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    The pH effect on the kinetics of 4-nitrophenol removal by CWPO with doped carbon black catalysts

    Year: 2020

    Journal: Catal. Today, Volume 356, OCT 1, page 216–225

    Authors: de Tuesta, Jose L. Diaz; Quintanilla, Asuncion; Casas, Jose A.; Morales-Torres, Sergio; Faria, Joaquim L.; Silva, Adrian M. T.; Gomes, Helder T.

    Organizations: North Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) [NORTE-01-0145-FEDER-000006]; FCT/MCTES (PIDDAC) [LSRE-LCM - UID/EQU/50020/2019]; FEDER under Program PT2020 [CIMO -UID/AGR/00690/2019]; University of Granada

    Keywords: Catalytic wet peroxide oxidation; Doped carbon black; Kinetic model; pH effect; Induction period; Nitrophenol

    P, B and N-doped carbon blacks prepared with H3PO4, urea and H3BO3 were tested as catalysts in the wet peroxide oxidation of a concentrated 4-nitrophenol (4-NP) model solution (C4-NP = 5 g center dot L-1). The highest catalytic activity was found for P-doped carbon black (complete removal of 4-NP after 4 h at 80 degrees C, C-cat = 2.5 g center dot L-1, C-H2O2 17.8 g center dot L-1 and initial pH 3, whereas 44-19% removals were reached with the other catalysts). That was ascribed to the strongest acidity (pH(PZC) = 3.5) and hydrophilic character of the catalyst. Initial pH affected the oxidation, allowing to increase strongly the conversion of 4-NP with the P-doped catalyst decreasing the initial pH from 4 to 2 (4-NP removal from 20% to 99% after 8 h of reaction time at 50 degrees C, C-cat = 2.5 g center dot L-1 and CH2O2 17.8 g center dot L-1). An autocatalytic-power-law kinetic model was developed to predict the observed induction period and the dependence on the pH of the 4-NP oxidation, H2O2 consumption and pH evolution (k(4-NP) = 2.2 center dot 10(-5)M(-2)min(-1), kH(2)O(2) = 4.0 center dot 10(-6) M-3 center dot min(-1) and k(H+) = 5.1 center dot 10(-3) M-0.23 min(-0.23) at 80 degrees C).
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