碱溶透析和酸析处理对碱木质素物化性质和Pb2+去除性能的影响

采用XPS、静态接触角、颗粒表面电荷、扫描电镜、官能团分析等方法来研究碱木质素经过碱溶透析和碱溶酸析处理后的物化性质的差异,探讨碱木质素分子聚集程度对Pb²⁺去除性能的影响。结果表明,碱溶透析木质素的比表面积是碱溶酸析木质素的4.77倍,碱溶透析样品较酸析样品的表面氧含量高48%、水/木质素薄膜的静态接触角低13°,反映出碱溶透析处理后的木质素比碱溶酸析处理后的木质素分子聚集程度低、分子链疏松、羧基和羟基等含氧官能团裸露程度增加。碱溶透析处理后的木质素与Pb²⁺的静电作用增强,对Pb²⁺的去除能力显著提高。Pb²⁺浓度为100 mg·L^-1时,碱溶透析木质素对Pb²⁺的去除量达136 mg·g^-1,去除率为81.8%,且去除性能受体系pH的影响小。与化学改性和表面功能化相比,利用碱溶透析处理以提高木质素对Pb²⁺的去除性能具有操作简单、无毒、能耗低的优点。

Effects of dialysis and acid precipitation treatment on physicochemical properties of alkali lignin and its lead ions removal properties

XPS, static contact angle, particle surface charge, scanning electron microscopy, functional group analysis and other methods were used to study the difference of physicochemical properties of alkali lignin after alkali-soluble dialysis and alkali-soluble acid precipitation treatment, and to explore the degree of alkali lignin molecular aggregation to Pb²⁺ removal. The results indicate that (1) after alkali-dialysis treatment, the specific surface area is 4.77 times compared with alkali-acid precipitation, and the contact angle of the water/lignin film decreased by 13° compared with alkali-acid precipitation, reflecting the degree of aggregation of lignin molecular is low and the molecular chain is loose; (2) the surface oxygen content increased by 48% compared with alkali-acid precipitation, reflecting the exposed degree of oxygen-containing functional groups such as carboxyl groups and hydroxyl groups are increased, so that the electrostatic interaction between the sample and Pb²⁺ is enhanced; (3) the lead ions removal performance is remarkably enhanced, while the removal capacity can reach 136 mg·g^-1 and the removal rate can reach 81.8% at the concentration of Pb²⁺ was 100 mg·L^-1, and the removal performance is little affected by the pH of the system. Compared with the chemical modifications and surface functionalizations which aim at improving the removal performance of lignin, the alkali-dialysis treatment has the characteristics of low toxicity and low energy consumption in the preparation process.