Activation Of Peroxymonosulfate By Nitrogen-doped Biochar Encapsulated Fe/Mn Nanoparticles For The Degradation Of Bisphenol-A:Mechanism Insight And Performance Assessment

In recent years,along with economic and social development,the water environment has been deteriorating,especially organic pollution has become one of the most important problems to be solved.The sulfate-radical(SO₄^·-)based advanced oxidation process（SR-AOPs）have proven to be an efficient means to solve organic pollution problems,and this technology has received widespread attention and favor from researchers due to its strong oxidation capacity and outstanding anti-interference ability.This study briefly describes the research progress and technical advantages of SR-AOPs.A high-performance heterogeneous catalyst(Fe/Mn@NBC₈₀₀)was developed using biochar as a carrier and synthesized by simultaneous nitrogen doping and metal nanoparticle loading to address the shortcomings of the existing peroxymonosulfate（PMS）activation method,such as high cost,unstable activation efficiency,and easy to cause secondary contamination.In this study,the structural properties and physical and chemical properties of the catalyst were analyzed using various characterization techniques;the performance and influencing factors of the material in activating PMS to remove bisphenol A（BPA）contamination from water were systematically investigated;the catalytic principle of the material for PMS and the degradation mechanism of BPA in the reaction were analyzed by combining experiments and theoretical calculations;the practical application potential of Fe/Mn@NBC₈₀₀was discussed in detail.The main research findings and innovations are as follows:A novel catalyst,nitrogen-doped biochar encapsulated Fe/Mn nanoparticles(Fe/Mn@NBC₈₀₀),was synthesized by impregnation followed by a one-step carbonization-activation process.The results showed that the simultaneous introduction of the three elements of iron,manganese and nitrogen led to a drastic change in the morphology of biochar,and a large number of filamentous carbon nanotubes appeared on its surface,accompanied by more holes.Compared with other catalysts,Fe/Mn@NBC₈₀₀possessed a higher BET specific surface area(247.66 m²·g^-1),a smaller average pore size（3.18 nm）,and a higher degree of graphitization,which facilitates electron transport.The surface content of Fe and Mn of this catalyst was only 0.34%and 0.76%,while the total content of Fe and Mn was as high as 10.12%and 8.85%,indicating that a large amount of Fe and Mn elements were encapsulated in the carbon skeleton.This property greatly improves the catalytic activity and recyclability of the material.This catalyst not only showed good adsorption of BPA（Q_e=49.58 mg/g）but also was able to drive the activation of PMS,completely degrading 20 mg/L BPA within 20 min with a reaction rate constant(k_obs=0.1897 min^-1)75.88 times higher than that of pristine biochar（BC）.The Fe/Mn@NBC₈₀₀+PMS system also demonstrated a better mineralization capacity with a TOC removal rate of 63.09%within 2 h.Quenching test and EPR detection showed that a variety of reactive oxygen species（ROS）were generated in the Fe/Mn@NBC₈₀₀+PMS system,including SO₄^·-,·OH,O₂^·-and ¹O₂,were generated in the Fe/Mn@NBC₈₀₀+PMS system.Radicals and non-radical mechanisms jointly drove the degradation of BPA,among which SO₄^·-and·OH played a leading role.Fe/Mn nanoparticles,graphitic/pyridine N,and electron-rich carbon network layers in the catalyst were potential active sites for activating PMS to generate these ROS.The synergistic process of radical and non-radical was less affected by p H and temperature,while higher catalyst dosage,PMS concentration,and the introduction of Cl^-could further increase the activity of the reaction system.According to the results of DFT and LC-MS,the benzene ring and phenolic hydroxyl groups in the BPA molecule were more susceptible to ROS attack,which led to its degradation to single-chain compound substances until complete mineralization.The evaluation of application potential shows that Fe/Mn@NBC₈₀₀has good separability,reusability,stability,and universality.In summary,nitrogen-doped Fe/Mn bimetallic biochar can effectively catalyze PMS to achieve efficient degradation of BPA,and show certain economic and practical properties,providing an effective disposal idea and method for the disposal of degraded organic wastewater.This study provided an effective idea for the disposal of refractory organic wastewater.