title: Different crystal-forms of one-dimensional MnO2 nanomaterials for the catalytic oxidation and adsorption of elemental mercury.
abstract: MnO2 has been found to be a promising material to capture elemental mercury (Hg(0)) from waste gases. To investigate the structure effect on Hg(0) uptake, three types of one-dimensional (1D) MnO2 nano-particles, α-, β- and γ-MnO2, were successfully prepared and tested. The structures of α-, β- and γ-MnO2 were characterized by XRD, BET, TEM and SEM. The results indicate that α-, β- and γ-MnO2 were present in the morphologies of belt-, rod- and spindle-like 1D materials, respectively. These findings demonstrated noticeably different activities in capturing Hg(0), depending on the surface area and crystalline structure. The performance enhancement is in the order of: β-MnO2<γ-MnO2<α-MnO2 at 150°C. The mechanism for Hg(0) removal using MnO2 was discussed with the help of results from H2-TPR, XPS and Hg(0) removal experiments in the absence of O2. It was determined that the oxidizability of three forms of MnO2 increased as follows: β-MnO2<γ-MnO2<α-MnO2. The mechanism for Hg(0) capture was ascribed to the Hg(0) catalytic oxidation with the reduction of Mn(4+)→Mn(3+)→Mn(2+). Furthermore, the interaction forces between mercury and manganese oxide sites are demonstrated to increase in the following order: β-MnO2<γ-MnO2<α-MnO2 based on the desorption tests.
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Haomiao
authors.initials: H
authors.lastname: Xu
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Zan
authors.initials: Z
authors.lastname: Qu
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Songjian
authors.initials: S
authors.lastname: Zhao
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Mei
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Fuquan
authors.initials: F
authors.lastname: Quan
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: nqyan@sjtu.edu.cn.
authors.forename: Naiqiang
authors.initials: N
authors.lastname: Yan
keywords: Adsorption; Elemental mercury; Manganese dioxide; One-dimensional