Natural Organic Matter Association Modulates Pyrite Surface Electron Transfer Kinetics and Path for Reactive Oxygen...

Area of Science:

• Environmental Chemistry
• Geochemistry
• Surface Science

Background:

• Surface electron transfer from iron minerals to O2 is a key source of reactive oxygen species (ROS).
• Natural organic matter (NOM) often associates with iron minerals in soils and water, influencing redox reactions.
• Understanding NOM's impact on ROS production at mineral surfaces requires insight into interfacial electron transfer.

Purpose of the Study:

• To investigate how NOM association affects electron transfer kinetics and pathways on pyrite surfaces.
• To quantify the changes in ROS production and selectivity due to NOM association.
• To assess the implications of altered ROS generation for organic pollutant degradation.

Main Methods:

• Experimental investigation of electron transfer rates and pathways on pristine and NOM-associated pyrite.
• Quantification of O2 reduction products (H2O and H2O2) using spectroscopic techniques.
• Measurement of ROS yields (H2O2 and •OH) and organic pollutant degradation rates.

Main Results:

• NOM association decreased pyrite surface electron transfer rates by 22.7-38.6%.
• O2 reduction shifted from a 4-electron to a 2-electron pathway, favoring H2O2 formation (selectivity increased from 29.6% to 49.2-67.1%).
• ROS yields (H2O2 and •OH) increased by 1.5-2.3-fold, enhancing organic pollutant degradation by 1.6-2.7-fold.

Conclusions:

• NOM significantly modulates electron transfer kinetics and pathways on pyrite surfaces.
• NOM association enhances ROS production, leading to increased organic pollutant degradation.
• These findings underscore the critical role of NOM in environmental redox processes involving iron minerals.