Abstract:

The new chemically modified lignin was prepared based on straw by pretreament, phenolation, polycondensation, chloration, amination and quaternarization reaction and was analyzed though FTIR, SEM and TG-DSC. The adsorption effects of the initial concentration of AuCl₄^-, adsorption time and concentration of hydrochloric acid on AuCl₄^- were investigated. Furthermore, the mechanism of adsorption was explored. The results indicated that chemically modified straw lignin was of excellent thermal stability below 217℃ and had plenty of primary amines and hydroxyls. The maximum adsorption capacity was 784.50 mg·g^-1 when the initial concentration of AuCl₄^- was 8.0 mmol·L^-1, the equilibrium adsorption time was 600 min when the initial concentration of AuCl₄^- was 1.0 mmol·L^-1 and the adsorption ratio was 98% when the concentration of hydrochloric acid was 0.5 mol·L^-1 and the initial concentration of AuCl₄^- was 1.0 mmol·L^-1. Equilibrium experiments and kinetics studies fitted well with the Langmuir model and pseudo-second-order model, respectively. Finally, the AuCl₄^- was reduced from hydrochloric acid medium in the form of Au(0) by phenolic hydroxyl.

Key words: lignin, preparation, adsorption, AuCl₄^-, reduction

摘要：

以稻草为原料，经预处理、酚化、交联、氯化、胺化、季铵化制备了一种新型的化学改性木质素并对其进行了FTIR，SEM，TG-DSC分析，考察了AuCl₄^-初始浓度、吸附时间、盐酸浓度对化学改性木质素吸附AuCl₄^-效果的影响，探讨了吸附过程的机理。结果表明，制备的化学改性木质素表面致密且在217℃以下具有良好的热稳定性和含有大量酚羟基及胺基。当AuCl₄^-初始浓度为8.0 mmol·L^-1时吸附容量达到最大，为784.50 mg·g^-1，在AuCl₄^-初始浓度为1.0 mmol·L^-1时吸附达到平衡的时间为600 min，当盐酸浓度为0.5 mol·L^-1和AuCl₄^-初始浓度为1.0 mmol·L^-1时吸附率为98%。吸附过程遵循准二级动力学模型，吸附等温模型与Langmuir拟合较好。AuCl₄^-被化学改性木质素中的酚羟基以金单质的形态还原出来。

关键词: 木质素, 制备, 吸附, AuCl₄^-, 还原