pH值和离子强度对针铁矿吸附磺胺二甲基嘧啶的影响机制

磺胺二甲基嘧啶作为普遍使用的抗生素代表,可通过动物粪便施肥及药物不规范使用进入到环境中.针铁矿是土壤中分布广泛且活性较高的一种矿物,会对磺胺二甲基嘧啶的环境行为产生一定的影响.为了正确评估磺胺二甲基嘧啶的环境风险,本文考察了溶液pH值、离子强度对针铁矿吸附磺胺二甲基嘧啶的影响.结果表明:磺胺二甲基嘧啶在针铁矿上的吸附具有明显的非线性,且吸附具有明显的滞后现象,吸附等温线可以用Freundlich模型较好的拟合(R~2=0.991);磺胺二甲基嘧啶在针铁矿上的吸附随着pH值的增加先增加后减小,随着离子强度的增加开始有微弱的增加然后保持不变;在酸性和中性条件下,表面络合作用是主导磺胺二甲基嘧啶在针铁矿表面上吸附的主要机制,在碱性条件下静电斥力是主导吸附的主要作用力.因此,在评估抗生素的环境行为时,应该考虑不同的环境条件对针铁矿吸附磺胺二甲基嘧啶的影响.

The influence of pH and ionic strength on the sorption of sulfamethazine by goethite

Sulfamethazine (SMT) as a typically ionic antibiotic could enter into the soil environment via application of livestock wastes in agricultural field and abuse of pharmaceuticals. Goethite as one of the most important iron oxides in soil might interact with SMT, which could influence its environmental behavior and bioavailability. In this study, the sorption properties of SMT on goethite in different solution chemistries were investigated. The sorption isotherm exhibited a significant nonlinear trend and desorption hysteresis, while the data could be fitted well with the Freundlich model (R²=0.991). Sorption capacity increased initially and then decreased as pH increased. The sorption increased slightly and then kept relatively constant as the ionic strength of solutions increased. The results indicated that the sorption mechanism would be altered in different solution conditions.1Under acidic and neutral condition, inner-sphere complexions could be one predominantsorption mechanism;2The sorption under alkali conditions could be due to electrostatic interactions between SMT and goethite. Overall, it should be noted that the heterogeneous sorption affinity of SMT on goethite at various solution chemistriescan impact its environmental fate.