Adsorption mechanism of eDNA by corn straw biochars prepared at different temperatures

Extracellular DNA (eDNA) is ubiquitous in the environment, posing potential ecological risks. The interactions between eDNA and biochar greatly affect the environmental behavior of eDNA. However, the adsorption mechanism of eDNA on biochar remains poorly understood. In this study, the biochars were prepared from corn straw at four pyrolysis temperatures, and the adsorption characteristics of eDNA on biochars were investigated by batch adsorption kinetics and thermodynamic experiments. The results showed that the adsorption of eDNA by biochar was enhanced with increasing pyrolysis temperature. The high-temperature biochars (BC500 and BC600) had larger specific surface area and fewer polar functional groups, which facilitated eDNA adsorption. The main adsorption mechanisms of eDNA on low-temperature biochar (BC400) were pore filling, ligand exchange, and hydrogen bonding, while the major adsorption mechanism on high-temperature biochar were π-π interaction, and ligand exchange. The divalent metal ions could not only promote the adsorption of eDNA on biochar through charge neutralization and ionic bridging, but also be related to the formation of complexes with eDNA. The cognition of DNA adsorption mechanisms on biochars provided date base and theoretical foundation for exploring the environmental behavior of eDNA and biochar.