碱性介质电催化体系活性氧的生成及其光谱学研究

亚熔盐液相氧化技术可在相对低温下实现难分解两性金属矿物的高效转化，基于此进一步提出了碱性介质电化学活性氧协同强化新方法。利用紫外-可见光光谱和电子自旋共振波谱等手段对电催化体系活性氧的生成与转化机理进行了系统解析。通过阴极电催化的作用，在电极表面定向进行两电子氧气还原反应，原位产生大量的活性氧组分。研究发现过渡金属离子与两电子氧气还原产物HO-₂之间的“自诱发”效应，可生成具有更高氧化活性的羟基自由基，大幅促进两性金属转化过程，实现了碱性介质电化学高级氧化过程。利用紫外-可见光光谱检测到电化学体系活性氧催化氧化低价两性金属氧化物(Cr₂O₃和V₂O₃)的转化过程。与此同时，根据标准自由能变化的热力学数据计算可知，V₂O₃比Cr₂O₃更易在活性氧存在的条件下发生溶出反应。采用电子自旋共振波谱(ESR)对电催化体系内的羟基自由基进行检测，结果表明由V₂O₃引发的电化学-类Fenton反应激发产生的羟基自由基ESR信号比Cr₂O₃信号强。利用猝灭剂实验验证了具有高氧化电位的羟基自由基可以对两性金属液相氧化起到促进作用。该研究为碱性介质电化学矿物溶出实际反应提供理论参考。

Electrocatalytic Generation and Spectroscopic Investigation of Reactive Oxygen Species in Alkaline Media

Liquid oxidation techniques by sub-molten salt media for the effective extraction of amphoteric metal from refractory minerals have been developed. An innovative synergistic process by electrochemical oxidation and reactive oxygen species (ROS) intensify was further proposed. In the present study, the mechanism of ROS formation and conversion in the electrocatalytic process was systematically revealed by UV-Vis spectra and electron spin resonance (ESR) measurement. The reactive species were in-situ generated by two-electron oxygen reduction reaction (ORR) at the cathode surface. The ·OH was produced from the self-induced reaction between amphoteric metal ions and HO-₂, which was beneficial for the oxidation dissolution process and considered as an alkaline electrochemical advanced oxidation process. The catalytic oxidation process of low-valance amphoteric metal oxides (Cr₂O₃ and V₂O₃) by ROS was illustrated by UV-Vis spectra. Furthermore, V₂O₃ was more easily dissolved than Cr₂O₃ with the presence of ROS according to the thermodynamic data of standard free energy change. The ·OH in the electrochemical system was detected by the ESR technique. The ESR signal of ·OH catalyzed by V₂O₃ was more remarkable than that of Cr₂O₃. The quenching experiment result proved that ·OH with high standard oxidation potential played a promoting role in the liquid oxidation process. The present investigation provides further standing for the electrochemical oxidative dissolution in alkaline media.