Liquid-Phase Exfoliation (LPE) is a process that can be used to produce small sheets of layered materials with remarkable properties and high-value end applications. Through LPE, interlayer interactions are weakened or even broken using sonication. A solvent that can effectively disperse and stabilize the nanostructures is needed. Unfortunately, the preferred solvents for exfoliation of layered materials possess several health risks to humans and the environment. For example, N-methyl-2-pyrrolidone (NMP) is the most common solvent for the production of graphene via LPE of graphite, although it is a well-known reprotoxic chemical. Biochar is a carbon-based material with graphene-like structure obtained from the pyrolysis of biomass. Besides being a tool for CO2 sequestration and presenting recognized climate change mitigation potential, biochar is an expensive material with porosity, surface area, and surface functionality. It has mainly been used as a soil amendment and a pollutant removal, the application of biochar in higher value-added fields has grown due to its remarkable chemical and physical properties. Moreover, the implementation of biochar in different sectors of our current chemical industry represents an important approach for the achievement of a circular and bio-based economy based on the principles of Green Chemistry. In this presentation, we will discuss the LPE of functionalized and pristine biochars from hard- and softwood biomass waste (e.g. sludge, bark, and sawdust) in greener solvents. Nanostructures of the respective bio-based materials could be obtained after LPE in a wide range of solvents to allow the identification of benign alternatives and a better understanding of the exfoliation mechanism. A correlation between LPE efficiency and different solvent parameters including density, surface tension, and Kamlet-Taft solvatochromic parameters were established. High mass % dispersions of exfoliated functionalized biochars could be obtained in solvents such as polyethylene glycol, glycerol formal, and ε-caprolactone, whereas pristine samples could be exfoliated in dimethyl carbonate, ethyl acetate, and solketal, giving similar results to NMP.

Production of biochar nanostructures in green solvents via liquid-phase exfoliation

ACS Spring Meeting 2021

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