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研究了奥德里奇公司提供的腐植酸和钴60的络合能力与腐植酸分子大小的关系以及腐植酸的结构对两者络合作用的影响。在腐植酸浓度较低时,钴60与分子量大于100000 Da[HA(100<)]的腐植酸相互作用,随着腐植酸浓度的增加,钴60倾向于与分子量在30000~100000 Da[HA(30~100)]之间的腐植酸相互作用。本研究用FTIR(傅里叶变换红外光谱),13C核磁共振光谱和酸碱滴定曲线表征分离出来的HA(100<)和HA(30~100)。实验发现,HA(10<)具有脂肪支链结构,-COOH较小,且具有较大的质子交换能力,该腐植酸成分在络合过程中共价键作用较小,离子交换作用起主要作用。此外,支链卷曲造成的空间位阻作用能影响两者的络合作用。HA(30~100)结构中以芳香-COOH和-OH为主,因此与钴60相互作用是以形成共价键为主,本研究用XPS测定了钴和腐植酸间的结合能,其结果证实了前面的假设。
The relationship between the complexation ability of humic acid and cobalt 60 and the molecular size of humic acid and the structure of humic acid on the complexation between the two were studied. At low humic acid concentrations, cobalt 60 interacts with humic acid with molecular weights greater than 100000 Da [HA (100 <)], and as the concentration of humic acid increases, cobalt 60 tends to react with humic acids with molecular weights between 30000 and 100000 Da [HA 30 ~ 100)] between the humic acid interaction. In this study, isolated HA (100 <) and HA (30-100) were characterized by FTIR (Fourier transform infrared) spectroscopy, 13C nuclear magnetic resonance spectroscopy and acid-base titration curves. It was found that the HA (10 <) had a fat-branched structure, a small -COOH, and a large proton exchange capacity. The humic acid component had less covalent bond in the complexation process and ion exchange played a major role. In addition, steric hindrance caused by branch curling can affect the complexation of the two. In the structure of HA (30-100), aromatic-COOH and -OH are dominant, so the interaction with cobalt 60 is dominated by the formation of covalent bonds. In this study, the binding energy between cobalt and humic acid was determined by XPS. Confirmed the previous assumptions.