Leach results, calculation

Column test (described in Dutch standard NEN 7343) is intended to simulate the percolation of (acidic) rainwater through granular materials in a road construction or landfill. The material is placed in a column with a diameter of 5 cm and height of 20 cm, and acidified demineralized water is then passed upwards through it. The eluate is collected in seven fractions at a liquid/solid ratio of between 0.1 and 101 kg-1. The leaching is calculated and expressed in mg kg 1 as a function of time, based on the analysis results. 

Referring to Figure 2, by considering solute mass balances over n, (n — 1),. .. 2, 1 units in turn and eliminating intermediate solute mass fractions and flow rates, the amount of solute associated with the leached sohd may be calculated in terms of the composition of the sohd and solvent streams fed to the system. The resulting equation is (2)... 

Comparing the results on direct discharges with the results of the SFA for Guiyu of 186 t of DeBDE accumulating over 1 year in a land disposal, the emission of 6 kg would account for 3 x 10 3% leached material within one year, which is in the range of 3 x 10-3 to 3 x 10 2% that have been calculated by Choi et al. (2009) [41] for leaching of DeBDE in contact with dissolved humic substances from TV housing plastics. 

Based on calculated soil adsorption factors (log Koc of 2.24, 2.98, and 4.3), hexachloroethane is expected to have medium to low mobility in soil (Howard 1989). Thus, leaching to groundwater could occur. Results of studies with low organic carbon (0.02%) soil material indicate that sorption to aquifer materials retards hexachloroethane migration in groundwater (Curtis et al. 1986). In aquatic environments, moderate to slight adsorption to suspended solids and partitioning to sediments is likely (Howard 1989). 

The temperature dependence of the reaction was studied, and the activation energy of the reaction was calculated to be approximately 100 kj mol The exponent n was found to lie in the range 1-2, which is consistent with a 2D diffusion controlled reaction mechanism with deceleratory nucleation. The rate of reaction increases markedly with the amount of water added to the LDH with very small amounts of water added, the deintercalation process does not go to completion. This effect is a result of the LiCl being leached into solution. An equilibrium exists between the LDH and gibbsite/LiCl in solution. The greater [LiCl], the further to the LDH side this lies. 

Better results were obtained by using in situ prepared palladium complexes of a G4 dendrimer (calculated molecular weight 20 564 Da for 100% palladium loading of the 32 diphosphines). After 100 residence times, the conversion had decreased from 100% to approximately 75% (Fig. 3). A small amount of palladium was leached from the catalyst during this experiment (0.14% per residence time), which only partly explains the decrease in conversion. The formation of inactive PdCl2 was proposed to account for the additional drop in activity. A sound conclusion about the effect of this dendritic catalyst requires more experiments. 

Leach rate measurements have been made on several waste forms, using the NAA technique. Some results are presented here as examples of the application of this method. Simulated wastes used in these studies consisted of two types of granules obtained from Battelle Pacific Northwest Laboratories. The differential leach rates of the bulk waste matrix were calculated with the equation ... 

Bulk chemical analysis of the solids. The three rock types were chemically analyzed by neutron activation (NAA) and x-ray fluorescence (XRF). The resulting data (not included in this report) were used for depth-of-leaching calculations given below. With the measurement of volatile components in the basalt and shale, the total measured abundances in all three samples was close to 100 percent. 

Leach test results were calculated in terms of normalized mass loss of the glass (mass loss/unit area) based on l Cs, 90gr> or 238pu, The appropriate equation is ... 

Experimental. Characteristics of a typical iodine-containing cement monolith are listed in Table V. The monoliths were suspended in glass beakers containing the leachant at ambient temperature (19-23°C), and the tests were peformed in air. The leachant-to-surface-area ratio was 10 1. The results are presented as the normalized fraction leached, which is calculated by multiplying the fraction leached by the sample s geometric volume-to-surface area ratio, normally 0.5 cm. 

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