Elsevier

Science of The Total Environment

Volume 682, 10 September 2019, Pages 340-347
Science of The Total Environment

Carbon nanotube-grafted chitosan and its adsorption capacity for phenol in aqueous solution

https://doi.org/10.1016/j.scitotenv.2019.05.148Get rights and content

Highlights

  • A novel material was synthesized by grafting chitosan onto carbon nanotubes.

  • The structural characteristics of the new biomaterial were determined.

  • The adsorptive properties of the biomaterial were comprehensively evaluated.

  • The isotherm equations and kinetic models for phenol adsorption were assessed.

Abstract

Chitosan was covalently grafted onto the surface of multi-walled carbon nanotubes to create a novel chitosan/multi-walled carbon nanotube. The structure of the new material was characterized using Fourier transform-infrared spectroscopy, cross polarization magic angle spinning 13C nuclear magnetic resonance, thermogravimetric analysis, XRD ray diffraction analysis, differential scanning calorimetry and scanning electron microscopy. The phenol adsorption capacity was determined and the Langmuir and Freundlich models were used to describe the adsorption isotherms. The adsorption capacity of the novel chitosan/multi-walled carbon nanotube material for phenol (86.96 mg/g) was improved compared to the original chitosan (61.69 mg/g). The kinetic studies showed rapid adsorption, exhibiting Lagergren second-order kinetics. Therefore, this study provides a reference for preparing functional materials from biological substrates that are able to remove toxic pollutants from an aqueous environment.

Graphical abstract

A novel chitosan/multi-walled carbon nanotube (CS/MWCNT) material was successfully prepared through covalently grafting chitosan (CS) onto the surface of multi-walled carbon nanotubes (MWCNT). The adsorptive ability of the CS/MWCNT was assessed for phenol. Theoretical models were used to describe the adsorption isotherms of phenol and the adsorption parameters were evaluated.

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Introduction

Nowadays, functional polymers are present in nearly all aspects of daily life. As the function of polymer is determined by its structure and the moieties attached to the carbon backbone, there is an intensive research focus on the synthesis of new polymers with novel structures and enhanced capabilities (Choi et al., 2010; Zare et al., 2018a, Zare et al., 2018b; Deng et al., 2019). Polymers from natural sources such as biomass, are a prospective research area that has future applications (Marin et al., 2002; You et al., 2018).

Many composite materials have been assessed for their capacity to remove contaminants from water (Wei et al., 2019; Yang et al., 2019). Superparamagnetic nanocomposites prepared using sodium alginate and chitosan as raw materials displayed good adsorptive capacities for heavy metal ions (Lakouraj et al., 2014a, Lakouraj et al., 2014b). Polyaniline/paste synthesized by in-situ polymerization was able to remove heavy metal ions such as Cu (II), Cd (II) and Pb (II) from water (Zare et al., 2015). Nanocomposites derived from cyclodextrin grafted to poly-m-phenylenediamine were able to effectively adsorb heavy metal cations as well as methylene blue (Zare et al., 2015; Nazarzadeh et al., 2018). Magnetic nanocomposites incorporating maleic anhydride were also effective at heavy metal ion removal (Nazarzadeh et al., 2014, Nazarzadeh et al., 2016; Hasanzadeh et al., 2016; Zare et al., 2018a, Zare et al., 2018b). In the current study, chitosan was used as a raw material to synthesize the adsorbent. Chitosan is a natural polysaccharide that is abundant, cheap, biodegradable and non-toxic (X. Liu et al., 2018; B. Liu et al., 2018). Its usage has increased in prominence. The development of new CS-based materials with novel structures and applications is important.

Phenol is prevalent in industrial effluents from coking, printing and dyeing, plastic production, chemical and petroleum processes (Guo et al., 2017; Zangrando et al., 2019). Phenolic wastewaters are highly toxic and detrimentally affect macrobiotic aquatic life, microbial growth and ecology (Fajardo et al., 2017; Yan et al., 2019). Adsorption is commonly used to remove phenol and other organic pollutants from aqueous media (Yu et al., 2014; Huang et al., 2018). It is necessary to find an efficient adsorbent, as large-scale application of adsorbents (such as activated carbon, biochar, clay or fly ash is hampered by less effective adsorption or recycling difficulties) (Mousset et al., 2016; Luo et al., 2018; Zhang et al., 2019).

Chitosan is the only alkaline polysaccharide. It is an excellent adsorbent (Cui et al., 2013) and considered environmentally-friendly because of its biodegradability (X. Liu et al., 2018; B. Liu et al., 2018). However, its use is restricted by a low adsorption capacity for organic matter due to its solubility in dilute acids (Li et al., 2017). The functional surface groups on adsorbents can be modified to improve its adsorption capacity (Wu et al., 2016, Wu et al., 2017; Li et al., 2019). In recent years, surface chemical modification of carbon nanotubes has become a popular topic in nanotechnology research (Phan et al., 2018). Biological materials such as chitosan, cyclodextrin, cellulose can be used to modify the surface carbon nanotubes to prepare functional materials with enhanced dispersibility and substrate binding ability (Phan et al., 2018; Xia et al., 2019). Adsorption materials using carbon nanotubes and chitosan as raw materials are of great interest (Wu et al., 2007; Dai et al., 2012; Ding et al., 2017) and various composite materials are able to efficiently remove heavy metal ions from aqueous solutions (Ke et al., 2007; Zhuang et al., 2016; Lu et al., 2018).

In this research, a functional CS/MWCNT graft polymer was prepared by chemical grafting. The static and dynamic adsorption properties of the graft polymer towards phenol were investigated.

Section snippets

Materials and reagents

The following compounds were used: CS (deacetylation degree ≥90%, Sinopharm Chemical Reagent Limited Company); carbon nanotubes (MWCNT, 95%, Shenzhen Bill Technology Company); thionyl chloride (SOCl2, AR, Shanghai Jinshan Tingxin Chemical Reagent Factory); N, N-dimethylformamide (DMF, 99%, Energy Chemical); H2SO4 (AR, Zhejiang Quzhou Juhua Reagent Limited Company). All other chemicals used in this study were of an analytical grade.

Preparation of CS/MWCNT

Carboxyl carbon nanotubes (MWCNT-COOH) were prepared according

Synthesis of CS/MWCNT

The surface of the MWCNT was enriched in carboxyl groups (via acidification) and then chloridated to MWCNT-COCl (by SOCl2). The MWCNT-COCl reacted with chitosan in DMF solution to generate the new covalently-bonded chitosan grafted to carbon nanotubes (CS/MWCNT). The grafting ratio (GP) of the CS/MWNTs copolymer was calculated using the formula (Eq. (1)):GP=W1W0W0where, W1 and W0 are the mass (g) of CS/MWNTs copolymer and MWNTs-COCl, respectively. According to the mass balance, the grafting

Conclusions

Chitosan (CS) was successfully grafted to the surface of carbon nanotubes (MWCNT). The CS/MWCNT graft polymer displayed an improved maximum adsorptive capacity for phenol (86.96 mg/g) compared to chitosan (61.69 mg/g). A pseudo-second order equation provided better correlation to the sorption data than first order kinetics. Therefore, this study can provide a reference for preparing functional materials from biological substrates to remove toxic pollutants from an aqueous environment.

Acknowledgments

This work was supported by the Natural Science Foundation of Zhejiang Province (LY18B070003), the National Natural Science Foundation of China (21577131, 21876027) and the Natural Science Foundation of Guangdong Province, China (2017A030311019).

References (58)

  • G. Ke et al.

    Covalent modification of multiwalled carbon nanotubes with a low molecular weight chitosan

    Chin. Chem. Lett.

    (2007)
  • M.M. Lakouraj et al.

    Nanogel and superparamagnetic nanocomposite based on sodium alginate for sorption of heavy metal ions

    Carbohydr. Polym.

    (2014)
  • H.S. Lee et al.

    Chitosan adsorption on hydroxyapatite and its role in preventing acid

    J. Colloid Interface Sci.

    (2012)
  • L. Li et al.

    Preparation of chitosan-based multifunctional nanocarriers overcoming multiple barriers for oral delivery of insulin

    Mater. Sci. Eng.

    (2017)
  • J. Li et al.

    Sorption mechanisms of lead on silicon-rich biochar in aqueous solution: spectroscopic investigation

    Sci. Total Environ.

    (2019)
  • X. Liu et al.

    One-step procedure for enhancing the antibacterial and antioxidant properties of a polysaccharide polymer: kojic acid grafted onto chitosan

    Int. J. Biol. Macromol.

    (2018)
  • B. Liu et al.

    A novel carboxyl-rich chitosan-based polymer and its application for clay flocculation and cationic dye removal

    Sci. Total Environ.

    (2018)
  • J. Luo et al.

    Sorption of norfloxacin, sulfamerazine and oxytetracycline by KOH-modified biochar under single and ternary systems

    Bioresour. Technol.

    (2018)
  • N. Marin et al.

    Copyrolysis of wood biomass and synthetic polymers mixtures. Part II: characterisation of the liquid phases

    J. Anal. Appl. Prolysis

    (2002)
  • E. Mousset et al.

    A complete phenol oxidation pathway obtained during electro-Fenton treatment and validated by a kinetic model study

    Appl. Catal. B Environ.

    (2016)
  • D.C. Phan et al.

    Biodegradability of carbon nanotube/polymer nanocomposites under aerobic mixed culture conditions

    Sci. Total Environ.

    (2018)
  • G.D. Vukovic et al.

    Removal of cadmium from aqueous solutions by oxidized and ethylenediamine-functionalized multi-walled carbon nanotubes

    Chem. Eng. J.

    (2010)
  • J. Wei et al.

    Carbon-coated montmorillonite nanocomposite for the removal of chromium(VI) from aqueous solutions

    J. Hazard. Mater.

    (2019)
  • Z. Wu et al.

    Preparation and characterization of chitosan-grafted multiwalled carbon nanotubes and their electrochemical properties

    Carbons

    (2007)
  • W. Wu et al.

    Unraveling sorption of lead in aqueous solutions by chemically modified biochar derived from coconut fiber: a microscopic and spectroscopic investigation

    Sci. Total Environ.

    (2017)
  • F. Yan et al.

    Multiple toxicity endpoint–structure relationships for substituted phenols and anilines

    Sci. Total Environ.

    (2019)
  • X. Yang et al.

    Surface functional groups of carbon-based adsorbents and their roles in the removal of heavy metals from aqueous solutions: a critical review

    Chem. Eng. J.

    (2019)
  • G. You et al.

    Influence of CeO2 nanoparticles on viscoelastic properties of sludge: role of extracellular polymeric substances

    Environ. Res.

    (2018)
  • J.G. Yu et al.

    Aqueous adsorption and removal of organic contaminants by carbon nanotubes

    Sci. Total Environ.

    (2014)
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