Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

<div> <div> <div> <div> <p>Liquid-phase exfoliation (LPE) is a process frequently used to overcome the interactions between layers in layered materials to produce small sheets of material, with remarkable properties and high value applications. Materials are prepared via direct or indirect sonication in a solvent that must be able to effectively disperse and stabilize the sheets produced. Unfortunately, the preferred solvents for exfoliation processes are often toxic and possess several health risks. In this work, we show that LPE in greener solvents can be used to access nanostructures of biochar and further improve the applications of this renewable and bio-based material. Herein, pristine and oxidized biochars prepared from hardwood and softwood biomass waste (e.g. sludge, bark, and sawdust) are exfoliated in a range of solvents to allow the identification of benign alternatives that could afford highly concentrated dispersions. The majority of biochar nanostructures produced after exfoliation are stacked nanosheets containing between 2-8 layers (average 15 nm thickness). Correlations between effective LPE of biochar in solvents and different solvent parameters, including Kamlet-Taft, were established and allowed greener solvents to be used. Surface modification of biochars (e.g. via oxidation) has potential to increase their dispersibility in more benign solvents. LPE of oxidized biochars is more efficient in hydrogen-bond accepting solvents due to the increased concentration of carboxylic acid and alcohol functional groups on the surface of particles, when compared to non- functionalized biochars. Dispersions containing 0.20-0.75 mg/mL exfoliated oxidized biochar were obtained in solvents such as polyethylene glycols, glycerol formal and e-caprolactone. Moreover, LPE of pristine biochars in dimethyl carbonate, ethyl acetate, and solketal gave similar yields to more commonly used solvent for this process, N-methyl-2-pyrrolidone (NMP) a known reprotoxic molecule. </p> </div> </div> </div><br></div>

Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

Liquid-phase exfoliation (LPE) is a process frequently used to yield small sheets of layered materials. These materials are prepared via direct or indirect sonication in an ideal solvent, and the sheets produced often present remarkable chemical and physical properties. Unfortunately, the preferred solvents for exfoliation processes are frequently toxic and possess several health risks. In this work, we show the use of LPE in green solvents to access nanostructures of biochar. Biochar is a material produced after thermochemical treatment of biomass residues and it is an important tool for the sequestration of greenhouse gases. Herein, hardwood and softwood biomass residues (e.g. sludge, bark, and sawdust) are used to prepare pristine and oxidized biochars which are then exfoliated in a range of solvents. Stable dispersions containing up to 75% by weight of exfoliated biochar could be obtained. A range of solvents were screened for LPE of biochars to identify ‘green' options that could afford highly concentrated dispersions. The properties of the biochar before and after exfoliation were evaluated using Raman spectroscopy and Transmission Electron Microscopy. Correlations between effective LPE of biochar in a solvent and different solvent parameters were established. For example, LPE of oxidized biochars is more efficient in hydrogen-bond accepting solvents due to the increased concentration of carboxylic acid and alcohol functional groups within this material, when compared with pristine biochars.<div><br></div>

Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

Liquid-phase exfoliation (LPE) is a process frequently used to yield small sheets of layered materials. These materials are prepared via direct or indirect sonication in an ideal solvent, and the sheets produced often present remarkable chemical and physical properties. Unfortunately, the preferred solvents for exfoliation processes are frequently toxic and possess several health risks. In this work, we show the use of LPE in green solvents to access nanostructures of biochar. Biochar is a material produced after thermochemical treatment of biomass residues and it is an important tool for the sequestration of greenhouse gases. Herein, hardwood and softwood biomass residues (e.g. sludge, bark, and sawdust) are used to prepare pristine and oxidized biochars which are then exfoliated in a range of solvents. Stable dispersions containing up to 75% by weight of exfoliated biochar could be obtained. A range of solvents were screened for LPE of biochars to identify ‘green' options that could afford highly concentrated dispersions. The properties of the biochar before and after exfoliation were evaluated using Raman spectroscopy and Transmission Electron Microscopy. Correlations between effective LPE of biochar in a solvent and different solvent parameters were established. For example, LPE of oxidized biochars is more efficient in hydrogen-bond accepting solvents due to the increased concentration of carboxylic acid and alcohol functional groups within this material, when compared with pristine biochars.<div><br></div>

Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

Liquid-phase exfoliation (LPE) is a process frequently used to yield small sheets of layered materials. These materials are prepared via direct or indirect sonication in an ideal solvent, and the sheets produced often present remarkable chemical and physical properties. Unfortunately, the preferred solvents for exfoliation processes are frequently toxic and possess several health risks. In this work, we show the use of LPE in green solvents to access nanostructures of biochar. Biochar is a material produced after thermochemical treatment of biomass residues and it is an important tool for the sequestration of greenhouse gases. Herein, hardwood and softwood biomass residues (e.g. sludge, bark, and sawdust) are used to prepare pristine and oxidized biochars which are then exfoliated in a range of solvents. Stable dispersions containing up to 75% by weight of exfoliated biochar could be obtained. A range of solvents were screened for LPE of biochars to identify ‘green' options that could afford highly concentrated dispersions. The properties of the biochar before and after exfoliation were evaluated using Raman spectroscopy and Transmission Electron Microscopy. Correlations between effective LPE of biochar in a solvent and different solvent parameters were established. For example, LPE of oxidized biochars is more efficient in hydrogen-bond accepting solvents due to the increased concentration of carboxylic acid and alcohol functional groups within this material, when compared with pristine biochars.<div><br></div>

Spin-echo small-angle neutron scattering (SESANS) studies of diblock copolymer nanoparticles

Concentrated dispersions of polymer nanoparticles with high contrast can be studied using SESANS in real space.