氯自由基介导的BDD电极选择性氧化脱氮

为实现氨氮的高效选择性转化,设计了一个氯自由基介导的电化学体系。该电化学体系以稳定性好、氧化能力强的掺硼金刚石(BDD)电极为阳极,以Pd-Cu修饰的泡沫镍材料(Pd-Cu/NF)为阴极,以氯化钠为电解质,对BDD电极选择性电催化氧化性能与机理进行了研究。结果表明：在4.0 V电压下,体系中的Cl⁻原位可转化成氯自由基(Cl·),Cl·可选择性地将氨氮转化为N₂和少量$ {rm{NO}}_3^ - $,副产物$ {rm{NO}}_3^ - $在Pd-Cu/NF阴极被高效还原为N₂;分别探究了阴极材料、电场强度、电极间距、溶液pH和电解质种类对氨氮转化性能的影响。通过电子顺磁共振和自由基捕获实验,证实了Cl·在氨氮转化过程中发挥了重要作用。在最优条件下,可实现40 min内100%的氨氮转化率和25 mg·L⁻¹的N₂生成量,以上研究结果可为解决水体中氨氮的污染问题提供参考。

Chlorine radical mediated selective oxidation denitrification by BDD electrode

An electrochemical oxidation system mediated by chlorine radical was designed to achieve the efficient selective transformation of ammonia nitrogen. In the electrochemical system, a boron-doped diamond (BDD) electrode with good stability and strong oxidation ability was used as anode, Pd-Cu-modified nickel foam material (Pd-Cu/NF) and sodium chloride were used as cathode and electrolyte, respectively. The results showed that at a voltage of 4.0 V, Cl− in the system could in situ convert into chlorine radical (Cl·), Cl· could selectively convert ammonia nitrogen into N2 and a small amount of $ {rm{NO}}_3^ - $, and the latter one as a by-product could be efficiently reduced to N2 at the Pd-Cu/NF cathode. In addition, the effects of cathode material, electric field intensity, electrode distance, solution pH and electrolyte type on the ammonia nitrogen conversion were studied. Electron paramagnetic resonance and free radical capture experiments confirmed that Cl· played an important role in ammonia nitrogen conversion. Under the optimal conditions, 100% ammonia nitrogen conversion rate and N2 production amount of 25 mg·L−1 could be achieved within 40 min, which can provide a new idea for solving the problem of ammonia nitrogen pollution in waterbody.