钡十字沸石吸附K~＋的热力学模拟及动力学实验

Thermodynamic simulation and kinetics experiment of K^+ adsorption by merlinoite

运用密度泛函理论模拟了钡十字沸石离子交换的热力学性质,确定钠型及铵型沸石与K^+交换时,为放热反应;铵型沸石与Na^+交换时,为吸热反应。采用水热法制备了钡十字沸石,并用XRD、FT-IR及SEM进行表征,制备的样品改性后用于模拟海水中K^+的吸附动力学实验。结果表明:沸石离子交换后,其骨架结构保持不变;铵型沸石在模拟海水中对K^+的吸附速率快于钠型沸石;钠型及铵型沸石在模拟海水中对K^+的吸附属于准二级反应,膜扩散是控速步骤。

The thermodynamic properties of merlinoite in the process of ion exchange were simulated by Density Functional Theory （DFT）.It can be found that the process of K＋-Na＋ and K＋-NH4＋ ion exchange for Na-merlinoite and NH4-merlinoite respectively was an exothermic reaction, however, the process of Na＋-NH4＋ ion exchange for NH4-merlinoite was an endother- mic reaction.Meanwhile ,merlinoite was prepared by hydrothermal method and characterized by X-ray diffraction （XRD）, Fourier transform infrared spectrum analyzer （FT-IR） as well as scanning electron microscopy （SEM）.The sample was modi- fied successively with NH4Cl and NaCl heated solution.Then, adsorption kinetics of separating potassium from simulated sea- water with the sample modified were investigated.Results indicated that the modified merlinoite had the same framework structure as the synthetic merlinoite ;the adsorption ratio of potassium from simulated seawater for NH4-merlinoite was more rapid than that for Na-merlinoite ; in addition, the adsorption kinetics of the merlinoite was best described by pseudo-second- order kinetic equation and the ion exchange process was controlled by liquid film diffusion.