Thi Tra My BUI PhD defense
Speciation and reactivity of Mn under variable environmental conditions
Wednesday 17 December, 14:00
Chemistry and Process Engineering (CIP) team
Abstract
Abstract : Manganese (Mn) has attracted increasing attention due to its abundance on Earth and its environmentally influential properties as a transition metal, particularly functioning as a major redox hub in natural environments. The dynamic speciation of Mn governs pollutant attenuation, organic carbon transformation, and biogeochemical cycling. Understanding Mn geochemical behavior of molecular, mineral, and environmental transport scales is thus crucial for predicting how these processes propagate to influence global ecosystem functioning. An integrated study of naturally occurring ligands, and organic carbon transformation with Mn species under the impact of common matrix constituents (pH, temperature, or flow patterns) was assessed. This thesis found that ligands controlled on Mn(III) stability and their oxidative capacity. Introducing minerals revealed substantial acceleration of pollutant turnover at environmental interfaces through surface complexation, reshaping Mn(III) reactivity. To address subsurface Mn cycling with carbon flux, MnO2-coated sand column experiments under saturated/ unsaturated conditions, demonstrating efficient Mn-driven transformation of small organic carbon molecules – a process with implications for carbon sequestration. Finally, Mn(II) oxidation across a range of climatic extremes, including ice environments, was explored. Freezing enhanced complexed-Mn(II) oxidation due to freeze concentration effects. These results may offer insights into Mn’s potential role in ongoing global environmental change.
Jury
Johannes LÜTZENKIRCHEN, Professor, Karlsruhe Institute of Technology, Germany / President
Caroline L. PEACOCK, Professor, University of Leeds, UK / Reviewer
ChangXun YU, A. Professor, Linnaeus University, Sweden / Reviewer
Naresh KUMAR, A. Professor, Wageningen University, Netherlands / Examiner
Khalil HANNA, Professeur des Universités, ENSCR, ISCR, France / PhD Director
Jean-François BOILY, Professor, Umeå University, Sweden / PhD Co-Director
Contacts
Thi Tra My Bui, thi-tra-my.bui@ensc-rennes.fr
Khalil Hanna, khalil.hanna@ensc-rennes.fr
