腐殖酸与稀土元素的结合点位及其表征研究

Study on the Binding Sites of Humic Acids with Rare Earth Elements and Its Characterization

采用红外光谱(FTIR)与核磁共振波谱(1H NMR和13C NMR)技术,对来自森林土壤和湖泊沉积物的两种腐殖酸及其与三价稀土离子(RE3+)沉淀反应的产物进行对比研究.结果表明,腐殖酸结构中活性官能团特征以及它的拥有量因腐殖化程度不同而存在较大差异.腐殖酸与RE3+沉淀反应产物在性质上属于一种有机弱酸盐,羧基-COOH和酚羟基-OH为主要结合点位,结合反应过程中它们的质子被RE3+交换出来.

Two types of humic acids taken from forest soil and lake sediment, and their precipitation reaction products with the trivalent rare earth elements are identified comparatively by FTIR,^1H NMR and ^13C NMR spectroscopy. The FTIR and NMR spectra indicate that the structural framework of two humic acids are similar principally due to their same origin,but there is great difference in the structural characteristics and functional groups amount of humic acids because of their different humification degree. Forest soil humic acid （FHA） has more Ar-COOH with strong binding strength than lake sediment humic acid （SHA） ,which has more Ph-OH with weak binding strength due to its high humification degree. The explicit evidences of humic acids binding with trivalent rare earth elements are found from FTIR and NMR spectroscopy, which the Ar-COOH and Ph-OH are the main binding sites of humic acids with RE^3＋. The precipitation reaction products of humic acids with RE^3＋ belong to a kind of undissolved organic weak acid salts, which are similar to the binding reaction mechanism of weak acid with metal ions. In the reaction procedure of humic acids with RE^3＋ ,the results of pH monitoring of the solutions demonstrate that the protons of Ar-COOH and Ph-OH can be exchanged out by RE^3＋.