Organic adsorbents modified with citric acid and Fe3O4 enhance the removal of Cd and Pb in contaminated solutions

Environmentally-friendly organic adsorbents with strong stability, magnetic property and great adsorption capacity for heavy metals have obtained great attention recently. We developed the citric acid- and Fe3O4-modified sugarcane bagasse (MSB) to investigate its behaviors and mechanisms of Cd and Pb adsorption in aqueous systems in comparison with sugarcane bagasse (SB). The MSB showed the highest adsorption capacity of 33.2 mg g(-1) for Cd and 116.7 mg g(-1) for Pb, which was mainly attributed to its O-containing functional groups (e.g. hydroxyl and carboxyl) and aromatic rings. In the binary system, Pb significantly suppressed the adsorption of Cd by MSB whereas Cd had weak inhibitive effects on Pb adsorption. The presence of Ca and Mg competed with the Cd and Pb for adsorption sites and their competition was stronger for Cd than Pb. Furthermore, MSB was easily regenerated and reused for three cycles with a higher adsorption capacity compared with SB. These findings provide new insights for development of novel adsorbents to remove heavy metals in aqueous systems.