Balog Renata, Manilo Maryna, Vanyorek Laszlo, Csoma Zoltan, Barany Sandor
The Transcarpathian II Ferenc Rakoczi Hungarian Institute Kossuth sq. 6 Beregovo Ukraine.
F. D. Ovcharenko Institute of Biocolloidal Chemistry, National Academy of Sciences of Ukraine Vernadsky blvd. 42 Kyiv Ukraine
RSC Adv. 2020 Jan 17;10(6):3184-3191. doi: 10.1039/c9ra09755d. eCollection 2020 Jan 16.
The principles and mechanisms of adsorption of Ni(ii) ions by well characterized pristine and oxidized N-doped multi-walled carbon nanotubes (N-CNTs) are described and discussed. The samples were synthesized by CCVD method using -butylamine as the carbon source and Ni(NO) + MgO as the catalyst and purified by treatment with HCl. The surface functionalization was performed using oxidation with a mixture of concentrated HSO and HNO. The morphology, nature and charge of surface groups were characterized by HRTEM, XPS, FTIR and micro-electrophoresis methods. It has been shown that: adsorption of Ni(ii) reaches an equilibrium value within 20-30 min; the degree of extraction of nickel ions from the solution increases with its dilution; adsorption of Ni(ii) results in an insufficient decrease in the suspension pH for pristine N-CNTs (0.5-0.6 pH unit) and considerable lowering of the pH for the oxidized sample (up to 2.5 pH unit); the adsorption isotherms are described by the Langmuir equation; the plateau amounts of adsorption (35-40 mg g) are almost the same for both as-prepared and oxidized samples; at pH 8 and higher a sharp increase in adsorption is observed which is caused by nickel hydroxide precipitation. The spectroscopic, adsorption, electrophoretic and pH measurement data testify that below pH 8 the major mechanism of adsorption by as-prepared N-CNTs is the donor-acceptor interaction between the free electron pair of N atoms incorporated into the nanotube lattice and vacant d-orbital of the adsorbing Ni(ii) ions. For the oxidized N-CNTs ion-exchange processes with a release of H play a decisive role.
描述并讨论了表征良好的原始和氧化的N掺杂多壁碳纳米管（N-CNTs）对Ni（II）离子的吸附原理和机制。采用CCVD法，以正丁胺为碳源，Ni（NO）+MgO为催化剂合成样品，并通过HCl处理进行纯化。使用浓HSO和HNO的混合物进行氧化以实现表面功能化。通过高分辨率透射电子显微镜（HRTEM）、X射线光电子能谱（XPS）、傅里叶变换红外光谱（FTIR）和微电泳方法对表面基团的形态、性质和电荷进行了表征。结果表明：Ni（II）的吸附在20-30分钟内达到平衡值；溶液中镍离子的萃取程度随其稀释而增加；原始N-CNTs对Ni（II）的吸附导致悬浮液pH值下降不足（0.5-0.6个pH单位），而氧化样品的pH值则显著降低（高达2.5个pH单位）；吸附等温线符合朗缪尔方程；制备的样品和氧化样品的吸附平台量（35-40mg/g）几乎相同；在pH值为8及更高时，观察到吸附急剧增加，这是由氢氧化镍沉淀引起的。光谱、吸附、电泳和pH测量数据证明，在pH值低于8时，原始N-CNTs的主要吸附机制是掺入纳米管晶格的N原子的自由电子对与吸附的Ni（II）离子的空d轨道之间的供体-受体相互作用。对于氧化的N-CNTs，释放H的离子交换过程起决定性作用。
