| The addition of Mo S2 nanosheets into the polymer nanofiltration functional layer can bring additional water transport channels to the nanofiltration functional layer,thereby enhancing the permeation performance of nanofiltration membranes.In this paper,molybdenum disulfide nanosheets（Mo S2）with lateral dimensions ranging from100 to 600 nm were prepared by liquid-phase ultrasonic exfoliation.Mo S2 nanosheets were successfully embedded into the thin-layer composite nanofiltration membrane functional layer,a highly negatively charged high-throughputβ-CD/Mo S2 loose polyurethane nanofiltration membrane（DSPU）,which can efficiently retain small organic molecules such as dyes,and a highly positively charged PEI/TA-Mo S2polyurea composite nanofiltration membrane（TSPU）that efficiently intercepts heavy metal ions.were constructed,respectively.In this paper,the preparation conditions of the functional layer of the composite nanofiltration membrane were optimized,the properties and structural parameters of the membrane interface were confirmed,and the action mechanism of Mo S2 nanosheets in the separation process of the nanofiltration membrane was analyzed.The main research contents are as follows:（1）With the help of the hydrogen bonding between the abundant hydroxyl functional groups outside theβ-CD ring and the Mo S2 nanosheets,the Mo S2 nanosheets were dispersed in theβ-CD aqueous solution,using toluene-2,4-diisocyanate（TDI）/n-hexane solution as the organic phase,a high-flux loose polyurethane nanofiltration membrane（DSPU）with high negative charge and good hydrophilicity was prepared by interfacial polymerization.Through infrared spectroscopy,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,EDS spectroscopy and other instrumental analysis techniques,the interface properties of DSPU were characterized,and the existence and distribution of Mo S2 nanosheets in DSPU were confirmed.The optimal composition ofβ-CD and Mo S2 in the water phase was optimized based on pure water flux,salt and dye rejection rates.The optimized DSPU-1.2-0.006 membrane has a pure water flux of 78.44 L/m2·h·bar,which is 2.4times higher than that of the DPU membrane without Mo S2,and can retain small molecules of highly negatively charged dyes with a molecular weight greater than 416g/mol.The correlation between the chemical composition ofβ-CD,Mo S2 nanosheet spacing ofβ-CD,interfacial properties and the interfacial properties,functional layer structure,separation performance of DSPU was analyzed.DSPU has long-term stable operation and good anti-pollution properties,and has potential application performance in the field of dye desalination and separation and purification.（2）Mo S2 nanosheets were dispersed in polyethyleneimine（PEI）aqueous solution by virtue of the adhesion effect of TA,and condensed with toluene-2,4-diisocyanate（TDI）interface to prepare positively charged TA-Mo S2-doped polyurea NF film（TSPU）.The interfacial properties of TSPU and the distribution behavior of Mo S2nanosheets were characterized,the concentration of organic phase and aqueous phase during the preparation of functional layer was optimized,and the influence of the relative content of TA and Mo S2 in the aqueous phase on the permeability of TSPU was investigated.The optimized TSPU-0.015 membrane showed an efficient rejection of Mg SO4(R（Mg SO4）=93.18%)and increased the salt flux J（Mg SO4）to 34.5 L/m2·h,which was 2.88 for TSPU-0 times,and showed better retention behavior for high-valent metal ions than monovalent metals.Combined with the hydration radius and hydration energy of heavy metal ions,the removal performance of TSPU for several heavy metal ions with different valence and charge was studied.TSPU has long-term stable operation and excellent anti-pollution properties,showing wide application potential in the fields of inorganic salt separation and heavy metal pollution. |
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