Integrated investigations on the adsorption mechanisms of fulvic and humic acids on three clay minerals

► More HA is adsorbed on kaolinite and smectite than FA via hydrophobic interaction. ► More FA is adsorbed on vermiculite than HA due to an electron transfer mechanism. ► Ligand exchange is an important mechanism for FA and HA adsorption on clay minerals. ► Iron cation plays an important role in the adsorption of FA and HA on vermiculite.