Fast removal of uranium from aqueous solutions using tetraethylenepentamine modified magnetic chitosan resin

Highlights

• Tetraethylenepentamine magnetic chitosan resin was prepared.

• Removal of uranium from aqueous solution was studied by batch and column methods.

• The sorption capacity reaches up to 1.8 mmol/g at pH close to 4.

• The kinetic and thermodynamic parameters of the adsorption process were estimated.

• The resin shows good sorption performance for 3 successive regeneration cycles.

Abstract

Chitosan was cross-linked using glutaraldehyde in the presence of magnetite. The resin was chemically modified through the reaction with tetraethylenepentamine (TEPA) to produce amine bearing chitosan. The resin showed a higher affinity towards the uptake of ${\text{UO}}_2^{2+}$ ions from aqueous medium: maximum sorption capacity reached 1.8 mmol g⁻¹ at pH 4 and 25 °C. The nature of interaction of ${\text{UO}}_2^{2+}$ ions with the resin was identified. Kinetics were carried out at different temperatures and thermodynamic parameters were evaluated. Breakthrough curves for the removal of ${\text{UO}}_2^{2+}$ were studied at different flow rates, bed heights and after 3 regeneration cycles. Hydrochloric acid (0.5 M) was used for desorbing ${\text{UO}}_2^{2+}$ from loaded resin: desorption yield as high as 98% was obtained.

Introduction

The mining of uranium ores and their hydrometallurgical processing as well as the operation of nuclear power plants and disposal of spent nuclear fuel are potential sources of radioactive pollution of the environment. About 40,000–50,000 tons of uranium are produced every year (OECD Nuclear Energy Agency, 2010). Uranium is considered to be not only an irreplaceable raw material for nuclear energy, but also a serious long-term potential environmental hazard (Zhang et al., 2011). Uranium ions often accumulate in both water and the environment because of its long half-life. Hence, its presence poses an environmental challenge. Over the past few decades, a variety of technologies including chemical and biological precipitation (Kim et al., 2011, Zhang et al., 2013), solvent extraction (Quinn et al., 2013), ion exchange (Pulhani et al., 2012), membrane processes (Kedari et al., 2013), and adsorption (Cao et al., 2013, Katsoyiannis and Zouboulis, 2013) have been developed for the removal and recovery of uranium from nuclear fuel effluents, mine tailings, seawater and other waste sources. Lately, adsorption, due to its high-efficiency and readily handling has been gradually utilized (Katsoyiannis and Zouboulis, 2013). Therefore, the design and preparation of adsorbents with low cost and high-stability, efficiency and selectivity has been drawing considerable interests in processing uranium recovery and decontamination.

Chitin is one of the most abundant polysaccharides after cellulose. It is a basic structural component of fungal and yeast cell walls, as well as of numerous invertebrates (Muzzarelli et al., 2012). Chitosan, the linear (1,4)-2-amino-2-deoxy-β-d-glucan, can be obtained from chitin by partial deacetylation. These biopolymers are potent sorbents for various transition metals and radionuclides (Guibal et al., 2009, Schleuter et al., 2013). Grafting of new functional groups and chemical crosslinking of chitosan increases its adsorption capacity, stability and/or selectivity towards metal ions through the formation of different chelates.

The ultimate goal of this study is the development of magnetic chitosan resin bearing supplementary amine groups for the removal of ${\text{UO}}_2^{2+}$ ions from aqueous solution. These methods are cheap and often highly scalable. Moreover, techniques employing magnetism are more amenable to automation (Atia et al., 2008). Magnetic separation techniques offer several advantages. The most attractive one for radioactive wastewater treatment is its good performance in difficult-to-handle samples. By using the magnetic separation techniques rather than centrifugation or filtration, it will reduce the chances of contacting with radiations. However, so far only limited knowledge exists concerning the removal of radioactive substances by magnetic separation method, especially uranium removal by magnetically modified chitosan, which is meaningful from the purification, environmental and radioactive waste disposal point of view.

To address this objective in this study we use chitosan modified with magnetite and tetraethylenepentamine (TEPA) for ${\text{UO}}_2^{2+}$ removal from aqueous media. U(VI) adsorption onto the TEPA-magnetic chitosan was investigated, including (a) pH optimization, (b) determination of sorption isotherms and uptake kinetics in batch system, and (c) evaluation of breakthrough curves (in fixed bed column).