Understanding of chemical reactions induced by argon plasma in contact with sodium halide solutions: importance of surface properties for plasma?liquid interactions
Understanding of chemical reactions induced by argon plasma in contact with sodium halide solutions: importance of surface properties for plasma?liquid interactions
复制标题
了解氩等离子体与卤化钠溶液接触引起的化学反应：表面特性对于等离子体-液体相互作用的重要性
DOI：
10.1088/1361-6463/ab5ebe
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Koichi Yasuoka
中科院分区：
文献类型：
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作者：
Kosuke Tachibana;Koichi Yasuoka
等离子体与液体的接触在水净化、纳米粒子合成、生物医学应用等领域得到了广泛的研究。然而，等离子体-液体相互作用，即发生在等离子体-液体界面的物理和化学现象，尚未完全理解。为了加深我们对相互作用的理解，在本研究中，我们研究了等离子体产生的特定短寿命活性物质在等离子体-液体界面与溶质发生反应的地方。我们采用氯离子（Cl−）、溴离子（Br−）和碘离子（I−）作为反应区域的指示剂，因为已知这些卤化物离子按I−、Br−和Cl−的顺序位于气液界面附近。将直流氩等离子体辐照于2.1 mol l−1氯化钠（NaCl）、溴化物（NaBr）和碘化物（NaI）溶液中，600 s等离子体辐照后未检测到氯，30 s等离子体辐照后可检测到溴和碘。为了解释卤素（氯、溴和碘）生成的不同特征，我们假设，由于等离子体产生的短寿命活性物质的表面活性和低动能，它们只能在水表面的最上层与溶质反应，这是一个与气相接触的液体原子单层。根据我们的建议，我们可以说，Cl -不能与活性物质反应成氯，因为这些离子被排除在最上层之外；相反，Br -和I -能够分别反应成溴和碘，因为其中一些离子位于最上层。为了更好地理解等离子体-液体相互作用，本文还讨论了等离子体诱导的化学反应与传统电解的区别。
Plasma in contact with liquid is widely studied in research involving water purification, nanoparticle synthesis, biomedical applications, and so on. However, plasma–liquid interactions, which are physical and chemical phenomena occurring at a plasma–liquid interface, have not yet been fully understood. To deepen our understanding of the interactions, in this study, we have investigated where specifically short-lived active species generated by plasma react with solutes at the plasma–liquid interface. We adopted chloride (Cl−), bromide (Br−) and iodide (I−) ions as indicators of the reaction region of the short-lived active species, because it is known that these halide ions are located closer to the gas–liquid interface in an order of I−, Br−, and Cl−. A DC argon plasma was irradiated to 2.1 mol l− 1 sodium chloride (NaCl), bromide (NaBr), and iodide (NaI) solutions, and we found that chlorine was not detected after 600 s plasma irradiation while bromine and iodine were observed after 30 s plasma irradiation. To explain the different characteristics of halogen (chlorine, bromine, and iodine) generation, we postulated that, because of the surface activity and low kinetic energy of the short-lived active species generated by plasma, they could react with the solutes only at the topmost layer of the water surface, which is an atomic monolayer in liquid in contact with the gas phase. Based on our suggestion, we could say that the Cl− is unable to react with the active species into the chlorine because the ions were excluded from the topmost layer, and that, by contrast, the Br− and I− were able to react into the bromine and iodine, respectively, because some of these ions were located in the topmost layer. For understanding the plasma–liquid interactions more, a difference between chemical reactions induced by plasma and conventional electrolysis has been also discussed.