title: Kinetic and isotherms studies of phosphorus adsorption onto natural riparian wetland sediments: linear and non-linear methods.
abstract: Riparian wetlands provide critical functions for the improvement of surface water quality and storage of nutrients. Correspondingly, investigation of the adsorption characteristic and capacity of nutrients onto its sediments is benefit for utilizing and protecting the ecosystem services provided by riparian areas. The Langmuir and Freundlich isotherms and pseudo-second-order kinetic model were applied by using both linear least-squares and trial-and-error non-linear regression methods based on the batch experiments data. The results indicated that the transformations of non-linear isotherms to linear forms would affect the determination process significantly, but the non-linear regression method could prevent such errors. Non-linear Langmuir and Freundlich isotherms both fitted well with the phosphorus adsorption process (r (2) > 0.94). Moreover, the influences of temperature and ionic strength on the adsorption of phosphorus onto natural riparian wetland sediments were also studied. Higher temperatures were suitable for phosphorus uptake from aqueous solution using the present riparian wetland sediments. The adsorption capacity increased with the enhancement of ionic strength in agreement with the formation of inner-sphere complexes. The quick adsorption of phosphorus by the sediments mainly occurred within 10 min. The adsorption kinetic was well-fitted by pseudo-second-order kinetic model (r (2) > 0.99). The scanning electron microscopy (SEM) and Fourier transformation infrared (FT-IR) spectra analyses before and after phosphorus adsorption revealed the main adsorption mechanisms in the present system.
authors.affiliation: Key Laboratory of Environment and Disaster Monitoring and Evaluation, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Du
authors.forename: Yun
authors.initials: Y
authors.lastname: Du
authors.forename: Meng
authors.initials: M
authors.lastname: Xu
authors.forename: Shijian
authors.initials: S
authors.lastname: Chen
authors.forename: Hongbin
authors.initials: H
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D017753:Ecosystem; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D053833:Wetlands
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus