A mechanistic study on removal efficiency of four antibiotics by animal and plant origin precursors-derived biochars.

Abstract Extensive research has been performed on the utilization of biochar for pollutant removal via sorption. Additionally, the relationship between sorption strength of organic pollutants by organic matter and nanomaterials and their sorption site energy distribution has been studied. However, the linkage between removal efficiency of organic pollutants and the sorption site energy distribution on biochars is unknown. As a first attempt to address this knowledge gap, three biochars were derived from two plant-origin precursors (corn straw-CS; birch sawdust-BS) and one animal-origin precursor (meat and bone meal-MBM) at 500 °C (CS-500, BS-500, and MBM-500). In addition, two biochars were prepared with CS at 300 and 800 °C (CS-300 and CS-800) to examine the relationship between their site energy distribution and removal efficiency of antibiotics including sulfadiazine (SDZ), sulfamethoxazole (SMX), tetracycline (TC) and ciprofloxacin (CFX) by these materials. Our findings showed that the antibiotic-biochar interactions can be well interpreted with site energy distribution and XPS analysis results. Polar interactions between CS-300, CS-500, and CS-800 and SDZ and SMX occurring at the high-energy sites dominated their removal. However, TC and CFX removal by these biochars was driven by their polar interactions occurring at high-energy sites and π-π interactions at low-energy sites. The π-π stacking mechanism tended to dominate their removal with increasing charring temperature. Abundance of polar functionalities on CS-500, BS-500, and MBM-500 and TC removal efficiency of these materials consistently followed an order of MBM-500 > CS-500 > BS-500, highlighting importance of precursors for making biochars and polar interactions in its removal.