Waste-derived non-metallic biochar catalyst with intrinsic heteroatoms for acceleration of Fe(III)/H2O2 activation: the electron transfer mechanism of biochar.

The reuse of traditional biomass waste has become a popular research direction in the fields of chemical engineering, catalysis and processing in recent years. The sustainable recycling of Fe(III)/Fe(II) is of vital importance in the Fenton treatment of various types of wastewater used in the chemical, pharmaceutical and other industries. In this study, a non-metallic biochar catalyst derived from peanut shell biomass waste was used to catalyze recyclable Fe(III)/Fe(II) through simple calcination treatment. The prepared biochar containing intrinsic nitrogen atoms was named NBC. The addition of NBC significantly accelerated the Fe(III)/H2O2 system, and achieved complete removal of diethyl phthalate (DEP) and efficient removal of other organic pollutants (> 94 %) within 60 min through the probable synergistic between the NaHCO3-induced adsorption and the catalytic activity determined by the calcination temperature. Notably, the use of non-metallic catalysts avoids secondary metal pollution, offering an environmentally benign alternative to traditional metal catalysts. Physicochemical and electrochemical characterizations confirmed that NBC acts as an efficient electron donor and medium, facilitating Fe(III) reduction and boosting Fenton reactions. The main catalytic sites, such as graphitic carbon, C-O dominated oxygenated groups, graphite-N, and pyridine-N, were identified as crucial for electron transfer. This work provides key mechanism support and technological basis for the green degradation of environmental pollutants and the efficient catalytic reuse of biomass waste.