Are Hansen solubility parameters relevant in predicting the post-treatment effect on polyamide-based TFC membranes?

Area of Science:

• Materials Science
• Chemical Engineering
• Membrane Science

Background:

• Polyamide-based thin film composite (TFC) membranes are crucial for nanofiltration (NF) and reverse osmosis (RO).
• Solvent post-treatment is explored to enhance TFC membrane performance, but its effectiveness is not fully understood.
• Hansen Solubility Parameters (HSP) are proposed to predict membrane-solvent interactions.

Purpose of the Study:

• To investigate the impact of solvent post-treatment on commercial NF and RO TFC membranes.
• To evaluate the correlation between Hansen Solubility Parameters (HSP) and membrane performance enhancement.
• To determine optimal post-treatment conditions for improved pure water permeance (PWP) and salt rejection.

Main Methods:

• Utilized Response Surface Methodology (Box-Behnken design) to optimize post-treatment variables.
• Tested aqueous solutions of dimethylformamide, acetonitrile, and ethanol with varying concentrations and treatment times.
• Measured Na2SO4 rejection and pure water permeance (PWP) as key performance indicators.

Main Results:

• Post-treatment effects were not solely governed by the disparity in Hansen Solubility Parameters (Ra).
• Acetonitrile (80% v/v, 30s) significantly enhanced PWP (124.5%) and reduced Na2SO4 rejection (3.5%) in NF membranes.
• RO membranes showed negligible changes under the same post-treatment conditions.

Conclusions:

• Hansen Solubility Parameters (HSP) alone are insufficient to predict solvent post-treatment outcomes for polyamide TFC membranes.
• Discrepancies in NF and RO membrane responses suggest limitations of the HSP model and potential interface effects.
• Further research is needed to understand complex solvent-membrane interactions and optimize post-treatment strategies.