Zhao Manshu, Wang Xinhua, Wang Shuguang, Lu Wenhui, He Maoxia, Gao Mingming
School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
Shandong Key Laboratory of Environmental Processes and Health, Shandong University, Qingdao 266237, China.
Proc Natl Acad Sci U S A. 2024 Sep 10;121(37):e2403072121. doi: 10.1073/pnas.2403072121. Epub 2024 Sep 3.
Homogenous advanced oxidation processes (AOPs) based on transition metal catalysts toward the activation of HO to hydroxyl radical (•OH) have been widely applied to organic pollutants removal, such as Fenton and Fenton-like processes. These transition metal catalysts mostly flocculate as the pH increases. It's worth noting that the formed transition metal flocs are complex heterogeneous aggregations with active substances, providing diverse reaction spaces and interfaces. However, it is a challenge to distinguish the roles of transition metal flocs in the organic pollutants removal from homogeneous catalytic reactions. Herein, we unveiled a pathway for the long-lasting removal of organic pollutants via Cr flocs adsorbed with •OH (HO-Cr flocs) using a stepwise method. First, adsorbed •OH (•OH) within the HO-Cr flocs was proved to be the active site forming hydrogen bond (H-bond) and van der Waals force with organic pollutants. Then, the presence of switchable electron transfer between Cr and OH groups within the HO-Cr flocs was revealed, contributing to the persistent existence of •OH and consequently ensuring the long-lasting organics removal. Further, this removal pathway of organic pollutants was confirmed during the leather wastewater treatment. These findings will complement a different pathway for organic pollutants removal via transition metal flocs and extend the lifetime of homogeneous AOPs based on transition metal catalysts, providing significant implications for their design and optimization.
基于过渡金属催化剂将过氧化氢（HO）活化生成羟基自由基（•OH）的均相高级氧化过程（AOPs）已广泛应用于有机污染物的去除，如芬顿和类芬顿过程。随着pH值升高，这些过渡金属催化剂大多会发生絮凝。值得注意的是，形成的过渡金属絮体是与活性物质的复杂非均相聚集体，提供了多样的反应空间和界面。然而，区分过渡金属絮体在有机污染物去除中相对于均相催化反应的作用是一项挑战。在此，我们采用分步方法揭示了一条通过吸附有•OH的Cr絮体（HO-Cr絮体）持久去除有机污染物的途径。首先，HO-Cr絮体内吸附的•OH（•OH）被证明是与有机污染物形成氢键（H键）和范德华力的活性位点。然后，揭示了HO-Cr絮体内Cr与OH基团之间存在可切换的电子转移，这有助于•OH的持续存在，从而确保有机污染物的持久去除。此外，在皮革废水处理过程中证实了这种有机污染物的去除途径。这些发现将补充通过过渡金属絮体去除有机污染物的不同途径，并延长基于过渡金属催化剂的均相AOPs的寿命，为其设计和优化提供重要启示。
