title: Preparation of highly ordered cubic NaA zeolite from halloysite mineral for adsorption of ammonium ions.
abstract: Well-ordered cubic NaA zeolite was first synthesized using natural halloysite mineral with nanotubular structure as source material by hydro-thermal method. SEM and HRTEM images indicate that the synthesized NaA zeolite is cubic-shaped crystal with planar surface, well-defined edges and symmetrical and uniform pore channels. The adsorption behavior of ammonium ions (NH(4)(+)) from aqueous solution onto NaA zeolite was investigated as a function of parameters such as equilibrium time, pH, initial NH(4)(+) concentration, temperature and competitive cations. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. A maximum adsorption capacity of 44.3 mg g(-1) of NH(4)(+) was achieved. The regeneration and reusable ability of this adsorbent was evaluated, and the results indicated that the recovered adsorbent could be used again for NH(4)(+) removal with nearly constant adsorption capacity. Thermodynamic parameters such as change in free energy (DeltaG(0)), enthalpy (DeltaH(0)) and entropy (DeltaS(0)) were also determined, which indicated that the adsorption was a spontaneous and exothermic process at ambient conditions. Compared with other adsorbents, the as-synthesized NaA zeolite displays a faster adsorption rate and higher adsorption capacity, which implies potential application for removing NH(4)(+) pollutants from wastewaters.
authors.affiliation: School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, PR China.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Zhao
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang
authors.forename: Jinhua
authors.initials: J
authors.lastname: Wang
authors.forename: Jindun
authors.initials: J
authors.lastname: Liu
authors.forename: Rongfeng
authors.initials: R
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D000465:Algorithms; D000538:Aluminum Silicates / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D000077215:Clay; D003080:Cold Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D000644:Quaternary Ammonium Compounds / Q000302:isolation & purification*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction; D017641:Zeolites / Q000138:chemical synthesis*
chemical_list: D000538:Aluminum Silicates; D002412:Cations; D000644:Quaternary Ammonium Compounds; D017641:Zeolites; D000077215:Clay