title: Effect of Na+ impregnated activated carbon on the adsorption of NH4(+)-N from aqueous solution.
abstract: Two kinds of activated carbons modified by Na+ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid (denoted as AC/N-Na and AC/HCl-Na, respectively), were used as adsorbents to remove NH4(+)-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4(+)-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na+ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4(+)-N. Na(+)-impregnated ACs had a higher removal capability in removing NH4(+)-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4(+)-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.
authors: Environmental Science and Engineering Department, Fudan University, Shanghai 200433, China. shi.moflyhigh@gmail.com
authors: Mo
authors: M
authors: Shi
authors: Environmental Science and Engineering Department, Fudan University, Shanghai 200433, China.
authors: Zhengfang
authors: Z
authors: Wang
authors: Environmental Science and Engineering Department, Fudan University, Shanghai 200433, China.
authors: Zheng
authors: Z
authors: Zheng
mesh_terms: D000327:Adsorption; D064751:Ammonium Compounds / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D012964:Sodium / Q000737:chemistry*; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D064751:Ammonium Compounds; D012996:Solutions; D014867:Water; D002244:Carbon; D012964:Sodium