Sorption and desorption of radiocobalt on montmorillonite - Effects of pH, ionic strength and fulvic acid
ABSTRACT Humic substances and clay minerals have been studied extensively in radioactive waste management. In our research, the sorption and desorption of radiocobalt on montmorillonite in the presence and absence of fulvic acid as a function of pH and ionic strength were investigated under ambient conditions by using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH values and independent of ionic strength. Surface complexation rather than cation exchange is considered as the main mechanism of cobalt sorption to montmorillonite. The presence of fulvic acid enhances cobalt sorption obviously at pH values<8. The desorption behavior changes of surface-sorbed cobalt from montmorillonite were studied by decreasing pH values and the solution cobalt concentrations independently. The results indicated that the sorption of cobalt on montmorillonite is irreversible.
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- ") satisfy the criteria outlined earlier (Cremers et al., 1988; Avery, 1996; Matishov et al., 1999; Real et al., 2002; Galabov et al., 2003; Khan, 2003; Caron and Mankarios, 2004; Payne et al., 2004; Shinonaga et al., 2005; Whicker and Ibrahim, 2006; Chen and Lu, 2008). Although both radionuclides have previously been used as sediment tracers (e.g. "
ABSTRACT: River floodplains act as sinks for fine-sediment and sediment-associated contaminants. Increasing recognition of their environmental importance has necessitated a need for an improved understanding of the fate and residence times of overbank sediment deposits over a broad range of timescales. Most existing investigations have focused on medium-term accretion rates, which represents net deposition from multiple flood events over several decades. In contrast, the fate of recently-deposited sediment during subsequent overbank events has received only limited attention. This paper presents a novel tracing-technique for documenting the remobilization of recent overbank sediment on river floodplains during subsequent inundation events, using the artificial radionuclides, caesium-134 (134 Cs) and cobalt-60 (60 Co). The investigation was conducted within floodplains of the Rivers Taw and Culm in Devon, UK. Small quan-tities of fine-sediment (< 63 μm dia.), pre-labelled with known activities of either 134 Cs or 60 Co, were deposited at 15 locations across each floodplain. Surface inventories, measured before and after three consecutive flood events, were used to estimate sediment loss (in g m –2). Significant reductions provided evidence of the remobilization of the labelled sediment by inundating floodwaters. Spatial variations in remobilization were related to localized topography. Sediment remobilized during the first two events for the River Taw floodplain were equivalent to 63 · 8% and 11 · 9%, respectively, of the original mass. Equivalent values for the River Culm floodplain were 49 · 6% and 12 · 5%, respectively, of the original mass. Sediment loss during the third event proved too small to be attributed to remobilization by overbank floodwaters. After the third event, a mean of 22 · 5% and 35 · 2% of the original mass remained on the Taw and Culm floodplains, respectively. These results provide evidence of the storage of the remaining sediment. The findings highlight the importance of remobilization of recently-deposited sediment on river floodplains during subsequent overbank events and demonstrate the potential of the tracing-technique.Earth Surface Processes and Landforms 02/2014; 39(2). DOI:10.1002/esp.3442 · 2.85 Impact Factor
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- "Considerable attention has been received the utilization of adsorption technique recently, in which the adsorbents are natural material or industrial and agricultural wastes, to passively remove of metal ions from aqueous effluents. Thus, the utilization of peat    living and death biomass    or clay and related minerals    offers an efficient and cost-effective alternative compared to traditional chemical and physical remediation and decontamination techniques Moreover, their regeneration does not present any problem and, when needed, the recovering of the fixed element could be reached even by leaching the loaded material. Carbon soot is a promising material for different industrial applications as a substitute for commercial powdered activated carbon    . "
ABSTRACT: Abstract. In this work, the removal of cobalt ions from aqueous solutions by carbon soot which is a very cheap industrial by-product has been studied. Its objective was to investigate the possibility of using carbon soot instead of high cost commercial adsorbent materials for the removal of cobalt from aqueous solution. Different adsorption isotherms (Langmuir, Freundlich, and Brauner-Emmett-Teller) were applied. The adsorption rate constant (Kad), rate constant for intraparticle diffusion (Kp), pore diffusion coefficient (D), overall reaction rate (K), equilibrium constant (Kc), activation energy (E) and the thermodynamic functions �G◦, �H◦ and �S◦ were estimated. Also the effect of time, sorbent dose, initial concentration and the pH at different temperatures were studied. The results were interesting, indicating that carbon soot is capable of removing cobalt(II) from an aqueous solution. The equilibrium time for cobalt(II) adsorption on soot is larger than that on powdered activated carbon. Cobalt adsorption is pH dependent. The kinetics of adsorption was investigated as first order diffusion controlled and spontaneous process.Main Group Chemistry 01/2014; 13(4):353. DOI:10.3233/MGC-140147 · 0.46 Impact Factor
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- "Based on the recent publications (Bhattacharyya and Gupta, 2008; Bradbury and Baeyens, 2005; Chen and Lu, 2008; Gaskova and Bukaty, 2008a), Co behavior during the overall sorption process can be described as follows. 1. "
ABSTRACT: Cobalt behavior during the oxidation of sulfide ores, unlike that during the oxidation of Co ores, is poorly known. Moreover, cobalt sulfates are rare in the world. Complex hydrous cobalt-containing and cobalt sulfates have been found in technogenic zones at the Letnee chalcopyrite deposit (Southern Urals). They have been identified at pit bottoms, in the ore stockpile, as well as directly on ore fragments and the evaporation barriers of underdump water puddles. The paper reports the first experimental data on the oxidative leaching of Co-containing sulfide ores in the laboratory. Also, parts of a thermodynamic model for Co behavior in oxidized zones are presented.Experiments have revealed an increase in acidity up to pH = 4.14, along with transport of sulfate sulfur and metals into solution. This suggests acid mine drainage during the development of the Letnee deposit. The published stability diagrams for hydrous Cu, Mg, Zn, Co, and Ni sulfates were analyzed and compared with mineralogical finds in a technogenic oxidized zone. This made it possible to explain the precipitation sequence of minerals from solutions during their concentration by evaporation. As salts of these elements are highly soluble, significant contents of toxic metals will inevitably remain in equilibrium solution, necessitating additional waste-water treatment (for example, creating sorption geochemical barriers). Therefore, the paper describes regularities in Co behavior during its sorption on solid phases.Russian Geology and Geophysics 02/2010; 51(2-51):176-185. DOI:10.1016/j.rgg.2009.12.016 · 1.31 Impact Factor