Lead sorption from aqueous solutions on chitosan nanoparticles

https://doi.org/10.1016/j.colsurfa.2004.10.010Get rights and content

Abstract

Chitosan nanoparticles with different mean size ranging from 40 to 100 nm, which are well dispersed and stable in aqueous solution, have been prepared by ionic gelation of chitosan and tripolyphosphate (CS-TPP). The physicochemical properties of nanoparticles were characterized by size and zeta-potential analyzer, atomic force microscopy, FTIR spectra, and X-ray powder diffraction. Its sorption capacity and sorption isotherms for lead ions were studied. Factors such as initial concentration of lead ions, sorbent amount, temperature, sorbent size, agitation period, and pH value of solution that influence sorption capacity were investigated. It is found that chitosan nanoparticles could sorb lead ions effectively, the sorption rate was affected significantly by initial concentrations of solutions, sorbent amount, size, agitation speed, and pH value of solution. The maximum capacity of lead sorption deduced from the use of Langmuir isotherm equation was 398 mg/g. The experimental data of lead ions sorption equilibrium correlated well with the Langmuir isotherm equation. New sorption sites were provided by introducing phosphoric groups, and the freeze-drying procedure led to the low crystallinity of chitosan nanoparticles; as a result, the sorption capacity was improved greatly.

Introduction

Biopolymers, chitosan is the deacetylated form of chitin and composed of glucosamine, known as (1–4)-2-amino-2-deoxy-β-d-glucose. Chitosan has three types of reactive functional groups, an amino group as well as both primary and secondary hydroxyl groups at the C-2, C-3 and C-6 positions, respectively [1]. This special structure makes it exhibit chelation with various metal ions [2]. Muzzarelli [3] pointed out that chitosan combines with metal ions by three forms: ion exchange, sorption and chelation. Chitosan has been broadly used for the sorption of heavy metal ions [4], [5], [6]. Further physical and chemical modifications of chitosan have been made to improve the selectivities and the capacities for metals ions [7], [8], [9], [10]. Chitosan is also characterized by weak diffusion properties: long contact times are required to reach equilibrium. Sorption capacity can be controlled by sorbent particle size [8]. Due to the low porosity of chitosan, sorption performances are frequently controlled by mass transfer resistance. To reduce this resistance to mass transfer, chitosan gel beads have been developed to expand the polymer structure and reduce its crystallinity favouring sorption rate [11], [12], [13]. However, these treatments results in either a decrease of the number of available sorption sites (cross-linking treatment), or the volumetric sorption capacity (the percentage of water in the gel beads can reach 95%) [14]. Controlled drying can increase the volumetric sorption capacity [15]. Another possibility for increasing this volumetric sorption capacity is the grafting of supplementary functional groups [16].

A number of nanoscale inorganic particles (NIPs) offer favourable properties in regard to selective removal of target contaminants. For example, hydrated Fe(III) oxides particles can selectively sorb dissolved heavy metals like zinc, copper or metalloids like arsenic oxyacids or oxyanions [17]. Amorphous and crystalline Fe(III) hydroxides have long been known to possess selective sorption properties toward arsenites and arsenates [18]. Polymer supported nanoparticles have been prepared and used for selective removal of target arsenic compounds and heavy metals [17]. Chitosan nanoparticles had been synthesized based on polymer and applied as drug carriers as reported in previous studies [19], [20], [21].

However, researches about the sorption properties of chitosan nanoparticles are seldom reported now. The unique character of nanoparticles for their small size, great surface area and quantum size effect could make it exhibit higher capacities for metal ions. The present work aims to synthesize chitosan nanoparticles by ionic gelation of chitosan and tripolyphosphate and evaluates their sorption capacity of lead ions. Freeze-drying was applied in preparation of chitosan nanoparticles, and new sorption sites polyphosphoric groups were introduced by slightly crosslinking with tripolyphosphate to increase the volumetric density of sorption sites and the sorption capacity.

Section snippets

Materials

Chitosan, obtained from Chitosan Company of Panan city of Zhejiang province in China, was refined twice by dissolving it in dilute acetic acid solution, filtered, precipitated with aqueous sodium hydroxide, and finally dried in vacuum at room temperature [22]. The degree of deacetylation was about 85%, and weight of chitosan was 220 kDa, determined by viscometric methods [23]. Sodium tripolyphosphate (TPP) was supplied by Sigma Chemical Co. (USA). Lead nitrate was purchased from Shanghai

Size and morphology of chitosan nanoparticles

The preparation of chitosan nanoparticles was based on an ionic gelation interaction between positively-charged chitosan and negatively-charged tripolyphosphate at room temperature [25], [26]. The chitosan nanoparticles prepared in the experiment exhibit white powder shape, and were insoluble in water, dilute acid, and alkalescent solution.

The mean size and size distribution of each batch of nanoparticles suspension was analyzed using the Zetasizer analysis. The size distribution profile, as

Conclusion

Different mean size of chitosan nanoparticles have been prepared by ions gelation of chitosan and tripolyphospahte. The morphology changes of nanoparticles after sorption of lead ions are revealed by AFM observations. FTIR spectra reveal the functional groups of chitosan nanoparticles and the interaction with lead ion, the amine and phosphoric groups of nanoparticles provide sorption sites for lead ions. Chitosan nanoparticles possess lower crystallinity than chitosan illuminated by XRD

Acknowledgements

We would like to thank Zhejiang Provincial Science and Technology Committee of China (No. 021102680) for financial support.

References (49)

  • F. Boukhlifi et al.

    Ann. Chim. Sci. Mater.

    (2000)
  • M. Jansson-Charrier et al.

    Water Res.

    (1996)
  • R. Kumar et al.

    React. Funct. Polym.

    (2000)
  • P. Chassary et al.

    React. Funct. Polym.

    (2004)
  • L. Cumbal et al.

    React. Funct. Polym.

    (2003)
  • K.A. Janes et al.

    J. Controlled Release

    (2001)
  • H. Ishii et al.

    Int. J. Biol. Macromol.

    (1995)
  • A. Heras et al.

    Carbohydr. Polym.

    (2001)
  • V.M. Ramos et al.

    Carbohydr. Polym.

    (2003)
  • S.-T. Lee et al.

    Polymer

    (2001)
  • E. Piron et al.

    Int. J. Biol. Macromol.

    (1998)
  • M.S. Dzul Erosa et al.

    Hydrometallurgy

    (2001)
  • K.H. Chu

    J. Hazard. Mater. B

    (2002)
  • A. Domard

    Int. J. Biol. Macromol.

    (1987)
  • W.J. Trahar et al.

    Int. J. Miner. Process

    (1997)
  • R.A.D. Pattrick et al.

    Miner. Eng.

    (1998)
  • J.C.Y. Ng et al.

    Chemosphere

    (2003)
  • G. Bayramoglu et al.

    Microchem. J.

    (2002)
  • W.S. Wan Ngah et al.

    React. Funct. Polym.

    (2002)
  • S. Fereidoon et al.

    Trends Food Sci. Technol.

    (1999)
  • R. A. A. Muzzarelli, Pergamon Press, Oxford,...
  • R.W. Coughlin et al.

    Environ. Prog.

    (1990)
  • P. Udaybhaskar et al.

    J. Appl. Polym. Sci.

    (1990)
  • E. Guibal et al.

    Langmuir

    (1995)
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