Wang Ziquan, Wang Fang, Xiang Leilei, Bian Yongrong, Zhao Zhiliang, Gao Zhengyuan, Cheng Jingxing, Schaeffer Andreas, Jiang Xin, Dionysiou Dionysios D
CAS Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
CAS Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Water Res. 2022 Jun 15;217:118377. doi: 10.1016/j.watres.2022.118377. Epub 2022 Mar 29.
Ferrate (Fe(VI)) salts like KFeO are efficient green oxidants to remediate organic contaminants in water treatment. Minerals are efficient sorbents of contaminants and also excellent solid heterogeneous catalysts which might affect Fe(VI) remediation processes. By targeting the typical polycyclic aromatic hydrocarbon compound - pyrene, the application of Fe(VI) for oxidation of pyrene immobilized on three minerals, i.e., montmorillonite, kaolinite and goethite was studied for the first time. Pyrene immobilized on the three minerals was efficiently oxidized by Fe(VI), with 87%-99% of pyrene (10 μM) being degraded at pH 9.0 in the presence of a 50-fold molar excess Fe(VI). Different minerals favored different pH optima for pyrene degradation, with pH optima from neutral to alkaline following the order of montmorillonite (pH 7.0), kaolinite (pH 8.0), and goethite (pH 9.0). Although goethite revealed the highest catalytic activity on pyrene degradation by Fe(VI), the greater noneffective loss of the oxidative species by ready self-decay in the goethite system resulted in lower degradation efficiency compared to montmorillonite. Protonation and Lewis acid on montmorillonite and goethite assisted Fe(VI) oxidation of pyrene. The intermediate ferrate species (Fe(V)/Fe(IV)) were the dominant oxidative species accountable for pyrene oxidation, while the contribution of Fe(VI) species was negligible. Hydroxyl radical was involved in mineral-immobilized pyrene degradation and contributed to 11.5%-27.4% of the pyrene degradation in montmorillonite system, followed by kaolinite (10.8%-21.4%) and goethite (5.1%-12.2%) according to the hydroxyl radical quenching experiments. Cations abundant in the matrix and dissolved humic acid hampered pyrene degradation. Finally, two different degradation pathways both producing phthalic acid were identified. This study demonstrates efficient Fe(VI) oxidation of pyrene immobilized on minerals and contributes to the development of efficient environmentally friendly Fe(VI) based remediation techniques.
高铁酸盐（Fe(VI)）盐类如KFeO是水处理中用于修复有机污染物的高效绿色氧化剂。矿物质是污染物的高效吸附剂，也是优良的固体多相催化剂，可能会影响Fe(VI)修复过程。以典型的多环芳烃化合物芘为研究对象，首次研究了Fe(VI)对固定在蒙脱石、高岭土和针铁矿三种矿物质上的芘的氧化作用。固定在这三种矿物质上的芘能被Fe(VI)有效氧化，在pH 9.0、Fe(VI)摩尔过量50倍的条件下，10 μM的芘有87%-99%被降解。不同矿物质对芘降解的最适pH值不同，最适pH值从中性到碱性的顺序为蒙脱石（pH 7.0）、高岭土（pH 8.0）和针铁矿（pH 9.0）。虽然针铁矿对Fe(VI)降解芘显示出最高的催化活性，但与蒙脱石相比，针铁矿体系中氧化物种因快速自分解而导致的无效损失更大，从而使降解效率较低。蒙脱石和针铁矿上的质子化和路易斯酸促进了Fe(VI)对芘的氧化。中间高铁酸盐物种（Fe(V)/Fe(IV)）是芘氧化的主要氧化物种，而Fe(VI)物种的贡献可忽略不计。羟基自由基参与了矿物质固定芘的降解，根据羟基自由基猝灭实验，在蒙脱石体系中对芘降解的贡献为11.5%-27.4%，其次是高岭土（10.8%-21.4%）和针铁矿（5.1%-12.2%）。基质中丰富的阳离子和溶解的腐殖酸阻碍了芘的降解。最后，确定了两条均产生邻苯二甲酸的不同降解途径。本研究证明了Fe(VI)对固定在矿物质上的芘的有效氧化，并有助于开发高效的基于Fe(VI)的环境友好型修复技术。
