Research articlePillared graphene oxide composite as an adsorbent of soluble hydrocarbons in water: pH and organic matter effects☆
Graphical abstract
Introduction
The mono-aromatic hydrocarbons benzene, toluene, and the poly-aromatic naphthalene are common pollutants that are constituents of gasoline and are widely used in numerous applications (Yakout, 2014). These pollutants are a matter of significant concern and have a relatively high water solubility compared to many others hydrocarbons, and thus a high bioavailability to aquatic organisms (Neff, 2002). Recent research on the remediation of water contaminated with mono-aromatic hydrocarbons uses a variety of physicochemical and biological approaches such as advanced oxidation, membrane filtration, and thermal processes (Bustillo-Lecompte et al., 2018; Jiménez et al., 2018; Ma et al., 2018; Xue et al., 2018). Adsorption-based technologies are the most widely applied treatment options due to their flexibility, high efficiency, and cost-effectiveness. Different types of organic (Tran et al., 2015) and inorganic (Wang and Peng, 2010) media have been evaluated as adsorbent materials for capturing aromatic compounds. Among them, activated carbons (AC) are particularly attractive due to comparatively high surface area, availability of adsorption sites, chemical stability, and low cost. New carbon-based nanomaterials have been considered as potential alternatives to conventional AC, and these include carbon nanofibers, carbon nanotubes, and fullerenes (Wang et al., 2014).
Recently graphene-based materials have been evaluated for removal of a wide range of pollutants from water (Wang and Zhao, 2016). Monolayer graphene and graphene oxide have ultra-high surface area, but upon drying often spontaneously restack to form ordered aggregates with greatly reduced area (Chen, 2015). Self-agglomeration of dried GO particles has restricted its application in large-scale adsorption processes (Kong, 2015). Hence, modification and functionalization of graphene sheets to prevent restakcing is a critical challenge in the synthesis of bulk sorbents from 2D nanosheet precursors.
One approach is to introduce organic molecules or polymers that spontaneously associate with the faces of graphene nanosheet and stearically hinder restacking. A cationic flocculating agent such as chitosan (CS) may be effective at the spontaneous association with negatively charged GO nanosheets through its abundant amine and hydroxyl groups, and also has its own high affinity for water-based pollutants such as metals and dyes that may contribute to the adsorption power of the composite (Crini and Badot, 2008; Wan Ngah et al., 2011). We hypothesized that such pillared graphene-based composites would have the potential for environmental capture of hydrocarbons with significant water solubility, such as benzene, toluene, and naphthalene.
Previous adsorption studies with the CS/GO composites employed pre-established ratios of both precursors for the synthesis of the final adsorbent. Here we show that a specific amount of soluble CS polymer promotes an optimal pillaring effect for the GO sheets, resulting a noticeable increase in the final CS/GO composite product specific surface area and adsorption capacity for water-based aromatic pollutants. This study also examines the effect of chitosan molecular weight in the optimization of composite sorbents. The composites are applied to three key water pollutants such as benzene, toluene and naphthalene, and we study the effects of pH and the fundamental adsorption mechanisms.
Section snippets
Materials
Three chitosan (CS) samples of low (50–90 kDa), medium (190–310 kDa) and high molecular weight (>310 kDa) with a given degree of deacetylation of ≥75% were purchased from Sigma Aldrich Co., Ltd. The source materials, solvents and adsorbates were of analytical reagent grade.
Characterization of the composites
Different mass fractions and molecular weights of CS were evaluated to optimize the pillaring effect for surface area enhancement. After many tests with various CS/GO mass fractions, the composite with 10% mass fraction of unmodified low-molecular-weight (LMW) CS provided the highest specific surface area (~70 m2/g) (see Fig. 1a). In comparison, the specific surface areas of GO and CS precursors were below 2.6 m2/g, close to the detection limit of the vapor adsorption method. The 10% CS
Adsorption experiments
Fig. 4 shows the benzene, toluene, and naphthalene adsorption isotherms of the modified composite at the optimal surface area enhancement. The adsorption isotherms of GO were also recorded. The CS/GO_0.1 composite enhbited a noticeable affinity for hydrocarbons, being their adsorption capacity of 147, 60, and 6 mg/g for benzene, toluene and naphthalene, respectively. Three adsorption models known as Langmuir, Freundlich and Sips were proposed to describe the relation between the amount of
CS/GO composite as an adsorbent of aromatic hydrocarbons
Different pillaring agents for graphene and graphene oxide have been reported in the literature, which mainly included carbon-based materials like carbon nanotubes, nanocarbon fibers, carbon black and fullerenes (Guo et al., 2014). Another type of agents included polymers, metallic cations and in minor proportion organic polymers. For that reason, it is difficult to establish a clear comparison of the pillaring capability of CS. However, similar CS/GO composites reported in the literature, and
Conclusions
The present study showed out that a chitosan/graphene oxide composite prepared with a low-molecular-weight chitosan achieved an optimized specific surface area of 70 m2/g by pillaring the interlayers of graphene oxide (GO) nanosheets. Medium and high molecular weight chitosan molecules produce a little or no pillaring effect on GO registered at a CS/GO ratio between 0.2 and 0.4. For the optimized composite, CS/GO_0.1, a suite of characterization techniques verified the presence of chitosan
Author contributions
Composites characterization and adsorption isotherm measurements were conducted and analyzed by C Chaparro and C.J. Castilho, with assistance in analysis from I Külaots, R Hurt and J Rangel-Mendez. This study was conceptualized and designed collaboratively by I Külaots, R Hurt and J Rangel-Mendez. C Chaparro wrote the initial manuscript in collaboration with C.J. Castilho.
Acknowledgements
This work was supported by grant PDCPN-01-247032 (Mexico). Carlos E. Flores-Chaparro acknowledges a doctoral fellowship and a stay of research fellowship from CONACYT, Mexico, No. 424187. This research was also supported by the Superfund Research Program of the National Institute for Environmental Health Sciences under grant P42 ES013660. The authors express their gratitude to Z. Saleeba, R. Spitz, E. Isaacs, D.I. Partida, G. Vidriales, J.P. Rodas, and M.C. Rocha for their invaluable assistance
References (46)
- et al.
Photochemical treatment of benzene, toluene, ethylbenzene, and xylenes (BTEX) in aqueous solutions using advanced oxidation processes: towards a cleaner production in the petroleum refining and petrochemical industries
J. Clean. Prod.
(2018) - et al.
Characterization of size fractionated dissolved organic matter from river water and wastewater effluent using preparative high performance size exclusion chromatography
Org. Geochem.
(2017) - et al.
Hydrodynamic studies on chitosans in aqueous solution
Carbohydr. Polym.
(2001) - et al.
Application of chitosan, a natural aminopolysaccharide, for dye removal from aqueous solutions by adsorption processes using batch studies: a review of recent literature
Prog. Polym. Sci.
(2008) - et al.
Preparation of novel magnetic chitosan/graphene oxide composite as effective adsorbents toward methylene blue
Bioresour. Technol.
(2012) - et al.
Synthesis of magnetic β-cyclodextrin–chitosan/graphene oxide as nanoadsorbent and its application in dye adsorption and removal
Colloids Surf. B Biointerfaces
(2013) - et al.
Porous structures in stacked, crumpled and pillared graphene-based 3D materials
Carbon
(2014) - et al.
Magnetic chitosan–graphene oxide composite for anti-microbial and dye removal applications
Int. J. Biol. Macromol.
(2016) - et al.
State of the art of produced water treatment
Chemosphere
(2018) - et al.
Chitosan-functionalized graphene oxide: a novel adsorbent an efficient adsorption of arsenic from aqueous solution
J. Environ. Chem. Eng.
(2016)
Impacts of inorganic anions and natural organic matter on thermally activated persulfate oxidation of BTEX in water
Chemosphere
Chapter 14 - monocyclic aromatic hydrocarbons in the ocean
Chitosan selectivity for removing cadmium (II), copper (II), and lead (II) from aqueous phase: pH and organic matter effect
J. Hazard Mater.
Removal of Acid Orange 7 from aqueous solution using magnetic graphene/chitosan: A promising nano-adsorbent
Int. J. Biol. Macromol.
Application of the kinetic and isotherm models for better understanding of the behaviors of silver nanoparticles adsorption onto different adsorbents
J. Environ. Manag.
Typical low cost biosorbents for adsorptive removal of specific organic pollutants from water
Bioresour. Technol.
Graphite oxide/chitosan composite for reactive dye removal
Chem. Eng. J.
Adsorption of dyes and heavy metal ions by chitosan composites: a review
Carbohydr. Polym.
Natural zeolites as effective adsorbents in water and wastewater treatment
Chem. Eng. J.
Simultaneous removal of benzene, toluene, ethylbenzene and xylene (BTEX) by CaO2 based Fenton system: enhanced degradation by chelating agents
Chem. Eng. J.
A novel modified graphene oxide/chitosan composite used as an adsorbent for Cr(VI) in aqueous solutions
Int. J. Biol. Macromol.
Scalable chitosan-graphene oxide membranes: the effect of GO size on properties and cross-flow filtration performance
ACS Omega
The reflection of X-rays by crystals
Proc. R. Soc. Lond.
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C.E. Flores-Chaparro and C.J. Castilho equally contributed as first authors.