Different adsorption of organic phosphorus on calcium modified biochar: comprehensive insights from molecular levels

Abstract Organic phosphorus can cause environmental pollution easily through leaching in natural systems. Here, calcium-modified biochar was prepared to adsorb inositol hexaphosphate (IHP), glycerophosphoric acid (GP), D-glucose 6-phosphate (G6P), and adenine nucleoside triphosphate (ATP), and the impacts of their molecular structures were explored via batch experiments, characterizations, and theoretical calculations. The adsorption of ATP occurred mainly through hydrogen bonding and electrostatic interactions, while that of the others took place through chemical precipitation, where calcium-based active sites functioned and maintained the adsorption stability in different environments. Further, the time-of-flight secondary ion mass spectrometry confirmed the roles of P groups and carbon chains through P-related and CN − signals. With more reactive P groups (P1,3 and P4,6) and lower molecular electrostatic potentials, IHP achieved significantly higher adsorption (292.1 mg P g −1 ) although its adsorption energy for a single P group was not optimized. As for GP, G6P, and ATP, the surface occupation by carbon chains became visually prominent. The desorption results showed that released OPs ranged from 20% to 80%, and the adsorption via multiple P groups reduced the desorption of IHP and ATP under different conditions. These results highlight the importance of biochar for OPs’ utilization, emphasize the necessity of multi-method sets, and elucidate the molecular mechanisms of interactions. Graphical Abstract