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首页> 外文期刊>Environmental Science & Technology >Hydrophilic and hydrophobic sorption of organic acids by variable-charge soils: Effect of chemical acidity and acidic functional group
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Hydrophilic and hydrophobic sorption of organic acids by variable-charge soils: Effect of chemical acidity and acidic functional group

机译：可变电荷土壤对有机酸的亲水和疏水吸附：化学酸度和酸性官能团的影响

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摘要

Sorption of organic acids by variable-charge soil occurs through both hydrophilic and hydrophobic sorption. In this study, the effect of chemical acidity and the type of acidic functional group on the relative contribution of hydrophilic and hydrophobic processes to sorption by a gibbsite-dominated and a kaolinite-dominated variable-charge soils was quantified by measuring sorption isotherms from different electrolytes (CaCl2, Ca(H2PO4)(2), and KCl). The All soil is dominated by gibbsite whereas the DRC soil is primarily kaolinite. The organic acids investigated include five chlorinated phenols (pentachlorophenol, 2,3,4,6-tetrachlorophenol, 2,4,6-trichlorophenol, 2,4,5-trichlorophenol, and 2,4-dichlorophenol) with pK(a) values ranging from 4.69 to 7.85 and two acidic herbicides (2,4-D (pK(a) = 2.8) and prosulfuron (pK(a), = 3.76)) that contain carboxyl and urea functional groups, respectively. Anion exchange of chlorinated phenols and prosulfuron on both variable-charge soils as well as 2,4-D sorption on the A1 soil was linearly correlated to chemical acidity. The effective positive surface charge [AEC/(AEC + CEC)] and the anionic fraction of the organic acid in solution, which are both pH-dependent, were sufficient to estimate the contribution of anion exchange to organic acid sorption except for 2,4-D sorption by DRC soil, The latter was much greater than would be predicted from the pK(a) of 2,4-D. Calcium bridging between silanol edge group and 2,4-D was hypothesized and corroborated by differences in sorption measured from KCl and CaCl2 solutions. For predicting contributions from hydrophobic processes, a log-log linear relationship between pH-dependent octanol-water (K-OW(pH)) and organic carbon-normalized sorption coefficients (K-OC(pH)) appeared adequate.
机译：电荷可变的土壤通过亲水性和疏水性吸附来吸附有机酸。在这项研究中，通过测量来自不同电解质的吸附等温线，量化了化学酸度和酸性官能团类型对亲水和疏水过程对由三水铝矿为主和高岭石为主的可变电荷土壤吸附的相对贡献的影响。 （CaCl2，Ca（H2PO4）（2）和KCl）。全部土壤以三水铝铁矿为主，而DRC土壤主要是高岭石。研究的有机酸包括五种具有pK（a）值的氯化苯酚（五氯苯酚，2,3,4,6-四氯苯酚，2,4,6-三氯苯酚，2,4,5-三氯苯酚和2,4-二氯苯酚）范围从4.69至7.85的两种酸性除草剂（2,4-D（pK（a）= 2.8）和前磺隆（pK（a），= 3.76）），分别含有羧基和尿素官能团。可变电荷土壤上的氯酚和丙磺隆的阴离子交换以及A1土壤上的2,4-D吸附与化学酸度线性相关。有效的正表面电荷[AEC /（AEC + CEC）]和溶液中有机酸的阴离子级分（均与pH值有关），足以估计阴离子交换对有机酸吸附的贡献，除了2,4 DRC土壤对-D的吸附，后者比2,4-D的pK（a）所预测的要大得多。通过从KCl和CaCl2溶液测得的吸附差异，对硅烷醇边缘基团与2,4-D之间的钙桥连接进行了假设和证实。为了预测疏水过程的贡献，pH依赖的辛醇-水（K-OW（pH））和有机碳归一化吸附系数（K-OC（pH））之间的对数线性关系似乎足够。

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