Preparation Of Magnetic Carbon Nanotube For The Adsorption Properties And Mechanisms Of Heavy Metals Ions From Aqueous Soultion

Multi-walled carbon nanotubes（MWCNTs）have received extensive attention in the field of heavy metal ion adsorption due to their advantages such as large specific surface area and rich pore structure.However,the traditional centrifugal separation and filtration methods are difficult to separate the carbon nanotubes from the aqueous solution,resulting in the industrial application of this technology.In order to solve the problem of difficult separation of carbon nanotubes,magnetic nanoparticles modified carbon nanotubes were proposed in this paper.In-depth research was carried out on the performance characterization of magnetic carbon nanotubes,the adsorption effect and adsorption mechanism of heavy metal ions in water environment,and the following innovative research conclusions were obtained:1.Using industrial-grade multi-walled carbon nanotubes（MWCNTs）as raw materials,different-surface-modified multi-walled carbon nanotubes（1O-MWCNT,3O-MWCNT,6O-MWCNT,and 9O-MWCNT）were prepared by wet chemical oxidation.Scanning electron microscope/Transmission electron microscopy（SEM/TEM）,X-ray diffraction（XRD）,and Raman spectroscopy（Raman）were used to characterize the structure and micromorphology of surface-modified carbon nanotubes（O-MWCNTs）.Studies have shown that the microstructure and morphology of O-MWCNTs have not changed during the surface modification process;Fourier transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）further illustrate the successful synthesis of different degrees Surface modified carbon nanotubes.2.The adsorption properties and mechanism of surface-modified carbon nanotubes for heavy metals were investigated.Batch adsorption experiments show that the maximum adsorption capacity of MWCNT for Pb（II）in aqueous solution is38.6 mg·g^-1.After surface modification,the adsorption capacity of Pb（II）in aqueous solution has been greatly improved.The maximum adsorption capacities of1O-MWCNT,3O-MWCNT,6O-MWCNT,and 9O-MWCNT are 82.4,89.8,101.1,and 99.7 mg·g^-1,respectively.In particular,6O-MWCNT with the highest surface modification has the highest adsorption capacity for Pb（II）.Further research shows that the carboxyl group（-COOH）on the surface of MWCNTs is the main adsorption site.In addition,isothermal adsorption experiments show that the adsorption process of O-MWCNTs is more in line with the Langmuir adsorption isotherm model and belongs to single-layer adsorption.Kinetic experiments show that O-MWCNTs have a very fast adsorption rate,which can reach adsorption equilibrium in only 10 minutes,and are more consistent A pseudo-second-order kinetic adsorption model;selectivity experiments show that O-MWCNTs have higher selectivity and binding capacity for Pb（II）than other competing ions.3.Combining the efficient adsorption performance of carbon nanotubes with the excellent magnetic separation performance of magnetic nanoparticles,a surface-functionalized multi-walled carbon nanotube was further magnetized by a solvothermal method to prepare a noval magnetic adsorbent with magnetic separation and efficient adsorption performance.Surface-functionalized 6O-MWCNT was used to prepare 6C-MWCNT with Fe Cl₃·6H₂O and CH₃COONa·3H₂O in a glycol solvent to prepare magnetic carbon nanotubes with magnetic separation performance（6O-MWCNT/Fe₃O₄）by solvothermal method.The results of SEM,XRD,and Raman showed that 6O-MWCNT/Fe₃O₄ did not change its microstructure and microstructure in the magnetization process.FT-IR and XPS confirmed that the corresponding Fe-O characteristics were detected after 6O-MWCNT/Fe₃O₄ was magnetized which illustrates the successful synthesis of magnetic carbon nanotubes.Isothermal adsorption experiments show that the maximum adsorption capacities of6O-MWCNT/Fe₃O₄ for Cu（II）,Cd（II）,and Pb（II）are 87.64 mg·g^-1,57.14 mg·g^-1,and215.05 mg·g^-1.Much stronger than the adsorption capacity of 6O-MWCNT,and the adsorption process is more consistent with the Langmuir adsorption isotherm model.Kinetic experiments show that 6O-MWCNT/Fe₃O₄ adsorbs Cu（II）,Cd（II）,and Pb（II）at very fast rates and the adsorption equilibrium are reached within 10 minutes,which is more in line with the pseudo-second-order kinetic adsorption model.Further mechanism analysis found that after 6O-MWCNT/Fe₃O₄ adsorbed Pb（II）,the absorption peaks generated by the-COOH and Fe-O stretching vibrations weakened,and O 1s and Fe 2p shifted to a lower binding energy direction,which proved that6O-MWCNT/Fe₃O₄ mainly chelate with Pb（II）through-COOH,Fe-O.Magnetic carbon nanotubes with magnetic separation characteristics were prepared by solvothermal method from 6O-MWCNT with Fe Cl₃·6H₂O and CH₃COONa·3H₂O,and analyzed by SEM,XRD,FT-IR,XPS and other characterization methods.The results showed that oxygen-containing functional groups（-COOH）and magnetic Fe-O groups were effectively introduced on the surface of MWCNTs,and their microstructure and microstructure did not change significantly,which proved that6O-MWCNT/Fe₃O₄ was successfully synthesized.The adsorption experiments showed that the maximum adsorption capacities of 6O-MWCNT/Fe₃O₄ for Cu（II）,Cd（II）and Pb（II）were 87.64 mg·g^-1,57.14 mg·g^-1,and 215.05 mg·g^-1,respectively,which are much stronger than the adsorption capacity of 6O-MWCNT.Further research shows that the main adsorption sites of 6O-MWCNT/Fe₃O₄ are-COOH and Fe-O.In addition,the adsorption of Cu（II）,Cd（II）,and Pb（II）by 6O-MWCNT/Fe₃O₄is more in line with Langmuir adsorption isotherm model and pseudo-second-order kinetic adsorption model,and the adsorption rate is extremely fast.4.Further explore the application prospect of 6O-MWCNT/Fe₃O₄ in actual wastewater.The results show that the removal rate of Cu（II）,Cd（II）,and Pb（II）by6O-MWCNT/Fe₃O₄ under the background of Ganjiang water quality reaches96.2～99.8%,and the effluent concentration meets the comprehensive wastewater discharge standard（GB8978-1996）.In addition,the 6O-MWCNT/Fe₃O₄ adsorbent can be effectively recovered through the addition of a magnet,and it is expected to become a new and efficient adsorbent for treating heavy metal ions in actual wastewater.