(593a) Adsorption of Microcystin-LR on Biochar Studied Using Molecular Simulations

Eutrophication of Great Lakes and coastal regions of the United States is responsible for frequent and unpredictable outbursts of harmful algal blooms (HABs). During HABs, uncontrolled growth of cyanobacteria (blue-green algae) occurs, which releases a toxin called Microcystin-LR in water. Even small concentrations of Microcystin-LR (> 1 μg/l) in the water supply make it unfit for human consumption. A way of reducing eutrophication is to recover nutrients from biowaste by converting them into a nutrient-rich hydrochar via Hydrothermal Carbonization (HTC). Furthermore, pyrolyzed hydrochar is a highly porous and hydrophobic material that can act as an adsorbent of nutrients and Microcystin-LR from water streams. The goal of this research is to employ molecular dynamics (MD) simulations to understand the adsorption behavior of Microcystin-LR on hydrochar surfaces of different chemistries. Our simulation system comprises of microcystin-LR, water, ions and biochar surfaces described in full-atomistic detail. Using advanced simulation methods like umbrella sampling, we are determining the adsorption free energy of Microcystin-LR on the hydrochar surfaces. By employing a new free energy sampling methodology, developed in our research group, we are determining the equilibrium adsorption morphologies of Microcystin-LR on hydrochar surfaces. We are also investigating the aggregation behavior of Microcystin-LR molecules in the bulk aqueous phase. Results from our simulations will complement the adsorption studies that are being performed by our experimental collaborators.