Preparation of Plant Carbon from Coffee Husk: Effect of Carbonization Conditions on Product Properties

Plant carbon has been used as one of the natural edible colorants, but it must meet the requirements of carbonization conditions and vegetable materials. To evaluate the effects of carbonization conditions on the properties of resulting biochar products from coffee husk, the process parameters were designed by the combinations of heating rate (i.e., 10 and 20°C/min), pyrolysis temperature (i.e., 800 and 850°C) and residence time (i.e., 0, 30 and 60 min) in this work. Based on the thermochemical properties like proximate anal-ysis and thermogravimetric analysis, this lignocellulose-rich biomass is an excellent precursor for producing carbon materials. Although the pore properties of resulting biochar products were not positively related to the carbonization conditions, but the maximal Brunner-Emmett-Teller (BET) surface area of 155.59 m2/g and 354.96 m2/g) were obtained at 850°C for holding 30 min under the heating rates of 10 and 20°C/min, respectively. The data on the observations by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) of coffee husk and resulting biochar were in accordance with the changes on their textures and elemental compositions. Under the proper carbonization conditions, the resulting plant carbon derived from coffee husk had a special feature due to its high values of carbon content (> 90wt%), microporosity (> 70wt%), and BET surface area (> 350 m2/g).