| With the increasing severity of water pollution,single pollution is gradually transitioning to multiple pollution,making pollution management more difficult.In this thesis,we successfully prepared a stable PDA/PEI-TPU nanofiber membrane with cationic properties through a simple and efficient green synthesis process.Specifically,using electrospun thermoplastic polyurethane(TPU)nanofiber membrane as the substrate and polyethyleneimine(PEI)as the modified monomer,and the oxidative selfpolymerization cross-linking ability of polydopamine(PDA)under weak alkaline aerobic environment was utilized.The morphological structure and chemical composition of PDA/PEI-TPU NFMs were analyzed by various characterizations.To further investigate the adsorption performance of PDA/PEI-TPU NFMs,the endocrine disruptor bisphenol A(BPA),anionic dyes,for example,Congo red(CR),Sunset yellow(SY),Methyl orange(MO)and Eosin y(EY)were used as the target pollutants in this thesis.The adsorption performance and mechanism analysis of PDA/PEI-TPU NFMs on single-and multicomponent pollutants were investigated by means of influence factor experiments(initial pH of solution,adsorbent dosing),adsorption kinetics,adsorption isotherms and cyclic regeneration experiments.The research work and achievements of this thesis are as follows:(1)The results of FTIR,SEM,and XPS characterization demonstrated that PDA/PEI was successfully grafted onto the surface layer of TPU NFMs.Hydrophilicity and zeta potential of the PDA/PEI-TPU NFMs film surface were improved to a great extent.The optimized preparation performance parameters were: the concentration ratio of DA:PEI was 2:2;the deposition time was 48 h.(2)The adsorption processes of BPA on TPU NFMs and PDA/PEI-TPU NFMs were in accordance with the Langmuir model and Pseudo-second-order-model,their maximum adsorption capacities were 78.59 mg/g and 63.39 mg/g,respectively.It was indicated that the modified adsorbents still had a good adsorption performance on BPA.From kinetic adsorption rates,the TPU NFMs were 0.22 g/(mg h)and the PDA/PEI-TPU NFMs were0.37 g/(mg h),the increase in adsorption rates indicated that the modified adsorbent could enter the membrane surface and interior more rapidly due to the enhanced hydrophilicity.In addition the main mechanisms of BPA adsorption including hydrogen bonding between N and O atoms on the adsorbent surface and the H atoms in BPA,the force of p-pconjugation,and the hydrophobic forces.(3)The PDA/PEI-TPU NFMs showed excellent adsorption capacity for CR,SY,EY and MO.Compared with CR,SY,MO and EY were more sensitive to pH,and the adsorption capacity decreased with increasing p H.The adsorption processes of the dyes were all consistent with the Langmuir model and Pseudo-second-order-model,the maximum adsorption capacities of CR,SY,EY,and MO were 262.95 mg/g,157.55 mg/g,117.56 mg/g,and 134.28 mg/g.From the analysis of the FT-IR results and the structural differences between the dye molecules,it can be concluded that electrostatic interactions are considered as the main mechanism of SY,MO,and EY adsorption.However,the synergistic effect of hydrogen bonding and electrostatic adsorption may be the key to the good adsorption of PDA/PEI-TPU NFMs on CR over a wide p H range.(4)In the binary composite system,the coexistence of BPA and dye affects the adsorption process.In the CR-BPA mixed solution,due to the existence of the same adsorption sites of CR and BPA,they compete with each other,leading to a decrease in adsorption capacity compared with the single-component solution;In the mixed EY-BPA solution,the hydrogen bonding between the O atom in EY and the H atom in BPA,as well as the force of p-p conjugation between the benzene rings enabled the mutual bridging between EY and BPA,which promoted promoting the adsorption of both;While in the mixed solution of SY-BPA,the two adsorptions were independent of each other.The mixture of the three dyes and BPA showed different trends,which provided a reference for the treatment of dye and BPA complex pollution. |
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