An approach on the comparative behavior of chloro / nitro substituted phenols photocatalytic degradation in water. Issue 3 (June 2019)

• Record Type: Journal Article
• Authors: Tolosana-Moranchel, A.; Ovejero, D.; Barco, B.; Bahamonde, A.; Díaz, E.; Faraldos, M.
• Is Part Of: Journal of environmental chemical engineering. Volume 7:Issue 3(2019)
• Publication Date: 2019-06
• Subjects: Hammett constant -- Photocatalytic degradation -- TiO2 -- Chlorophenols -- Nitrophenols; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2019.103051
• Languages: English
• ISSNs: 2213-2929

Abstract

Highlights: Cl −, NH4 +, NO2 − and NO3 − produced during the process fulfil Cl and N mass balances. An increase of pollutant concentration barely affect initial TOC degradation rate. More substituents meant higher initial rates of Cl − and NO3 − and lower TOC rates. Ecotoxocity is related to the position, not to the number of Cl − and NO2 − groups. Initial degradation rate could correlate with the Hammett constant of substituents. Abstract: The study of position and number of substituents on the photocatalytic removal of some mono-, di- and tri-, chloro- and nitrophenols, as well as more known initial TOC concentration effect, has revealed the noteworthy impact on the process efficiency. Despite the complex effect of multiple substituents directing the HO attack to their preferential positions, Hammett constant could be used to predict photocatalytic degradation performance. TiO2 P25 was able to mineralize initial TOC concentrations up to 25–50 mg·L −1 . Higher TOC concentrations constitute a drawback and drive to residual parent pollutants and organic by-products, which become more important when raising the starting TOC loading. Increasing the number of chloro- or nitro- groups in the aromatic ring does not imply higher ecotoxiticy values; contrarily, the position of the substituent can lead to significant differences. TOC conversion values are hardly affected by the substituent position, but by the number of groups in the organic molecule, probably due to steric hindrance. The formation of chloride and nitrogen inorganic ions, inherent to photocatalytic degradation, fulfills the Cl and N mass balances. Finally, the effect of number, position and electronic nature of substituents on contaminant initial photocatalytic degradation rates was studied by corresponding Hammett constant correlations.