有机质和重金属对抗生素在多壁碳纳米管上吸附的影响

Most current research is focused on the sorption of metals, antibiotics or organic matter by carbon nanotubes (CNTs) in isolation in single-solute system. A single-solute system may not adequately represent the majority of mixed contaminant water systems commonly encountered in the water environment, where complex mixtures of contaminants containing organic matter, heavy metals and antibiocss may coexist at many contaminated water bodies. To the best of our knowledge, the question as to whether and how organic matter and heavy metals affect the sorption of antibiotics on CNTs has not been adequately addressed...Therefore, this proposal will apply dialysis equilibrium system to investigate the role of organic matter and heavy metals on sorption of antibiotics by functionalized multiwalled carbon nanotubes (MWCNTs) at various pHs. Special attention would be given on which interaction mechanism dominates the sorption of an antibiotic as affected by a certain organic matter and metals. Therefore, Fourier transform infrared spectroscopic, and X-ray absorption spectroscopic, and X-ray diffraction spectroscopic, and nuclear magnetic resonance, and ultraviolet-visible spectroscopic studies will be applied subsequently to provide insight into the organic matter-metals-antibiotics interactions in aqueous solutions and on the surface of functionalized MWCNTs.The results will shed light on the mechanism between complex mixtures of contaminants and MWCNTs.The resulsts will also provide new insight into the environmental behaviors of antibiotis and MWCNTs and ecological risk assessment.

近来，人们分别研究了碳纳米管(CNTs)-重金属、CNTs-抗生素和CNTs-有机质等单一体系中的吸附行为，并取得一定进展。但是，单一的纯水体系不能充分反映多种污染物共存的真实环境。迄今为止，对水环境中广泛存在的有机质和重金属对抗生素在CNTs上吸附的影响少有研究。本项目拟研究不同pH时，有机质和重金属对抗生素在功能化多壁碳纳米管（MWCNTs）上吸附的影响，并应用多种光谱和波谱技术，如傅里叶变换红外光谱、X-射线吸收光谱、X-射线粉末衍射、核磁共振、紫外-可见光谱等技术，观测MWCNTs分散性及表面性质变化、污染物在溶液中的形态、污染物在MWCNTs上的吸附位点，在分子水平阐明有机质和重金属影响抗生素吸附的机理。该研究对于了解共存污染物在MWCNTs上的作用机制具有科学意义，对于了解抗生素和MWCNTs的环境行为及环境健康风险评价具有现实意义。

选用石墨化（P-MWCNTs）、羧基化（C-MWCNTs）和羟基化（H-MWCNTs）碳纳米管，研究了溶液性质对MWCNTs吸附抗生素SMZ的行为及机制;探讨了腐殖酸（HA）对MWCNTs吸附SMZ的影响机制;研究了不同HA对MWCNTs分散性的影响机制；考察了可溶性有机质（（DOM）对金属纳米颗粒（NPs）悬浮及植物毒性影响机制。.1.溶液中不同金属阳离子（0.5 mM）对MWCNTs吸附SMZ的影响各不相同。当溶液pH 为2.3 和4.9时，, 归因于Cu2+ 与SMZ+和SMZ±对MWCNTs上吸附位点的竞争，抑制SMZ的吸附(10%~20%)。pH 为7.4和10.0时， Cu2+与SMZ- 络合形成Cu2+-SMZ导致的促进效应，促进SMZ的吸附（20%~ 60%）。溶液pH为2.3, 4.9 和7.4时，吸附到MWCNTs上的Al3+通过金属桥键作用促进SMZ吸附。.2.水溶液中HA抑制SMZ在MWCNTs的吸附，归因于HA和SMZ对MWCNTs上吸附位点的竞争、分子筛作用和孔的阻塞作用。吸附到MWCNTs的HA减弱了SMZ和MWCNTs之间的静电和疏水作用，也降低了SMZ的吸附。傅里叶变换显微红外光谱揭示π-π作用和氢键作用在HA和SMZ吸附中发挥重要作用。.3．在离子强度0~0.04 M，pH3~7范围内，MWCNTs的分散浓度和HA的吸附量呈现正相关，这归因于吸附在MWCNTs表面的腐植酸分子含有的大量亲水官能团，增强了MWCNTs和水分子之间的亲水作用，促进了MWCNTs在溶液中的分散性。.4. 森林土壤HA（FHA）和Aldrich HA（AHA）腐殖酸都能够有效分散并稳定水溶液中的MWCNTs。FHA具有更高的MWCNTs稳定能力，原因在于其具有较高的芳香性和分子量。.5.单宁酸显著改变Nd2O3 NPs的溶液行为，并使Nd2O3NPs的表面电荷从正变副；溶液中60 mg L-1的单宁酸显著减低了100 mg L-1 of NPs暴露下Nd在植物体内的积累，有效恢复了植物体内S, Ca, K 和Mg等元素的含量，减轻了NPs的植物毒性，其机制为单宁酸通过调高Cu/Zn SOD、APX1、TRDX和GST根部基因的表达来减缓Nd2O3纳米颗粒对植物的毒性。.以上研究结果对于评价金属纳米材料的环境风险及生态毒性具有重要意义。