Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 178, Issue 1-3, Pages 658-664Publisher
ELSEVIER
DOI: 10.1016/j.jhazmat.2010.01.136
Keywords
NaA zeolite; Hydro-thermal method; Ammonium ions; Halloysite mineral; Adsorption
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Funding
- National Natural Science Foundation of China [20871105]
- Henan Outstanding Youth Science Fund [0612002400]
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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 (NH4+) from aqueous solution onto NaA zeolite was investigated as a function of parameters such as equilibrium time, pH, initial NH4+ 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 NH4+ 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 NH4+ removal with nearly constant adsorption capacity. Thermodynamic parameters such as change in free energy (Delta G(0)), enthalpy (Delta H-0) and entropy (Delta S-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 NH4+ pollutants from wastewaters. (C) 2010 Elsevier B.V. All rights reserved.
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