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Relating Cd2+ binding by humic acids to molecular weight: A modeling and spectroscopic study

文献类型： 外文期刊

作者： Bai, Hongcheng 1 ; Jiang, Zhenmao 1 ; He, Minjin 1 ; Ye, Biying 1 ; Wei, Shiqiang 1 ;

作者机构： 1.Southwest Univ, Dept Environm Sci & Engn, Coll Resources & Environm, Chongqing 400715, Peoples R China; Chongqing Key Lab Agr Resources & Environm, Chongqing 400715, Peoples R China; Minist Educ, China Key Lab Three Gorges Reservoir Reg Ecoenvir, Chongqing 400715, Peoples R China

关键词： Humic acid; Molecular weight; NICA-Donnan; Fluorescence excitation-emission matrix quenching; Cadmium

期刊名称：JOURNAL OF ENVIRONMENTAL SCIENCES （ 影响因子：5.9； 五年影响因子：5.6 ）

ISSN： 1001-0742

年卷期： 2018 年 70 卷

页码：

收录情况： SCI

摘要： Molecular weight (Mw) is a fundamental property of humic acids (HAs), which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid (HA) extracted from Jinyun Mountain, Chongqing was ultra-filtered into four fractions according to the molecular weight, and their properties were characterized. Complexation of cadmium was investigated by titration experiments. For the first time, Langmuir and non-ideal competitive adsorption-Donna (NICA-Donnan) models combined with fluorescence excitation-emission matrix (EEM) quenching were employed to elucidate the binding characteristics of individual Mw fractions of HA. The results showed that the concentration of acidic functional groups decreased with increasing Mw, especially the phenolic groups. The humification degree and aliphaticity increased with increasing Mw as indicated by elemental composition analysis and FT-IR spectra. The binding capacity of Cd2+ to Mw fractions of HA followed the order UF1 (< 5 kDa) > UF2 (5-10 kDa) > UF4 (> 30 kDa) > UF3 (10-30 kDa). Moreover, the distribution of cadmium speciation indicated that the phenolic groups were responsible for the variations in binding of Cd2+ among different Mw fractions. The results of fluorescence quenching illustrated that the binding capacity of Cd2+ to Mw fractions was controlled by the content of functional groups, while the binding affinity was largely influenced by structural factors. The results provide a better understanding of the roles that different HA Mw fractions play in heavy metal binding, which has important implications in the control of heavy metal migration and bio-toxicity. (C) 2017 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

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