Phytoremediation is a potentially cost-effective and environmentally friendly remediation method for environmental pollution. However, the safe treatment and resource utilization of harvested biomass has become a limitation in practical applications. To address this, a novel manganese-carbon-based single-atom catalyst (SAC) method has been developed based on the pyrolysis of a manganese hyperaccumulator, Phytolacca americana. In this method, manganese atoms are dispersed atomically in the carbon matrix and coordinate with N atoms to form a Mn–N4 structure. The SAC developed exhibited a high photooxidation efficiency and excellent stability during the degradation of a common organic pollutant, rhodamine B. The Mn–N4 site was the active center in the transformation of photoelectrons via the transfer of photoelectrons between adsorbed O2 and Mn to produce reactive oxygen species, identified by in situ X-ray absorption fine structure spectroscopy and density functional theory calculations. This work demonstrates an approach that increases potential utilization of biomass during phytoremediation and provides a promising design strategy to synthesize cost-effective SACs for environmental applications.

Root concentration factor (RCF) is an important characterization parameter to describe accumulation of organic contaminants in plants from soils in life cycle impact assessment (LCIA) and phytoremediation potential assessment. However, building robust predictive models remains challenging due to the complex interactions among chemical–soil–plant root systems. Here we developed end-to-end machine learning models to devolve the complex molecular structure relationship with RCF by training on a unified RCF data set with 341 data points covering 72 chemicals. We demonstrate the efficacy of the proposed gradient boosting regression tree (GBRT) model based on the extended connectivity fingerprints (ECFP) by predicting RCF values and achieved prediction performance with R-squared of 0.77 and mean absolute error (MAE) of 0.22 using 5-fold cross validation. In addition, our results reveal nonlinear relationships among properties of chemical, soil, and plant. Further in-depth analyses identify the key chemical topological substructures (e.g., −O, −Cl, aromatic rings and large conjugated π systems) related to RCF. Stemming from its simplicity and universality, the GBRT-ECFP model provides a valuable tool for LCIA and other environmental assessments to better characterize chemical risks to human health and ecosystems.

Advanced oxidation processes (AOPs) have revealed wide prospects in the application of the degradation of organic contaminants in ground water and soil. High-performance, environmentally friendly, and low-cost single-atom catalysts (SACs) are promising approaches to active persulfate in AOPs. However, the practical application of SACs is restricted by high preparation costs and tedious procedures. Herein, a manganese (Mn) hyperaccumulator, Phytolacca americana, was successfully exploited as a precursor to synthesize a novel Mn SAC (SPBC-700N) via a one-step pyrolysis method. In SPBC-700N, Mn atoms are dispersed atomically upon the carbon matrix and coordinate with four N atoms to form Mn–N4 active sites, which exhibits an extraordinary catalytic activity for peroxymonosulfate (PMS) activation. A large number of reactive oxygen species are formed during the reaction, and over 90% of the antibiotic (chloroquine phosphate/CQP) could be removed within 30 min. The superior catalytic performance of the Mn SAC/PMS system for CQP degradation is ascribed to the synergistic effect of the maximized utilization of Mn atoms and the neighboring pyrrolic N sites, as identified by X-ray absorption fine structure spectroscopy and density function theory calculations. This work not only provides a green and low-cost strategy for synthesizing SACs but also gives an atomic-level insight into the catalytic activity of the Mn–N4 sites for PMS activation.