钛酸盐纳米管对水中氨氮的吸附特性

以P25和Na OH为原料,采用水热法制备钛酸盐纳米管(TNTs),利用X射线衍射(XRD)、透射电镜(TEM)对材料的组成和形貌进行表征,通过其对水中氨氮的静态吸附实验,考察TNTs对水中氨氮的吸附特性及规律.结果表明碱浓度为10mol·L-1时,可以获得管长约120 nm,管径约为8 nm的钛酸盐纳米管,其对氨氮的平衡吸附量达到10. 67 mg·g-1. p H值介于3～8时,TNTs能有效地吸附水中的氨氮.吸附过程在1 h基本达到平衡,符合准二级动力学方程.颗粒内扩散方程拟合结果发现,TNTs对氨氮的吸附过程由表面吸附和颗粒内扩散共同控制. Temkin方程能较好地描述TNTs对氨氮的吸附行为.热力学实验表明钛酸盐纳米管对氨氮的吸附是自发进行的吸热过程.共存阴阳离子对氨氮的吸附具有抑制作用,分别表现为SO_4~(2-) Cl~- H_2PO_4~-、K~+ Na~+ Ca~(2+).再生的钛酸盐纳米管对氨氮循环吸附5次仍有88. 64%的吸附效果.红外光谱(FT-IR)研究表明钛酸盐纳米管对氨氮的吸附机制是TNTs层间的Na~+与溶液中的NH_4~+之间发生离子交换.钛酸盐纳米管的优良循环使用性能和大吸附容量使得其能有效地去除水中氨氮.

Ammonium Adsorption Characteristics in Aqueous Solution by Titanate Nanotubes

Titanate nanotubes (TNTs) were synthesized via a hydrothermal method using P25 and NaOH as the raw materials. The composition and morphology of the nanotubes were characterized by X-ray diffraction and transmission electron microscopy. The adsorption characteristics and the rules of ammonium in aqueous solutions were tested in the static system. The results showed that when the alkali concentration was 10 mol·L^-1, titanate nanotubes with a length of approximately 120 nm and a diameter of approximately 8 nm were obtained. The equilibrium adsorption capacity of ammonium was 10.67 mg·g^-1. When the pH ranged between 3 and 8, TNTs effectively adsorbed ammonium. The equilibrium adsorption time was 1 h, and this followed the pseudo second-order model. The results from the intra-particle model also showed that the adsorption process of ammonium by TNTs was controlled by surface adsorption and inter-particle diffusion. The Temkin model gave the best fit for the adsorption of ammonium onto TNTs. The thermodynamic experiments showed that the adsorption of titanate nanotubes on ammonium was a spontaneous endothermic process. Coexisting anions and cations had an inhibitory effect on the adsorption of ammonium. The order of influence was SO₄^2- > Cl^- > H₂PO₄^- and K⁺ > Na⁺ > Ca²⁺, respectively. The adsorption effect of ammonium by regenerated TNTs remained more than 88.64% after five repeat usages. The results of Fourier transform infrared spectroscopy showed that the ammonium adsorption mechanism of titanate nanotubes was ion-exchange between NH₄⁺ and Na⁺ in the TNTs. Titanate nanotubes can effectively remove ammonium from water because of their good recycling capacity and large adsorption capacity.