Role of nanomaterials in water treatment applications: a review.

Water pollution is a global problem threatening the entire biosphere and affecting the life of many millions of people around the world. Not only is water pollution one of the foremost global risk factors for illness, diseases and death, but it also contributes to the continuous reduction of the available drinkable water worldwide. Delivering valuable solutions, which are easy to implement and affordable, often remains a challenge. Here we review the current state-of-the-art of available technologies for water purification and discuss their field of application for heavy metal ion removal, as heavy metal ions are the most harmful and widespread contaminants. We consider each technology in the context of sustainability, a largely neglected key factor, which may actually play a pivotal role in the implementation of each technology in real applications, and we introduce a compact index, the Ranking Efficiency Product (REP), to evaluate the efficiency and ease of implementation of the various technologies in this broader perspective. Emerging technologies, for which a detailed quantitative analysis and assessment is not yet possible according to this methodology, either due to scarcity or inhomogeneity of data, are discussed in the final part of the manuscript.

Sustainable technologies for water purification from heavy metals: review and analysis

During the last decade, two-dimensional materials (2DMs) have attracted great attention due to their unique chemical and physical properties, which make them appealing platforms for diverse applications in opto-electronic devices, energy generation and storage, and sensing. Among their various extraordinary properties, 2DMs possess high surface area-to-volume ratios and ultra-high surface sensitivity to the environment, which are key characteristics for applications in chemical sensing. Furthermore, 2DMs’ superior electrical and optical properties, combined with their excellent mechanical characteristics such as robustness and flexibility, make these materials ideal components for the fabrication of a new generation of high-performance chemical sensors. Depending on the specific device, 2DMs can be tailored to interact with various chemical species at the non-covalent level, making them powerful platforms for fabricating devices exhibiting a high sensitivity towards detection of various analytes including gases, ions and small biomolecules. Here, we will review the most enlightening recent advances in the field of chemical sensors based on atomically-thin 2DMs and we will discuss the opportunities and the challenges towards the realization of novel hybrid materials and sensing devices.

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Chemical sensing with 2D materials

Recent advances in the use of graphene-family nanoadsorbents for removal of toxic pollutants from wastewater

In the past three years, we have seen intense interest grow in graphene (G) and graphene oxide (GO) as new sorbents in analytical chemistry. This article focuses on the adsorptive properties of G and GO and their application in preconcentrating organic compounds and trace-metal ions, including trace analysis of water, food, biological and environmental samples using chromatography and spectroscopy techniques. Some methods of modification or chemical functionalization of G and GO are also discussed. The article shows that G, GO and their derivatives or composites can be very attractive as sorbents due to their adsorption capacities being much higher than those of any of the currently reported sorbents.

Graphene as a new sorbent in analytical chemistry

Graphene oxide (GO) prepared by modified hummers method was used as adsorbent for removal of heavy metal ions. The oxygenous functional groups on the surface of GO were primarily responsible for the sorption of metal ions. The effects of the parameters of pH value, contact time, Cu(II) concentration, and adsorbent dosage on adsorption were examined. The sorption process conformed to the Freundlich isotherm, and the maximum sorption capacity of 117.5 mg g−1 was observed at an initial pH value of 5.3 after agitating for 150 min. It was also found that Cu-pretreated GO could be desorbed by HCl and the reusability of GO could still maintain above 90 % of its initial capability after ten cycles. The results suggest that GO is an effective adsorbent for copper ions removal in water treatment.

Highly Efficient Removal of Cu(II) from Aqueous Solution by Using Graphene Oxide

Cross-linked chitosan(CS), cross-linked chitosan/graphene(CS/RGO10) and cross-linked chitosan/graphene oxide(CS/GO10) were prepared as adsorbents for Cu(II). The effects of pH, contact time, adsorbent dosage and initial concentration of Cu(II) on the adsorbing abilities of CS,CS/RGO10 and CS/GO10 to Cu(II) were investigated. The results demonstrate that the adsorption capacities of CS/GO10 and CS/RGO10 are greater than that of CS, especially at pH 5.0 and the adsorption capacities are 202.5, 150 and 137.5 mg/g, respectively. Their behaviors obey the Freundlich isotherm model very well. Additionally, CS/GO10 has the shortest time to achieve adsorption equilibrium among them and can be used as a perspective adsorbent for Cu(II).

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Yan Yang

Papers

Highly Efficient Removal of Cu(II) from Aqueous Solution by Using Graphene Oxide

Adsorption behavior of cross-linked chitosan modified by graphene oxide for Cu(II) removal