Green Graphene-Chitosan Sorbent Materials for Mercury Water Remediation.

Bruno Henriques,Paula A. A. P. Marques,Eduarda Pereira,Gil Gonçalves,Eddy M. Domingues,Ana Bessa

doi:10.3390/nano10081474

Bruno Henriques, Paula A. A. P. Marques + Show 4 more

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https://doi.org/10.3390/nano10081474

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Abstract

The development of new graphene-based nanocomposites able to provide synergistic effects for the adsorption of toxic heavy metals in realistic conditions (environment) is of higher demand for future applications. This work explores the preparation of a green nanocomposite based on the self-assembly of graphene oxide (GO) with chitosan (CH) for the remediation of Hg(II) in different water matrices, including ultrapure and natural waters (tap water, river water, and seawater). Starting at a concentration of 50 μg L–1, the results showed that GO–CH nanocomposite has an excellent adsorption capacity of Hg (II) using very small doses (10 mg L–1) in ultrapure water with a removal percentage (% R) of 97 % R after only two hours of contact time. In the case of tap water, the % R was 81.4% after four hours of contact time. In the case of river and seawater, the GO–CH nanocomposite showed a limited performance due the high complexity of the water matrices, leading to a residual removal of Hg(II). The obtained removal of Hg(II) at equilibrium in river and seawater for GO–CH was 13% R and 7% R, respectively. Our studies conducted with different mimicked sea waters revealed that the removal of mercury is not affected by the presence of NO3– and Na+ (>90% R of Hg(II)); however, in the presence of Cl–, the mercury removal was virtually nonexistent (1% R of Hg(II)), most likely because of the formation of very stable chloro-complexes of Hg(II) with less affinity towards GO–CH.

Highlights

Water pollution is one of the most severe problems our planet faces, and managing water resources sustainably under climate change, population growth, and economic development poses novel challenges in the 21st century, termed the Century of the Environment [1,2]
Heavy metals are an extremely hazardous class of nonbiodegradable and bioaccumulative elements that present a serious threat to all forms of life, even at trace levels concentrations [3]
Aquatic ecosystems are an important part of the global biogeochemical cycle of Hg

Summary

Introduction

Water pollution is one of the most severe problems our planet faces, and managing water resources sustainably under climate change, population growth, and economic development poses novel challenges in the 21st century, termed the Century of the Environment [1,2]. Heavy metals are an extremely hazardous class of nonbiodegradable and bioaccumulative elements that present a serious threat to all forms of life, even at trace levels concentrations [3]. Aquatic ecosystems are an important part of the global biogeochemical cycle of Hg. Inorganic Hg can convert to toxic methyl Hg form (CH3Hg) in water (river and sea), driving one of the main human exposure path by the consumption of fish, if caught in the sea [5]. Inorganic Hg can convert to toxic methyl Hg form (CH3Hg) in water (river and sea), driving one of the main human exposure path by the consumption of fish, if caught in the sea [5] Once it reaches the food chain, Hg tends to bioaccumulate, causing harmful effects to human health [6,7]. Hg presents a significant risk to both the global environment and human health alike, as it is well expressed in Europe Comission’s environment report [8]

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