Performance of Chitosan Micro/Nanoparticles to Remove Hexavalent Chromium From Residual Water

Performance of Chitosan Micro/Nanoparticles to Remove Hexavalent Chromium From Residual Water

Jimena Bernadette Dima (CONICET-CENPAT, Argentina) and Noemí Zaritzky (CIDCA-UNLP-CONICET, Argentina)
DOI: 10.4018/978-1-5225-2136-5.ch010
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Hexavalent chromium Cr(VI) is toxic to living systems and must be removed from wastewater. Chitosan is a cationic, biocompatible, biodegradable, biopolymer obtained from marine wastes. The performance of chitosan particles (CH) and chitosan nanoparticles (CHN) to remove Cr(VI) from aqueous solutions is discussed in the present chapter. CHN were obtained by reticulation with tripolyphosphate (TPP), and physico-chemically characterized. The performance of CHN decreased at higher pH due to the cross-linking process with TPP. Langmuir isotherm described the equilibrium adsorption values and pseudo-second order rate provided the best fitting to the kinetic data. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the CHN as Cr(III). Chitosan crosslinking was essential to adsorb Cr(VI) at pH<3 due to the dissolution of CH in acid media.
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1. Introduction

Industrial and mining wastewaters are important sources of pollution of heavy metals. The use of chromate and dichromate has many industrial applications such as in textile, electroplating, leather tanning, cement preservations, paints, pigments and metallurgy industries. Chromium is a metal potentially toxic to humans as it is considered carcinogenic. Cr (VI) is toxic to living systems and must be removed from wastewater before it can be discharged. Cr(II), Cr(III) and Cr(VI) are the three oxidation states for chromium in nature, but only the last two are stable. Cr(VI) is 500 times more toxic, mutagenic and carcinogenic than Cr(III). The maximum permissible limit of for Cr(VI) in wastewater has been recommended as 0.005mg L−1 by World Health Organization.

For the removal of toxic pollutants from water and wastewater differences methods, such as oxidation/reduction, filtration, coagulation, membrane process, adsorption, osmosis, biological methods, etc, have generally been used. However, adsorption process is often considered the most appropriate technique owing to its advantages such as a variety of adsorbent materials and high efficiency.

Over the years, a wide range of clean-up technologies has been developed to remove toxic metals from water. The removal of metals, compounds, and particulates from solution by the biological material is recognized as an extension to adsorption and is named as biosorption.

Biosorbents have been given increasing attention as they can significantly reduce the cost of an adsorption system. Chitosan is an excellent biopolymer obtained cost-effectively by the derivation of chitin, which is a natural, abundance and non-toxicity, the material found widely in crustacean shells. Chitosan is the N-deacetylated derivative of chitin (2-acetamido-2-deoxy-β-D-glucose through a β (1→4) linkage).

Figure 1.

Chitin and Chitosan

Chitin and chitosan are of commercial interest due to their high percentage of nitrogen (6.89%) compared to synthetically substituted cellulose (1.25%); this makes chitin a useful chelating agent. As most of the present-day polymers are synthetic materials, their biocompatibility and biodegradability are much more limited than those of natural polymers such as cellulose, chitosan, and their derivations. This biopolymer represents an attractive alternative to other biomaterials because of its physico-chemical characteristics, chemical stability, high reactivity, excellent chelation behavior and high selectivity toward pollutants.

Chitosan has been shown to effectively remove metals such as chromium, copper, mercury and lead from aqueous solutions (Schmuhl et al.,2001; Ngah et al., 2002; Ng et al.,2003; Qi &Xu, 2004;Laus et al., 2010; Hena, 2010; Yu et al., 2013,Sivakami, et al,2013).The adsorption of a metal ion on chitosan depends strongly on the pH of the solution. Chemical and physical modifications of chitosan have been commonly used to increase the stability of the polymer in acid solution and improve its adsorption capacity. In recent years, much active research has been performed on novel adsorbents and has explored various configurations of adsorbents to maximize their adsorptive capacity, particularly incorporating micro-nanoparticles

The general objective of this chapter was to analyze the use of contaminating crustaceans shellfish wastes for water purification, determining the simultaneous effects of pH and ionic crosslinking of chitosan particles on the removal of hexavalent chromium.

In this chapter the following topics are discussed:

  • 1.

    Production of chitosan from seafood processing wastes (shrimp shells);

  • 2.

    Synthesis of nanoparticles combining chitosan dissolved in acid solution with a nontoxic crosslinking agent;

  • 3.

    Characterization of the obtained micro/nanoparticles by Scanning Electron Microscopy, particle size distribution, zeta potential and Infrared spectroscopy (FTIR);

  • 4.

    Analysis of the performance of chitosan (CH) and chitosan nanoparticles (CHN) in the adsorption process of Cr from aqueous solutions at different pH values, initial chromium concentrations and contact times; and

  • 5.

    Mathematical modeling of the equilibrium isotherms and the adsorption kinetics.

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