Abstract:

Two types of lignin activated carbon with different structures were prepared from kraft lignin using phosphoric acid activation or mixed acid consisting of phosphoric acid and sulfuric acid as activating agents, respectively. The activated carbon was characterized by scanning electron microscope (SEM), infrared spectrum (FTIR), nitrogen adsorption and desorption, elemental analysis and Boehm acid value titration. The prepared activated carbon was applied to the adsorption of methylene blue (MB) dye wastewater. The results showed that the specific surface area, total pore volume, mesoporous volume and oxygen content of the carbon activated by mixed acid were 27.9%, 26.4%, 29.3% and 29.2% higher than those of the carbon activated by phosphoric acid alone, respectively, and distribution becomes more concentrated. Thus, the carbon activated by mixed acid has excellent adsorption performance for methylene blue in the range of pH 2—9, and the maximum saturated adsorption capacity reaches 1118.90 mg·g^-1, which is 20.3% higher than that of the carbon activated by phosphoric acid, showing good adsorption performance. The adsorption rate is fast, the adsorption process follows Langmuir adsorption isotherm and the pseudo-second-order kinetic equation, and the intra-particle diffusion is not the only decisive step.

Key words: lignin, activated carbon, phosphoric acid, sulfuric acid, methylene blue, adsorption

摘要：

以硫酸盐造纸黑液木质素为原料，分别采用磷酸活化和磷酸、硫酸混合酸活化制备了两类不同结构的木质素活性炭，对其进行了扫描电镜（SEM）、红外光谱（FTIR）、氮气吸附脱附、元素分析和Boehm酸值滴定等表征分析，并将制备的活性炭应用于模拟亚甲基蓝（MB）染料废水的吸附。结果表明，混合酸活化制备的木质素活性炭比单独磷酸活化的木质素活性炭的比表面积、总孔体积、介孔体积、氧含量分别增加了27.9%、26.4%、29.3%和29.2%，并且孔径分布更趋集中。混合酸活化活性炭在pH为2~9的范围内对亚甲基蓝均有优异的吸附性能，最大饱和吸附量达到1118.90 mg·g^-1，比磷酸活化木质素活性炭的吸附量增加了20.3%，表现出良好的吸附性能。吸附速率快，吸附过程遵循Langmuir等温线和伪二级动力学方程，颗粒内扩散不是唯一的决速步骤。

关键词: 木质素, 活性炭, 磷酸, 硫酸, 亚甲基蓝, 吸附