漆酶改性木质素磺酸钠的结构表征及吸附特征

采用漆酶对木质素磺酸钠(木钠)进行改性, 通过凝胶渗透色谱、 电位滴定、 红外光谱和核磁共振等测试方法研究了漆酶改性木钠的结构特征, 结果表明, 漆酶改性对木钠的磺酸基及表面电荷含量影响很小; 在漆酶对木钠的改性过程中既有解聚作用, 又有聚合作用, 反应初期, 漆酶使木钠发生脱甲基反应及部分链接键的断裂, 使酚羟基含量增大和分子量降低, 随着改性时间的延长, 酚羟基含量减少, 分子量变大, 聚合作用占主导地位. 采用静电逐层自组装技术研究了漆酶改性对木钠吸附特征的影响, 紫外光谱以及原子力显微镜的研究结果表明, 当漆酶改性时间为2 h时, 在平板上的吸附量及吸附膜的表面粗糙度最大, 木钠分子呈扁长的椭球形, 而改性时间为36 h时, 木钠聚合为近似球形的大分子结构, 空间位阻增大, 吸附量及吸附膜的表面粗糙度降低.

Structure and Adsorption Characterization of Sodium Lignosulfonate by Laccase Modification

Sodium lignosulfonate(SL) was modified by commercial laccase and the structural characterization of SL by laccase modification was determined by the gel permeation chromatography(GPC), potentiometric titration, infrared spectroscopy(IR) and nuclear magnetic resonance(NMR). It suggests that the modification does not affect the content of sulfonic group and the surface charge. Laccase is able to promote both polymerization and depolymerization. In the beginning, some linkages broken and demethylation by laccase oxidation decrease the molecular weight(M_w) of SL, accompanied by the increase of the content of phenolic group. With the increase of the incubation time, the content of the phenolic group decreases and the M_w of SL increases, which indicates that the polymerization is predominant. The adsorption of SL by laccase modification was studied by electrostatic self-assembly technology. The results of UV-Vis spectra and atomic force microscopy(AFM) indicate that with laccase incubated for 2 h, the SL macromolecule is an ellipsoidal microgel form, which is helpful to adsorption process, so the adsorbed amount and root-mean-square(RMS) are largest. However, with laccase incubated for 36 h, the SL macromolecule shifts to a more spherical form, the stronger steric hindrance between SL macromolecule makes weaker adsorption.