Photochlorination-induced transformation of graphene oxide: Mechanism and environmental fate

Abstract

a b s t r a c tWith the increasing production and wide utilization of graphene oxide (GO), the nanomaterials are expected to be released into the environment, and end up in surface waters, and/or wastewater treatment plants. This study explored the changes in the physicochemical properties of GO resulting from photochlorinationd simulating the reactions that occur during water and wastewater treatment. Photochlorination resulted in significant changes in the surface oxygen-functionalities of the nanomaterials, and fragmenting of the graphenic carbon sheets was observed. We found that photochlorination can enhance the decomposition of GO through the formation of reduced GO. The changes in surface oxygenfunctionalities of GO were attributed to the oxidation by chlorine of the nanomaterials' quinone groups, and further oxidation by and/or radicals. The surface charge of GO, measured by its zeta potential, increased in magnitude with chlorination but decreased in magnitude with photochlorination, leading to the decrease in the colloidal stability of the photochlorinated nanomaterials. The antibacterial effect of the nanomaterials increased with both chlorination and photochlorination. This study clearly shows how the physicochemical properties, and environmental fate and effect of GO are modified by photochlorination.

Detection and Quantification of Graphene-Family Nanomaterials in the Environment

“…193 In the case of GO, sunlight reduces the primary particle size and colloidal stability, which may interfere with techniques such as UV-Vis spectroscopy and fluorimetry. 40, 43, 72, 95 These transformations should be considered when quantifying sunlight-exposed GO with spectroscopic and thermal techniques. 8, 40 GFNs in the natural environment are also subject to chemical transformation by strong, naturally occurring oxidizing agents such as hydrogen peroxide (H 2 O 2 ), found in rain and natural waters.…”

“…69, 70 Bacterial effects generally occurred at GFN concentrations ranging from 5 to 100 mg/L. 52, 71, 72 A bacterial community from a wastewater treatment plant (WWTP) showed effects at GO concentrations less than 10 mg/L. 73 Graphene and GO inhibited algal growth at ≥ 0.675 mg/L and ≥ 1.25 mg/L, respectively.…”

Environmental degradation of carbon nanomaterials and related degradation mechanisms

“…Li等 [76] [87] , 有研究 表明这些强氧化性的活性卤素化合物可降解微囊藻毒 素 [88] . Du等 [64] 在Cl [13,24,58] ; 但也有研究 表明GO光氯作用后对铜绿假单胞菌的抗菌性显著增 加 [64] .…”

The Puzzling Potential of Carbon Nanomaterials: General Properties, Application, and Toxicity

“…As nanotechnology has bloomed and still has a lot to go until reaching its zenith, the impact of nanomaterials is of utmost importance to be fully addressed. The possible risks [ 6 , 7 ] and toxicity of nanomaterials ( Figure 1 ) have attracted the interest of scientists worldwide. Although a great amount of research has been performed so far, this venture is still in its infancy.…”