Adsorption of (poly)maleic acid and an aquatic fulvic acid by goethite

被引:108
作者
Wang, LL
Chin, YP [1 ]
Traina, SJ
机构
[1] Ohio State Univ, Dept Geol Sci, Columbus, OH 43210 USA
[2] Ohio State Univ, Environm Sci Program, Columbus, OH 43210 USA
关键词
D O I
10.1016/S0016-7037(97)00338-4
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The adsorption of Suwannee River fulvic acid (SRFA) and a synthetic organic polymer, polymaleic acid (PMA) by goethite was studied. The adsorption density of the sorbates decreased with increasing pH, and the data could best be described by the Langmuir adsorption equation. The number- and weight-averaged molecular weights, M-w and M-n, of the sorbates in the solution phase before and after adsorption by goethite were measured by high-pressure size exclusion chromatography. The observed decreases in the M-n and M-w of SRFA in the solution phase after adsorption demonstrated that fractionation of SRFA on the basis of molecular size occured. UV molar absorptivities measured at 280 nm also decreased, which suggests that the more aromatic moieties are preferentially adsorbed. Potentiometric titrations conducted on SRFA revealed changes in the conditional acidity constants (expressed as the negative logarithm, pK(a)) of the fulvic acid after adsorption. The increased pK(a) value of the humic material remaining in the solution after adsorption implies that the strongly sorbing compounds possessed stronger acidic functional groups. Fractionation of PMA after adsorption, however, did not occur to the same extent compared to SRFA because PMA is relatively homogeneous. The experimental results confirm that molecular weight, aromaticity, and organic acidity are major factors controlling the fractionation of natural organic matter (NOM) by adsorption onto hydrous mineral oxides. PMA, a relatively uniform and less polydisperse organic polymer, may serve as an endmember material characteristic of NOM that exhibits the least amount of fractionation upon adsorption. Copyright (C) 1997 Elsevier Science Ltd.
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页码:5313 / 5324
页数:12
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