Sorption and Desorption Analysis of Nitrobenzene on Differently Functionalized Multiwalled Carbon Nanotubes and Implications on the Stability

Zhanhua Ji,Dengyu Li

doi:10.3390/w13101426

Abstract

The stability of carbon nanotubes (CNTs) suspension is a key factor in determining their transport, fate, and toxicity in an aquatic environment, which is significantly influenced by CNTs’ nature and water chemistry. Macromolecular dissolved organic matter (DOM) is reported to influence the stability of CNTs aggregation. However, little is known on small polar dissolved organic compound’s effects on CNTs aggregation. Nitrobenzene was selected to investigate its interaction with three different functionalized multiwalled CNTs (MWCNTs). Both the stability of CNTs aggregation and sorption hysteresis were affected by the initial concentration of nitrobenzene and the surface functionalization coverage of MWCNTs. At the initial concentration below 580 mg/L, the thermodynamic index of irreversibility (TII) and turbidity of CNTs suspension had the same tendency, indicating that the underlying mechanism is closely related. A conceptual adsorption–desorption model was proposed to further explain the relationship between the sorption hysteresis and stability of MWCNTs suspension under different initial concentrations of nitrobenzene. This provided data support to further clarify the environmental behaviors and risks of CNTs.

Highlights

Carbon nanotubes (CNTs) are gaining increasingly more attention since their first discovery in 1991 [1]
The three functionalized multiwalled CNTs (MWCNTs) produced by different treatments had similar length and size, their oxygen element distributions were different
Our experiments demonstrated that the adsorption of nitrobenzene can affect CNTs’ stability

Summary

Introduction

Carbon nanotubes (CNTs) are gaining increasingly more attention since their first discovery in 1991 [1]. Once released into the aquatic environment, CNTs inevitably interact with the co-existing media in water Due to their strong hydrophobicity and high specific surface area, CNTs concentrate pollutants in water, especially organic pollutants, and enter the food chain together, through the ingestion of floating organisms, posing potential threats to the environment and human health [10]. Organic molecules like dissolved organic matter and surfactants, can help enhance the stability of CNTs suspension in aqueous solution, and affect the aggregation behavior of CNTs [11]. This can affect the cloudiness or haziness (turbidity) of CNTs suspension

Methods

Results

Conclusion