Exploring the ability of cations to facilitate binding between inorganic oxyanions and humic acid

Abstract

The mobility and fate of inorganic oxyanions in the environment can be greatly influenced by interactions with natural organic matter (NOM). There is increasing evidence that this interaction between two anionic species is facilitated by cationic bridges, but detailed mechanistic studies into this system are challenging due to the heterogeneous nature of NOM. This work examines the ability of cations (Fe, Cr, Al, or Ga) to form ternary complexes with Suwannee River humic acid (SRHA) and the oxyanions of As (As and As) and Se (Se and Se). Complexes were characterized by separating SRHA from unbound species using size exclusion chromatography coupled to ICP-MS to determine its metal content. Unlike Cr and Fe, the post-transition metal ions Al and Ga proved ineffective at forming ternary complexes with any of the oxyanions, although minor complexation was observed with Ga, suggesting that electrostatic interactions are not the primary driving force behind the stabilization of these ternary complexes. The results also show differences in the behavior of Fe and Cr that may indicate that the two cations stabilize the ternary complexes by different mechanisms.

Effect of bicarbonate and phosphate on arsenic release from mining-impacted sediments in the Cheyenne River watershed, South Dakota, USA

“…However, detailed mechanistic studies of NOM are challenging in environmental systems due to the heterogenous nature of NOM and the estimated organic content in our samples is only 2–3%. 64 Based on our present data, we cannot definitely conclude which of these or other potential mechanisms affect anion-induced As release in the WW and DR sediments.…”

Behavior of potentially toxic elements from stoker-boiler fly ash in Interior Alaska: paired batch leaching and solid-phase characterization

“…DOM-metal(loid) interactions may either facilitate or inhibit dissolution, complicating the processes described above (Aiken et al 2011). Interactions with metal(loid)s can occur through complexation, either directly between an element and DOM as may be the case for cationic forms or via ternary complexation with elements such as Fe for oxyanions (Martin et al 2017;Peel et al 2017). The loss of color of the solutions after 7 days suggests a decrease in the freely dissolved DOM in the supernatant (there was not enough sample to submit for DOC measurement).…”

Computational Investigation on Interactions between Some Munition Compounds and Humic Substances

“…Martin tion chemistry is critical for fate and transport modeling of compounds within humic-rich environments. 29 This study seeks to build toward meeting this need by simulating the interactions of a model HA structure with various MCs and evaluating changes in the binding energies, redox properties, electron affinities, and ionization potentials of the complexes. This data illustrates the various interactions, mechanisms, and some impacts of how HAs affect fate and transport of MCs in the environment.…”

“…The works of Mark et al , on 3-nitro-1,2,4-triazol-5-one (NTO) binding in soils reveal that organic content dramatically impacts the compound’s fate and transport properties and has a strong dependence on pH. Additionally, the experimental results of Martin et al on the binding of oxyanions with humic substances probe ternary complexation and conclude that charge neutralization alone is insufficient to explain the binding mechanism. Martin et al conclude that fundamental coordination chemistry is critical for fate and transport modeling of compounds within humic-rich environments .…”

“…Additionally, the experimental results of Martin et al on the binding of oxyanions with humic substances probe ternary complexation and conclude that charge neutralization alone is insufficient to explain the binding mechanism. Martin et al conclude that fundamental coordination chemistry is critical for fate and transport modeling of compounds within humic-rich environments . This study seeks to build toward meeting this need by simulating the interactions of a model HA structure with various MCs and evaluating changes in the binding energies, redox properties, electron affinities, and ionization potentials of the complexes.…”