Composite nanofiltration membrane with asymmetric selective separation layer for enhanced separation efficiency to...

Area of Science:

• Materials Science
• Environmental Engineering
• Chemical Engineering

Background:

• Effective nanofiltration membranes are essential for treating industrial wastewater, particularly from the dye and textile sectors.
• Existing membranes often face challenges with separation efficiency and fouling.
• Developing high-performance membranes is crucial for improving wastewater treatment processes.

Purpose of the Study:

• To design and fabricate a novel thin-film composite nanofiltration membrane with improved perm-selectivity and antifouling properties.
• To create an asymmetric separation layer for enhanced performance in treating dye and textile industry wastewaters.
• To investigate the impact of a secondary surface reaction on membrane characteristics.

Main Methods:

• Interfacial synthesis of a nascent composite membrane with a loose poly(piperazine amide) (PA) separation layer.
• Secondary surface reaction using an aqueous tannic acid (TA) solution to form a compact TA skin.
• Membrane characterization to verify the formation of a covalent bond via esterification and assess structural integrity.
• Performance evaluation including pure water permeability, dye rejection, and antifouling properties.

Main Results:

• Successful fabrication of a PA/TA asymmetric separation layer with a compact TA skin on a loose PA body.
• The PA/TA membrane demonstrated a 28.0% higher pure water permeability compared to a symmetric PA membrane with similar glucose rejection (82.0%).
• Significantly enhanced water fluxes for anionic dyes (alizarin yellow R, sunset yellow, Congo red) ranging from 36.1% to 50.3%.
• Reduced steady-state flux declines (23.5% to 43.4%) and improved antifouling properties were observed.

Conclusions:

• The developed PA/TA thin-film composite nanofiltration membrane exhibits superior perm-selectivity and antifouling capabilities.
• The asymmetric structure created by the secondary tannic acid treatment is key to enhanced performance.
• This novel membrane shows significant potential for efficient treatment of dye and textile industry wastewaters.