铅离子印迹磁性材料的制备及其对Pb(Ⅱ)的吸附去除研究

The preparation of Pb-imprinted magnetic polymer and its application for the removal of Pb(Ⅱ)

[目的]制备铅离子印迹和非印迹磁性材料,研究两种材料对Pb（Ⅱ）的吸附去除行为,考察两种材料对Pb（Ⅱ）的吸附选择性,探索其脱附和循环利用性。[方法]采用透射电镜、红外光谱、X射线衍射光谱和能量色散谱等方法对两种材料的形貌和结构进行表征;采用静态吸附法,以原子吸收为检测手段,探讨了p H值、反应时间及Pb（Ⅱ）初始浓度等因素对Pb（Ⅱ）吸附能力的影响;采用Langmuir等温吸附模型和Ho准二级动力学方程对其进行热力学和动力学模拟研究;以Cd（Ⅱ）为竞争离子,研究两种材料对Pb（Ⅱ）吸附选择性;以硝酸为脱附试剂,考察其脱附和循环利用性。[结果]1）与Fe3O410 nm的粒径相比,铅离子印迹磁性材料粒径增至80~90 nm;两种材料红外光谱图中557 cm^-1处出现强吸收峰,证实Fe—O键存在,2 940 cm^-1和1 084 cm^-1处的吸收峰证实C—H和Si—O键存在;X射线衍射光谱图显示,它们都具有Fe3O4晶型及Si O2壳层;能量色散谱结果显示,它们主要构成元素为C、O、Si、S和Fe,说明Fe3O4磁核已被Si O2包覆,且巯基已成功键合至两种材料的表面。2）在低酸度时Pb（Ⅱ）基本不被两种材料吸附;当p H值从3增至7时,吸附率不断增大并达到最大,且非印迹材料对Pb（Ⅱ）的吸附率低于印迹材料对Pb（Ⅱ）的吸附率。3）铅印迹磁性材料对Pb（Ⅱ）的吸附量随时间的增加而升高,最后达到平衡吸附。4）随着溶液中Pb（Ⅱ）初始浓度的增加,铅印迹磁性材料对Pb（Ⅱ）的吸附量先是急剧上升,然后达到饱和吸附。5）铅印迹磁性材料对Pb（Ⅱ）的吸附动力学和热力学分别符合准二级吸附模型和Langmuir等温吸附模型。6）铅印迹磁性材料对Pb（Ⅱ）/Cd（Ⅱ）选择吸附系数K为29.75,对Pb（Ⅱ）/Cd（Ⅱ）的相对选择系数是非印迹磁性材料的5.86倍,说明该材料对Pb（Ⅱ）具有良好的吸附选择性。7）研究了HNO3对保留在铅印迹磁性材料上Pb（Ⅱ）的脱附影响,结果显示0.5 mol·L^-1HNO3可定量脱附Pb（Ⅱ）,且材料可重复使用5次而脱附率无变化。[结论]在p H 7、反应时间为60 min及Pb（Ⅱ）初始质量浓度为10 mg·L^-1时铅印迹磁性材料对Pb（Ⅱ）的最大吸附容量可达38 mg·g^-1,可有效去除水中Pb（Ⅱ）;该材料对Pb（Ⅱ）具有一定的选择性且具有很好的再生性。

[ Objectives] The purpose of this work is to prepare Pb （ Ⅱ ）-imprinted magnetic polymer and non Pb （Ⅱ ）-imprinted magnetic polymer, to investigate the removal of Pb （ Ⅱ ） using the above two materials as absorbents, to study the adsorption selectivity of two materials and to evaluate the desorption and regeneration of Pb （ Ⅱ ） -imprinted magnetic polymer. [ Methods ] The two materials are characterized by transmission electron microscope, infrared spectrum, X-ray diffraction spectrum and energy dispersive spectrum. The effects of pH ranging from 2-7, reaction time varying from 5 to 90min and the initial concentration of Pb （Ⅱ）in the range of 1-20 mg.L-1 on the adsorption rate of Pb（ Ⅱ ）using static adsorption method are examined in detail in this study. The Pb （ Ⅱ ） concentrations are determined using flame atomic absorption spectrometry. The Langmuir isotherm model is used to for the isotherms study and Ho pseudo-second order kinetic equation is used to study the sorption kinetics. The adsorption selectivity of two materials for Pb（Ⅱ） is investigated using Cd（ Ⅱ ）as competitive ion and the desorption and regeneration of Pb（ Ⅱ ）from Pb（ Ⅱ ）- imprinted magnetic polymer are evaluated also. [ Results] 1 ）Compared with Fe304 having a diameter of 10 nm, the diameter of Pb （ Ⅱ ） -imprinted magnetic polymer is increased up to 80-90 nm;the peak at 557 em-lobserved in both infrared spectrums of the two materials is related to Fe-O and the peak at 2 940 cm^-1 and 1 084 cm^-1 is ascribed to C-H and Si-O;the X-ray diffraction spectrum results show that both materials have Fe3O4 crystal and the shell of SiO2 and the energy dispersive spectrum results demonstrate that the main composites of both materials are C, O, Si, S and Fe,which indicates that Fe3O4 has been successfully coated with SiO2 and thiol. 2）The adsorption rates of Pb（ Ⅱ] ）on both materials are enhanced with the increase of pH value from 2 to 7 and then remain constant. The adsorption rate of Pb （ Ⅱ ） on Pb（ Ⅱ ）-imprinted magnetic polymer is higher than that on non-Pb （ Ⅱ ）-imprinted magnetic polymer. 3 ）The adsorption capacity of Pb（ Ⅱ ）on Pb （ Ⅱ ）-imprinted magnetic polymer increases with the increasing of reaction time and then obtains equilibrium adsorption. 4）The adsorption capacity of Pb（ Ⅱ ）on Pb（Ⅱ ）-imprinted magnetic polymer improves rapidly with the increasing of initial Pb （ Ⅱ ） concentration and then keeps unchanged. 5 ） The dynamical and the equilibrium isotherm adsorption studies of Pb（ Ⅱ ）on Pb（ Ⅱ ）-imprinted magnetic polymer follows Ho pseudo-second-order rate and the Langmuir isotherm equation. 6）The selectivity coefficient of Pb （ Ⅱ ）-imprinted magnetic polymer for Pb （ Ⅱ ）/Cd（ Ⅱ ）is 29.75 and the relative selectivity coefficient of Pb（ Ⅱ）-imprinted magnetic polymer for Pb（ Ⅱ ）/Cd（ Ⅱ ）is 5.86 times as large as that of non-Pb（ Ⅱ ）-imprinted magnetic polymer. 7）The effect of HNO3 on the desorption rate of Pb（ Ⅱ ）from Pb （ Ⅱ ）-imprinted magnetic polymer is studied and the result shows that 0.5 mol·L^-1 HNO3 can quantificationally desorb Pb（ Ⅱ ）from it and it can be reused 5 times without any decrease of desorption rate. [ Conclusions ] The maximum adsorption capacity of Pb （ Ⅱ ） on Pb （ Ⅱ ） -imprinted magnetic polymer can be 38 mg· g^-1 when pH value is 7, reaction time is 60 min and the initial concentration of Pb （ Ⅱ ） is 10 mg· L^-1. Moreover, Pb（ Ⅱ ）-imprinted magnetic polymer has very good adsorption selectivity and regeneration, which displays that it is an excellent adsorption material.