Nanoscale zerovalent iron (nZVI) shows great promise in valuable metal recovery from wastewater due to its high removal capacity. However, nZVI-based processes mainly focus on the sequestration step, ignoring the desorption step, which is crucial for recovery. In this study, a novel method for simultaneous Mo(VI) recovery and hazardous metal ions immobilization by nZVI was developed and the reaction mechanism was further investigated. Results shown that removal capacity of nZVI was significantly influenced by surface charge and the number of active adsorption sites. X-ray photoelectron spectroscopy analysis demonstrated that Mo(VI) reduction occurred in the inner Fe(0) core. K-edge X-ray Absorption Near Edge Structure analysis further confirmed that 5.4% and 18.0% of Mo(VI) are reduced to Mo(IV) at pH 6 and 9, respectively, suggesting that high pH favors for Mo(VI) reduction and H⁺ is responsible for the hollow-out structure at pH 6. Through adjusting the pH of wastewater from 3 to 12, over 80% of adsorbed Mo(VI) could be recovered while other metal ions remained immobilized and limited influence with common ions/anions. Overall, the proposed mechanism was significant to the research of metal reduction and competition for proton of nZVI, and the developed method had great prospects in valuable anions recovery.

中文翻译：

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通过纳米零价铁同时回收钼酸盐（Mo（VI））和固定有害离子

纳米级零价铁（nZVI）由于具有很高的去除能力，因此有望从废水中回收有价值的金属。但是，基于nZVI的工艺主要集中在螯合步骤上，而忽略了解吸步骤，解吸步骤对于回收至关重要。在这项研究中，开发了一种同时回收Mo（VI）和nZVI固定有害金属离子的新方法，并进一步研究了反应机理。结果表明，nZVI的去除能力受到表面电荷和活性吸附位点数量的显着影响。X射线光电子能谱分析表明Mo（VI）还原发生在内部Fe（0）核中。K边缘X射线吸收近边缘结构分析进一步证实，在pH 6和9下，分别有5.4％和18.0％的Mo（VI）还原为Mo（IV），⁺负责pH值为6时的中空结构。通过将废水的pH值从3调整为12，可以回收超过80％的吸附的Mo（VI），而其他金属离子仍保持固定状态，并且对普通离子/阴离子的影响有限。总体而言，所提出的机理对金属还原和nZVI质子竞争的研究具有重要意义，所开发的方法在有价值的阴离子回收方面具有广阔的前景。