| Metal-Organic-Frameworks?MOFs?have unique structure,physical and chemical properties,such as large specific surface area,high porosity,good crystalline structure and thermal stability,thus devoted to broad development in the field of water treatment.This article selects the multi-walled carbon nanotubes?MWCNTs?and polyethyleneimine?PEI?modified MIL-100?Fe?and NH2-MIL-101?Fe?respectively to prepare the adsorption material,and study the adsorption beha?or of Neutral Red?NR?,Oxytetracycline?OTC?and heavy metal ions Cr???,Cu???,and further discusses the mechanism of adsorption process.In this paper,a series of methods were used to characterize the adsorbents,including Isoelectric point(p Hzpc),Fourier transform infrared spectroscopy?FTIR?,Scanning Electron Microscope?SEM?,Brunauer-Emmett-Teller method?BET?,X-ray photoelectron spectroscopy?XPS?,X-ray diffraction?XRD?.The main research results are as follows:MIL-100?Fe?was prepared from Fe?NO3?3·9H2O and H3BTC by hydrothermal method.The experimental results showed that the adsorption capacity of NR was highest under weak alkaline conditions and the adsorption quantity was to 320 mg·g-1at 293 K,while the presence of coexisting ions does not affect its adsorption capacity.The adsorption process conforms to the Freundlich and Temkin isotherm models and the pseudo-second-order kinetic model,electrostatic attraction and?-?stacking are the main mechanisms of NR adsorption.Thermodynamic data show that adsorption is a spontaneous,endothermic and entropy increasing physicochemical adsorption process.75%ethanol?p H=2?can be used for multiple desorption and regeneration after the adsorption of NR by MIL-100?Fe?.MWCNTs were added during the synthesis of MIL-100?Fe?by hydrothermal method.The adsorbent MIL-100?Fe?-CNTs was successfully prepared and the addition of MWCNTs did not cause damage to the structure of MIL-100?Fe?.The OTC adsorption experimental results show that the adsorption capacity of OTC is the highest under acidic conditions and the maximum adsorption capacity of OTC+is 179mg·g-1 at p H of 8.Langmuir model is suitable for describing the adsorption process of MIL-100?Fe?-CNTs on OTC.The adsorption kinetic conforms to the Elovich model,indicating that the adsorption process is accompanied by ion exchange.Thermodynamic results show that the adsorption is a spontaneous and endothermic physico-chemical process.MIL-101?Fe?@PEI particles were synthesized through a simple hydrothermal process by cross-linking NH2-MIL-101?Fe?and PEI which were uesd to adsorb Cr???and Cu???in aqueous solution.The maximum adsorption capacity was to under the339 mg·g-1 for Cr?VI??p H 5.5?and 32.9 mg·g-1 for Cu?II??p H 5.0?from experimental results at 293 K,respectively.Combined with the influence of salt concentration and Freundlich isotherm model description of adsorption process,show that multilayer chemical reactions occur in the adsorption process of Cr???and Cu???.Pseudo-second-order model and Elovich model can be respectively used to describe the Cr???and Cu???adsorption process,speculated that the adsorption process is homogeneous chemical adsorption,adsorption mechanism mainly for ion exchange and coordination complexation respectively.Thermodynamic parameters show that the Cr???and Cu???adsorption processes are spontaneous and entropy increase reaction. |
PDF Full Text Request