Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum(III) ion cross-linking
Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum(III) ion cross-linking
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DOI：
10.2134/jeq2004.1314
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发表时间：
2004-07-01
影响因子：
2.4
通讯作者：
Pignatello, JJ
中科院分区：
文献类型：
--
作者：
Lu, YF;Pignatello, JJ
疏水性化合物在土壤中的吸附往往表现出非线性、竞争性和滞后性。由于这种行为与玻璃态的有机聚合物有关，因此假定某些形式的土壤腐殖物质是玻璃态的。玻璃态有利于降低大分子柔性的性质，如交联、不饱和键的存在和高分子量。土壤中大量存在的多价金属离子可通过与不同链上的多个官能团配位而交联腐殖物质。因此，我们通过絮凝技术从土壤腐殖酸的H+形式（H-HA）制备Al 3+交联腐殖酸（AI-HA），该絮凝技术使Al离子结合到有机基团。萘和1，2，4-三氯苯（TCB）的吸附H-HA是非线性的，竞争性的，略有滞后，与以前的研究表明，玻璃化转变温度高于室温的腐殖酸。非线性，竞争，和滞后都增强铝-HA，验证了假设，金属离子交联增强非理想吸附。玻璃态聚合物吸附模型的应用表明，交联增加了溶质的亲和力的孔域相对于溶解域。结果（i）表明分离、纯化的土壤腐殖酸表现得像玻璃状固体，（ii）表明金属离子交联产生了更刚性的链结构，并支持非理想吸附和土壤有机物的玻璃状特征之间的联系，和（iii）强调金属离子对腐殖酸结构与疏水性有机化合物吸附相关的重要性。
Sorption of hydrophobic compounds in soils often shows nonlinearity, competition, and hysteresis. Since such behaviors have been associated with organic polymers in glassy state, it has been postulated that some forms of soil humic substances are glassy. The glassy state is favored by properties that decrease the flexibility of macromolecules, such as cross-linking, presence of unsaturated bonds, and high molecular weight. Polyvalent metal ions, which are abundant in soils, may cross-link humic substances by coordinating to multiple functional groups on different strands. Accordingly, we prepared an Al3+-crosslinked humic acid (AI-HA) from the H+ form (H-HA) of a soil humic acid by a flocculation technique that leaves A] ions bound to organic groups. Sorption of naphthalene and 1,2,4-trichlorobenzene (TCB) on H-HA was nonlinear, competitive, and slightly hysteretic, in agreement with previous studies showing glass transition temperatures of humic acids that lie above room temperature. Nonlinearity, competition, and hysteresis were all enhanced in Al-HA, validating the hypothesis that metal ion cross-linking enhances nonideal sorption. Application of a glassy polymer sorption model reveals that cross-linking increases the affinity of solutes for the hole domain relative to the dissolution domain. The results (i) indicate that isolated, purified soil humic acid behaves like a glassy solid, (ii) indicate that metal-ion cross-linking creates a more rigid-chain structure and supports a link between nonideal sorption and the glassy character of soil organic matter, and (iii) underscore the importance of metal ions on humic structure in relation to sorption of hydrophobic organic compounds.