胺化氰乙基木素吸附剂对Cr(Ⅵ)的吸附行为研究

Adsorption Behavior of Cr(Ⅵ) on Aminated Cyanoethyl Lignin Adsorbent

关键词:  木素  Cr(Ⅵ)  吸附  动力学  热力学

Key Words:lignin  Cr(Ⅵ)  adsorption  kinetics  thermodynamics

摘要:通过对球形木素珠体(SLB)进行两步化学改性,接枝具有固化SLB自身结构和造孔功能的氰基官能团以及对重金属离子存在吸附作用的胺基官能团,得到胺化氰乙基木素吸附剂(SLBAN)。实验探索了SLBAN对Cr(Ⅵ)溶液的吸附行为,考察了SLBAN用量、吸附时间和pH值等因素对吸附的影响,并依据动力学和热力学模型进行分析。结果表明,SLBAN对Cr(Ⅵ)的吸附符合准二级动力学模型；当吸附剂用量为2 g/L,pH值为2时,吸附约3 h达到平衡,Cr(Ⅵ)去除率达到86%左右,在328 K,SLBAN的饱和吸附容量为102 mg/g；吸附过程同时符合Langmuir和Freundlich方程,整个过程是自发的吸热反应过程,吸附过程为熵推动过程。

Abstract:The aminated cyanoethyl lignin adsorbent, denoted as SLBAN, was prepared by grafting acrylonitrile monomer onto spherical lignin beads (denoted as SLB) to further improve its physicochemical properties and pore structure, denoted as SLBA, and then grafted ethylene diamine monomer which could adsorb metal ions onto SLBA. The adsorption experiments regarding the adsorption behavior of Cr(Ⅵ) solution on SLBAN were conducted. And the factors affecting the adsorption i.e., the adsorbent dosage, adsorption time and solution pH etc., were optimized. The results concluded that the adsorption kinetics process was conformed to the pseudo second kinetics model. The removal rate of Cr(Ⅵ) could reach 86% when dosage of SLBAN was 2 g/L and solution pH=2 adsorption time was 3hrs. The maximum saturated adsorption capacity reached 102 mg/g under the ambient temperature of 328 K, and the adsorption process was in accordance to the Langmuir and Freundlich equation. Additionally, the whole process belonged to spontaneous and exothermic reaction process.