Unprecedented adsorption of chlorpyrifos (CP), endosulfan (ES), and malathion (ML) onto graphene oxide (GO) and reduced graphene oxide (RGO) from water is reported. The observed adsorption capacities of CP, ES, and ML are as high as ~1200, 1100, and 800 mg g(-1) , respectively. Adsorption is found to be insensitive to pH or background ions. The adsorbent is reusable and can be applied in the field with suitable modifications. A first-principles pseudopotential-based density functional analysis of graphene-water-pesticide interactions showed that the adsorption is mediated through water, while direct interactions between graphene and the pesticides is rather weak or unlikely.

Pradeep Thalappil

Department Of Chemistry

Maliyekkal S.M

Sreeprasad T.S

Krishnan V

Kouser S

Mishra A.K

Waghmare U.V

Pradeep T.

Adsorption capacities

CHLORPYRIFOS

Direct interactions

ENDOSULFANS

First-principles calculation

Graphene oxides

Reduced graphene oxides

Calculations

Density functional theory

Graphene

Pesticides

Adsorption

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Small

This paper explores the reduction of water dispersed graphene oxide (GO) by sunlight. The electronic and structural properties of the sunlight reduced GO are compared with that of GO reduced by conventional methods.

Fulltext

RSC Advances

Solar mediated reduction of graphene oxide

This paper reports dehalogenation of various organohalides, especially aliphatic halocarbons and pesticides at reduced graphene oxide-silver nanocomposite (RGO@Ag). Several pesticides as well as chlorinated and fluorinated alkyl halides were chosen for this purpose. The composite and the products of degradation were characterized thoroughly by means of various microscopic and spectroscopic techniques. A sequential two-step mechanism involving dehalogenation of the target pollutants by silver nanoparticles followed by adsorption of the degraded compounds onto RGO was revealed. The composite showed unusual adsorption capacity, as high as 1534 mg/g, which facilitated the complete removal of the pollutants. Irrespective of the pollutants tested, a pseudo-second-order rate equation best described the adsorption kinetics. The affinity of the composite manifested chemical differences. The high adsorption capacity and re-usability makes the composite an excellent substrate for purification of water. © 2016 Elsevier B.V.

Journal of Hazardous Materials

Rapid dehalogenation of pesticides and organics at the interface of reduced graphene oxide-silver nanocomposite

This paper describes an unusual chemical reaction that takes place on a graphene composite in a concerted fashion. The reaction shows the conversion of a persistent organochlorine pesticide, lindane (C<inf>6</inf>H<inf>6</inf>Cl<inf>6</inf>), present in water, to different isomers of trichlorobenzenes (TCBs, C<inf>6</inf>H<inf>3</inf>Cl<inf>3</inf>) on the surface of reduced graphene oxide-silver composites (RGO@Ag). The reaction is unique to the composite and does not occur on RGO and nanoparticles of Ag separately. The products of the reaction were isolated and extensively characterized using analytical techniques such as gas chromatography-mass spectrometry, electrospray ionization mass spectrometry, infrared and NMR, which unequivocally confirmed their identity. The as-formed TCBs were removed from the aqueous medium by adsorption on the same composite. Adsorption of lindane is physical in nature, but that of TCBs is through - interactions. The study reveals the unusual chemical reactivity of graphene-metal composites and their potential for water treatment. The uniqueness of the reaction on RGO@Ag is due to the simultaneous removal of three HCl molecules, leading to the formation of aromatic compounds and concomitant formation of silver chloride. Recycling capacity and effect of diverse species present in natural waters were tested for potential applications in sustainable water treatment. © 2015 American Chemical Society.

ACS Sustainable Chemistry and Engineering

Simultaneous dehalogenation and removal of persistent halocarbon pesticides from water using graphene nanocomposites: A case study of lindane

Noble metal nanostructures are widely explored as they have unusual size- and shape-dependent physical, chemical, and optical properties. Silver and gold nanosystems were synthesized in a variety of forms-including spherical, rod, wire, triangle, star, and flower shapes. These systems were used for applications in catalysis, sensing, surface-enhanced Raman scattering, and many others. When the size of the particles of noble metal nanosystems (NMNs) reaches in-between molecules and nanoparticles (NPs), they exhibit molecular properties such as discrete optical absorption and photoluminescence. Use of bulk noble metals in water treatment and medicine is very well documented since ancient times. In recent history, water pollution has become one of the major problems throughout the world. The intensity of water contamination is becoming more complex with time because of the addition of a large number of chemicals and biological species, mainly because of anthropogenic activities. Permissible limits for most of the contaminants have decreased as time progressed. Technologies to be developed must be able to detect ultralow concentrations and remove large amounts of pollutants. NMNs promise to be efficient adsorbents for the treatment of polluted water as they exhibit high absorption and scattering cross-sections. In the recent past, noble metal clusters, a new category of materials, were employed in selective and sensitive detection of heavy metals and anions using their optical properties, efficient adsorption capacities, and high reactivity. Some of them were demonstrated as practical devices for these purposes. NMNs were found to exhibit affinity toward pesticides and novel mineralization reactions were seen with halocarbons. NPs of silver, palladium, and gold were also used for the removal of other organic molecules such as pharmaceuticals, dyes, explosives, and for the catalytic degradation of chlorinated solvents. Silver NPs and clusters have been shown to be useful as antimicrobial agents. In all the above applications, NMNs were used alone or as a component of the composite. In some cases, NMNs were supported onto metal oxide surfaces such as Fe2O3, TiO2, MgO, Al2O3, and Mn2O3 as the separation of materials and purified water is easy after treatment. Alloy NPs, alloy clusters, and composites are emerging materials, and they need to be explored as they provide new opportunities in comparison to the known materials. © 2014 Elsevier Inc. All rights reserved.

Water Reclamation and Sustainability

Noble Metal Nanosystems for the Detection and Removal of Pollutants in Drinking Water

Intensive farming, rapid industrialization, and increasingly sophisticated lifestyles have added artificial chemicals into many water bodies. While pesticide residues in groundwater was unexpected years ago as soil was thought to act as a filter, it is an established fact that groundwater sources in many parts of the world are heavily contaminated with them. Although these levels are significant vis†-vis the permissible limits, the concentrations are low in comparison to those of other commonly encountered chemicals and the purification technologies have to be efficient for them to be removed at affordable cost. For such a solution to be useful for all strata of the society, it needs to be economically attractive, requiring zero electricity and minimum maintenance. Any novel technology should solve the problem in its entirety and not result in toxic by-products or residuals. These requirements pose numerous challenges to chemistry and engineering, some of which are discussed here. © 2014 Elsevier Inc. All rights reserved.

Nanotechnology Applications for Clean Water: Solutions for Improving Water Quality: Second Edition

Detection and Extraction of Pesticides from Drinking Water Using Nanotechnologies

Graphene: A reusable substrate for unprecedented adsorption of pesticides

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm 2) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications. © 2011 American Chemical Society.

ACS Applied Materials and Interfaces

Transparent, luminescent, antibacterial and patternable film forming composites of graphene oxide/reduced graphene oxide

This paper describes a versatile, and simple synthetic route for the preparation of a range of reduced graphene oxide (RGO)-metal/metal oxide composites and their application in water purification. The inherent reduction ability of RGO has been utilized to produce the composite structure from the respective precursor ions. Various spectroscopic and microscopic techniques were employed to characterize the as-synthesized composites. The data reveal that the RGO-composites are formed through a redox-like reaction between RGO and the metal precursor. RGO is progressively oxidized primarily to graphene oxide (GO) and the formed metal nanoparticles are anchored onto the carbon sheets. Metal ion scavenging applications of RGO-MnO2 and RGO-Ag were demonstrated by taking Hg(II) as the model pollutant. RGO and the composites give a high distribution coefficient (Kd), greater than 10Lg-1 for Hg(II) uptake. The Kd values for the composites are found to be about an order of magnitude higher compared to parent RGO and GO for this application. A methodology was developed to immobilize RGO-composites on river sand (RS) using chitosan as the binder. The as-supported composites are found to be efficient adsorbent candidates for field application. © 2010 Elsevier B.V.

Reduced graphene oxide-metal/metal oxide composites: Facile synthesis and application in water purification

Water is one of the essential enablers of life on earth. Beginning with the origin of the earliest form of life in seawater, it has been central to the evolution of human civilizations. Noble metals have been similarly associated with the prosperity of human civilizations through their prominent use in jewellery and medical applications. The most important reason for the use of noble metals is the minimal reactivity at the bulk scale, which can be explained by a number of concepts such as electrochemical potential, relativisitic contraction, molecular orbital theory, etc. Recently, water quality has been associated with the development index of society. A number of chemical and biological contaminants have endangered the quality of drinking water. An overview of important events during last 200 years in the area of drinking water purification is presented. Realizing the molecular nature of contamination in drinking water, significant progress has been made to utilize the chemistry of nanomaterials for water purification. This article summarizes recent efforts in the area of noble metal nanoparticle synthesis and the origin of their reactivity at the nanoscale. The application of noble metal nanoparticle based chemistry for drinking water purification is summarized for three major types of contaminants: halogenated organics including pesticides, heavy metals and microorganisms. Recent efforts for the removal, as well as ultralow concentration detection of such species, using noble metal nanoparticles are summarized. Important challenges during the commercialization of nano-based products are highlighted through a case study of pesticide removal using noble metal nanoparticles. Recent efforts in drinking water purification using other forms of nanomaterials are also summarized. The article concludes with recent investigations on the issue of nanotoxicity and its implications for the future. © 2009 Elsevier B.V. All rights reserved.

Thin Solid Films

Noble metal nanoparticles for water purification: A critical review

A simple nanomaterial-based reduction strategy that can form leaf-like graphenic structures from graphite oxide (GO) at room temperature is described. Mixing of Te nanowires (Te NWs) with GO at room temperature was found to reduce GO while Te NWs are oxidized to TeO32-. The reaction was followed time-dependently with use of UV/vis spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM). Raman spectroscopy was used to characterize the graphenic material. The G band, which was blue-shifted (with respect to graphite) in the case of GO, came back to the original position confirming the reduction. From IR spectroscopy, it was confirmed that the carboxylic acid groups in the GO are not getting reduced and the product gets stabilized electrostatically because of the repulsion between the negatively charged carboxylic acid groups. Reduction was confirmed by X-ray photoelectron spectroscopy (XPS) also. The reaction showed strong pH dependence and was found to be happening only in basic pH. In acidic medium, GO aggregates, making reduction difficult, while at higher temperature, the reaction was faster and at lower temperature it was retarded considerably.© 2009 American Chemical Society.

Journal	Small
ISSN	16136810
Open Access	No