Effect of iron substitution in cryptomelane on the heterogeneous reaction with isoprene

Peng Liu; Yilian Kong; Xiaoliang Liang; Yuxi Liao; Tan Li; Daoyong Tan; Runliang Zhu; Mingli Fu; Steven L Suib; Daiqi Ye

doi:10.1016/j.jhazmat.2022.129293

Effect of iron substitution in cryptomelane on the heterogeneous reaction with isoprene

J Hazard Mater. 2022 Sep 5:437:129293. doi: 10.1016/j.jhazmat.2022.129293. Epub 2022 Jun 6.

Authors

Peng Liu¹, Yilian Kong², Xiaoliang Liang³, Yuxi Liao², Tan Li², Daoyong Tan⁴, Runliang Zhu⁵, Mingli Fu¹, Steven L Suib⁶, Daiqi Ye⁷

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China.
² School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
³ CAS Key Laboratory of Mineralogy and Metallogeny, Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China. Electronic address: [email protected].
⁴ Key Laboratory of Solid Waste Treatment and Resource Recycle, Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China.
⁵ CAS Key Laboratory of Mineralogy and Metallogeny, Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
⁶ Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA.
⁷ School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; National Engineering Laboratory for VOCs Pollution Control Technology and Equipment, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China. Electronic address: [email protected].

PMID: 35724618
DOI: 10.1016/j.jhazmat.2022.129293

Abstract

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⁺-O^2- 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⁺O_6-δ. As the heat facilitates the breakage of Mn⁴⁺-O^2-, 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.

Keywords: Adsorption-oxidation; Cryptomelane; DFT calculation; Fe substitution; Isoprene.