Effect of iron substitution in cryptomelane on the heterogeneous reaction with isoprene
Effect of iron substitution in cryptomelane on the heterogeneous reaction with isoprene
复制标题
钾锰矿中铁取代对异戊二烯非均相反应的影响
DOI：
10.1016/j.jhazmat.2022.129293
复制
发表时间：
2022
影响因子：
13.6
通讯作者：
Daiqi Ye
中科院分区：
文献类型：
--
作者：
Peng Liu;Yilian Kong;Xiaoliang Liang;Yuxi Liao;Tan Li;Daoyong Tan;Runliang Zhu;Mingli Fu;Steven L. Suib;Daiqi Ye
生物源异戊二烯是影响区域空气质量的重要污染物。锰（氢）氧化物广泛分布于地球表面，在异戊二烯的转化过程中起着至关重要的作用。隐黑烷是一种典型的以铁取代锰的同晶氧化锰，但其与异戊二烯的非均相反应研究较少。当Fe3+取代Mn3+时，K+被耗尽，Mn3+被氧化为Mn4+。相反，当Fe3+取代Mn4+时，形成氧空位。铁取代形成弱晶和丰富的介孔，导致异戊二烯吸附量增加。理论计算发现，隧道横截面上的Mn4+- o2 -键比隧道外壁上的Mn4+- o2 -键更活跃。异戊二烯吸附后产生桥接羧酸类和氢键水，表面八面体发生畸变，即Mn4+O6→Mn3+O6-δ。由于热量有利于Mn4+- o2 -的断裂，环境温度的升高促进了异戊二烯的氧化。上述发现揭示了铁取代对隐黑烷中异戊二烯氧化的促进作用，并说明了与异戊二烯的非均相反应会影响其他环境物质对隐黑烷的转化。
Biogenic isoprene is an important pollutant for regional air quality. Being ubiquitously distributed on the earth surface, manganese (hydr)oxides should play a vital role in the transformation of isoprene. Cryptomelane is a typical manganese oxide with isomorphous substitution of Fe for Mn, but less attention has been paid to its heterogeneous reaction with isoprene. When Fe3+ replaces Mn3+, K+ is depleted and Mn3+ is oxidized to Mn4+. In contrast, oxygen vacancies are formed when Fe3+ substitutes Mn4+. Fe substitution creates weak crystallites and abundant mesopores, resulting in the increase of isoprene adsorption. As found by theoretical calculations, the Mn4+-O2- bonds at the cross sections of the tunnels is more active than that on the outer wall of the tunnels. After the adsorption of isoprene, bridging carboxylate species and hydrogen-bonding water are produced and the surface octahedra are distorted, i.e., Mn4+O6 → Mn3+O6-δ. As the heat facilitates the breakage of Mn4+-O2-, the increase of environmental temperature enhances the oxidation of isoprene. The above findings shed light on the effect of Fe substitution in cryptomelane to enhance the oxidation of isoprene, and illustrates that heterogeneous reaction with isoprene impairs the transformation of other environmental substances on cryptomelane.