Evaluation of the Performance of Different Anodes in the Electrochemical Oxidation of Ammonia
2015
He, Shi-Long | Huang, Qing | Zhang, Yong | Nie, Yu-Lun
Three commercial electrodes, Ta-Ir/TiO₂, Rh-Ir/TiO₂, and PbO₂/TiO₂, were used as electrochemical anodes, and their performance was evaluated by the electrochemical oxidation of ammonia at neutral pH in a continuous electrochemical quadrangular reactor. Based on the cyclic voltammetry scans and volt-ampere relation analysis, in direct oxidation, the oxygen evolution from H₂O₂decomposition was completely inhibited, and more•OH radicals could be then generated over PbO₂/TiO₂and in the presence of powder activated carbon (PAC). PbO₂/TiO₂can be indicated as an appropriate for the direct electrooxidation of ammonia in an unpacked bed reactor. While the efficiency for direct oxidation of ammonia was similar for the three anodes in a PAC packed reactor due to the presence of PAC could avoid short circuit and enhance electric efficiency. In indirect oxidation mediated by active free chlorine, Rh-Ir/TiO₂was the most effective in ammonia removal when chloride was present in the reaction system, and the disappeared ammonia was mainly transferred to N₂, and only a small part was converted into nitrate (there was no nitrite detected during the reaction). The results indicated that Rh-Ir/TiO₂had the highest oxidation capability for ammonia compared with Ta-Ir/TiO₂and PbO₂/TiO₂. Hence, Rh-Ir/TiO₂based on a PAC packed bed reactor provides an alternative for the treatment of ammonia wastewater with high chloride concentration.
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