Keywords: 
• iron-oxide-coated sand /
• adsorption /
• surface modification /
• humic acid

Abstract: The preparation of multielement modified iron-oxide-coated sand (IOCS) by adding diatomite, bentonite, fly ash or active carbon was investigated. The effect of added adsorbent on adsorption capacity of various modified IOCS and the adsorption characteristics and mechanism were discussed respectively.The effects of diatomite, bentonite, activated carbon and fly ash on improvements of adsorption capacity of the multi-element modified IOCS are different. The adsorption capacity of multi-element modified IOCS depends on the surface characteristics coating mixture. Results of adsorption isotherm and continuous filtration experiments indicated that activated carbon and diatomite improved the adsorption capacity, but bentonite and fly ash improved a little or even lowered the adsorption capacity.Activated carbon modified IOCS’s adsorption isotherm is suitable for Langmuir model; both the Langmuir model and Freundlich model have upper pertinence to diatomite modified IOCS, bentonite modified IOCS and fly ash modified IOCS’s adsorption isotherm. The adsorption pattern of natural organic matter onto multi-element modified IOCS is single molecule layer adsorption; the adsorption mechanisms include electrostatic interactions, ligand exchangesurface complexation and hydrophobic interactions.Solution’s pH is an important factor that affects adsorption of NOM by multi-element modified IOCS. Higher adsorption of NOM was achieved under acid conditions, while relative lower adsorption was obtained under alkaline conditions. Phosphate can compete with humic acid while adsorbed onto the surface of multi-element modified IOCS, especially in case of active carbon modified IOCS.