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

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.

Concurrent and dual N-doping of graphene/ZnO nanocomposites for enhanced Cr(vi) photoreduction activity under visible-light irradiation

“…The precursor GO/Zn(HCO 3 ) 2 with different theoretical loadings of GO was prepared by a procedure similar to our previous work. 66 In brief, ZnSO 4 $7H 2 O (21.57 g) dissolved in 100 mL H 2 O and different volume of GO solution was added. Then the solution was ultrasonicated for another 30 min to ensure the uniform adsorption of Zn 2+ onto the surface of GO nanosheets.…”

Photoluminescence Emission during Photoreduction of Graphene Oxide Sheets as Investigated with Single-Molecule Microscopy

“…As known, GO sheets are composed of many π-electron conjugated sp 2 domains isolated by sp 3 structures mainly composed of oxygen-containing groups, 24 has been confirmed with high-resolution transmission electron microscope (HRTEM). 25,26 There are big variations in sizes of these sp 2 domains, making the photoluminescence (PL) of GO widely range from 500 to 800 nm.…”

“…As known, GO sheets are composed of many π-electron conjugated sp 2 domains isolated by sp 3 structures mainly composed of oxygen-containing groups, has been confirmed with high-resolution transmission electron microscope (HRTEM). , There are big variations in sizes of these sp 2 domains, making the photoluminescence (PL) of GO widely range from 500 to 800 nm. − When GO sheets were reduced, many oxygen-containing functional groups are removed, and many sp 3 bonds transform to sp 2 bonds . Furthermore, defects may form during this sp 3 to sp 2 transition, and these defects make the π-electron conjugated sp 2 domains isolated .…”

Visible‐light driven photodegradation of phenol over niobium oxide‐loaded fibrous silica titania composite catalyst

“…These results signifying that upon the photoreduction reaction, the TEMPO-e − adducts were not formed, indicating the absence of e − species within the system. 46,47 Fig. 8(B) shows the ESR signal of DMPO − •OH of 5 Nb/FST in an aqueous dispersion.…”