Leaching test developments

During development, evaluation of the consolidated materials was based primarily on two criteria, leachability and the concentration factor, i.e., the concentration of waste oxides on a volume basis. The concentration factor is directly affected by the residual porosity in a consolidated waste as well as by the dilution caused by the addition of consolidation aids. This factor can be as high as 1.2 g/cm3 for a fully dense ( 5 g/cm ) titanate waste prepared from the projected Barnwell plant solution composition. The factor is slightly lower for a titanate waste containing silicon and zeolite additions, which has a typical density of U.2 g/cm3. The leachability was determined by an "instantaneous leach test developed for fast, comparative evaluations of materials, the details of which are described elsewhere (l6). 

Release rate data from actual radioactive waste forms is needed to evaluate the safety of emplacing nuclear wastes in geologic media. However, in addition to waste form development studies, such as the leach test just described, a comprehensive program was started to obtain release data from candidate waste forms for geologic disposal. 

WASTOXHAS was developed for assessing leaching hazardous impact of wastes in laboratory and field situations. It is a part of a tiered approach (Fig. 1). It assumes that classical batch leaching tests (see for example Sahuquillo et al., 2003), followed by application of relevant bioassays, have been initially undertaken for i) deciding to continue ecotoxic hazard assessment and ii) selecting adequate and sensitive bioassays. It can be eventually followed by a more complex and elaborate hazard assessment scheme based on microcosms or mesocosms. ... 

Briefly recalled, the WASTOXHAS approach consists in characterizing the ecotoxicological hazard potential of contaminant fluxes from waste leachate obtained under defined conditions with two different dynamic leaching procedures laboratory simulated leaching tests and field leaching tests. The approach developed below considered a specific scenario that simulates a waste deposit receiving rain or run-off water (Perrodin et al., 2002). 

A plethora of leaching tests has been developed, many of which were developed or are used based on a poor understanding of the controlling factors and leaching processes. The tests have been developed for many different purposes and most have been developed in isolation from each other. In effect, the tests... 

Verification tests generally comprise tests other than leaching tests. They usually comprise checks on pH, appearance, odour and occasionally analysis of the total concentration of contaminants in a material. They may comprise shortened compliance type tests. There are no standard verification type tests that are used widely but CEN is developing such tests. 

ANS 16.1 Tank leach test NEN 7345 Swedish MULP Compliance and basic characterisation tank tests are being developed by CEN TC/292 ... 

Wallis, S.M., Scott, P.E. Waring, S. (1992) Review of leaching test protocols with a view to developing an accelerated anaerobic leaching test. AEA-EE-0392. Environment Safety Centre. 

Development and Harmonization of Leaching Test Procedures From a practical point of view, leaching test procedures can be classified into static, dynamic and diffusion tests, and there are special concepts related to the long-term prognosis of metal release from waste materials ... 

Actually basic characterization tests are developed as standards combining percolation test and pH static leach test. 

Ham R, Anderson MA, Stegmann R, Stanforth R (1979) Background study on the development of a standard leaching test (EPA-600/2-79-109). Environmental Protection Agency, Washington, DC,p 342... 

Van der Sloot HA (1996) Developments in evaluating environmental impact from utilization of bulk inert wastes using laboratory leaching tests and field verification. Waste... 

A fundamental understanding of factors that govern the leaching of inorganic and organic contaminants and standard leaching tests has been developed for a... 

The standard diffusion protocol that is imposed by Vlarea is the Dutch standard NEN 7345. This test, however, takes 64 days. This is too long to allow a fast evaluation of candidate secondary building materials. Therefore, a two-step leaching test is under development (prEN 12457-3). This test takes only 24 h. It is the latter that has been used to evaluate Graveliet and its use as a shaped material. 

F. Castro and G. Pereira Characterization of the Nickel Laterite Sample and Guidelines for Column Leach Tests Project AMIRA P986, (Vale Mineral Development Center, Brazil, 2009). 

R. K. Ham, M. A. Anderson, R. Stanforth, and R. Stegmann, The development of a leaching test for industrial wastes, Presented at the Fourth Annual Research Symposium on Land Disposal of Hazardous Waste, San Antonio, Texas, March 6-8, 1978. 

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