Effect of humic acids on the adsorption of paraquat by goethite.
Effect of humic acids on the adsorption of paraquat by goethite.
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DOI：
10.1016/j.jhazmat.2010.08.028
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发表时间：
2010-12
影响因子：
13.6
通讯作者：
M. Brigante;Graciela P. Zanini;M. Avena
中科院分区：
文献类型：
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作者：
M. Brigante;Graciela P. Zanini;M. Avena
通过静态吸附实验，研究了不同pH值、支持电解质浓度和温度条件下，百草枯（PQ 2+）在针铁矿和胡敏酸-针铁矿二元体系上的吸附行为。采用毛细管电泳法测定了溶液中PQ ~（2+）与腐殖酸（HA）分子的结合等温线。PQ 2+吸附在裸针铁矿表面上是可以忽略的，但在HA-针铁矿吸附剂上是重要的。在最后一种情况下，通过增加pH和降低电解质浓度来增加吸附。温度对吸附无明显影响。吸附通过PQ 2+与吸附的HA分子直接结合而发生，导致针铁矿-HA-PQ 2+类型的表面物种的形成。结果与PQ 2+结合HA（羧酸盐和酚盐）的带负电荷基团形成离子对或外球复合物的机制一致。由于针铁矿在自然界中通常含有吸附的HA分子，它可以作为一个很好的吸附剂的阳离子除草剂。这不仅有利于除草剂的失活，而且还能减少其通过地下水的沥滤和迁移。
The adsorption of the herbicide paraquat (PQ2+) on goethite and on the binary system humic acid–goethite has been studied in batch experiments by performing adsorption isotherms under different conditions of pH, supporting electrolyte concentration and temperature. The results were completed with capillary electrophoresis (CE) in order to measure the binding isotherm between PQ2+and humic acid (HA) molecules in solution. PQ2+adsorption is negligible on the bare goethite surface but important on the HA–goethite adsorbent. In this last case, the adsorption increases by increasing pH and decreasing electrolyte concentration. There are no significant effects of temperature on the adsorption. The adsorption takes place by direct binding of PQ2+to adsorbed HA molecules leading to the formation of surface species of the type goethite–HA–PQ2+. The results are consistent with a mechanism where PQ2+binds negatively charged groups of HA (carboxylates and phenolates) forming ionic pairs or outer-sphere complexes. Since goethite in nature usually contains adsorbed HA molecules, it may act as a good adsorbent for cationic herbicides. This will not only benefit the deactivation of the herbicides but also reduce their leaching and transport through groundwater.