Preparation Of Polyethylenimine Functionalized Magnetic Carbon Nanotubes And Research On Its Adsorption Performance For Methyl Orange(MO) And Cr(?) From Aqueous Solution

Dyes and heavy metals have been widely existing in printing and dyeing,textile and other industrial production,which were directly discharged into the natural water environment causing irreversible pollution to the ecologial system.In ordering to removal of the dyes and heavy metal,many scholars have studied and investigated,in which adsorption as a method because of its simple operation,cheap cost,not easy to cause the secondary pollution etc.In this study,adsorption was uesed to remove methyl orange and hexavalent chromium in waste water,which were the representative pollutants of dyes and heavy metal,respectively.In this study magnetic multi-walled carbon nanotubes?MWCNTs@Fe₃O₄?were prepared by a solvothermal method,followed by modification using polyethylenimine?PEI?as modifier,getting the PEI modified magnetic multiwalled carbon nanotubes?PEI/MWCNTs@Fe₃O₄?composite.The physic-chemical properties of the material and the success of the material synthesis were characterized by various techniques,such as FT-IR,SEM,TEM,TGA,XRD,VSM,etc.Composite material have combined the large specific surface area and rich oxygen containing functional groups of the carboxyl of multi-walled carbon nanotubes,quickly realizing the solid-liquid separation of Fe₃O₄ magnetic particles and amino groups in the polyethylene having good affinity to dyes and heavy metals of these three adbantages.Composite material enhanced the adsorpton capacity of methyl orange and hexavelent chromium and has good stability.The experimental results are as follows;The results of the adsorption of methyl orange in the PEI/MWCNTs@Fe₃O₄:the optimal pH was 3.0,the adsorpion capacity of PEI/MWCNTs@Fe₃O₄ decreased with increasing solution pH values;the NaCl has no obvious influence on the adsorption capacity of methyl orange;humic acid concentration in the range of natural water has little impact on the adsorption capacity of methyl orange;the pseudo-second-order kinetics model and Langmuir model fitted the experimental results well,the adsorption quantity can reach 1727.6 mg/g;thermodynamic analysis showed that adsorption process was a spontaneous endothermic reaction;the removal rate of methyl orange was still 90%after six adsorption-desorption cycels;the PEI/MWCNTs@Fe₃O₄ as a new type of compostie can effectively remove the methyl orange in the printing and dyeing wastewater.The adsorption capacity of Cr???on the PEI/MWCNTs@Fe₃O₄ was decreased with increasing the pH values.The ionic strength inhibited the adsorption of Cr???,but natural organic matter?NOM?had little influence on removal of Cr???.The pseudo-second-order equation and the Langmuir isotherms model can well describe the adsorption process,the adsorption quantity can reach 98.8 mg/g.Also,the adsorbent has excellent magnetic separation performance and reusability even after six adsorption-desorption cycles,indicating that PEI/MWCNTs@Fe₃O₄ could be used as an efficient new adsorbent for removal of Cr???from industrial wastewater.It's worth mentioning that adsorption of Cr???enhanced,but adsorption of MO decreased in the MO-Cr???binary experiments.Moreover,after 3 cycles of adsorption-desorptin,pollutants still has good removal rates,the regeneration and stability test demonstrated the PEI/MWCNTs@Fe₃O₄ have no significant loss in the model textile effluent.PEI/MWCNTs@Fe₃O₄ can be used for removing dyes and heavy metals in practical printing and dyeing wastewater.