Nitrogen-doped biochar/MnO2 as an efficient PMS activator for synergistic BPA degradation via non-free radical pathways in the water

It is crucial to adopt strategies to reduce the inherent flaws of materials for the development of stable and efficient heterogeneous catalysts. Herein, we successfully prepared nitrogen self-doped biochar-supported MnO2 (NCM-x) through the in-situ growth of MnO2 on the surface of biochar derived from alfalfa and evaluated its efficiency in activating PMS for BPA degradation in water. Specifically, NCM-x prepared with 0.6 g of biochar (NCM-0.6) exhibited the capability to remove 92.8% of BPA (20 mg·L−1) within 20 min, wherein nitrogen self-doped biochar and MnO2 primarily governed the processes of adsorption and oxidation, respectively. The addition of NC not only greatly increased the specific surface area, but also facilitated the formation of metal defects and significantly reduced ion leaching in the NCM-0.6/PMS system while enhancing its electron transfer ability. Non-free radical 1O2 oxidation and electron transfer oxidation dominated the BPA degradation, with graphite C, graphite N, Mn(III), surface hydroxyl groups (-OH), and CO serving as the main active sites. Importantly, NCM-0.6 exhibited stable activation performance in various complex water conditions, encompassing a wide pH (3−9) range and the presence of multiple co-existing anions. Moreover, it displayed universal degradation capabilities towards a variety of electron-rich pollutants, underscoring its immense potential for practical wastewater treatment applications.