Waste studies, leaching

Lee, C. T. Clark, D. E. 1985. Electrokinetics, adsorption and colloid study of simulated nuclear waste glasses leached in aqueous solutions. In Jantzen, C. M., Stone, J. A. Ewing, R. C. (eds) Scientific Basis for Nuclear Waste Management VIII. Materials Research Society Symposia Proceedings, 44, 221-228. 

The use of inorganic ion exchangers to solidify liquid radioactive waste followed by pressure sintering to produce a ceramic waste form appears to be a viable alternative to calcina-tion/vitrification processes. Both the process and waste form are relatively insensitive to changes in the composition of the waste feed. The stability of the ceramic waste form has been shown to be superior to vitrified wastes in leaching studies at elevated temperatures. Further studies on the effects of radiation and associated transmutation and the influence of temperature regimes associated with potential geologic repositories are needed for a more definitive comparison of crystalline and amorphous waste forms. 

Kenna, B.T., Murphy, K.D., and Levine, H.S., "Studies of Waste Form Leaching Part I. Long Term Elevated Temperature Leaching," to be published in J. Amer. Cer. Soc. 

Recently, it is reported that Xi02 particles with metal deposition on the surface is more active than pure Ti02 for photocatalytic reactions in aqueous solution because the deposited metal provides reduction sites which in turn increase the efficiency of the transport of photogenerated electrons (e ) in the conduction band to the external sjistem, and decrease the recombination with positive hole (h ) in the balance band of Xi02, i.e., less defects acting as the recombination center[l,2,3]. Xhe catalytic converter contains precious metals, mainly platinum less than 1 wt%, partially, Pd, Re, Rh, etc. on cordierite supporter. Xhus, in this study, solutions leached out from wasted catalytic converter of automobile were used for precious metallization source of the catalyst. Xhe XiOa were prepared with two different methods i.e., hydrothermal method and a sol-gel method. Xhe prepared titanium oxide and commercial P-25 catalyst (Deagussa) were metallized with leached solution from wasted catalytic converter or pure H2PtCl6 solution for modification of photocatalysts. Xhey were characterized by UV-DRS, BEX surface area analyzer, and XRD[4]. 

This study allows a better understanding of the Ni geochemistry in near-neutral conditions. Kinetic cell tests run for 75 weeks on 6 waste rock samples suggest that the pH will remain near neutral in the waste rock piles. Sorption phenomena seem to drive Ni leaching in laboratory kinetic cells, and the sorption type and capacity vary between fresh and... 

Soil monitoring data in the peer reviewed literature could not be located. It can be predicted that chloroform contamination occurs at hazardous waste sites where chloroform-containing leachate moves through the soil to groundwater. An explanation of the lack of data results from the fact that any chloroform in the soil is expected to either rapidly volatilize or leach. Laboratory studies using a variety of different soil types document the effectiveness of volatilization in removing chloroform from soils (Park et al. 1988). 

For this reason, additional studies on carbon tetrachloride flux rates into and out of surface water, as well as refined quantitative estimates of aquatic fate processes would be valuable. The chemical is expected to evaporate rapidly from soil due to its high vapor pressure and may migrate into groundwater due to its low soil adsorption coefficient. No data are available on biodegradation in soil. Additional studies to determine degradation rates and the extent to which adsorption has occurred would be useful. These data are also useful in evaluating the impact of carbon tetrachloride leaching from hazardous waste sites. 

Timmons, D. M. Thompson, L. E. 1996. Geochemical and petrographic studies and the relationships to durability and leach resistance of vitrified products from the in-situ vitrification process. In Proceedings of the International Topical Meeting on Nuclear and Hazardous Waste Management SPECTRUM 96. American Nuclear Society, Inc., La Grange Park, 1026-1029. 

Saether (1980), Saether Runnells (1980), and Stollenwerk Runnells (1981) studied the leaching of various retorting residues from US Green River oil shales. Alkaline pH values were established even before 25% of the first pore-volume had passed through the waste, and were maintained at high levels for the first 15 pore-volumes. The main potentially toxic elements mobilized under such alkaline conditions were found to be As, B, F, Mo, and Se. In contrast, base metals such as Cu, Ni, Pb, and Zn will be immobilized under such alkaline conditions (Baes Mesmer 1976 Bell 1976). 

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