Mechanism exploration of ammonium oxidation behaviors for improved ammonia nitrogen removal efficiency in electrochemically coupled reverse osmosis membrane systems
To enhance the removal rate of ammonia nitrogen in domestic wastewater by reverse osmosis(RO)membrane systems,a novel electrochemically coupled RO membrane system was designed.Compared with conventional RO systems,this system featured an innovative conductive treatment of the feed spacer and permeate carrier,which were connected to the negative and positive poles of an external power supply,respectively.The results indicated that with an applied voltage of 4 V,the ammonia nitrogen removal rate in the RO membrane system increased from 94.51％without applied voltage to 99.91％.This enhanced ammonia nitrogen removal rate was attributed not only to the drag force of the reverse electric field on ammonium ions but also to ammonium oxidation behaviors.Through cyclic voltammetry,a series of electrolysis experiments,electron paramagnetic resonance,and radical quenching experiments,ammonium oxidation behavior was demonstrated to occur at the permeate carrier anode under high applied voltages in the electrochemically coupled membrane system.The mechanism was identified as the chlorine-mediated indirect ammonium oxidation reaction with the breakpoint chlorination reaction pathway.Additionally,in the chlorine-mediated indirect ammonium oxidation process,the active species were found to be active chlorine rather than chlorine radicals.These findings revealed the crucial role and mechanism of ammonium oxidation behavior in the enhanced removal rate of ammonia nitrogen in electrochemically coupled RO membrane systems,thereby providing new theoretical foundations for future wastewater resource recovery technologies.Furthermore,this system offers a simple design,exceptional scalability,and low maintenance costs,highlighting its significant potential for practical applications.
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维普
