Guan Chaohong, Xu Zhenming, Zhu Hong, Lv Xiaojun, Liu Qingsheng
University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.
University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; John. A. Paulson School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA 02138, USA.
J Hazard Mater. 2022 Feb 5;423(Pt B):127109. doi: 10.1016/j.jhazmat.2021.127109. Epub 2021 Sep 7.
Activated alumina is the most common adsorbent for purifying fluoride in water, however, little is known so far about the adsorption mechanisms and comparison of adsorption behaviors for F on different crystal phase alumina surfaces, which seriously obstacles the development of high-performance sorbents. Herein, employing the density functional theory approach, we have studied F adsorbed on α-AlO(0001), γ-AlO(110), and θ-AlO(010) surfaces. Results accentuate that the θ-AlO (010) is the most reactive than ɑ-AlO (0001) and γ-AlO (110) for F adsorption and the high reactivity is mainly attributed to the high unsaturation level of Al atoms. Detailly, the most stable adsorption sites are top of Al1 site, bridge of Al6 and adjacent Al atom, and bridge of Al atoms for α, γ, θ-alumina, respectively. The bonding picture shows that the bonding between F and alumina surface is attributed to the hybridization between F-p orbitals and Al-s,p orbitals. In addition, the alumina surfaces are hydroxylated with water molecules when exposing to the atmosphere, exhibiting a great impact on the performance of purifying F element. Results suggest that the hydroxylated θ-AlO (010) adsorbs F with the smallest adsorption energy than other hydroxylated alumina surfaces, exhibiting the lowest performance of purifying F element.
活性氧化铝是水中净化氟最常用的吸附剂，然而，目前对于不同晶相氧化铝表面上氟的吸附机制和吸附行为比较了解甚少，这严重阻碍了高性能吸附剂的发展。在此，我们采用密度泛函理论方法，研究了氟在α-AlO(0001)、γ-AlO(110)和θ-AlO(010)表面的吸附情况。结果表明，θ-AlO(010)对氟吸附的反应活性比α-AlO(0001)和γ-AlO(110)更高，且高反应活性主要归因于铝原子的高不饱和程度。具体而言，α、γ、θ-氧化铝最稳定的吸附位点分别是Al1位点顶部、Al6与相邻铝原子之间的桥位以及铝原子之间的桥位。键合情况表明，氟与氧化铝表面之间的键合归因于F-p轨道与Al-s、p轨道之间的杂化。此外，氧化铝表面暴露于大气中时会被水分子羟基化，这对氟元素的净化性能有很大影响。结果表明，羟基化的θ-AlO(010)吸附氟的吸附能比其他羟基化氧化铝表面更小，净化氟元素的性能最低。
