Biomass pretreatment method affects the physicochemical properties of biochar prepared from residues of lignocellulosic ethanol production

This work investigated the influence of pretreatment methods (using sulfuric acid, sodium hydroxide, or calcium hydroxide) on the characteristics of biochar prepared from residues generated by lignocellulosic ethanol production. As a result, the biochar prepared from the residue of an acid pretreatment-based process showed better thermal stability than the other two biochars. The weight loss rates of three kinds of biochar at 900 °C were 17.85%, 30.95%, and 36.76%. The specific surface areas of the three biochars were 3.03 m 2 /g, 1.24 m 2 /g, and 8.04 m 2 /g, respectively, with the largest specific surface area found on the biochar of calcium hydroxide pretreatment-based process. FTIR analysis showed that the types of surface functional groups of the biochars were basically the same. The maximum theoretical adsorption capacities of the three biochars for methylene blue were 37.3 mg/g, 48.7 mg/g, and 58.2 mg/g, respectively. The adsorption capacity of biochar from alkali pretreatment for methylene blue was significantly better than that from acid pretreatment. The overall results showed that the properties of biochars prepared from fermentation residues under different pretreatment methods were quite different.