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Extremely Efficient Decomposition of Ammonia N to N2 Using ClO from Reactions of HO and HOCl Generated in Situ on a Novel Bifacial Photoelectroanode

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journal contribution
posted on 22.05.2019, 00:00 by Yan Zhang, Jinhua Li, Jing Bai, Linsen Li, Shuai Chen, Tingsheng Zhou, Jiachen Wang, Ligang Xia, Qunjie Xu, Baoxue Zhou
The conversion of excess ammonia N into harmless N2 is a primary challenge for wastewater treatment. We present here a method to generate ClO directionally for quick and efficient decomposition of NH4+ N to N2. ClO was produced and enhanced by a bifacial anode, a front WO3 photoanode and a rear Sb–SnO2 anode, in which HO generated on WO3 reacts with HClO generated on Sb–SnO2 to form ClO. Results show that the ammonia decomposition rate of Sb–SnO2/WO3 is 4.4 times than that of WO3 and 3.3 times than that of Sb–SnO2, with achievement of the removal of NH4+ N on Sb–SnO2/WO3 and WO3 being 99.2 and 58.3% in 90 min, respectively. This enhancement is attributed to the high rate constant of ClO with NH4+ N, which is 2.8 and 34.8 times than those of Cl and HO, respectively. The steady-state concentration of ClO (2.5 × 10–13 M) is 102 times those of HO and Cl, and this is further confirmed by kinetic simulations. In combination with the Pd–Cu/NF cathode to form a denitrification exhaustion system, Sb–SnO2/WO3 shows excellent total nitrogen removal (98.4%), which is more effective than WO3 (47.1%) in 90 min. This study provides new insight on the directed ClO generation and its application on ammonia wastewater treatment.