磷酸活化沙柳制备活性炭工艺

沙柳资源丰富且含有大量的纤维素和半纤维素,可作为制备活性炭的潜在原料。本研究以沙柳为原料、磷酸为活化剂,采用正交试验法确定沙柳基活性炭的制备工艺,探究浸渍比、活化温度和活化时间3个因素对沙柳基活性炭得率及亚甲基蓝吸附性能的影响。通过扫描电子显微镜(SEM)和X-射线衍射仪(XRD)对所制备活性炭的微观形貌和石墨层结构进行分析和表征,并利用氮气吸附和脱附曲线计算出BET比表面积、BJH孔径分布。试验结果表明:制备沙柳基活性炭的较理想工艺条件为,活化时间80 min,浸渍比3:1(磷酸与原料的质量比),活化温度450 ℃; 在此条件下制备的沙柳基活性炭平均得率为46.48%,亚甲基蓝吸附值为135.0 mg/g,BET比表面积为1 015.144 m2/g,孔径大小平均为4.23 nm。
As one of abundant timber resources, the Salix psammophila can be used as the potential raw material to prepare activated carbons. The activated carbon preparation process by taking Salix psammophila with H3PO4 as an activating agent was optimized with orthogonal experiment. The suitable technological conditions of preparing activated carbons were determined. The influences of impregnation ratio, activation temperature and activation time on the yield and methylene blue adsorption properties of activated carbons were investigated. The surface morphology and graphite layer structure of the activated carbons were characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD). The scanning electron microscopy(SEM)analyses showed that the uneven surface of activated carbon was comprised of intensive pore structures with uniform pore size and similar shape; with the deepening of the activation, the pores were expanded and formed the mesopores and macropores. It could be seen from the XRD that the surface structure was changed after carbonization and activation processes, mainly reflected in the crystallization with destroying the original structures of raw materials and created new ones as the increase of hardness. In addition, the half peak width of diffraction peaks of the activated carbon samples was become wider, indicating that the crystal structure of activated carbon samples turned small, which means the smaller pores were formed. BET surface area and BJH pore size distribution of the samples were calculated by Nitrogen adsorption-desorption isotherms. The optimum conditions of process were obtained, as the activation temperature, impregnation ratio and activation time were 450 ℃, 3:1 [m(H3PO4):m(raw material)] and 80 min, respectively. Under this ideal condition, the average yield rate of activated carbon, average value of methylene blue adsorption, surface area and average pore size of Salix psammophila activated carbon were up to 46.48%, 135.0 mg/g, 1 015.144 m2/g and 4.23 nm, respectively