National-Local Joint Engineering Research Center of Heavy Metals Pollutants Control and Resource Utilization, Nanchang Hangkong University, 330063, Nanchang, P. R. China.
Department of Chemical Engineering, Chongqing University of Science and Technology, 401331, Chongqing, P. R. China.
Nat Commun. 2023 Mar 13;14(1):1365. doi: 10.1038/s41467-023-37143-2.
Silver ions in wastewater streams are a major pollutant and a threat to human health. Given the increasing demand and relative scarcity of silver, these streams could be a lucrative source to extract metallic silver. Wastewater is a complex mixture of many different metal salts, and developing recyclable sorbents with high specificity towards silver ions remains a major challenge. Here we report that molybdenum oxide (MoO) adsorbent with mixed-valence (Mo(V) and Mo(VI)) demonstrates high selectivity (distribution coefficient of 6437.40 mL g) for Ag and an uptake capacity of 2605.91 mg g. Our experimental results and density functional theory calculations illustrate the mechanism behind Ag adsorption and reduction. Our results show that Mo(V) species reduce Ag to metallic Ag, which decreases the energy barrier for subsequent Ag reductions, accounting for the high uptake of Ag from wastewater. Due to its high selectivity, MoO favorably adsorbs Ag even in the presence of interfering ions. High selective recovery of Ag from wastewater (recovery efficiency = 97.9%) further supports the practical applications of the sorbent. Finally, MoO can be recycled following silver recovery while maintaining a recovery efficiency of 97.1% after five cycles. The method is expected to provide a viable strategy to recover silver from wastewater.
废水中的银离子是一种主要的污染物，对人类健康构成威胁。鉴于银的需求不断增加而相对稀缺，这些废水可能成为提取金属银的有利来源。废水是多种不同金属盐的复杂混合物，开发对银离子具有高特异性的可回收吸附剂仍然是一个主要挑战。在这里，我们报告说，具有混合价态（Mo(V) 和 Mo(VI)）的氧化钼（MoO）吸附剂对 Ag 表现出高选择性（分配系数为 6437.40 mL g）和 2605.91 mg g 的摄取能力。我们的实验结果和密度泛函理论计算说明了 Ag 吸附和还原背后的机制。我们的结果表明，Mo(V) 物种将 Ag 还原为金属 Ag，这降低了随后 Ag 还原的能垒，解释了从废水中高摄取 Ag 的原因。由于其高选择性，即使存在干扰离子，MoO 也有利于吸附 Ag。从废水中高选择性回收 Ag（回收率为 97.9%）进一步支持了该吸附剂的实际应用。最后，MoO 在回收银后可以回收利用，在经过五个循环后，回收率仍保持在 97.1%。该方法有望为从废水中回收银提供一种可行的策略。
