Elucidating microcystin-LR adsorption on pyrolyzed hydrochars via experiments and molecular simulations

C Chambers and H Nagar and S Sharma and MT Reza, JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS, 176, 106243 (2023).

DOI: 10.1016/j.jaap.2023.106243

This study focuses on synthesizing pyrolyzed hydrochar from corn stover to adsorb MCLR from aqueous solutions. The underlying hypothesis of this study is that both porosity and surface functional groups play a role in MCLR adsorption. To test the hypothesis, wet waste corn stover was first hydrothermally carbonized (HTC) at 260 degrees C for 30 min to enhance the surface functionality and hydrophobicity. Hydrochars, which are solid products of HTC, were then pyrolyzed at 400, 600, and 800 degrees C for 60 min which enhanced the BET surface area (SBET) from 1.97 +/- 0.92 m2/g up to 277.53 +/- 7.6 m2/g. Oxygen containing functional groups increase from 833.54 mu mol/g up to 1604.24 mu mol/g at pyrolysis temperature 400 degrees C then decrease as low as 211.74 mu mol/g with increase in pyrolysis temperatures. Higher SBET (CS-P800) facilitated high uptake of MCLR compared to the other pyrolyzed hydrochars suggesting pore-filling interactions as a possible adsorption mechanism. Adsorption isotherms studies indicated that MCLR follows Freundlich-type adsorption. Fully atomistic simulations showed that MCLR molecules have a propensity to aggregate, which supports the Freundlich adsorption isotherm. Furthermore, atomistic simulations provided insight on MCLR behavior with graphene sheet proving high affinity for adsorption as the molecule conforms to stable configuration in the adsorbed state.

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