Mechanism and efficiency of ammonia absorption in dual-phase hollow fiber membrane contactors: A comparative analysis of liquid-liquid vs. gas-Liquid interfacial dynamics

Liquid-liquid membrane contactors (LLMC) and Gas-liquid membrane contactors (GLMC) have emerged as promising candidates for energy-efficient ammonia recovery, leveraging their unique interfacial transport characteristics and superior thermal/chemical stability. However, critical knowledge gaps persist in their mass transfer resistance and operational parameter sensitivity during ammonia absorption. This study conducts a systematic comparative analysis of LLMC and GLMC systems through integrated mass transfer modeling and experimental validation under equivalent operating conditions. Results showed that higher pH value is beneficial to the increase of ammonia absorption rate and the reduction of ammonia mass transfer in the LLMC system, whereas the GLMC shows stronger dependence on the feed flow velocity. The long-term stability testing demonstrates that the LLMC was more suitable for the treatment of wastewater with higher ammonia concentration, whereas the GLMC had an advantage for treating wastewater with lower ammonia concentration particularly under the intermittent operation. This work provides guidance in selection criteria for membrane contactor implementation, advancing the development of precise-controlled ammonia recovery systems in wastewater treatment. • Two types of membrane contactors have been systematically compared • LLMC was more sensitive to the pH value of feed solution • The feed flow velocity had more influences on GLMC • A critical absorbent concentration threshold existed in LLMC and GLMC • LLMC was more suitable for wastewater with higher ammonia concentration