title: Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon.
abstract: OBJECTIVE
  Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe(II) and AC/N-Fe(III)), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions.
  
  
  METHODS
  The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors.
  
  
  RESULTS
  Maximum removals of phosphate are obtained in the pH range of 3.78-6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe(II) and AC/N-Fe(III) is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon.
  
  
  CONCLUSIONS
  Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe(II) has a higher phosphate removal capacity than AC/N-Fe(III), which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol(-1) for AC/N-Fe(II) and AC/N-Fe(III), respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.
authors.affiliation: Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, People's Republic of China.
authors.forename: Zhengfang
authors.initials: Z
authors.lastname: Wang
authors.forename: Er
authors.initials: E
authors.lastname: Nie
authors.forename: Jihua
authors.initials: J
authors.lastname: Li
authors.forename: Mo
authors.initials: M
authors.lastname: Yang
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xingzhang
authors.initials: X
authors.lastname: Luo
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zheng
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; D014874:Water Pollutants, Chemical; D002244:Carbon; D007501:Iron