Ji Liangliang, Chen Wei, Zheng Shourong, Xu Zhaoyi, Zhu Dongqiang
State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu 210093, China.
Langmuir. 2009 Oct 6;25(19):11608-13. doi: 10.1021/la9015838.
The presence of sulfonamide antibiotics in aquatic environments has been recognized as an issue warranting consideration. In this study, we evaluated multiwalled carbon nanotubes (MWNT) as a potential effective adsorbent for removal of two sulfonamide antibiotics, sulfapyridine and sulfamethoxazole, from aqueous solutions. Nonporous, functionality-free graphite was included as a comparative adsorbent. Despite the very low hydrophobicity, the two sulfonamides adsorbed strongly to MWNT and graphite, a fact attributed to pi-pi electron coupling with the graphene surface of the adsorbent. For both sulfonamide antibiotics, similar patterns of pH-dependent adsorption were observed between MWNT and graphite, implying the predominance of graphene structures for the adsorption to MWNT. Moreover, the observed pH effects on adsorption indicate that the protonated neutral form of sulfonamide adsorbs much more strongly than the deprotonated anionic counterpart does. The effects of ionic strength (NaCl and CaCl2) and the presence of a dissolved soil humic acid on adsorption of the two antibiotics to MWNT and graphite were also assessed. Ring current-induced 1H NMR upfield chemical shifts further verified face-to-face complex formation between neutral sulfamethoxazole and model pi-electron donor compounds (naphthalene, phenanthrene, and pyrene) in solution.
水生环境中磺胺类抗生素的存在已被视为一个值得关注的问题。在本研究中，我们评估了多壁碳纳米管（MWNT）作为一种潜在的有效吸附剂，用于从水溶液中去除两种磺胺类抗生素——磺胺吡啶和磺胺甲恶唑。将无孔、无官能团的石墨作为对比吸附剂。尽管这两种磺胺类药物疏水性极低，但它们都能强烈吸附到MWNT和石墨上，这一事实归因于与吸附剂石墨烯表面的π-π电子耦合。对于这两种磺胺类抗生素，在MWNT和石墨之间观察到类似的pH依赖性吸附模式，这意味着石墨烯结构在吸附到MWNT过程中占主导地位。此外，观察到的pH对吸附的影响表明，磺胺类药物的质子化中性形式比去质子化阴离子形式吸附得更强。还评估了离子强度（NaCl和CaCl2）以及溶解的土壤腐殖酸的存在对这两种抗生素吸附到MWNT和石墨上的影响。环电流诱导的1H NMR高场化学位移进一步证实了溶液中中性磺胺甲恶唑与模型π电子供体化合物（萘、菲和芘）之间形成了面对面的复合物。
