Hierarchical-Porous Gas-Permeable Membrane toward Efficient and Robust Ammonia Recovery

Area of Science:

• Membrane Science and Technology
• Environmental Engineering
• Chemical Engineering

Background:

• Ammonia recovery from wastewater is crucial for resource reuse and pollution control.
• Hydrophobic gas-permeable membranes (GPMs) face a trade-off between ammonia permeability and antiwettability.
• Existing GPMs limit efficient ammonia recovery from complex wastewater streams.

Purpose of the Study:

• To design and fabricate a hierarchical-porous GPM (HGPM) that overcomes the permeability-antiwettability trade-off.
• To establish a transfer model for ammonia diffusion across the HGPM layers.
• To evaluate the performance of HGPMs in real wastewater treatment.

Main Methods:

• Facile fabrication of a tailored hierarchical-porous GPM (HGPM).
• Development of a membrane transfer model to elucidate ammonia diffusion pathways.
• Experimental evaluation of HGPMs using alkaline/acidic liquids and real anaerobic digestate wastewater.
• Measurement of mass transfer coefficient, liquid entrance pressure, and ammonia recovery flux.

Main Results:

• The HGPM exhibited a superior mass transfer coefficient of 3.3 × 10^-5 m/s due to molecular diffusion.
• Achieved high liquid entrance pressure (182 kPa), indicating excellent wetting resistance.
• HGPMs demonstrated a 150-200% increase in both ammonia permeability and antiwettability compared to commercial GPMs.
• Robust ammonia recovery flux of 75-80 g N/m² h from real wastewater, three times higher than commercial GPMs.

Conclusions:

• The developed HGPM effectively balances ammonia permeability and antiwettability, breaking previous performance limitations.
• This hierarchical structure facilitates efficient ammonia diffusion and provides robust resistance to wetting.
• The HGPM shows significant potential for scalable and efficient recovery of valuable volatile compounds from complex wastewater, contributing to a circular economy.