Highly efficient activation of persulfate by encapsulated nano-Fe⁰ biochar for acetaminophen degradation: Rich electron environment and dominant effect of superoxide radical

In this study, an encapsulated nanoscale zero-valent iron biochar (BC-Fe⁰) derived from waste lignocellulose rice straw (RS) was synthesized. BC-Fe⁰ has excellent properties, including long-term stability, a large specific surface area, many micropore structures, active defects active and oxygen-containing groups. The material was first used to activate persulfate (PDS), showing a highly efficient catalysis for acetaminophen (ACT) degradation. The removal efficiency of ACT within 20 min reached 100%, and the degradation rate constant (k_obs) reached 0.37475 min⁻¹ at the ACT concentration of 10 mg/L, BC-Fe⁰ of 0.5 g/L, temperature of 298 K. EPR demonstrated that ·OH, SO₄^−·, ·O₂⁻ and ¹O₂ occurred during the reaction process, and ·O₂⁻, ¹O₂ and electron transfer played major roles in PDS/BC-Fe⁰ system. Fe⁰ nanoparticles promoted the activation of PDS to generate ·O₂⁻, which induced a series of other reactive oxygen species (ROS) to attack ACT. C = O might also contribute to the production of ¹O₂. In addition, graphitic carbon, C–O, defects and micropores on BC-Fe⁰ together created a rich electron environment, which is conducive to the redox reaction between ACT and ROS. Satisfyingly, BC-Fe⁰ not only had a high catalytic activation capacity, but also exhibited a desirable durability and recyclability. The development of BC-Fe⁰ catalysts and the study of PDS activation for organic pollutant degradation are significant to biomass conversion and advanced oxidation processes in environmental remediation.