Abstract:

The structural characteristic and surface physicochemical properties of bagasse magnesium lignosulfonate(MLS) are investigated by means of GPC,UV,IR and ¹³C NMR. Four purified MLS fractions with different molecular weights were obtained by fractionation using ultrafiltration and analyzed. The results show that MLS contained more syringin phenyl propane, and less guaiacol phenyl propane comparing with woody calcium lignosulfonate (CLS). The average molecular weight of MLS and the content of sulfonic and phenolic hydroxyl group are lower than that of CLS. As the increasing of molecular weight of MLS, the mass fraction of sulfonic and phenolic hydroxyl group increases. The relative molecular weight distribution and the content of sulfonic and phenolic hydroxyl group are the main affecting factors on the adsorption characteristic of MLS on cement-water interface and the surface charge of cement particle absorbing MLS. With the increasing of molecular weight of MLS, the Zeta potential absolute value of cement particle increases. The adsorbing amount and the Zeta potential absolute value of the surface of cement particle adsorbing MLS fraction with the molecular weight more than 50000, is similar to that of CLS, and its adsorption isotherm follows Langmuir type.

Key words: 木质素磺酸镁, 分子量, 吸附, 表面电位

摘要：

通过紫外、红外光谱、核磁共振和电位滴定等方法研究了蔗渣木质素磺酸镁(MLS)的结构特征和表面物化性能，并与杨木木质素磺酸钙(CLS)进行了对比。与CLS相比，MLS含有较多量的紫丁香基结构和较少的愈创木基结构；MLS的重均分子量、磺酸基和酚羟基含量较低。采用超滤法将MLS分离成不同分子量的级份，发现随着分子量的提高，MLS中的3种基本结构单元的含量均一化，磺酸基与酚羟基含量增加，羧基含量减少。表面物化性能测试结果表明，分子量、磺酸根和酚羟基是影响MLS在水泥颗粒表面吸附及表面电位的主要因素。随着分子量的增加，MLS使水泥颗粒表面电位显著增加，截留分子量大于50000的MLS可使水泥颗粒表面的Zeta电位绝对值达到14.6 mV，饱和吸附量达到6. 0 mg·g^-1，吸附等温线近似为Langmuir型，与CLS相似。

关键词: 木质素磺酸镁, 分子量, 吸附, 表面电位