Iron oxides are usually preloaded within nanoporous supports of large particle size to improvetheir feasibility for practical environmental remediation including arsenic and heavy metals removal, andeffect of co-ions on the performance of the resulting composites has been well investigated. However, noattempt has been made to investigate their adsorption behavior of heavy metals in the presence ofcounter-ions, such as sulfate. In this study, two hybrid sorbents (denoted as HFO-PS-and HFO-PS0respectively) were prepared by loading hydrous ferric oxide (HFO) nanoparticles onto different porouspolystyrene hosts, PS-, negatively charged with sulfonic acid groups, and PS0, covalently bonded neutralchloromethyl groups. Experimental results showed clear differences between HFO-PS-and HFO-PS0in theirCu uptake capabilities in the presence of sulfate. The amount of Cu adsorbed on HFO-PS0was markedlypromoted by introducing sulfate, being consistent with bulky HFO particles. As for HFO-PS-, withmonovalent cation as background (Na), it exhibited an apparent decrease in Cu adsorption as a result of thecompeting effect of Na cations and the solution complexation between Cu and sulfate ions. Contrarily, theadsorbed Cu was increased by introducing sulfate in the divalent cation background (Ca), because sulfateions were allowed to access to the loaded HFO nanoparticles due to the screening of the sulfonic acid groupscaused by Ca ions. XPS spectroscopy further demonstrated that the formation of Cu-SO4ternary complexesaccounted for the enhanced Cu sorption both on bulky HFO and hybrid HFO sorbents in the presence ofsulfate. These results indicated that effect of sulfate ligand on metal adsorption to hybrid iron oxides waslargely dependent on the surface properties of the host materials, as well as the loaded HFO.
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