Photoformation of persistent free radicals on a montmorillonite-humic acid complex simulated as particulate organic matter in an aqueous solution
Photoformation of persistent free radicals on a montmorillonite-humic acid complex simulated as particulate organic matter in an aqueous solution
复制标题
蒙脱石-腐植酸复合物上持久性自由基的光形成，模拟为水溶液中的颗粒有机物
DOI：
10.1039/d0em00009d
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发表时间：
2020
影响因子：
5.5
通讯作者：
Baocheng Qu
中科院分区：
文献类型：
--
作者：
Xintong Li;Chen Shen;Hongxia Zhao;Jingqiu Jiang;Zixin Ban;Zhenyu Chen;Baocheng Qu
本文研究了水中颗粒有机物（POM）在辐照下持久性自由基（PFR）的形成。制备了蒙脱石-腐殖酸复合物（Mnt-HA复合物）模拟POM，并利用电子顺磁共振（EPR）技术对生成的PFR进行了检测。辐照8 d后，EPR信号呈现先增大后减小的趋势，g因子在2.0034-2.0039之间，表明产生了具有亲电基团的碳中心自由基。不同浓度和类型的卤代酚和过渡金属离子分别吸附在Mnt-HA复合物上，以探讨它们对PFR形成的影响。Mnt-HA复合物中PFR生成量的大小顺序为：2-溴苯酚（2-BP）> 2，4-二溴苯酚（2，4-DBP）> 2，4-二氯苯酚（2，4-DCP），表明卤代苯酚的卤素取代和取代基的数目会影响PFR的生成。过渡金属离子对PFR还原的影响顺序为：Fe ~（3+）> Zn ~（2+）> Cu ~（2+）> Mn ~（2+），这与它们的氧化还原能力相一致。通过分析辐照诱导POM产生活性氧和电子的过程，发现卤代酚和过渡金属离子也影响了这一过程。这些结果表明，POM上的光生成PFR可能是水环境中PFR的一个来源，需要进一步关注。
This study investigates the formation of persistent free radicals (PFRs) on particulate organic matter (POM) under irradiation in water. A montmorillonite–humic acid complex (Mnt–HA complex) was prepared to simulate POM, and the generated PFRs were detected by the electron paramagnetic resonance (EPR) technique. EPR signals with the trend of an initial increase and then a decrease were observed under irradiation for 8 days, and the g factors were in the range of 2.0034–2.0039, which indicated the generation of carbon-centered radicals with electrophilic moieties. Different concentrations and types of halophenols and transition-metal ions were respectively adsorbed on the Mnt–HA complex to probe their influence on the formation of PFRs. The amount of PFRs generated in the Mnt–HA complexes was in the order: 2-bromophenol (2-BP) > 2,4-dibromophenol (2,4-DBP) > 2,4-dichlorophenol (2,4-DCP), which implied that halogen substitution and the number of substituents in the halophenols could affect the generation of PFRs. The effects of transition-metal ions that resulted in the reduction of PFRs when adsorbed on the Mnt–HA complex were as follows: Fe3+ > Zn2+ > Cu2+ > Mn2+, and this is in agreement with their redox capacity. Analyzing the induced generation of reactive oxygen species (ROS) and electrons on POM, it is found that halophenols and transition metal ions also affected this process under irradiation. These findings indicate that the photoformation of PFRs on POM could be a source of PFRs in aqueous environments and requires further attention.