title: Ascorbate-Promoted Surface Iron Cycle for Efficient Heterogeneous Fenton Alachlor Degradation with Hematite Nanocrystals.
abstract: This study reports the H2O2activation with different hematite nanocrystals and ascorbate ions for the herbicide alachlor degradation at pH 5. We found that hematite nanoplates (HNPs) exposed with {001} facets exhibited better catalytic performance than hematite nanocubes (HNCs) exposed with {012} facets, which was attributed to the formation of inner-sphere iron-ascorbate complexes on the hematite facets. The 3-fold undercoordination Fe cations of {001} facet favors the formation of inner-sphere iron-ascorbate complexes, while the 5-fold undercoordination Fe cations of {012} facet has stereo-hindrance effect, disfavoring the complex formation. The surface area normalized alachlor degradation rate constant (23.3 × 10-4min-1L m-2) of HNPs-ascorbate Fenton system was about 2.6 times that (9.1 × 10-4min-1L m-2) of HNCs-ascorbate counterpart. Meanwhile, the 89.0% of dechlorination and 30.0% of denitrification in the HNPs-ascorbate Fenton system were also significantly higher than those (60.9% and 13.1%) of the HNCs-ascorbate one. More importantly, the reductive dissolution of hematite by ascorbate was strongly coupled with the subsequent H2O2decomposition by surface bound ferrous ions through surface iron cycle on the hematite facets in the hematite-ascorbate Fenton systems. This coupling could significantly inhibit the conversion of surface bound ferrous ions to dissolved ones, and thus account for the stability of hematite nanocrystals. This work sheds light on the internal relationship between iron geochemical cycling and contaminants degradation, and also inspires us to utilize surface iron cycle of widely existent hematite for environmental remediation.
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Huang
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Hou
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Falong
authors.initials: F
authors.lastname: Jia
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Fahui
authors.initials: F
authors.lastname: Song
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Jincai
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Lizhi
authors.identifier: http://orcid.org/0000-0002-6842-9167
authors.initials: L
authors.lastname: Zhang
keywords: alachlor degradation; ascorbate ions; hematite nanocrystals; heterogeneous Fenton oxidation; surface iron cycle