紫薇嵌入磁性纳米粒子的合成、表征及其对水溶液中 Cr(VI) 的吸附应用。

Synthesis, characterization and application of Lagerstroemia speciosa embedded magnetic nanoparticle for Cr(VI) adsorption from aqueous solution.

作者信息

Srivastava Shalini, Agrawal Shashi Bhushan, Mondal Monoj Kumar

机构信息

Department of Botany, Institute of Science, Banaras Hindu University, Varanasi 221005, India.

Department of Chemical Engineering and Technology, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India.

出版信息

J Environ Sci (China). 2017 May;55:283-293. doi: 10.1016/j.jes.2016.08.012. Epub 2016 Sep 27.

Abstract

Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe and Fe salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM-EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption-desorption cycles.

摘要

通过铁和铁盐溶液与氨水以及紫薇树皮(LB)共沉淀法制备了负载紫薇树皮的磁性纳米颗粒,用于从水溶液中去除六价铬(Cr(VI))。采用扫描电子显微镜-能谱仪(SEM-EDX)、透射电子显微镜(TEM)、比表面积分析仪(BET)、傅里叶变换红外光谱仪(FT-IR)、X射线衍射仪(XRD)和热重分析仪(TGA)对天然紫薇树皮、磁性纳米颗粒(MNP)、负载紫薇树皮的磁性纳米颗粒(MNPLB)以及吸附了Cr(VI)的MNPLB颗粒进行了表征。TEM分析证实MNP呈近似球形,平均直径为8.76nm,XRD分析表明表面改性并未导致MNP的相变,而导致形成了直径为18.54nm的MNPLB二次颗粒。表征结果揭示了MNP的羟基与LB颗粒的羧基之间存在共价键结合,并进一步证实了其有利于Cr(VI)吸附的物理化学性质。以MNPLB颗粒作为吸附剂,在不同接触时间、初始Cr(VI)浓度、吸附剂剂量、初始pH值、温度和搅拌速度下测试了对Cr(VI)的吸附情况。吸附平衡和动力学结果分别用朗缪尔等温线和准二级模型进行了很好的描述。热力学参数表明Cr(VI)吸附到MNPLB上是自发的且吸热的。计算得出MNPLB的最大吸附容量为434.78mg/g,这些颗粒即使在吸附Cr(VI)后也能通过磁铁轻松地从水溶液中收集。发现吸附了Cr(VI)的MNPLB的解吸率超过93.72%,用过的MNPLB可进行十一次连续的吸附-解吸循环。

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