This project is funded by the Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation. It represents a collaboration between Dr. Joseph Pignatello at the Connecticut Agricultural Experiment Station, Professor Klaus Schmidt-Rohr at Brandeis University, and Professor Jingdong Mao at Old Dominion University. Together with their postdocs and graduate students, they investigate properties and behavior of biomass chars in the environment. Biochar particles are partially burned plant matter with blackened surfaces. Char results from natural and deliberately-set fires and are common components of soil and aquatic sediments. Activated carbon (a form of charcoal) and biochar can be beneficial soil additives for use in agricultural processes. Important attributes of chars include their ability to strongly bind pollutant and to change the identity of the pollutant molecules. Air may be present or absent during the charring process. It is usually present during the weathering of chars in the environment. The oxygen in air can have major effects on the physical and chemical properties of chars and can impact their functions as materials that absorb and change pollutants. This research examines the absorption and change in pollutants on biochar surfaces using carefully controlled experiments at both room temperatures and higher temperatures. This project provides benefits to society by studying how biomass chars affect the fate of pollutants in the environment. It also provides valuable information that may be useful in efforts to clean up contaminated sites, as well as in agricultural applications. In addition to fostering the training of students and postdoctoral fellows, this project incorporates a visiting scholars program for PhD students and professors, an internship program for undergraduate students, an Honors College program to foster involvement of undergraduate students in active research, and mentorship programs for high school students. The project has strong outreach and education components directed at engaging prospective scientists among historically disadvantaged groups, especially at Old Dominion University, which is an urban campus with a significant minority population.
Biomass chars are ubiquitous components of soil and sediment from fires and also have attracted interest as soil amendments in agriculture and environmental remediation. Important attributes of chars include their ability to effectively adsorb organic and inorganic compounds and to mediate electron transfer reactions to/from or between organic species. Air present during or after pyrolysis can have major effects on the physical-chemical properties of chars that impact these functions, yet this subject has received little attention. The objectives of this project are to determine the underlying structural and chemical alterations of char caused by both thermal and ambient air oxidation (AO), and to determine the effects of these alterations critical to their interactions with emerging pollutants. In the laboratory chars are made from wood and switchgrass. The test compounds are phosphate, arsenate, arsenite, selenite, aquatic herbicides (diquat and paraquat), and model organic compounds. Advanced solid-state nuclear magnetic resonance (NMR) spectroscopy is employed to identify and quantify changes in functional group composition and fused aromatic ring size. This also allows detection of signals coming from exceptionally strong hydrogen bonds formed between surface groups and weak acid adsorbates. NMR sensitivities are enhanced by using 13C-enriched switchgrass as the biomass precursor and 13C-labelled compounds as adsorbates. The project investigates the consequences of air oxidation on the formation of exceptionally strong hydrogen bonds. It also addresses cation exchange interactions, dissolved organic matter competition for adsorption sites, oxidation-reduction reactions mediated by chars, and the concentrations of persistent free radicals formed by the pyrolysis process. The findings are expected to provide novel insights for char structure and weak acid solute behavior in the environment. The project has outreach and education components and aims to engage students among historically disadvantaged groups.
