Green and Effective Removal of Aqueous Graphene Oxide under UV-Light Irradiation

Xiaoya Yuan,Xin Cheng,Zijuan Feng,Dong Peng,Qiuye Jing,Jiawei Niu,Xue Wu

doi:10.3390/nano8090654

Abstract

The potential extensive application of graphene oxide (GO) in various fields results in the possibility of its release into the natural environment with negative impacts on humans and the ecosystem. The UV-induced removal behavior of aqueous GO was evaluated in this study, and the effect of various parameters (including initial GO concentration, initial solution pH and co-existing ions) on removal rate of GO were investigated in detail. The results showed that UV-light induced a maximum removal rate of GO of 99.1% after 32 h irradiation without any additives, and that the photo-induced removal process in all cases fitted well with pseudo-first-order kinetics. Under optimal conditions, GO was completely removed, with initial GO concentrations of 10 mg/L while adjusting solution pH to 3 or adding Ca2+-containing salt. The GO and photoreduced graphene oxide (prGO) were characterized using High-resolution Transmission Microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS), and Fourier-transform Infrared Spectroscopy (FT-IR). The radical species trapping experiments and Electron Spin Resonance (ESR) tests indicated that self-reduction of GO upon UV-light exposure could be achieved via photogenerated electrons from a GO semiconductor. Further mechanism study showed that the high efficiency of UV-induced GO removal came from UV-induced photoreduction, and pH-induced or cation-induced coagulation. This study provided a green and effective method to remove GO from aqueous solutions.

Highlights

Graphene oxide (GO), one of the most important derivatives of graphene, has many potential applications owing to its unique structures and outstanding physicochemical properties [1,2,3,4]
With its increasingly widespread use in the fields of hybrid materials, environmental pollutant removal, sensors, nanoelectronics, batteries, and hydrogen storage, photocatalyst, biomedicine and biotechnology, etc. [7,8,9], GO was inevitably introduced into the aquatic environment
The UV-light induced removal rates were 77.1%, 72.4%, 67.6%, 69.8%, and 56.2% for initial GO concentration of 10, 15, 20, 25, and 30 mg/L after 12 h irradiation, respectively, indicating that the removal process driven directly only by UV-light was significantly affected by the initial concentration of aqueous GO solution

Summary

Introduction

Graphene oxide (GO), one of the most important derivatives of graphene, has many potential applications owing to its unique structures and outstanding physicochemical properties [1,2,3,4]. Because it has many hydrophilic oxygen-containing functional groups, such as hydroxyl and epoxy on the basal planes and carboxylic and carbonyl groups at the edge of sheets, GO can be well dispersed in an aqueous medium, without adding amphiphilic stabilizers [5,6]. It is very urgent to eliminate GO from aqueous solution

Methods

Results

Conclusion