Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

► Organic acids either stabilize or destabilize oxide nanoparticles in natural waters. ► The stabilizing/destabilizing effect depends on pH, salinity and organic concentration. ► Specific configuration of carboxylic groups is necessary to surface complexation. ► Surface complexation leads to high-affinity adsorption isotherms. ► Higher molecular weight organic acids provide better stability than smaller ones.