Abstract
Electrochemical oxidation of ammonia was studied with an objective to enhance the selectivity of ammonia to nitrogen gas and to remove the by-products in an undivided electrochemical cell, in which various cathodes and Ti/RuO 2-Pt anode were assembled. In the present study, anodic oxidation of ammonia and cathodic reduction of by-products were achieved, especially with Cu/Zn as cathode. In the presence of 1.0 g/L NaCl the ammonia-N decreased from 100.0 to 0 after 120 min electrolysis at current density of 30 mA/cm2, and no nitrite was detected in the treated solution. The lowest amount of nitrate was formed with Cu/Zn as cathode during electrolysis due to its high reduction ability. Initial pH range from 7 and 9 and uncontrolled temperature were favorable for electrochemical ammonia oxidation and the ammonia oxidation rates with Cu/Zn cathode was higher than that with Ti and Fe cathode. The reduction rate increased with increasing current density in the range of 5 - 50 mA/cm2. As ammonia could be completely removed by the simultaneous oxidation and reduction in this study, it is suitable for deep treatment of ammonia polluted water.
Highlights
Nowadays, around the world most of the water bodies are polluted and some are heavily polluted
In order to completely electrochemical oxidize ammonia and reduce the formation of by-products, cathodic reduction of by-products and anodic oxidation of ammonia were investigated in an undivided cell
Increasing temperature could affect ammonia oxidation rate in several ways, the uncontrolled temperature was favorable for electrochemical oxidation of ammonia
Summary
Around the world most of the water bodies are polluted and some are heavily polluted. Active chlorine effectively removes ammonia from an acidic solution, while the formation of by-products such as chlorate and possibly perchlorate is minimized [12]. Most researchers focused on the effect of anode on ammonia oxidation, seldom has focused on the cathode, which may play an important role on the side products generated during electrochemical ammonia oxidation [17]. In order to completely electrochemical oxidize ammonia and reduce the formation of by-products, cathodic reduction of by-products and anodic oxidation of ammonia were investigated in an undivided cell. The effect of ammonia removal by varies cathodes (Fe, Cu/Zn, Ti) was investigated, with aim to completely destroy ammonia, to reduce the formation of by-products and enhance current efficiency simultaneously. Ti/RuO2-Pt anode was reported to have good oxidation ability, it is employed as anode in the present study
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