Uranium(VI) Removal by Nanoscale Zerovalent Iron in Anoxic Batch Systems

Abstract

This study investigated the influences of pH, bicarbonate, and calcium on U(VI) removal and reduction by synthetic nanoscale zerovalent iron (nanoFe(0)) particles under anoxic conditions. The results showed that the rates of U(VI) removal and reduction by nanoFe(0) varied significantly with pH and concentrations of bicarbonate and/or calcium. For instance, at pH 6.92 the pseudo-first-order rate constants of U(VI) removal decreased by 78.5% and 81.3%, and U(VI) reduction decreased by 90.3% and 89.3%, when bicarbonate and calcium concentrations were increased from 0 to 1 mM, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of UO(2) and iron (hydr)oxides as a result of the redox interactions between U(VI) and nanoFe(0). The study demonstrated the potential of using nanoFe(0) for U(VI)-contaminated site remediation and highlighted the impacts of pH, bicarbonate, and calcium on the U(VI) removal and reduction processes.

Uranium(VI) reduction by nanoscale zero-valent iron in anoxic batch systems: The role of Fe(II) and Fe(III)

“…) and ternary calcium-uranyl-carbonate species (e.g., CaUO 2 (CO 3 ) 3 2À and Ca 2 UO 2 (CO 3 ) 3 ) has been known to increase the mobility of U(VI) (Clark et al, 1995;Hua et al, 2006;Yan et al, 2010;Stewart et al, 2011). In contrast, U(IV) is stable in the anoxic groundwater as sparingly soluble solids, even in the presence of common groundwater ligands such as carbonate, and thus tends to be relatively immobile.…”

“…The solubility, and hence mobility, of uranium in the environment is controlled by its oxidation state (Abdelouas et al, 1999), which is influenced by numerous factors such as bacterial activity (Lovley et al, 1991;Suzuki et al, 2002), the mineralogy and organic content of the system (Langmuir, 1997;Wan et al, 2008;Shi et al, 2009;Latta et al, 2012;Fox et al, 2013), and solution composition (Clark et al, 1995;Yan et al, 2010;Singh et al, 2012;Stylo et al, 2013). U(VI) is stable in oxic environments and commonly exists as soluble carbonate complexes in aerobic groundwater under neutral to alkaline conditions.…”

Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron

“…Groundwater has long been used as a drinking water resource in parts of China and many other countries [1][2][3][4], but the presence of pollutants in groundwater is a common problem [1,5,6]. Nanoscale zerovalent iron (nZVI) has been extensively considered for in situ groundwater remediation [7][8][9][10] of a wide range of groundwater pollutants including chlorinated solvents [11,12], chlorinated pesticides [13], heavy metals [14][15][16], and nitrate [17][18][19].…”

“…Pb 2+ pollution results mainly from leakage of leaded gasoline and poor management of wastes from industrial processes such as mining, coal burning, battery production, and smelting [27], while nitrate contamination is mainly from fertilizer application, irrigation with untreated wastewater, and industrial processes [2,28]. Nitrate concentrations as high as 300 mg/L have been detected in groundwater [2].nZVI is easily oxidized on exposure to water, hence the Fe(0) core is surrounded by an oxide layer [6,29]. The core-shell structure is key for Pb 2+ sequestration (partly reduction by core but mainly adsorption and co-precipitation on shell) [15,29,30], but this unique structure is destroyed during the nitrate reduction process as Fe(0) may be oxidized completely [19].…”

Illite-supported nanoscale zero-valent iron for removal of 238U from aqueous solution: characterization, reactivity and mechanism

“…The advantages of nZVI facilitate remediation of hazardous wastes contamination that the small particle size and large surface area per unit mass of nanoparticles [12,[14][15][16]. Nanoscale zero-valent iron has the potential for efficient and cost effective remediation of contaminated solutions [13,[17][18][19].…”