Surface functionalization of the Graphene Oxide by

Proceedings of the 7th International Conference on Nanostructures (ICNS7) 27Feb- 1 Mar 2018, Tehran, Iran

Surface functionalization of the Graphene Oxide by modified EDTA as a methylene blue absorbent Z. Karimzadeh a, H. Hashemia, S. Javanbakht a, H. Namazia,b * a Research

Laboratory of Dendrimers and Nanopolymers, Faculty of Chemistry, University of Tabriz, P.O. Box 51666, Tabriz, Iran. b Research Centre for Pharmaceutical Nanotechnology (RCPN), Tabriz University of Medical Science, Tabriz, Iran. *[email protected]

Abstract: In this work, graphene oxide surface functionalized with modified EDTA as a Methylene Blue absorbent due to its high adsorbance capacities, ease of adjusting, recycling and stability. Based on the huge and multivalent EDTA molecular structure, it could be used as strong agent to complex with pollutant and hence an increase in the adsorbance efficiency. The synthesized composite has been characterized with X-ray Powder diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transformed Infrared Spectroscopy (FT-IR), Ultraviolet-Visible spectroscopy (UV-Vis). 5 mg/L of Synthesised composite has been used for treatment of methylene blue (15 mg/L) at pH=6. The results indicate 69% degradation efficiency in first 10 min compared to the 44% of the pure GO, verifying the modification of the GO has a positive effect on removal efficiency.

Keywords: graphene oxide; surface functionalization; EDTA; methylene blue Introduction There are many uses of water in industry and, in most cases, the used water also needs treatment to render it fit for re-use or disposal. Raw water entering an industrial plant often needs treatment to meet tight quality specifications to be of use in specific industrial processes. Water pollution due to the indiscriminate disposal of metal ions and organic contaminants has been a rising worldwid e environmental concern. For example, wastewater from many industries such as metallurgical and chemical manufacturing, mining, battery, etc., contains one or more toxic metal ions[1]. For environmental protection, it is necessary to remove these metal contaminants from the wastewater before releasing into the environment.3 Entire removal of heavy metals and organic contaminants in natural water resources can not only protect the environment itself, but also stop the toxic contaminant transfer in food chains. Adsorption is a wastewater purification technique for removing a wide range of compounds from industrial wastewater. Adsorption is most commonly implemented for the removal or low concentrations of non-degradable organic compounds from groundwater, drinking water preparation, process water or as tertiary cleansing after, for example, biological water purification. Adsorption takes place when molecules in a liquid bind themselves to the surface of a solid substance. Adsorbents have a very high internal surface area that permits adsorption[2]. Traditional techniques for treatment of metal ions include reduction, coprecipitation, membrane filtration, ion exchange and adsorption. Among the above methods, the most promising process for the removal of metal ions is adsorption. Several adsorbents that have been studied for

metal removal include activated carbon (AC), zeolite, inorganic materials, and resins. However, these adsorbents have been suffering from either low adsorption capacities or low efficiencies. Therefore, tremendous effort has been made in recent years to seek new adsorbents and develop new techniques. An ideal adsorbent should have the ability to rapidly and efficiently remove toxic contaminants from environments to a safety level[3]. Nanotechnology and nanomaterials have gradually demonstrated playing an important role in this aspect. The benefits from the use of nanomaterials for metal removal may derive from their enhanced reactivity, higher specific surface area and sequestration characteristics. So far, a variety of nanomaterials are in various stages of research and development, each possessing unique functionalities that are potentially applicable to the remediation of industrial effluents, groundwater, surface water, and drinking water. Carbon-based nanomaterials are one type of these materials that have potential applications in the wastewater treatment system. Carbon-based nanomaterials have been studied as superior adsorbents for their potential environmental applications to remove pollutants, such as organic pollutants and metals with high capacity and selectivity in aqueous solutions. One of the advantages of carbon-based nanoparticles as attractive adsorbents is that they have much larger specific surface areas. For example, carbon nanotubes (CNTs) have been suggested as “a superior adsorbent” for dioxins with excellent adsorption capacity because CNTs provide geometry sites for stronger interactions with organic pollutants. Many methods have been exploited for the preparation of various functional CNTs[4]. The surface oxidized CNTs have showed exceptional adsorption capacity and high adsorption efficiency for metal removal. Earlier studies indicate that CNTs can be promising adsorption materials used for environmental protection regardless of their high cost at


present. The prospect of using carbon nanotubes for water pollution control appears to be very favorable, but largescale applications of CNTs in the near future are limited by cost and availability. So far, it is difficult to predict in general which of these CNTs-based adsorbents will be commercialized because of cost concerns. Therefore, the rational design of adsorbents with lower cost is a challenge. Greater efforts are made to seek the lower cost carbon-based nanomaterials as adsorbents for environmental applications. Graphene or graphene oxide, a CNT-substituted material and a product of graphite from an oxidization process, may be an ideal material for wastewater treatment. Normally, graphene obtained from graphite exists in two states, i.e., graphene oxide (GO) and reduced graphene oxide (RGO). Graphene oxide (GO) is water-soluble with low conductivity while RGO has good conductivity with poor solubility in water[5,6]. The oxidation process of graphite to graphene oxide can introduce abundant functional groups on GO surface that can be used as anchoring sites for metal ion complexation , making it a potential material as a super adsorbent.31 Unlike CNTs, which need a special oxidation process to introduce hydrophilic groups for metal removal, the formation process from graphite to GO already introduces many functional groups, such as −COOH, −CO and −OH on GO surface[7]. These groups are the essential chemical skeletons for an ideal adsorbent. Ethylenediaminetetraacetic acid (EDTA) is well-known for forming stable chelates with metal ions. Therefore, it can be ideally used for metal removal. Immobilization of EDTA on different supporting materials for adsorption purpose as received widespread attention, these substrate include silica gel, polymer resin,and cellulose. In a previous study, we reported a method to chemically functionalize graphene sheets with N(trimethoxysilylpropyl) ethylenediamine triacetic acid via a silanization reaction. EDTA-GO is found to be an ideal adsorbent for heavy metal removal. Upon linked to substrate, EDTA serves as a chelating group to form a stable chelate with metal ions. This laboratory research was designed to investigate the adsorption behavior of Pb(II) on EDTA-GO surface and the potential applications of EDTAGO for heavy metal removal. We found that Pb(II) concentration in Pb(II) contaminated water could be decreased to ∼0.5 ppb or less after the treatment with EDTA-GO[8].

Materials and method Chemicals were purchased from Merck Company and were used as received. Photoluminescence spectra (200– 700 nm) were acquired by a Hitachi F7000 Luminescence spectrophotometer. Fourier-transformed infrared spectroscopy (FTIR) study was conducted with a VERTEX 70 FTIR (KBr wafer technique) in cm1.Morphology of samples were measured by scanning electron microscopy (FE-SEM) model HITACHI (S-460).

Results and Discussion In FT-IR spectrum of GO as it is shown in the Fig. 1, (the blue curve), the appearance of absorption peaks at 3613, 3131, 1608, 1387, and 1067 cm-1 are related to the alcoholic hydroxyl group, carboxylic acid hydroxyl group, carbonyl band, epoxy group, and C-O bond respectively. In the FT-IR spectrum of the synthesized compound ELA (the green curve), the absorption peaks at 3446, 3072, 1693, 1614 cm-1 are related to the amine group, hydroxyl group of carboxylic acid, carbonyl group of carboxylic acid and amide functional group, while the peaks in the 1468 and 1406 cm-1 are corresponded to the aromatic group. The peak at the 1312 and 1074 cm-1 are related to the epoxy band and C-O bond respectively. In the FT-IR spectrum of the hybrid (the green curve), the wide peak at 3100 cm-1 is related to the OH group, the peak at the 1842 and 1709 and 1564 cm-1 are related to the anhydride, carboxyl group and amide band respectively. And the peaks at 1338, 1233, and 1049 are related to the C-O, epoxy group and C-N group. Therefore the appearance of the amide and anhydride bands indicate the successful attachment of the EDTA, aspartic acid and lysine to the GO surface.

Fig. 1 the comparison of FT-IR spectrum of GO, ELA, and GOELA

In the XRD spectrum of the GO (the black curve), a peak at 2ϴ=12/54 is related to the go flakes fabrication, and a weak 2ϴ=42/7 indicate the presence raw graphite remained unchanged during the oxidation process. The blue curve (GO hybrid) shows no obvious variation compared to the GO spectrum indicating the stable structure of the GO hybrid is stable under reaction condition.


The adsorption capacity of the sorbent was measured in the pH 6 at the certain time intervals of 10, 20, 30, 40, 50, 60 minutes. Up to 96% of the methylene blue with initial concentration of 15 ppm was adsorbed, indicated the high adsorption capacity.

Fig. 2 XRD spectrum of the GO and GO-ELA

Fig. 3, 4 shows the SEM results of the GO and GO hybrid. The formation of GO nanoflake aat 35.82 nm and also the appearnece of the white crvey pieces on the GO surface show the chemical attachment of the ELA on the Go surface was carried out successfully.

Fig. 5 the adsorption of M B in the certain time intervals

Conclusions In this work the GO hybrid was synthesized successfully via the covalent attachment of the ELA on the GO. The XRD analysis indicates no obvious variation to the GO sample. the obtained hybrid removed 96% of MB with initial concentration of 15 ppm in the first 10 minutes from the solution.

References [1] Lee C. K., Low K. S., Gan P. Y., Removal of some organic dyes by acid-treated spent bleaching earth, Environmental technology., 20: 99-104 (1999). Fig. 3 the SEm image of the GO nanofalkes with approximate thikness of 35 nm

[2] Aksu, Z., Biosorption of reactive dyes by dried activated sludge: equilibrium and kinetic modelling , Biochemical Engineering Journal., 7: 79-84 (2001). [3] Ardejani F. D., Badii K., Limaee N. Y., Mahmoodi N. M., Arami M., Shafaei S. Z., Mirhabibi A. R., Numerical modelling and laboratory studies on the removal of Direct Red 23 and Direct Red 80 dyes from textile effluents using orange peel, a low-cost adsorbent, Dyes and Pigments., 73:178-185 (2007). [4] Mungasavalli D. P., Viraraghavan T., Jin Y. C., Biosorption of chromium from aqueous solutions by pretreated Aspergillus niger: batch and column studies, Colloids and Surfaces A: Physicochemical and Engineering Aspects., 301: 214-223 (2007).

Fig.4 the SEM image of the GO-ELA hybrid in 200 nm magnification

[5] Yusuf M., Elfghi F. M., Zaidi S. A., Abdullah E. C., Khan M. A., Applications of graphene and its derivatives as an adsorbent for heavy metal and dye removal: a systematic and comprehensive overview, RSC Advances., 5: 50392-50420 (2015).


[6] Zhao C., Ma L., You J., Qu F., Priestley R. D., EDTAand amine-functionalized graphene oxide as sorbents for Ni (II) removal, Desalination and Water Treatment., 1-10 (2015). [7] Madadrang C. J., Kim H. Y., Gao G., Wang N., Zhu J., Feng H., Hou S., Adsorption behavior of EDTA-graphene oxide for Pb (II) removal, ACS applied materials & interfaces., 4:1186-1193 (2012). [8] Jiao T., Guo H., Zhang Q., Peng Q., Tang Y., Yan X., Li B., Reduced Graphene Oxide-Based Silver Nanoparticle-Containing Composite Hydrogel as Highly Efficient Dye Catalysts for Wastewater Treatment, Scientific reports., 5 (2015).