Plasma-based water treatment: development of a general mechanistic model to estimate the treatability of different types of contaminants
Plasma-based water treatment: development of a general mechanistic model to estimate the treatability of different types of contaminants
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DOI：
10.1088/1361-6463/50/1/014003
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发表时间：
2017-01
期刊：
影响因子：
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通讯作者：
S. Mededovic Thagard;G. R. Stratton;Fei Dai;C. Bellona;T. Holsen;D. Bohl;Eunsu Paek;E. Dickenson
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文献类型：
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作者：
S. Mededovic Thagard;G. R. Stratton;Fei Dai;C. Bellona;T. Holsen;D. Bohl;Eunsu Paek;E. Dickenson
为了确定基于等离子体的水处理（PWT）最适合的应用类型，通过在具有氩气鼓泡的气体放电反应器（称为增强接触反应器）中处理来评估23种环境污染物的可处理性。在混合物中处理污染物以使反应条件和对流传输限制标准化。根据观察到的去除速率常数（kobs）比较可治疗性。为了表征界面过程对kobs的影响，开发了一种模型，该模型准确地预测了每种化合物的kobs，以及被认为发生在气液界面处或附近的三种一般降解机制中的每一种对kobs的贡献：“次表面”、“表面”和“表面以上”。亚表面反应发生在污染物和溶解的等离子体产生的自由基之间的气液界面的正下方，显著有助于去除缺乏表面活性剂性质的化合物，因此在界面处没有高度浓缩。表面反应发生在污染物和溶解的自由基之间的界面处，显著有助于去除具有高界面浓度的表面活性剂样化合物。污染物的界面浓度计算使用的表面活性参数通过表面张力测量确定。提出了在高能等离子体物质与延伸出界面的化合物的暴露部分之间的等离子体内部中发生表面反应。这种机制在很大程度上解释了含有高度疏水的全氟化碳基团的表面活性剂类污染物的降解，这些基团最有可能从界面突出。对于一些化合物，暴露于等离子体内部的程度得到了新的和以前报道的分子动力学模拟结果的支持。通过回顾三种一般机制的预测贡献，确定表面浓度是决定化合物可处理性的主导因素。这些见解表明，PWT将是最可行的表面活性剂类污染物的处理。
To determine the types of applications for which plasma-based water treatment (PWT) is best suited, the treatability of 23 environmental contaminants was assessed through treatment in a gas discharge reactor with argon bubbling, termed the enhanced-contact reactor. The contaminants were treated in a mixture to normalize reaction conditions and convective transport limitations. Treatability was compared in terms of the observed removal rate constant (kobs). To characterize the influence of interfacial processes on kobs, a model was developed that accurately predicts kobs for each compound, as well as the contributions to kobs from each of the three general degradation mechanisms thought to occur at or near the gas–liquid interface: ‘sub-surface’, ‘surface’ and ‘above-surface’. Sub-surface reactions occur just underneath the gas–liquid interface between the contaminants and dissolved plasma-generated radicals, contributing significantly to the removal of compounds that lack surfactant-like properties and so are not highly concentrated at the interface. Surface reactions occur at the interface between the contaminants and dissolved radicals, contributing significantly to the removal of surfactant-like compounds that have high interfacial concentrations. The contaminants’ interfacial concentrations were calculated using surface-activity parameters determined through surface tension measurements. Above-surface reactions are proposed to take place in the plasma interior between highly energetic plasma species and exposed portions of compounds that extend out of the interface. This mechanism largely accounts for the degradation of surfactant-like contaminants that contain highly hydrophobic perfluorocarbon groups, which are most likely to protrude from the interface. For a few compounds, the degree of exposure to the plasma interior was supported by new and previously reported molecular dynamics simulations results. By reviewing the predicted contributions from the three general mechanisms, it was determined that surface concentration is the dominant factor determining a compound’s treatability. These insights indicate that PWT would be most viable for the treatment of surfactant-like contaminants.