Hydroxylated Hexagonal Boron Nitride-Assisted Retention of Phenol-Derived Self-Catalysts in Fe(III)/H2O2 System for Sequential Diethyl Phthalate (DEP) Degradation

Fe(III)-mediated Fenton-like oxidation is widely used for refractory organic pollutants, but its efficiency is often constrained by slow Fe(III)/Fe(II) cycling. Phenolic pollutants can partly overcome this limitation because oxidation-derived hydroquinone/quinone species promote Fe(III) reduction and generate self-catalytic feedback. Here, hydroxylated boron nitride (BN) nanoplates were used as a recoverable interface to regulate phenol self-catalysis and to transfer the resulting redox activity to the non-self-catalytic pollutant diethyl phthalate (DEP) in an Fe(NO3)3/H2O2 system. BN surface chemistry was tuned by calcination from 500 °C to 900 °C (BN500 to BN900). Phenol degradation exhibited two-stage kinetics in the BN/Fe(NO3)3/H2O2 system. The initial rate constant was 0.004 min−1, whereas the accelerated stage depended strongly on BN surface state. BN700 exhibited the highest second-stage rate constant (0.23 min−1) compared with pristine BN (0.11 min−1), while further heating to 800–900 °C decreased it to 0.15 min−1. This activity maximum is consistent with a favorable B–OH/boron–oxygen interfacial environment rather than a greater total surface oxygen content; more severe thermal treatment was associated with removable boric-acid-related species. BN recovered after phenol oxidation markedly promoted DEP degradation, with two-stage rate constants of 0.044/0.0095 min−1 for phenol-used BN and 0.033/0.011 min−1 for phenol-used BN700. The activity-transfer results are consistent with a reaction-derived, multicomponent redox-active interfacial state and support a strategy for sequential treatment of phenolic and non-phenolic contaminants.