Institute of Minerals and Materials Technology, Bhubaneswar, Orissa, India.
Dalton Trans. 2012 Mar 21;41(11):3302-12. doi: 10.1039/c2dt11651k. Epub 2012 Jan 30.
Nano-structured 2-line ferrihydrite was synthesized by a pH-controlled precipitation technique at 90 °C. Chemical, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman analyses confirmed the sample to be 2-line ferrihydrite. The nano nature of the prepared sample was studied by transmission electron microscopy (TEM). The surface area obtained by the Brunauer-Emmett-Teller (BET) method was 175.8 m(2) g(-1). The nanopowder so obtained was used to study its behaviour for the removal of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions. The relative importance of experimental parameters such as solution pH, contact time and concentration of adsorbate on the uptake of various cations was evaluated. By increasing the pH from 2.0 to 5.5, adsorption of the four cations increased. The kinetics parameters were compared by fitting the contact time data to both linear as well as non-linear forms of pseudo-second-order models. Linear forms of both Langmuir and Freundlich models fitted the equilibrium data of all the cations except for Pb(II) which was also fitted to the non-linear forms of both the models as it gave a low R(2) value of 0.85 for the Langmuir model. High Langmuir monolayer capacities of 366, 250, 62.5 and 500 mg g(-1) were obtained for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. Presence of chloride or sulfate had an adverse effect on cation adsorption. The interactive effects on adsorption from solutions containing two, three or four cations were studied. Surprisingly no Cd(II) adsorption was observed in Pb(II)-Cd(II), Pb(II)-Cd(II)-Zn(II) and Pb(II)-Cd(II)-Cu(II)-Zn(II) systems under the studied concentration range. The overall loading capacity of the adsorbent decreased in mixed cation systems. Metal ion loaded adsorbents were characterized by XRD, FTIR and Raman techniques. The high adsorption capability of the 2-lines ferrihydrite makes it a potentially attractive adsorbent for the removal of cations from aqueous solutions.
纳米结构的 2 线水铁矿是通过在 90°C 下使用 pH 控制沉淀技术合成的。化学、X 射线衍射 (XRD)、傅里叶变换红外 (FTIR) 和拉曼分析证实该样品为 2 线水铁矿。通过透射电子显微镜 (TEM) 研究了制备样品的纳米特性。通过 Brunauer-Emmett-Teller (BET) 方法获得的表面积为 175.8 m(2) g(-1)。由此获得的纳米粉末用于研究其从水溶液中去除 Pb(II)、Cd(II)、Cu(II)和 Zn(II)的行为。评估了实验参数（如溶液 pH、接触时间和吸附物浓度）对各种阳离子吸收的相对重要性。通过将 pH 从 2.0 增加到 5.5，四种阳离子的吸附增加。通过将接触时间数据拟合到线性和非线性形式的伪二阶模型来比较动力学参数。除 Pb(II)外，所有阳离子的平衡数据均拟合线性形式的 Langmuir 和 Freundlich 模型，Pb(II)也拟合非线性形式的两种模型，因为它对 Langmuir 模型的 R(2)值为 0.85 较低。对于 Pb(II)、Cd(II)、Cu(II)和 Zn(II)，分别获得了 366、250、62.5 和 500 mg g(-1)的高 Langmuir 单层容量。氯离子或硫酸根离子的存在对阳离子吸附有不利影响。研究了含有两种、三种或四种阳离子的溶液中吸附的相互作用效应。令人惊讶的是，在所研究的浓度范围内，在 Pb(II)-Cd(II)、Pb(II)-Cd(II)-Zn(II)和 Pb(II)-Cd(II)-Cu(II)-Zn(II) 系统中没有观察到 Cd(II)吸附。在混合阳离子系统中，吸附剂的整体负载能力下降。金属离子负载吸附剂的特性通过 XRD、FTIR 和拉曼技术进行了表征。2 线水铁矿的高吸附能力使其成为从水溶液中去除阳离子的潜在有吸引力的吸附剂。
