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·L−1). The highest catalytic
activity was found for P-doped carbon black (complete removal of 4-NP after 4 h at 80 °C, Ccat=2.5 g·L−1,
CH2O2 17.8 g·L
= 1 and initial pH 3, whereas 44-19% removals were reached with the other catalysts). That was
ascribed to the strongest acidity (pHPZC=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 °C, Ccat=2.5 g·L−1
andCH2O2 17.8 g·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 (k4-
NP=2.2·10−5M−2min−1, kH2O2 4.0·10 M ·min
= 6 3 1 and k 5.1·10 M min H
+ = 3 0.23 1 at 80 °C).
This work is a result of: Project “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER-000006, supported by North Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the
European Regional Development Fund (ERDF); Associate Laboratory LSRE-LCM - UID/EQU/50020/2019 - funded by national funds throughmFCT/MCTES (PIDDAC); and CIMO - UID/AGR/00690/2019 through FEDER under Program PT2020. S. Morales Torres acknowledges the financial support from University of Granada (Reincorporación Plan Propio).
