Aging alters the physicochemical properties of biochar, enhances its adsorption performance for tris-(1-chloro-2-propyl) phosphate, and changes the adsorption mechanism

When introduced into the environment, biochar undergoes various aging processes, which can affect its ability to adsorb and immobilize pollutants. However, only a few reports exist regarding the effect of biochar aging on its ability to adsorb tris-(1-chloro-2-propyl) phosphate (TCIPP). Therefore, this study considers five near-natural aging processes (alternating dry-wet, alternating freeze-thaw, acid rain, microbial, and alternating dry-wet and freeze-thaw) to explore the impacts of biochar aging on its adsorption performance and mechanisms for TCIPP. The results indicate that following aging, the polarity of biochar undergoes a notable increase, while its aromaticity and hydrophobicity decrease notably. Additionally, the specific surface area decreases and the overall quantity of acidic oxygen-containing functional group increases significantly. These changes also alter the capability and underlying mechanisms of biochar in adsorbing TCIPP. Specifically, the highest adsorption capacities of biochar regarding TCIPP increase by 51.73 %, 80.59 %, 53.89 %, and 15.11 % after alternating dry-wet aging, microbial aging, alternating freeze-thaw aging, and alternating dry-wet and freeze-thaw aging, respectively. However, the maximum adsorption capacity decreases by 53.37 % after acid rain aging. Aging does not alter the types of interactions involved in the adsorption process of TCIPP by biochar, which include pore filling, hydrophobicity, hydrogen bonding, van der Waals forces, π-π interactions, pnicogen-π interactions, and more; however, it does change their intensities. This suggests that natural aging can enhance the capacity of biochar to adsorb TCIPP, thereby improving its effectiveness in remediating TCIPP-contaminated soil. This study provides a scientific rationale for utilizing biochar in the treatment of soil contaminated with TCIPP. • Natural aging significantly alters the biochar’s physicochemical properties. • Natural aging enhances the adsorption capacity of biochar for TCIPP. • Microbial aging increases the adsorption capacity of biochar for TCIPP by 80.59 %. • Natural aging alters the mechanism of biochar’s adsorption of TCIPP. • Biochar holds great potential for remediation of TCIPP-contaminated soil.