分级木质素基活性炭的制备及其吸附效果研究

Preparation and Adsorption Performance of Fractionated Lignin-based Activated Carbon

关键词:  木质素  有机溶剂分级  活性炭  重金属离子

Key Words:lignin  organosolv fractionation  activated carbon  heavy metal ion

摘要:本研究采用4种有机溶剂对碱木质素进行分级，得到4种不同相对分子质量的木质素级分；以磷酸为活化剂，在高温条件下制备木质素基活性炭（LAC），探讨不同制备条件及外部环境因素对LAC吸附效果的影响。结果表明，在越高的磷酸含量和活化温度下，相对分子质量较大的木质素级分制备的LAC对Cu²⁺的吸附效果越好。采用1,4-二氧六环分级的木质素级分在浸渍质量比2.5∶1、活化温度800 ℃下制备的LAC比表面积最大（806.74 m²/g），吸附效果最好，Cu²⁺去除率达98.3%。同时，LAC在不同环境温度和pH值下，对Cu²⁺去除率均保持较高水平；经过4次吸附-解吸循环后，吸附效率达81%以上，解吸效率在73%以上，表明分级木质素制备的LAC具有良好的环境稳定性和可循环利用性。

Abstract:In this study， four kinds of kraft lignin fractions with different relative molecular weight were obtained by four kinds of organic solvents fractionation， and these fractions were used to synthesize lignin-based activated carbon （LAC） at high temperature with phosphoric acid as an activating agent subsequently. The effects of different preparation conditions and external environmental factors on LAC adsorption performance were investigated. The results showed that under high phosphoric acid concentrations and activation temperature， the LAC prepared by lignin fraction with large relative molecular weight had a better adsorption performance towards Cu²⁺. Especially， the LAC prepared from dioxane-fractionated lignin fraction with a phosphoric acid to lignin mass ratio of 2.5∶1 at an activation temperature of 800 ℃ exhibited the highest specific surface areas （806.74 m²/g） and best adsorption performance with the removal rate of 98.3% towards Cu²⁺. Furthermore， Cu²⁺could be removed by LAC at a high level under different temperature and pH value. After four adsorption-desorption cycles， it still had adsorption efficiency of 81% and desorption efficiency of 73%， indicating that the LAC synthesized from fractionated lignin had good environmental stability and reusability.