水体净化用木质素基活性炭的制备及其吸附动力学

Preparation of lignin-based activated carbon for water purification and its adsorption kinetics

为研究木质素基活性炭的吸附机理,选用环境友好型木质素作为碳基原材料,通过溶液混合和浸渍沉淀相转化成膜技术制得硫酸盐木质素/醋酸纤维素复合膜(KL/CA-M),经高温炭化和磷酸活化处理得到吸附性能优异的木质素基活性炭,并对其结构、热性能和吸附性能进行测试分析。结果表明:活性炭的结构稳定,吸附性能优异;最佳制备工艺条件为木质素质量分数为50%的复合膜为初始基膜,最佳炭化活化温度800℃,活化时间60 min,磷料质量比为1,该条件下所得木质素基活性炭比表面积达1 375.649 m2/g,微孔体积为0.714 m3/g,对亚甲基蓝的吸附量达到157.24 mg/g,远高于商品活性炭;木质素基活性炭对亚甲基蓝的吸附属于放热过程,吸附行为兼具有单层和多层吸附的特点;吸附过程包括物理吸附和化学吸附共同作用,且受多个扩散过程控制。

In order to study the adsorption mechanism of lignin-based activated carbon,Kraft lignin/cellulose acetate composite membrane(KL/CA-M)was prepared through solution mixing and immersion precipitation phase conversion coating technology followed by high temperature carbonization and phosphoric acid activation to form lignin-based activated carbon with excellent adsorption performance.The structure,thermal property and adsorption property of activated carbon were tested and analyzed.The results showed that the obtained lignin-based activated carbon had stable structure and excellent adsorption property.The optimum technological conditions for preparing the lignin-based activated carbon were 50%lignin content for the initial membrane,800℃for carbonization activation temperature,60 min for activation time and the mass ratio of phosphoric acid to initial membrane with the number of 1.Thus,the resulting lignin-based activated carbon is with the specific surface area of 1 375.649 m2/g,the micropore volume of 0.714 m3/g,and the adsorption capacity for Methylene Blue of 157.24 mg/g,which were higher than the one of commercial activated carbon.The adsorption of Methylene Blue onto lignin-based activated carbon was an exothermic process involving monolayer and multilayer adsorption.The lignin-based activated carbon absorbed Methylene Blue via both physical adsorption and chemical adsorption and the adsorption process was controlled by multiple diffusion.