College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China.
College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China; The Beijing Innovation Center for Engineering Science and Advanced Technology (BIC-ESAT), Peking University, Beijing, 100871, China; Beijing Engineering Research Center for Advanced Wastewater Treatment, Department of Environmental Engineering, Peking University, Beijing, 100871, China.
Chemosphere. 2020 Jun;248:126033. doi: 10.1016/j.chemosphere.2020.126033. Epub 2020 Jan 25.
Degradation of phenols with different substituent groups (including -OCH, -CHO, -NHCOCH, -NO, and -Cl) at boron-doped diamond (BDD) anodes has been studied previously based on the removal efficiency and •OH detection. Innovatively, formations of CO gas and various inorganic ions were examined to probe the mineralization process combined with quantitative structure-activity relationship (QSAR) analysis. As results, all phenols were efficiently degraded within 8 h with high COD removal efficiency. Three primary intermediates (hydroquinone, 1,4-benzoquinone and catechol) were identified during electrochemical oxidation and degradation pathway was proposed. More importantly, CO transformation efficiency ranked as: no N or Cl contained phenols (p-CHO, p-OCH and Ph) > N-contained phenols (p-NHCOCH and p-NO) > Cl-contained phenols (p-Cl and o,p-Cl). Carbon mass balance study suggested formation of inorganic carbon (HCO, CO and HCO) and CO after organic carbon elimination. Inorganic nitrogen species (NH, NO and NO) and chlorine species (Cl, ClO and ClO) were also formed after N- and Cl-contained phenols mineralization, while no volatile nitrogen species were detected. The phenols with electron-withdrawing substituents were easier to be oxidized than those with electron-donating substituents. QSAR analysis indicated that the reaction rate constant (k) for phenols degradation was highly related to Hammett constant (∑σ) and energy gap (E - E) of the compound (R = 0.908), which were key parameters on evaluating the effect of structural moieties on electronic character and the chemical stability upon radical attack for a specific compound. This study presents clear evidence on mineralization mechanisms of phenols degradation at BDD anodes.
先前已有研究报道，在掺硼金刚石（BDD）阳极上，不同取代基（包括-OCH、-CHO、-NHCOCH、-NO 和-Cl）的酚类物质可通过去除效率和•OH 检测进行降解。本研究创新性地考察了 CO 气体和各种无机离子的形成，以结合定量结构-活性关系（QSAR）分析来探究其矿化过程。结果表明，所有酚类物质在 8 h 内均被高效降解，COD 去除效率高。在电化学氧化过程中鉴定出三种主要的中间产物（对苯二酚、1,4-苯醌和邻苯二酚），并提出了降解途径。更重要的是，CO 转化效率的顺序为：不含 N 或 Cl 的酚类物质（p-CHO、p-OCH 和 Ph）>含 N 的酚类物质（p-NHCOCH 和 p-NO）>含 Cl 的酚类物质（p-Cl 和邻位-Cl 和对位-Cl）。碳质量平衡研究表明，在有机碳去除后形成了无机碳（HCO、CO 和 HCO）和 CO。含 N 和 Cl 的酚类物质矿化后还形成了无机氮物种（NH、NO 和 NO）和氯物种（Cl、ClO 和 ClO），但未检测到挥发性氮物种。含有吸电子取代基的酚类物质比含有供电子取代基的酚类物质更容易被氧化。QSAR 分析表明，酚类物质降解的反应速率常数（k）与哈米特常数（∑σ）和化合物的能隙（E-E）（R=0.908）高度相关，这两个参数是评价结构基团对特定化合物电子特性和自由基攻击时化学稳定性影响的关键参数。本研究为 BDD 阳极上酚类物质降解的矿化机制提供了明确的证据。
