Kang Li, Liu Wen, Liu Xiao-Na, Liu Hong-Fang, Li Yi-Fei
College of Environment and Safety, Taiyuan University of Science and Technology, Taiyuan 030024, China.
College of Environmental Science and Engineering, Peking University, Beijing 100871, China.
Huan Jing Ke Xue. 2018 Jul 8;39(7):3212-3221. doi: 10.13227/j.hjkx.201706108.
Niobate-modified titanate nanosheets (Nb-TNS) were synthesized through a hydrothermal method and used to remove Cd(Ⅱ) from water. TEM and SEM characterizations indicated that the new nanocomposites were non-curled nanosheets. XRD showed that the material was composed of sodium tri-titanate and niobate, and titanate was the primary component. Ion exchange between Cd and Na in the interlayers of the Nb-TNSs was the dominant mechanism for Cd(Ⅱ) adsorption, leading to good adsorption performance. The material exhibited rapid adsorption kinetics for Cd(Ⅱ), reaching equilibrium within 60 min, and the data fit well with the pseudo-second order model (=1). The maximum adsorption capacity of Cd(Ⅱ) was 287.9 mg·g, according to the Langmuir isotherm model, which was larger than that of most of traditional adsorbents. Higher pH promoted adsorption because the negatively charged material could capture Cd(Ⅱ) cations more easily. Co-existing inorganic ions (Naand Ca) were unfavorable to the adsorption of Cd(Ⅱ) by Nb-TNS owing to the competition for adsorption sites. In addition, a slight inhibition effect on the adsorption in the presence of humic acid (HA) was found. Cd(Ⅱ) was efficiently desorbed from Nb-TNS after HNO treatment, and -ONa sites were restored with NaOH treatment. Considering its simple synthesis method, high removal efficiency for heavy metals, and good reusability, Nb-TNS is a promising material for remediation of areas contaminated by heavy metals.
通过水热法合成了铌酸盐改性钛酸盐纳米片（Nb-TNS），并用于去除水中的Cd(Ⅱ)。透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征表明，新型纳米复合材料为非卷曲纳米片。X射线衍射（XRD）表明该材料由三钛酸钠和铌酸盐组成，且钛酸盐是主要成分。Nb-TNS层间Cd与Na的离子交换是Cd(Ⅱ)吸附的主要机制，从而导致良好的吸附性能。该材料对Cd(Ⅱ)表现出快速的吸附动力学，在60分钟内达到平衡，且数据与准二级模型（=1）拟合良好。根据朗缪尔等温线模型，Cd(Ⅱ)的最大吸附容量为287.9 mg·g，大于大多数传统吸附剂。较高的pH值促进吸附，因为带负电荷的材料更容易捕获Cd(Ⅱ)阳离子。共存的无机离子（Na和Ca）由于对吸附位点的竞争而不利于Nb-TNS对Cd(Ⅱ)的吸附。此外，发现腐殖酸（HA）的存在对吸附有轻微的抑制作用。经硝酸处理后，Cd(Ⅱ)能有效地从Nb-TNS上解吸下来，用氢氧化钠处理可使-ONa位点恢复。考虑到其简单的合成方法、对重金属的高去除效率和良好的可重复使用性，Nb-TNS是一种用于修复重金属污染区域的有前景的材料。
