Electrochemical process combined with UV light irradiation for synergistic degradation of ammonia in chloride-containing solutions.
An electrochemical process combined with ultraviolet light irradiation (UPE) using nonphotoactive dimensionally stable anodes (DSAs) like RuO2/Ti and IrO2/Ti in the presence of chlorides was investigated for ammonia degradation. In this process, the in situ electrogenerated active chlorine and in situ photogenerated chlorine radicals were responsible for the high efficiency of ammonia degradation. More than 97% of ammonia was converted to nitrogen and a significantly synergistic effect was confirmed. Compared with the single electrochemical (E) and photochemical (P) process, the degradation rates of ammonia and the average current efficiencies (ACEs) of the UPE process increased by 1.5 and 1.7 times using RuO2/Ti and IrO2/Ti electrodes, respectively. On the basis of the linear voltammograms, Electrochemical Impedance Spectra (EIS), UV-vis spectra, Electron Spin Resonance (ESR) analysis and a series of experiments designed, the synergistic mechanism was investigated. In addition, this unique process succeeded in transferring the reaction from the electrode surface to the bulk of the solution compared with the conventional photoelectrocatalytic (PEC) process. The loss of chloride decreased from 21.0% to 7.2% and the recycle of chloride was accelerated in the UPE process. Finally the effects of initial pH, current density and ammonia-nitrogen concentration were discussed. Results indicated that pH and ammonia concentration exerted little influences on the degradation rates and current density was the "rate-determining" factor.
Xiao
Shuhu
S
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Graduate School, Chinese Academy of Sciences, Beijing 100039, China.
Qu
Jiuhui
J
Zhao
Xu
X
Liu
Hujuan
H
Wan
Dongjin
D
D000641:Ammonia / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry; D004560:Electricity; D004563:Electrochemistry / Q000379:methods*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007753:Laboratories; D009584:Nitrogen / Q000737:chemistry; D012996:Solutions; D013431:Sulfates / Q000737:chemistry; D014466:Ultraviolet Rays
D002712:Chlorides; D012996:Solutions; D013431:Sulfates; D002713:Chlorine; D000641:Ammonia; D009584:Nitrogen