Leachable lead

Mundell JA, Hill KR, Weaver JW II. 1989. In situ case history Leachable lead required precipitation immobilization. Hazardous Waste Management 23-27. 

At Kirtland Air Force Base in New Mexico, an in situ application of MAECTITE was used to treat 2000 yd of soil contaminated with lead and cadmium. Following MAECTITE treatment, leachable lead and cadmium levels in soils were less than residential human health standards. In addition, contaminant levels were low enough that the treated waste could be categorized as nonhazardous by Resource Conservation and Recovery Act (RCRA) standards. Total costs for the project were 125,000, which was almost 40% less than alternative stabilization techniques considered at the site (D21483F, p. 3). 

The Lead Check test kit now also sold by Sensidyne has been tested by the Food and Drug Administration (FDA) and the National Institnte of Standards and Technology (NIST). The FDA reported that the swabs were able to detect the presence or absence of lead in 96.6% of the pieces tested. The NIST found that the swabs were able to detect lead in paint as well as or better than other methods. The product literature indicates that 1 to 2 j,g of leachable lead can be detected. 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

The primary leachable hazardous constituents of EAF emission control dust/sludge are lead, cadmium, and hexavalent chromium. Generally, 20 to 40 lb of EAF dust per ton of steel are generated, depending on the mill s specific operating practices, with an average of about 35 lb/t of steel melted.1 Table 2.11 shows the typical ranges of concentration of each of these elements in EAF dust. 

The ARS Technologies, Inc., Ferox process is an in situ remediation technology for the treatment of chlorinated hydrocarbons, leachable heavy metals, and other contaminants. The process involves the subsurface injection and dispersion of reactive zero-valence iron powder into the saturated or unsaturated zones of a contaminated area. ARS Technologies claims that Ferox is applicable for treating the following chemicals trichloroethene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride, 1,1,2,2-tetrachloroethane, lindane, aromatic azo compounds, 1,2,3-trichloropropane, tetrachloroethene (PCE), nitro aromatic compounds, 1,2-dichloroethene (DCE), vinyl chloride, 4-chlorophenol, hexachloroethane, tribromomethane, ethylene dibromide (EDB), polychlorinated biphenyls (PCBs), Freon-113, unexploded ordinances (UXO), and soluble metals (copper, nickel, lead, cadmium, arsenic, and chromium). 

Tons of spent abrasives result each year from the removal of old paint from bridges. Because the spent abrasives contain metals from the paint, some spent abrasives may be considered hazardous by the Toxicity Characteristic (TC) criteria. Incorporation of the spent blasting abrasives in nonstructural concrete offers an opportunity to recycle the spent abrasives while immobilizing potentially leachable metals. Solvents that are less aggressive will mean that abrasives will be necessary in some applications. Study results indicated that considerable quantities of these spent abrasives can be solidified/stabilized while reducing the leachability of cadmium, chromium, and lead and producing compressive strengths over 6895 kN/m2 (1000 psi) (Brabrand and Loehr, 1993). 

Many different chemical treatment systems have been developed to reduce the leachability of lead and cadmium compounds in flue dust. These systems usually rely on stabilization/solidification, adsorption, chemical reduction, or pH control. Chemical reduction employing the use of metallic iron has been successful in reducing the leachability of lead to below EP-Toxicity levels. Adding a 5 percent by weight dose of iron filings to cupola furnace emissions control sludge, for instance, reduced lead leaching from 28.6 mg/1 to less than 0.1 mg/1 (Stephens 1984). 

The exposure of soil to phosphorus aerosols will upset the pH of the soil and create a more acidic layer of soil. This decrease in pH often can exceed the buffering capacity of the surface layer of the soil depending upon the amount of applied phosphorus. This process can be mitigated by a larger soil volume area so that phosphorus speciation on a field scale will be minimal. The interaction of metals with phosphorus condensates could lead to their leachability and possible trace metal migration from the soil (Van Vorris et al. 1987). 

The presence of lead and cadmium in the cement matrix with those concentrations did not lead to decreasing of samples strengths. Lead showed better improvement in stabilization and then cadmium. Lead dissolution at low pH values corresponded closely with the loss of aluminum, suggesting an ettringite or ferrite stabilization mechanism. The leachability of cadmium is continuous as the pH decreases from 9.5 to lower values during the batch leaching steps, and confirms a simple insoluble hydroxide stabilization mechanism and pH-controlled dissolution. 

Wang SY, Vipulanandan C (1996) Leachability of lead from solidified cement-fly ash binders. Cem Concr Res 26 895-905... 

The objective is to demonstrate that the sample filtration does not affect the analytical result due to adsorption and/or extraction of leachables. A word of caution here is that filter studies should be performed to ensure that no adsorption of the compound on the filter is observed. This is particularly the case with protein and peptide samples. Note that for proteins and peptides the impact of centrifugation (speed and time) must be investigated because this may lead to increased aggregate formation. Also, for protein and peptides the initial concentration of the sample could also have an impact on the concentration gradient of the sample in the centrifuge tube, and the concentration of the top, middle, and bottom portions should be assessed. 

In liquid contact media (e.g., foodstuffs, oils, solvents), the rate of loss of antioxidants from the polymer surface depends both on their diffusion coefficient and their partition coefficient between the liquid and the polymer. This is complicated by the varying ability of different solvents (liquid media) to swell polymers, giving rise to an increase in the diffusion coefficient of the antioxidant, which leads to higher loss rates. As in the case of volatilization, the rate of leachability of antioxidants from the surface of polymers into liquid contact media increases with temperature and surface area-to-volume ratio, e.g., in thin polymer samples. 

T.G. Townsend, S. Mussen, Y.-C. Jang, and I.-H Chung, Characterization of lead leachability from cathode ray tubes using the toxicity characteristic leaching procedure, Florida Center for Solid and Hazardous Waste Management, Report 99-5, Gainesville, FL, 1999. 

Ash Product Incineration of combustible materials produces a volume reduction, which can lead to higher concentrations of inorganic contaminants in the ash product and create leachability problems. Incineration of most contaminated soils produces only modest volume reductions, so inorganics are not significantly concentrated in the treated soil. 

Copper and Cr are prevalently held in the oxidizable (-68%) and residual (-24%) fractions, with other forms making up much less than 10%. Pb is primarily held in the residual mineral fraction (77%) with smaller amounts held in the oxidizable (18%) and reducible (3%) forms. Zn is uniformly distributed between easily extractable (23%), reducible (24%) and residual (49%) fractions, with very small percentage occurring in oxidizable forms (4%). Thus, only Zn appears to occur in the studied soils in consistent amounts as bioavailable and leachable forms. Copper and Cr, which are mainly associated with organic matter, for which both metals have high affinity are characterised by a lower mobility, unless the occurrence of oxidising conditions may induce their release in solution. Lead, and in lower proportion also Cu and Cr, extracted mainly by the fourth step, result relatively immobile. 

Volume reduction as described above usually leads to a product that still contains considerable quantities of water or that is quite easily leached or dissolved by water. The policy as to the degree of immobilization required for final disposal varies in different countries. As yet, there is no official regulation in the United States requiring that non-hi -level waste be inunobilized before disposal. It is, however, practiced in many places. In West Germany, by regulation, any non-high-level waste has to be immobilized before disposal in such a way that low leachability is warranted over a sufficient period of time. 

Loss of leachable and volatile products leading to material shrinkage. 

What are the reported bad effects of nitrification The more important are (1) the greatly increased leachability of nitrites and nitrates in comparison with ammonia (2) the instability and reactivity of nitrites which may lead to volatile losses of nitrogen (3) the increase in soil acidity as a result of nitrate formation, especially where the nitrates are lost by leaching. With increase in acidity there may be toxic effects on plants produced by nitrites and aluminum and also excessive loss of mineral elements. 

Other cardiovascular uses have included coatings on pacemakers and pacemaker lead-wires for purposes of insulation and for achieving biocompatibility. Medical grade silicone elastomer has been widely used as a material of construction in experimental artificial hearts and heart assist devices. Silicone tubing is often preferred for use in roller-type blood pumps during cardiopulmonary bypass. Medical grade silicone elastomer contains no leachable or organic plasticizers and thus contributes minimal contamination in blood contact applications. 

A further feature of PEG-based copolyesters is that since the copolymers comprised self-solvating molecules, their conversion to a hydrogel about a drug provides a uniform distribution of the therapeutic agent and thus a more predictable release profile. This is in contrast to conventional systems in which the presence of leachable solvents leads to complex physical events that can alter the kinetics of the system. ... 

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