The aim of this study was to understand the water−surface interactions of two chars obtained by gasification(pyrochar) and hydrothermal carbonization (hydrochar) of a poplar biomass. The two samples revealed different chemicalcompositions as evidenced by solid state13C NMR spectroscopy. In fact, hydrochar resulted in a lignin-like material stillcontaining oxygenated functionalities. Pyrochar was a polyaromatic system in which no heteronuclei were detected. Aftersaturation with water, hydrochar and pyrochar were analyzed by fastfield cycling (FFC) NMR relaxometry. Results showed thatwater movement in hydrochar was mainly confined in very small pores. Conversely, water movement in pyrochar led to theconclusion that a larger number of transitional and very large pores were present. These results were confirmed by porosityevaluation derived from gas adsorption. Variable-temperature FFC NMR experiments confirmed a slow-motion regime due to apreferential diffusion of water on the solid surface. Conversely, the higher number of large pores in pyrochar allowed slowmovement only up to 50°C. As the temperature was raised to 80°C, water interactions with the pore surface became weaker,thereby allowing a three-dimensional water exchange with the bulk liquid. This paper has shown that pore size distribution wasmore important than chemical composition in affecting water movement in two chemically different charred systems.
|Numero di pagine||7|
|Rivista||Journal of Agricultural and Food Chemistry|
|Stato di pubblicazione||Published - 2014|
All Science Journal Classification (ASJC) codes