温度对合成钛酸盐纳米材料的影响及其对水中Cd (Ⅱ)的去除效果

为有效去除水中Cd（Ⅱ），以TiO₂纳米粉和NaOH为原料，调节水热反应温度分别为100、120、150和190℃，制备出了不同形貌的TNs（钛酸盐纳米材料），分别记为TNs-100、TNs-120、TNs-150和TNs-190，并对其形貌、结构、比表面积、化学组成等物理化学性能进行了表征；通过对水中Cd（Ⅱ）的静态吸附试验，考察了TNs对Cd（Ⅱ）的吸附性能.结果表明:随着合成温度的升高，TNs的形貌逐渐从纳米片演变成纳米管，管长逐渐变长，最后变成纳米棒.TNs-100的晶型结构主要是锐钛矿型；随着温度升高，结晶度逐渐增强；TNs-190出现了部分金红石相.TNs-150对Cd（Ⅱ）的吸附能力最强，最大平衡吸附量为254.66 mg/g，最佳吸附pH为5.0.再生的TNs-150对Cd（Ⅱ）循环吸附6次的去除率和解吸率均可达93%以上.TNs-150对Cd（Ⅱ）的吸附过程符合准二阶动力学方程和Langmuir吸附等温模型，吸附机制主要是TNs层间Na+和H+与溶液中Cd（Ⅱ）的离子交换.研究显示，TNs的饱和吸附量均高于同类吸附剂，能有效去除水中Cd（Ⅱ）. 

Influence of Temperature on Synthesis of Titanate Nanomaterials and Their Removal of Cadmium(II) from Aqueous Solution

A series of titanate nanomaterials (TNs) were synthesized hydrothermally using TiO₂ nano powder and NaOH. The morphology of TNs was tuned by regulating the reaction temperature. The physical-chemical properties of the TNs, such as morphology, structure, surface area and chemical composition were characterized by TEM, XRD, BET and FTIR, respectively. Cadmium, Cd(Ⅱ) adsorption properties of TNs in aqueous solutions were measured in the static system to reveal their ability to remove Cd(Ⅱ). The results showed that the morphology of TNs evolved from nanosheets into nanotubes with increasing temperature. In addition, the nanotube became a nanorod as it kept growing in length. The crystal structure of TNs which were synthesized at 100℃ was mainly anatase phase. Its crystallinity was enhanced as the temperature increased. Upon reaching 190℃, the phase transformation from anatase to rutile emerged though. TNs-150 that was prepared at 150℃ showed the highest adsorption capacity of Cd(Ⅱ) as 254.66 mg/g, while the optimum pH was 5.0. A proportion of 93% of adsorbed Cd(Ⅱ) was released at acid condition (pH=1), which enabled the reuse of TNs-150. The adsorption isotherm of TNs-150 was best fitted with the Langmuir model. The kinetics of adsorption followed the pseudo-second-order model. The adsorption mechanism was mainly ion exchange between Cd(Ⅱ) and Na+/H+ in TNs. In conclusion, TNs are promising materials for efficient and economical removal of cadmium ion from various aqueous waste streams.