The sorption interactions of humic acid onto Beishan granite

- The sorption of HA on Beishan granite (BsG) is strongly pH and ionic strength-dependent.
- Parts of HA tend to enter into the pores formed by close-packing of BsG particles.
- Precipitation, ligand exchange-surface complexation and electrostatic interaction may dominate the sorption behaviors of HA on BsG.
- The colloidal properties of HA under certain conditions may significantly affect its sorption interactions with BsG.