Preparation of carbon black from rice husk by hydrolysis, carbonization and pyrolysis

Carbon black is a form of amorphous carbon that is produced by incomplete combustion of petroleum- or some plant-derived materials and has a number of industrial uses. A process consisting of hydrolysis, carbonization and pyrolysis of rice husk was developed. Under optimal hydrolysis conditions (72 wt.% sulfuric acid, 50 °C, 10 min), a hydrolysis ratio of 52.72% was achieved. After carbonization of the hydrolysis solution by water bath, the solid carbon was further pyrolyzed. As the pyrolysis temperature was increased from 400 to 800 °C, the carbon content increased from 83.41% to 94.66%, the number of O–H, C–H, CO, and CC surface functional groups decreased, and based on Brunauer–Emmett–Teller (BET) results, the specific surface area and pore volume of carbon black increased from 389 to 1034 m2/g and from 0.258 to 0.487 cm3/g, respectively. X-ray diffraction pattern (XRD) and Raman spectroscopy analyses of samples pyrolyzed at 400–800 °C showed a localized graphitic structure. It is possible that the hydrolysis/carbonization/pyrolysis process developed in this study could also be applicable to the preparation of carbon black from other types of biomass.