Synthesis Of MgAl-LDHs/MgFe₂O₄ Using Pine Pollen As Template And Its Adsorption Properties

LDHs is widely used in adsorption field, because of its high surface area, good thermal stability, interlayer ion interchangeability. But LDHs also exists some problems such as difficult to recycle after adsorbed. In this article, the magnetic Mg Fe2O4 was synthesized by pine pollen as biological template, and then put it in Mg Al precursor solution, using hydrothermal method to synthesis Mg Al-LDHs loaded on MgFe2O4. The as-prepared MgAl-LDHs/MgFe2O4 was characterizated by SEM, TEM, XRD, infrared analysis, surface area analysis, and then study the adsorption performance of Congo red solution and doxycycline solution on it and its calcined product CLDHs.The Mg Al-LDHs/MgFe2O4 composite material was successfully prepared. SEM displayed that the composite material maintained the original micro morphology of pine pollen, the sheet Mg Al-LDHs loaded on the MgFe2O4 material uniformly. XRD revealed that the MgAl-LDHs/MgFe2O4 composite material existed two phase of Mg Fe2O4 and [Mg6Al(OH)16]CO3.4H2 O. The specific surface area of Mg Fe2O4, Mg Al-LDHs and the composite material were 89.734,59.640 and 108.660 m2/g and the pore volume were 0.100,0.380 and 0.510 cm3/g, reflected that the composite material had bigger surface area and pore volume. Adsorption experiments displayed that the adsorption process to Congo red solution and doxycycline solution on the as-prepared samples conformed to the pseudo second-order model and Langmuir model, the maximum adsorption capacity was 219.30 mg/g and 214.73 mg/g, respectively. In addition, the adsorption capacity of congo red solution on the as-prepared sample was better in acid condition, the adsorption process was a spontaneous endothermic reaction. And the adsorption capacity of doxycycline solution was best in neutral condition, the adsorption process was spontaneous exothermic reaction. Mg Al-LDHs/Mg Fe2O4 could be regenerated and used, the adsorption capacity was high after three adsorption cycles. The main adsorption mechanism was anion exchange and electrostatic attraction between the samples and adsorbates.The XRD pattern of CLDHs/Mg Fe2O4 showed that characteristic diffraction peaks belonged to Mg Al-LDHs were disappeared. When the calcination temperature of MgAl-LDHs/MgFe2O4 exceed 700 oC, MgAl2O4 diffraction peak appeared. The specific surface area of calcined product was 79.793 m2/g, less than the samples before calcination. The adsorption process of congo red on calcined product CLDHs/MgFe2O4 from MgAl-LDHs/MgFe2O4 composite material conformed to the pseudo second-order model and Langmuir model. The maximum adsorption capacity calculated from Langmuir model was up to 404.86 mg/g. The adsorption effect was best in acidic environment. The adsorption process was a spontaneous endothermic reaction. The adsorption process of doxycycline solution on the calcinated product CLDHs/MgFe2O4 was according with the pseudo second-order model and freundlich model. In neutral solution, the adsorption effect of doxycycline solution was best. The adsorption process was a spontaneous endothermic reaction.Thus, the MgAl-LDHs/MgFe2O4 composite material is a kind of green, efficient, fast recovery adsorbent.