Preparation of magnetic Fe3O4 nanocomposites and their adsorption to Pb(II)
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摘要: 为解决磁性纳米Fe3O4易被腐蚀、团聚等问题,可对其进行功能化修饰。在超声波辐照下首先制备磁性纳米Fe3O4颗粒,然后选用2,5-二氨基苯磺酸(SP)和间苯二胺(mPD)单体为引入剂进行功能化修饰,制备得到富含氨基、磺酸基和亚氨基活性官能团的金属基复合材料Fe3O4-mPD/SP(95∶5),并采用FTIR、TEM、XRD等手段对其进行表征,证实了超声波辐照法制得的磁性纳米复合材料具有稳定性好、反应活性高、粒径小和比表面积更大等特点。同时考察其对Pb(II)的吸附性能,结果表明:mPD和SP摩尔比、溶液pH值、竞争性阳离子种类和反应温度等因素均会影响吸附效果;等温吸附过程符合Freundlich模型,吉布斯自由能∆G0<0,吸附是一个自发过程;Pb(II)的吸附行为符合准二级动力学,速率常数k2=3.61×10−3 g·mg−1·min−1,平衡吸附量qe=63.297 mg·g−1;推测得到吸附机制主要为离子交换、络合吸附和静电引力等。Abstract: In order to solve the problem that Fe3O4 nanoparticles were easy to be corroded and agglomerated, it was decided to functionalize it. Magnetic nano-Fe3O4 particles were prepared under ultrasonic irradiation, then 2-diaminobenzenesulfonic acid (SP) and m-phenylenediamine (mPD) monomers were selected as introduction agents to prepare metal matrix composites Fe3O4-mPD/SP(95∶5), which were rich in amino, sulfonic acid and imine active functional groups, and nanocomposites were characterized by FTIR, TEM, XRD and other methods. The characterized results show that the magnetic nanocomposites prepared by ultrasonic strengthening method have the characteristics of good stability, high reaction activity, small particle size and larger specific surface area. The adsorption properties of Pb(II) by Fe3O4-mPD/SP were investigated which showed that the molar percentage of SP and mPD, reaction temperature, sorts of competitive cations and the pH value of solution all had effect on the adsorption of Pb(II). The adsorption isotherm conforms to the Freundlich model, and the adsorption of Pb(II) is a spontaneous process, Gibbs free energy ∆G0<0. It is found that the adsorption behavior of Pb(II) on nanocomposites can be well described by quasi secondary dynamics equation, kinetic constant k2=3.61×10−3 g·mg−1·min−1, equilibrium adsorption capacity qe=63.297 mg·g−1. It is speculated that the adsorption mechanism of this adsorbent includes ion exchange, complex adsorption and electrostatic adsorption.
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Key words:
- ultrasound /
- magnetic properties /
- metal-matrix composites /
- adsorption /
- freundlich model /
- Fe3O4 nanoparticles
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表 1 不同吸附剂对Pb(II)的吸附容量比较
Table 1. Comparison of adsorption capacity of Pb(II) by different adsorbents
Adsorbent Saturated adsorption capacity/(mg·g−1) Ref. Magnetic ion-imprinted and —SH functionalized polymer 32.58 [3] MNPs-Ca-alginate immobilized Phanerochaete chrysosporium 56.18 [6] Magnetic alginate beads 50.00 [7] Fe3O4@SiO2-NH2 40.10 [8] Fe3O4@SiO2-NH-COOH 34.27 [9] Magnetic chitosan/graphene oxide 76.94 [13] Fe3O4-mPD/SP(95∶5) 95.24 This study Note: MNPs—Magnetic nanoparticles. 表 2 Pb(II)吸附动力学方程拟合及各参数值
Table 2. Pb(II) adsorption kinetic equation fitting and parameters
Dynamics model R2 Rate constant qe,cal/(mg·g−1) qe,exp/(mg·g−1) Quasi-first-order kinetics 0.627 k1=1.65×10−2 min−1 — — Quasi-second-order kinetics 0.999 k2=3.61×10−3 g·mg−1·min−1 63.297 62.493 Internal diffusion equation 0.557 kp=2.005 mg·(g·min1/2)−1 — — Notes: qe,cal—Theoretical saturated adsorption capacity; qe,exp—Experimental saturated adsorption capacity; k1—Quasi-first-order kinetic constant; k2—Quasi-second-order kinetic constant; kp—Internal diffusion coefficient; R2—Correlation coefficient. 表 3 Fe3O4-mPD/SP(95∶5)对Pb(II)各吸附动力学模型参数
Table 3. Kinetic model parameters of adsorption of Pb(II) by Fe3O4-mPD/SP(95∶5)
Model Parameters and values Langmuir model KL/(L·mg−1) qm/(mg·g−1) R2 0.068 95.24 0.979 Freundlich model KF/(mg1−(1/n)·L1/n·g−1) 1/n R2 23.53 0.268 0.994 Temkin model Kt Bl R2 3.513 13.55 0.952 Notes: KL—Langmuir adsorption constant; KF—Freundlich adsorption coefficient; Kt, Bl—Temkin adsorption isotherm; qm—Saturated adsorption capacity; R2—Linear correlation coefficient; n—Empirical constant. 表 4 Fe3O4-mPD/SP(95∶5)吸附Pb(II)热力学常数
Table 4. Thermodynamic constants of Fe3O4-mPD/SP(95∶5) adsorption of Pb(II)
C0/(mg·L−1) ∆G0/(kJ·mol−1) ∆H0/(kJ·mol−1) ∆S0/(J·mol−1·K−1) 293 K 303 K 313 K 323 K 90 3.404 −4.570 5.561 6.807 30.766 116.620 100 3.342 4.197 4.768 5.542 21.703 85.479 110 2.937 −3.677 −4.361 −5.183 18.749 74.014 Notes: C0—Initial concentration of solution; ∆G0—Gibbs free energy; ∆H0—Enthalpy change; ∆S0—Entropy change. 表 5 Fe3O4和Fe3O4-mPD/SP(95∶5)抗氧化性实验
Table 5. Antioxidant activity of Fe3O4 and Fe3O4-mPD/SP(95∶5)
Sample Sample state during adsorption qe/(mg·g−1) Fe3O4 Fresh preparation 23.19 Exposed to air for 48 h 17.51 Fe3O4-mPD/SP(95∶5) Fresh preparation 40.46 Exposed to air for 48 h 37.73 -
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