title: Effect of humic acid preloading on phosphate adsorption onto zirconium-modified zeolite.
abstract: A zirconium-modified zeolite (ZrMZ) was prepared, and then, humic acid (HA) was immobilized on the ZrMZ surface to prepare HA-loaded ZrMZ (HA-ZrMZ). The obtained ZrMZ and HA-ZrMZ were characterized by energy dispersive X-ray spectroscopy, elemental analyzer, N2adsorption/desorption isotherms, pH at the point of zero charge, and X-ray photoelectron spectroscopy. The adsorption characteristics of phosphate on ZrMZ and HA-ZrMZ were comparatively investigated in batch mode. The adsorption mechanism of phosphate on ZrMZ and HA-ZrMZ was investigated by ionic strength effect and31P nuclear magnetic resonance. The mechanism for phosphate adsorption onto ZrMZ was the formation of inner-sphere phosphate complexes at the solid/solution interface. The preloading of HA on ZrMZ reduced the phosphate adsorption capacity, and the more the HA loading amount, the lower the phosphate adsorption capacity. However, the preloading of HA on ZrMZ did not change the phosphate adsorption mechanism; i.e., the formation of inner-sphere phosphate surface complexes was still responsible for the adsorption of phosphate on HA-ZrMZ. The decreased phosphate adsorption capacity for ZrMZ after HA coating could be attributed to the fact that the coating of HA on ZrMZ reduced the amount of binding active sites available for phosphate adsorption, changed the adsorbent surface charges, and reduced the specific surface areas and pore volumes of ZrMZ.
authors.affiliation: College of Marine Science, Shanghai Ocean University, No. 999 Hucheng Huan Road, Shanghai, 201306, China. jwlin@shou.edu.cn.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Lin
authors.affiliation: College of Marine Science, Shanghai Ocean University, No. 999 Hucheng Huan Road, Shanghai, 201306, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: College of Marine Science, Shanghai Ocean University, No. 999 Hucheng Huan Road, Shanghai, 201306, China.
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Zhan
mesh_terms: D000327:Adsorption; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000737:chemistry; D017641:Zeolites / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry
chemical_list: D006812:Humic Substances; D010710:Phosphates; D017641:Zeolites; D015040:Zirconium
keywords: Adsorption; Humic acid; Phosphate; Preloading; Zirconium-modified zeolite