Kondo Yoshifumi, Goto Tomoyo, Sekino Tohru
The Institute of Scientific and Industrial Research (ISIR), Osaka University 8-1 Mihogaoka, Ibaraki Osaka 567-0047 Japan
Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University 2-1 Yamadaoka, Suita Osaka 565-0871 Japan.
RSC Adv. 2020 Nov 11;10(67):41032-41040. doi: 10.1039/d0ra06662a. eCollection 2020 Nov 9.
The development of new technologies for securing and recycling water resources are in high demand. A key focus of these technologies is the development of various ion exchangers or adsorbents that are used for the purification of aqueous solutions. Layered sodium titanate is one of the cation exchangers utilised in the removal of heavy metals and radionuclides from wastewater. To enhance the removal efficiency, the precise design of the crystal morphology, structure, and chemical composition is important. Herein, we synthesised a unique seaweed-like sodium titanate mat (SST) using a template-free alkaline hydrothermal process. The Co sorption capacity of SST was investigated by batch testing with cobalt(ii) nitrate. SST, which was synthesised from titanium sulphate in a 10 M NaOH solution at 200 °C, had a seaweed-like structure composed of randomly distributed nanofibres of layered sodium titanate that is approximately 9 nm in diameter. The crystal shape changed from roundish crystals to fibrous crystals as the hydrothermal reaction period increased. The Co sorption isotherm of SST was fitted with the Langmuir isotherm model and the maximum sorption density was 1.85 mmol g. The selectivity of the Co sorption on SST was high in comparison to that of Ca and Mg. Herein, the Co sorption mechanisms of SST were studied in comparison with commercially available sodium titanate. Results show that controlling the crystal morphology, structure, and Na concentration of the layered titanate that can be ion-exchanged determines the cation sorption properties of sodium titanate.
对保障和循环利用水资源的新技术的需求很高。这些技术的一个关键重点是开发用于净化水溶液的各种离子交换剂或吸附剂。层状钛酸钠是用于从废水中去除重金属和放射性核素的阳离子交换剂之一。为了提高去除效率，精确设计晶体形态、结构和化学成分很重要。在此，我们使用无模板碱性水热法合成了一种独特的海藻状钛酸钠毡（SST）。通过用硝酸钴（II）进行批量测试来研究SST对钴的吸附能力。在200°C下由硫酸钛在10M氢氧化钠溶液中合成的SST具有由随机分布的层状钛酸钠纳米纤维组成的海藻状结构，其直径约为9nm。随着水热反应时间的增加，晶体形状从圆形晶体变为纤维状晶体。SST的钴吸附等温线符合朗缪尔等温线模型，最大吸附密度为1.85mmol/g。与钙和镁相比，SST对钴的吸附选择性较高。在此，与市售钛酸钠相比，研究了SST对钴的吸附机制。结果表明，控制可离子交换的层状钛酸盐的晶体形态、结构和钠浓度决定了钛酸钠的阳离子吸附性能。
