Preparation And Characterization Of PDCPA Composite Membranes

Currently, self-polymerization and composite technology has become a hotspot research,which based on DOPA biomimetic adhesive. DOPA molecule containing catechol and aminofunctional groups, in the alkaline solution and the presence of oxygen, DOPA can beself-polymerization in the surface, and formed the Polydopamine layer which has high adhesion.We use this technology to prepare PS/PDOPA composite UF membranes and composite NFmembranes.Firstly, we prepare PS/PDOPA composite UF membranes; Secondly, as the superior adhesionof DOPA, PS/D-PDOPA composite NF membrane can be prepared by two composite densificationof the composite UF membranes; Thirdly, DOPA contains catechol group, which can occurMichael addition reaction with the amino group in PEI, PS/PDOPA/PEI composite NF membranecan be prepared by PEI grafting on composite UF membranes; Lastly, To improve theperformance of the composite NF membranes, cross-linking is reacted on the PS/PDOPA/PEIcomposite NF membranes, and PS/PDOPA/PEIc composite NF membranes are prepared.When we prepare PS/PDOPA composite UF membranes, we study the performance ofdifferent solvents （such as Tris-HCl buffer solution, phosphate buffer solution, deionized water,seawater and artificial seawater）, and the redox environment （the oxidizing NaIO₄, reductive Znpowder）; When we prepare PS/D-PDOPA composite NF membranes, we study the performance ofdifferent solvents （PBS buffer solution, seawater and artificial seawater）; When we studyPS/PDOPA/PEI composite NF membranes, artificial sea water is treated as the solvent, and theconditions, such as the concentration of PEI, PEI soaking time and temperature are alsoinvestigated; When we study PS/PDOPA/PEIc composite NF membranes, the PEI soakingcondition is1000mg·L^-1, soak for4h at60℃, and the concentration of ECH, GA, and thesoaking time are also investigated. The conclusions are:1、PS/PDOPA composite UF membranes: composite membrane prepared by seawater obtained maximum load, which increased44.46%than base membrane; While compositemembrane prepared by PBS buffer solution obtained the maximum of elongation at break, whichincreased61.08%than base membrane; The hydrophilicity and anti-pollution performance ofcomposite UF membranes are improved in varying degrees than base membrane, as well aspermeable stablity at long-running, and anti-acid stability; HA rejection rate of the compositemembrane prepared by PBS buffer solution was99.99%, increased21.60%than the basemembrane, and the following are artificial seawater, Tris-HCl buffer solution and seawater, whichhaving a substantially the same HA rejection rate, while the HA rejection rate of deionized waterwas the lowest; The HA rejection rate of composite membrane added of Zn powder is declined,while the HA rejection rate of composite membrane added of NaIO₄is improved.2、PS/D-PDOPA composite membranes: L_p of PS/D-PDOPA composite NF membraneprepared by three solvents is18.59,15.85,23.46L·h^-1·m（-2） MPa^-1; contact angles are47.32°,40.36°,42.98°; at a pressure of0.8MPa, the rejection for2000mg·L^-1MgCl₂is95.77%,98.02%and87.62%, respectively, with a flux of9.39,6.58and19.60L·h^-1·m（-2） MPa^-1; The roughness ofPS/D-PDOPA composite NF membrane prepared by seawater is5.18nm, which proves thatsurface defects of such composite NF membrane are small.3、PS/PDOPA/PEI composite membranes: At a pressure of0.8MPa, three conditions arechoiced as the better preparation conditions, which had the highest rejection for2000mg·L^-1MgCl₂. They are1000mg·L^-1, soak for4h at60℃,1000mg·L^-1, soak for4h at40℃,2000mg·L^-1, soak for4h at40℃, correspondingL_p are48.20,43.66,44.93L·h^-1·m（-2） MPa^-1,respectively. At a pressure of0.8MPa, the rejection for2000mg·L^-1MgCl₂, NaCl, MgSO₄andNa₂SO₄are83.50%,39.69%,57.82%and26.73%, respectively, with a flux of25.20,18.28,15.40and14.03L·h^-1·m（-2）.4、PS/PDOPA/PEIc composite membranes: The contact angles of these two PS/PDOPA/PEIcare48.26°,45.92°, respectively; The roughness are21.09nm,27.73nm, respectively; And L_p are38.42,41.39L·h^-1·m（-2） MPa^-1, respectively; At a pressure of0.8MPa, the rejection ofPS/PDOPA/PEIc with ECH for2000mg·L^-1MgCl₂, CaCl₂, NaCl, MgSO₄and Na₂SO₄are92.37%,91.32%,51.40%,62.29%,15.74%, respectively, and the flux are12.84,10.49,12.04,11.75,9.43L·h^-1·m（-2）, respectively; While the rejection of PS/PDOPA/PEIc with GA for2000mg·L^-1MgCl₂, CaCl₂, NaCl, MgSO₄and Na₂SO₄are92.67%,91.13%,51.53%,61.49%,24.82%, respectively,and the flux are21.86,15.28,13.59,13.30,11.93L·h^-1·m（-2）, respectively.