Study On Improving Hydrophilicity Of Polysulfone Separation Membranes By Blending With Amphiphilic Polyamide

Polysulfone(PSf)membranes have been widely applied in microfiltration and ultrafiltration processes due to their excellent properties,such as chemical inertness,good mechanical and anti-compaction properties,strong chemical and thermal stabilit ies.However,its hydrophobic nature often causes serious membrane fouling and drastically decreased membrane permeability.In this study,an amphiphilic sulfobetaine polyamide with sulfobetain as end groups and polyamide as backbone was synthesized as a novel pore formation additive for the preparation of antifouling polysulfone membranes.This amphiphilic additive showed good solubility and compatibility w ith membrane casting solut ion due to its self-assembly behavior in organic solvent.The membrane properties were characterized by common methods,including XPS,SEM,porosity,contact angle,pure water flux,BSA rejection,flux recovery rate,BSA adsorption,antibacterial performance,thermal stability and mechanical properties,and the effects of hydrophobic chain length and additive dosage on membrane morphology,hydrophilicity,permeability,antifouling and mechanical properties were systematically studied in order to determine the role of the additive.Membranes with enhanced hydrophilicity,porosity and antifouling property were achieved as a result of the enrichment of zwitterionic moieties on membrane surfaces during phase inversion process.Consequently,under optimal conditions the pure water flux increased from 68.2 L/(m2 h)to a maximum of 205.2 L/(m2 h)without sacrifice the high protein rejection ratio,and the flux recovery ratio can be promoted from 68.3% to 86.4%.The excellent fouling resistance imparted by the zwitterionic moieties was further demonstrated by significantly reduced protein/bacterial adhesion.More importantly,the blend membrane exhibited remarkable thermal stability and tensile strength.Investigations showed consistent high-performance in separation after treatment at 90 oC.Among all the blend membranes,sulfobetaine polyamide with medium hydrophobic chain exhibited best performance in water permeability and protein resistance.The structure of additive blended in PSf membrane was changed from curve to straight,and the influence of the additive structure to the properties of the polysulfone membrane was investigated.When the structure of sulfobetaine polyamide was changed from curve to straight,the property of PSf membrane had little change,such as permeation separation property,hydrophilic property,antifouling property and thermal stability.However,the mechanical strength of the membrane imcreased obvious.The increase could be increased from 1.8 MPa to 4.6 MPa.This study provided a facile method for the preparation of a wide range of membranes with substantially promoted performances such as separation,thermal resistance,mechanical strength,antibacterial,etc.