摘要
采用体积排阻色谱和总有机碳分析法,分别测定腐殖酸体系中加入盐酸、甲酸、乙酸和丙酸后其分子量和溶解性发生的变化;通过分析抗坏血酸、苯甲酸、苯酚和邻苯二酚4种模型化合物在甲酸影响下的紫外光谱,以验证电荷辅助氢键的存在。结果表明:小分子有机酸能够明显降低腐殖酸的分子量;此外,当腐殖酸体系pH接近小分子有机酸的pKa时(DpKa<0.5),腐殖酸溶解性明显增大。小分子有机酸可能与腐殖酸之间形成电荷辅助氢键,从而打破弱作用力维持的腐殖酸超分子的稳态结构,导致腐殖酸分子量的降低和溶解性的增加;且弱酸与有机物之间的pKa相差越小,形成的电荷辅助氢键能量越高,腐殖酸分子结构受到的扰动程度越大。一维紫外光谱和同步二维相关紫外光谱分析进一步表明,小分子有机酸可能与pKa接近的化合物之间形成电荷辅助氢键,整体跃迁所需能量提高,造成低波长吸收增大而高波长吸收减小的结果。
Changes in molecular weight and solubility of humic acid were investigated when hydrochloric acid,formic acid,acetic acid and propionic acid were spiked,by volumetric exclusion chromatography and TOC analysis.To verify the existence of charge-assisted hydrogen bonds(CAHB),formic acid was added into four kinds of model chemicals(i.e.ascorbic acid,benzoic acid,phenol,and catechol),and then excursion of their ultraviolet spectra were detected.Molecular weight of humic acid was reduced by the small molecular organic acids spiked.Additionally,solubility of humic acid significantly increased at pH approaching the pKa of small molecular organic acids.All the findings demonstrate that CAHB possibly forms between small molecular organic acids and humic acid,which would destroy the supramolecules structure maintained by weak forces,thus leading to reduction of molecular weight and enhancement of solubility of humic acid.Moreover,the smaller the pKa difference is,the stronger CAHB formed and the greater the molecule structure disturbance is.Small molecular organic acid could interact with some chemicals of humic acid bonded by CAHB when both have similar pKa,and the energy for transition increases,which were indicated by UV spectrum and synchronous 2D correlation UV spectrum analysis.
作者
石林
曹艳贝
张凰
张迪
SHI Lin;CAO Yanbei;ZHANG Huang;ZHANG Di(Faculty of Environmental Science and Engineering,Kunming University of Science&Technology,Kunming 650500,China;Yunnan Institute of Food Safety,Kunming University of Science&Technology,Kunming 650500,China;Yunnan Key Laboratory of Carbon Sequestration and Pollution Controlling,Kunming 650500,China)
出处
《土壤学报》
CAS
CSCD
北大核心
2020年第1期251-257,共7页
Acta Pedologica Sinica
基金
国家自然科学基金项目（41663014）
云南省中青年学术和技术带头人项目（2018HB008）资助~~
关键词
电荷辅助氢键
腐殖酸
超分子结构
溶解性
分子量
Charge-assistant hydrogen bonds
Humic acids
Supramolecule structure
Solubility
Molecular weight
作者简介
通讯作者:张迪,E-mail:zhangdi2002113@sina.com;石林(1992—),男,山东人,博士研究生,主要从事土壤污染物环境行为研究。E-mail:shilinfs@163.com。
