Supending Of Carbon Nanotubes In Aquatic Enviroment And Sorption Mechanisms Of Antibiotics On Carbon Nanotubes

Carbon nanotubes (CNTs) as a novel carbon nanomaterials have many unique properties, such as electrical conductivity, optical activity, and mechanical strength, which make CNTs attract special attention. This fascinating new class of materials has shown promising application in many areas since its discovery However, during its production, usage and discharge,various forms of CNTs are being spread quickly in the environment because of their growing use through different pathways. Several studies indicate that CNTs are toxic to organisms and human beings, and their environmental risks are influenced by their environmental behavior as well,take the suspending in the water as an example. Additionally, the presence of CNTs in the environment can also affect the behavior of pollutants and then the toxicity, transformation, fate and potential risks of other pollutants, because CNTs have strong adsorption affinity and capacity. Because of their hydrophobic surfaces, strong interactions between CNTs and organic chemicals are expected. Increasing concern has been raised regarding the potential risks of antibiotics to human and ecological health because of their extensive use. Therefore, to study the suspending of CNTs in aquatic environment and the interaction between CNTs and antibiotics has great necessity.Many types of CNTs were used in this study to investigate their dispersion and aggregation in the aquatic environment. The effects of ultrasonic treatment, natural dissolved organic matter and surfactants on the dispersion of CNTs were studied, and the concentration of CNTs suspended in water were determined ere measured with a uv-visible scanning spectrophotometer. Norfloxacin (NOR) and oxytetracycline (OTC) were chosen as common antibiotics, and the sorption behavior of them on CNTs were studied. The results got in this study are as follows:Compared with the oscillation treatment, ultrasonic treatment can be greatly enhanced ability of CNTs suspended in water, but the relationship between ultrasonic time and suspended CNTs is not linear, there is an optimum ultrasonic time. The presence of DOM or surfactants will largely influence the dispersion of CNTs,and the relationship between the concentration of DOM or surfactants is not linear either, there is an optimal concentration of DOM or sufactants. Thus, the properties of the DOM and surfactants are the main factor affecting the dispersion of CNTs.All sorption isotherms were highly nonlinear and were fitted well by Freundlich and Polanyi-Manes models for NOR, Langmuir model failed to fit any isotherm in this study. AC showed the highest NOR sorption capacity because of its highest surface area. Comparison of sorption coefficients at different pHs indicates that hydrophobic and electrostatic interaction also play major roles in sorption of NOR on CNTs.H-CNTs had much higher NOR sorption than C-CNTs,and theπ-πelectron donor-acceptor (EDA) interactions could explain the distinction between the two types of CNTs Furthermore, high sorption capacity and hysteresis of NOR on CNTs were demonstrated in this study, which needs to be considered for predicting environmental risks of CNTs and NOR.The results from thermodynamic analysis show that sorption of NOR on AC and CNTs was thermodynamically favorable and generally endothermic Sorption site energy analysis illustrates a distribution of sorption energy, consistent with nonlinear isotherms, which indicates the heterogeneous sites on CNTs for NOR adsorption.The presence of Ca2+ in the solution could affect the the UV response significatanly, but ionic strength caused by Na could not Batch experiments were carried out by OTC on the G-CNTs, C-CNTs and H-CNTs.The results showed that the sorption isotherms were highly nonlinear but were fitted not well by Freundlich and Polanyi-Manes models for OTC.H-CNTs showed the higher OTC sorption than G-CNTs and C-CNTs.By changing the system pH, ionic strength and the presence of Ca2+, the ionic strength caused by Na showed no significant effect on the OTC sorption process on CNTs.However, the Ca2+ may affect the sorption of OTC on CNTs greatly by 'cation bridging' mechanism. In addition, EDA reaction is the adsorption of OTC in the main mechanism of carbon nanotubes.