磷酸法玉米秸秆基活性炭的制备及其表征

以成型、烘焙处理后的玉米秸秆为原料,磷酸作为活化剂制备了玉米秸秆基活性炭,并对活性炭样品进行表征。同时以碘吸附值、亚甲基蓝吸附值和焦糖脱色率为指标测定其吸附性能,并对制备条件进行优化。实验结果表明:玉米秸秆制备活性炭的最佳工艺条件为浸渍比即m(55%H₃PO₄)∶m(玉米秸秆)为4∶1、活化温度400℃、活化时间100 min,此条件下活性炭的得率为47.78%,制得的活性炭具有良好的吸附性能,碘吸附值、亚甲基蓝吸附值及焦糖脱色率分别达到864 mg/g、 210 mg/g和100%。活性炭比表面积可达1 105 m²/g,总孔容积为0.745 cm³/g,微孔孔容为0.287 cm³/g,中孔孔容为0.354 cm³/g,孔径分布集中于5 nm以内,约占73.56%,平均孔径为2.697 nm。FT-IR分析显示:在活化过程中磷酸与玉米秸秆发生交联作用,生成的活性炭损失了玉米秸秆的部分官能团。

Preparation and Characterization of Corn Straw Based Activated Carbon by Phosphoric Acid Activation

Corn straw based activated carbon was prepared from corn straw after formed and torrefied by H₃PO₄ activation and characterized by N₂ adsorption, elemental analysis and FT-IR. The results showed that the optimal conditions were the impregnated ratio of 4∶1, the activation temperature of 400 ℃ and the activation time of 100 min. Under these conditions, the yield of activated carbon was 47.78% and the activated carbon showed excellent adsorption capacity with the iodine adsorption value of 864 mg/g, the methylene blue adsorption of 210 mg/g and the caramel decolorization of 100%. The specific surface area and the total volume of activated carbon reached 1 105 m²/g and 0.745 cm³/g, the micropore volume was 0.287 cm³/g, the mesopore volume was 0.354 cm³/g. Meanwhile, the distribution of pore was concentrated within 5 nm, accounting for 73.56%, and the average pore diameter is 2.697 nm. The FT-IR results showed that the crosslinking reaction was occured between H₃PO₄ and corn straw during octivation and the activated carbon lost some functional groups of corn straw.