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Download fileBipolar Membrane Electrodialysis for Ammonia Recovery from Synthetic Urine: Experiments, Modeling, and Performance Analysis
journal contribution
posted on 12.10.2021, 17:35 authored by Yujiao Li, Ruoyu Wang, Shaoyuan Shi, Hongbin Cao, Ngai Yin Yip, Shihong LinRecovering nitrogen from source-separated
urine is an important
part of the sustainable nitrogen management. A novel bipolar membrane
electrodialysis with membrane contactor (BMED–MC) process is
demonstrated here for efficient recovery of ammonia from synthetic
source-separated urine (∼3772 mg N L–1).
In a BMED–MC process, electrically driven water dissociation
in a bipolar membrane simultaneously increases the pH of the urine
stream and produces an acid stream for ammonia stripping. With the
increased pH of urine, ammonia transports across the gas-permeable
membrane in the membrane contactor and is recovered by the acid stream
as ammonium sulfate that can be directly used as fertilizer. Our results
obtained using batch experiments demonstrate that the BMED–MC
process can achieve 90% recovery. The average ammonia flux and the
specific energy consumption can be regulated by varying the current
density. At a current density of 20 mA cm–2, the
energy required to achieve a 67.5% ammonia recovery in a 7 h batch
mode is 92.8 MJ kg–1 N for a bench-scale system
with one membrane stack and can approach 25.8 MJ kg–1 N for large-scale systems with multiple membrane stacks, with an
average ammonia flux of 2.2 mol m–2 h–1. Modeling results show that a continuous BMED–MC process
can achieve a 90% ammonia recovery with a lower energy consumption
(i.e., 12.5 MJ kg–1 N). BMED–MC shows significant
potential for ammonia recovery from source-separated urine as it is
relatively energy-efficient and requires no external acid solution.
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sustainable nitrogen managemente ., 12bmed – mc8 mj kgone membrane stackmultiple membrane stacksbipolar membrane electrodialysisspecific energy consumptionlower energy consumptionexternal acid solutionaverage ammonia fluxammonia transports acrossmodeling results show5 mj kgpermeable membranemembrane contactorrelatively energyenergy requiredacid streamammonia strippingscale systemsscale systemimportant partdirectly usedcurrent densityapproach 25ammonium sulfate