不同原料和炭化温度下制备的生物炭结构及性质

以麦秆、稻杆和松木屑3种生物质为原料,在控制热分解条件下制备生物炭利用TG/DTG、Boehm滴定、FT-IR、XRD、TEM和吸附实验等方法对不同原料在350、550和750℃ 3个炭化温度下制备的生物炭形貌及其表面化学性质进行了表征。结果表明:最大热解速率所对应温度以松木屑为最高,表示热稳定性最好;不同原料在相同炭化温度下所制得的生物炭所含表面含氧官能团种类和总量相近,但pH值和吸附能力差别较大,其中麦秆制得的生物炭pH值最大,松木屑制得的生物炭吸附能力最强;随着炭化温度升高,相同原料制得生物炭表面含氧官能团总量减少,pH值升高,纤维素和半纤维素特征峰消失,芳构化程度增加,吸附性能总体呈先上升后下降的趋势。

Structure and properties of biochar under different materials and carbonization temperatures

Biochar was prepared from 3 kinds of biomass, viz. wheat straw, rice straw, and pine sawdust, under the controlling pyrolytic condition at 350, 550, and 750℃, respectively. The carbon morphology and surface chemical properties of biochar were characterized using TG/DTG, Boehm titration, FT-IR, XRD, TEM, adsorption capacity tests, etc. The results showed that pine sawdust had the highest temperature at which a peak pyrolytic rate occurred, which indicated that its thermal stability was the highest among the three biomass raw materials. The total amount of surface oxygen groups in biochar derived from the different raw materials at the same temperature was almost the same, although the pH and adsorption capacity were significantly different. Biochar derived from wheat straw had the highest pH, while that derived from pine sawdust had the highest adsorption capacity. Biochar derived from the same raw material showed that the amount surface oxygen groups decreased in content and increased in pH, while XRD analysis indicated that cellulose and hemicellulose nearly disappeared and the aromaticity of biochar increased. As a whole, on increasing the pyrolyzing temperature, the adsorption capacity of biochar peaked at 550℃ in the studied temperature range.