School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, PR China.
J Hazard Mater. 2010 Jun 15;178(1-3):658-64. doi: 10.1016/j.jhazmat.2010.01.136. Epub 2010 Feb 2.
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.
采用具有纳米管状结构的天然埃洛石矿物为原料，通过水热法首次合成了有序立方 NaA 沸石。SEM 和 HRTEM 图像表明，所合成的 NaA 沸石为具有平面表面、边缘清晰、对称且均匀的孔道的立方晶型。研究了铵离子（NH(4)(+)）在水溶液中吸附到 NaA 沸石上的行为，考察了平衡时间、pH 值、初始 NH(4)(+)浓度、温度和竞争阳离子等参数的影响。应用 Langmuir 和 Freundlich 吸附模型描述了平衡等温线。NH(4)(+)的最大吸附容量为 44.3mg g(-1)。评价了该吸附剂的再生和可重复使用能力，结果表明，回收的吸附剂可以再次用于 NH(4)(+)去除，且具有几乎恒定的吸附容量。还确定了热力学参数，如自由能变化（DeltaG(0)）、焓变（DeltaH(0)）和熵变（DeltaS(0)），表明在环境条件下，吸附是一个自发的放热过程。与其他吸附剂相比，所合成的 NaA 沸石具有更快的吸附速率和更高的吸附容量，这意味着其在去除废水中的 NH(4)(+)污染物方面具有潜在的应用前景。
