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Jan 23, 2013 - Remediation of Uranium-contaminated Groundwater by Sorption onto Hydroxyapatite Derived from Catfish Bones. S. A. Chattanathan & T. P. ...
Water Air Soil Pollut (2013) 224:1429 DOI 10.1007/s11270-012-1429-5

Remediation of Uranium-contaminated Groundwater by Sorption onto Hydroxyapatite Derived from Catfish Bones S. A. Chattanathan & T. P. Clement & S. R. Kanel & M. O. Barnett & N. Chatakondi

Received: 19 June 2012 / Accepted: 18 December 2012 / Published online: 23 January 2013 # Springer Science+Business Media Dordrecht 2013

Abstract Hydroxyapatite (HA) was prepared from catfish bones, identified as catfish HA (CFHA), using mechanical and chemical treatment methods. CFHA was characterized by x-ray diffraction (XRD) and scanning electron microscope (SEM) techniques to confirm the presence of HA. The ability of CFHA to remove uranium (U(VI)) from aqueous phase was investigated using both batch and column experiments. Adsorption experiments in batch experiments were carried by varying pH, preparation temperature, and particle size. The data shows that the maximum adsorption occurred between pH5.5 and 7. The adsorption of U(VI) on CFHA was greater at 300 °C than at 100 °C. Batch data shows that the smallest particles, with maximum surface area, exhibited significant U (VI) removal efficiency. Column experiments were conducted using the smallest CFHA particles at different flow rates and breakthrough profiles were

S. A. Chattanathan : T. P. Clement : S. R. Kanel : M. O. Barnett Department of Civil and Environmental Engineering, Auburn University, Auburn, AL 36849, USA S. R. Kanel (*) Air Force Institute of Technology, Wright Patterson AFB, OH 45433-7765, USA e-mail: [email protected] N. Chatakondi USDA–ARS Catfish Genetics Research Unit, Mississippi State University, Mississippi State, MS 39762, USA

obtained. The scalability of the U(VI) removal process was tested by comparing the performances of columns packed with different CFHA. The results indicated that the reaction scales to the mass concentration of the reactants (CFHA and U(VI)). We also found that at pH7, the CFHA packed in the column has the potential to remove about 3.9 mg of U(VI) per gram. Our study shows that CFHA may be used in permeable reactive barriers for remediating U(VI)-contaminated groundwater plumes. Keywords U(VI) . Hydroxyapatite . Permeable reactive barrier . Groundwater remediation

1 Introduction The development of nuclear technologies has led to the increase of nuclear wastes containing radionuclides being released into the environment. Pollution caused by radionuclides is a serious problem throughout the world (Das 2012). In the United States, groundwater aquifers in several Department of Energy (DOE) sites have been severely contaminated with radionuclides. Due to its chemical and radiological toxicity, migration of U(VI) from these sites can pose considerable health and environmental hazard. The United States Environmental Protection Agency (USEPA) has set the maximum contaminant level (MCL) for U(VI) in drinking water as 30 μg/L since December 2003 (Han et al. 2007).

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Permeable reactive barrier (PRB) is one of the most promising technologies that has the potential to treat subsurface U(VI) plumes (Fuller et al. 2003). Various types of sorbent materials have been used within the PRB to remove U(VI) from groundwater. These materials include reactive sorption media such as activated carbon, zero-valent iron (ZVI), zeolites, phosphate rocks, and hydroxyapatites (HAs) (Han et al. 2007; Phillips et al. 2008; Raicevic et al. 2006b; Saxena et al. 2006). Among these alternatives, HA has received considerable attention in recent years for treating metal-contaminated groundwater (Thakur et al. 2005). This is because HA can react with heavy metals and radionuclides forming minerals that are stable across a wide range of geological conditions (Nriagu 1974; Raicevic et al. 2006a). For example, the solubility product of unreacted apatite is Ksp =10−20 (Raicevic et al. 2006a), whereas reacted U (VI)-apatite minerals such as autonite have a very low Ksp value of 10−49 (Raicevic et al. 2006a) and chernikovite around 10−45 (Raicevic et al. 2006b). It has also been observed that sedimentary and/or biogenic apatites deposited by seawater can sequester metals and radionuclides into their apatite structure for many years (Wright et al. 1987). These sequestered metals are difficult to remove via desorption, leaching, or ion exchange processes, even under extreme diagenetic conditions such as changes in pore water chemistry, pH, temperature variations (of more than 500 °C), and/or under tectonic disruptions (Wright 1990; Wright et al. 1987). Researchers have used both natural and synthetic HA to remove U(VI) from contaminated water. Natural HA can be derived from bones and phosphate-rich rocks. Synthetic HA can be prepared by chemically reacting a hydroxide source such as calcium hydroxide and phosphoric acid (Bouyer et al. 2000). The efficiency of synthetic HA for treating U(VI) has been studied previously (Arey et al. 1999; Fuller et al. 2002; Krestou et al. 2004; Simon et al. 2008; Wellman et al. 2008). Cheaper alternative to HA is highly desirable for the remediation of actinides as synthetic HA is expensive while practically applying for large-scale remediation. Thomson et al. (2003) compared the efficiencies of different sorbents (synthetic apatites, tricalcium phosphate bones char, and activated magnetite) in batch for removing dissolved metals and radionuclides (As, Am, Pu, Se, Tc, and U) (Thomson et al. 2003). However, the sorption capacity estimated from batch experiments might not be applicable for the PRB system where the contact time might not be

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sufficient to reach equilibrium. Hence, the efficiency of commercially viable natural HA should be studied through column experiments. In this study, we provide feasibility data for using natural HA obtained from farmed catfish (a cross between the channel catfish, Ictalurus punctatus (female) blue catfish, Ictalurus furcatus (male)) bones to treat uranium plumes. Catfish farming is one of the major agricultural industries in the southeastern regions of the United States, and reusing the fish bones from the industry offers both economic and environmental benefits (Chatakondi et al. 2005). The goal of this research is to study the feasibility of using HA derived from these catfish bones (identified as catfish HA (CFHA)) to remove U(VI) from contaminated groundwater. The specific objectives are to: (1) prepare and characterize the HA materials derived from the catfish bones, (2) conduct batch experiments to study the influence of various chemical conditions (pH, preparation temperature, and initial concentrations) on CFHA and U(VI) interaction, and (3) perform column experiments to investigate U(VI) removal by CFHA under dynamic flowing conditions.

2 Material and Methods 2.1 Materials All the chemicals used in the experiments were of reagent grade. Several chemicals including sodium nitrate, sodium bicarbonate, sodium hydroxide and nitric acid were purchased from Fisher Scientific (Fairlawn, NJ, USA). Commercial HA (CHA) was purchased from Sigma-Aldrich (St. Louis, MO, USA). American Chemical Society (ACS) reagent-grade chemicals such as hydrogen peroxide were purchased from Sigma-Aldrich (St. Louis, MO, USA). All reagents were used as received without further alteration. Ultrapure water (Millipore, 18.2 MΩ cm) was used to prepare all solutions. The acids were of trace-metal grade. The U (VI) solution was prepared from plasma-grade U(VI) standard made using depleted U(VI). Catfish bones were collected from a catfish processing plant near Selma, AL, USA and were boiled for about an hour in a pressure cooker. The cooked bones were washed in a flowing stream of water to remove flesh and fat materials. The remaining bones were soaked in 30 % hydrogen peroxide for a day to

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remove all residual organic matter. The peroxidetreated bones were air dried for 2 days and then crushed into smaller pieces and heated in an oven for 3 days at 100 °C unless otherwise specified. In order to investigate the effects of heat treatment, two types of fish bones were prepared by heating the bones at 100 °C and 300 °C. Also, to study the size effects, the fish bones prepared at 100 °C were mechanically crushed and sieved to yield samples having large (>2,000 μm), medium (300–2,000 μm), and small (2,000 μm, between 2,000 μm and 300 μm, and