Impact of characteristic membrane parameters on the transfer rate of ammonia in membrane contactor application

• Ammonia mass transfer of hydrophobic membranes in a membrane contactor application.
• Characterization of those membranes with the most common membrane parameters.
• Identification of the impact of those membrane characteristics on the mass transfer.
• Presentation of a simple model to predict the free ammonia mass transfer.

Membrane contactors are a promising approach for ammonia removal from waste streams. The objective of this research was to evaluate the potential of common membrane parameters (bubble point, breakthrough pressure, airflow, pore size, contact angle and thickness) to predict the free ammonia mass transfer coefficient of hydrophobic membranes. 22 flat sheet membranes from different manufacturers and of various compositions were included in this study. Their main characteristics as well as the corresponding mass transfer coefficients were determined and statistically analyzed.Mass transfer coefficients between 0.04 × 10−3 and 24.59 × 10−3 m/h were obtained. Using multilinear regression, the relative impact of each parameter on the mass transfer was identified. The developed statistical models successfully explain up to 63.2% of the observed variation. The parameters bubble point, airflow and pore size which are related to the void space of the membrane, as well as membrane thickness, determining the transport length, showed the strongest impact. In the simplest version a statistically significant model, explaining 55.3% of the variation, was obtained using only bubble point and thickness.Obtained results can facilitate the design of suitable membranes with improved ammonia transfer and assist researchers or practitioners to choose appropriate membranes for screening tests.