Leaching tests

Most leach rate measurements of both matrix elements and radionuclides were performed at 90 °C using MCC-1 or PCT tests. According to these tests, leach rates range from 10 1 to 10g m 2 d (Lutze 1988). For example, the mass and elemental leach rates (in g-m 2-d ) for the PNL 76-68 glass containing 33 wt% waste oxides were determined at mass - 0.42, Ca - 0.068, Cs - 1.03, Mo - 1.40, Na - 1.32, Sr - 0.075, B - 1.12, and Si - 0.73. These values are typical for borosilicate waste glass as measured by the MCC-1 procedure (90 °C, 28 d). Leach rates of Fe-group elements and ACTs under the same test conditions are considerably lower (10-3 and 10 4g-m 2-d , respectively). 

As in all the waste forms discussed above, the TCLP results showed excellent retention of the hazardous contaminants in the matrix (Cd, Cr, Ag, Pb, and Zn) for both waste forms. The leaching levels for these contaminants were either below the detection limit or well below the UTS limits. While conducting this test for the sludge waste form, the investigators also tested leaching of Na, which is a bulk component, and Cs and Re, which are used as surrogates of radioactive Cs and Tc. 

Desai and Clarke (149) reported successful results using zinc-containing compounds. Sell et al. (ISO, 151) described surface treatment with chromium-copper-boron salts. Field weathering tests, leaching tests, and electron-probe microanalysis showed that this treatment was resistant to leaching and weathering. Water-soluble extractives in redwood and redcedar were fixed by treating the wood surface with dilute solutions of copper and chromium salts. This treatment permits direct application of latex paints to these woods (146). 

Iron and aluminum oxides present no special problem within the range of occurrence in commercial phosphate rocks these oxides usually are dissolved in nitric acid and reprecipitated during ammoniation as citrate-soluble phosphates, TVA tested leached-zone" Florida phosphate containing a high percentage of aluminum phosphate minerals in a special nitrophosphate process... 

European Standard EN 84, 1997. Wood preservatives Accelerated ageing tests of treated wood prior to biological testing Leaching procedure. 

However, rotary furnaces tend to produce more exhaust gas and fumes, require more skill fill manipulation, and are more labor intensive. Also, the slags produced in the rotary furnaces, soda or fayaUte [13918-37-1] slags, normally do not pass the toxic characteristic leach procedure (TCLP) test and pose a disposal problem. 

Increasingly, plastics are being used as parenteral packaging (qv) materials. Plastics such as poly(vinyl chloride), polyethylene, and polypropylene are employed. However, plastics may contain various additives that could leach into the product, such as plasticizers (qv) and antioxidants. PermeabiUty of plastics to oxygen, carbon dioxide, and water vapor must be tested in the selection of plastic containers. Furthermore, the plastic should withstand sterilization. Flaking of plastic particles should not occur and clarity necessary for inspection should be present. 

Rubber is a popular closure component, and additives such as vulcanizers, pigments (qv), or antioxidants may leach into the product. In cases where mbber closures are penetrated by needles in dosing, bits of the closure (coring) could enter the product. Thus, such closure components must be sufficiendy tested before use. 

A pressure leaching system to handle copper sulfide called the Sherritt-Cominco (SC) copper process was developed by these two Canadian firms. Pilot-plant testing was completed in 1976 (29), but commercial appHcation of this technology has not been achieved. 

Australian Vanadium—Uranium Ore. A calcareous camotite ore at YeeHrrie, AustraHa, is iU-suited for salt roasting and acid leaching. Dissolution of vanadium and uranium by leaching in sodium carbonate solution at elevated temperature and pressure has been tested on a pilot-plant scale... 

J. L. Anastasi and co-workers, "Molten-Caustic-Leaching (Gravimelt Process) Integrated Test Circuit Operation Results," Report to the Gravimelt Process Advisory Board, Summer 1989. 

Usually, however, it is not feasible to establi a stage or overall efficiency or a leaching rate index (e.g., overall coefficient) without testing small-scale models of likely apparatus. In fact, the results of such tests may have to be scaled up empirically, without explicit evaluation of rate or quasi-equilibrium indices. 

In the present work it has been shown that on-line coupling of flowthrough fractionation in RCC with ICP-EAS detection enables not only the fast and efficient fractionation of trace elements (TE) in environmental solids to be achieved but allows real-time studies on the leaching process be made. A novel five-step sequential extraction scheme was tested in on-line mode. The optimal conditions for the fractionation were chosen. Investigating elution curves provides important information on the efficiency of the reagents used, the leaching time needed for the separation of each fraction, and the potential mobility of HM forms. 

Physical and chemical tests of the final product may need to address two concerns (1) whether the solidified waste exhibits any RCRA defined toxicity characteristics or could be delisted and (2) the potential long term fate of treated materials in the disposal environment. Three tests are available which address the first concern. These are the Extraction Procedure (EP Tox) (40 CFR 261, Appendix II, 1980) and the Toxicity Characteristic Leaching Procedure (TCLP) (40 CFR 261, Appendix II, 1986), and the Multiple Extraction Procedure Test (40 CFR 261, Appendix II, January 1989). It is important to note that these tests are not indicators of expected leachate quality but of potentials. A solidified product which cannot pass the appropriate test (EP Tox or TCLP) would be subject to classification as a hazardous waste. 

Leach or extraction testing undertaken on anhydrous salts embedded in bitumen as a matrix indicates that rehydration of the embedded compound can occur. When the sample is soaked in water, the asphalt or bitumen can swell and split apart, thereby greatly increasing the surface area and rate of waste loss. 

Diatomaceous earth A fine, siliceous (made of silica) "earth" composed mainly of the skeletal remains of diatoms (single cell microscopic algae with rigid internal structure consisting mainly of silica). Tests prove that DE leaches unacceptable amounts of silicate into the water for fish health. If used as a filter substance, a silicone removing resin should be employed afterwards. 

Although the reactants have only limited solubility in the catalyst phase, the rates of hydrogenation in [BMIM][SbFg] are almost five times faster than for the comparable reaction in acetone. All ionic catalyst solutions tested could be reused repeatedly. The loss of rhodium through leaching into the organic phase lay below the detection limit of 0.02 %. These results are of general importance for the field of... 

Good rhodium retention results were obtained after several recycles. However, optimized ligand/metal ratios and leaching and decomposition rates, which can result in the formation of inactive catalyst, are not known for these ligands and require testing in continuous mode. As a reference, in the Ruhrchemie-Rhone-Poulenc process, the losses of rhodium are <10 g Rh per kg n-butyraldehyde. 

Wooden racks used in sea-water tests are likely to be subject to severe damage by marine borers. The wood used, therefore, must be treated with an effective preservative, for example creosote applied under pressure, if the test is to extend for several years. Organic copper compound preservatives may suffice for shorter tests, for example 2 or 3 years. Since the leaching of such preservatives may have some effects on corrosion, metal racks fitted with porcelain or plastics insulators have an advantage over wooden racks. 

During the first trials with synthetic separators around 1940 it had already been observed that some of the desired battery characteristics were affected detrimentally. The cold crank performance decreased and there was a tendency towards increased sulfation and thus shorter battery life. In extended test series, these effects could be traced back to the complete lack of wooden lignin, which had leached from the wooden veneer and interacted with the crystallization process at the negative electrode. By a dedicated addition of lignin sulfonates — so called organic expanders -— to the negative mass, not only were these disadvantages removed, but an improvement in performance was even achieved. 

Miscellaneous Identified Inhibitors. 3-Acetyl-6-methoxy-benzaldehyde is present in the leaves of the desert shrub Encelia farinosa. It is apparently leached from the leaves and washed into the soil by rain. Concentrations of approximately 0.5 mg. per gram of dried leaf material have been measured. In sand culture studies, growth of tomato seedlings was inhibited by 50 p.p.m. while 115 p.p.m. reduced growth by 50% (53). A concentration of 250 p.p.m. killed the test plants within one day. The structure was confirmed by synthesis, and the synthetic material was shown to be as active as the natural product (54). Derivatives were also prepared in which a cyano, nitro, or amino group was substituted for the aldehyde moiety. The amino derivative was reported to be the most highly toxic. 

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