 7 suspension. With the commencement of UV irradiation of reaction mixtures a gradual increase in the concentration of micropollutants reduction in aqueous solutions was observed. This indicates the decomposition of compounds as a result of their reaction with highly reactive OH • radicals or other reactive oxygen species generated during the process. For reaction mixtures of pH 7, already in the first 15 minutes, higher degrees of removal of micropollutants ware observed compared to suspension of pH 6. The obtained micropollutants removal degrees exceeded 91% for diclofenac, octylphenol, pentachlorophenol and amounted to 100% for anthracene and benzo(a)pyrene.
Highlights
Literature data indicate a continuous increase in the number of organic micropollutants in the water environment
The adsorption degrees of the micropollutants were estimated on the basis of the changes in their concentration in water solution subjected to 15 minute contact time with the catalyst
It was observed that the adsorption degrees of OP and PCP increases with the increase of the pH of water solutions (Time of UV iradiation = 0)
Summary
Literature data indicate a continuous increase in the number of organic micropollutants in the water environment. These compounds belong to different chemical groups and have a differentiated impact on the water quality and pose a serious threat to aquatic ecosystems [1,2,3]. The oxidation and reduction of compounds by means of highly reactive free hydroxyl radicals OH formed during the process depends on different operating parameters of the process, which include the wavelength emitted by the applied UV irradiation source [6], oxygen concentration in the irradiated water solution [7], catalyst dose and type [8] and the physicochemical composition of the treated water [9, 10].
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