Revisiting the adsorption of antimony on manganese dioxide: The overlooked dissolution of manganese
Revisiting the adsorption of antimony on manganese dioxide: The overlooked dissolution of manganese
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重新审视二氧化锰上锑的吸附：被忽视的锰溶解
DOI：
10.1016/j.cej.2021.132468
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发表时间：
2022
影响因子：
15.1
通讯作者：
Luo X.B.
中科院分区：
文献类型：
--
作者：
Nie J.;Yao Z.W.;Shao P.H.;Jing Y.P.;Bai L.;Xing D.F.;Yi G.P.;Li D.W.;Liu Y.B.;Yang L.M.;Yu K.;Luo X.B.
二氧化锰(MnO2)对废水中的锑(Sb)有很大的吸附潜力。许多研究致力于提高MnO2对Sb的固存能力。然而，锰的溶解行为被忽视了，Sb(III)的吸附与锰的溶解之间的内在关系还不清楚。在本研究中，批量实验证明，在MnO2上吸附Sb(III)的过程中，有明显的锰溶解。相关分析表明，MnO2的溶出量取决于MnO2对Sb(III)的吸附能力，与MnO2的晶相无关。进一步的实验和理论结果(以α-MnO2为例)揭示了锰的溶解经历了以下几个阶段。首先，Sb(Ⅲ)吸附在α-MnO2的(3+1+0)晶面上形成两个Mn-O-Sb键的络合物，这可以从−4.04 eV的精细吸附构型和相应的吸附能(Ead)得到证明。然后，来自α-MnO2的三个O原子分别从Sb(OH)3中逐渐失去了两个H原子，从与Sb(OH)3结合的水分子中分别失去了一个H原子。这一过程通过过渡态(过渡态#3)的构型和电子转移的发生(即净电荷的变化)得到了验证。最后，α-MnO2中的Mn-O键被削弱和破坏，导致Mn释放到水溶液中。这项工作加深了对MnO2吸附Sb的基本认识，不仅有助于重新评价MnO2对Sb(III)的去除效果，而且为设计性能良好的MnO2基吸附剂提供了理论指导。
Manganese dioxide (MnO2) exhibits great potential for the uptake of antimony (Sb) from wastewater. Much research has been dedicated to enhancing the capacity of MnO2for Sb sequestration. However, the dissolution behavior of Mn has been overlooked, and the underlying relationship between Sb(III) adsorption and Mn dissolution is not clear. In this study, batch experiments evidenced that there was a noticeable dissolution of Mn during the adsorption of Sb(III) on MnO2. A correlation analysis demonstrated that the amount of Mn dissolved was dependent on the Sb(III) adsorption capacity of MnO2, regardless of the crystalline phase of MnO2. Further experimental and theoretical results (taking α-MnO2as an example) unveiled that Mn dissolution involved the following stages. First, Sb(III) adsorbed onto the (3 1 0) crystal plane of α-MnO2to form a complexviatwo Mn-O-Sb bonds, which can be proven by the delicate adsorption configuration and corresponding adsorption energy (Ead) of −4.04 eV. Then, three O atoms from the α-MnO2progressively deprived two H atoms from Sb(OH)3and one H atom from a water molecule bound to Sb(OH)3, respectively. This process was verified by the configuration of the transition state (transition state #3) and the occurrence of electron transfer (i.e., the net charge changed by + 2e). Finally, the Mn-O bonds of α-MnO2were weakened and disrupted, leading to the release of Mn into the aqueous solution. This work advances the fundamental understanding of Sb adsorption onto MnO2, which not only promotes a re-evaluation of the utility of MnO2for Sb(III) elimination but also provides a theoretical guide for the design of robust MnO2-based adsorbents.