PubMed · 6209119
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E Caplun, D Petit, E Picciotto. 1984. Lead in petrol.. https://doi.org/10.1016/0160-9327(84)90007-3
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Cutting oils are emulsionable fluids widely used in metalworking processes. Their composition is normally oil, water, and additives (fatty acids, surfactants, biocides, etc.) generating a toxic waste after a long use. Generally, it is a waste too dilute to be incinerated and it is difficult to treat biologically. Other conventional treatment methods currently used are not satisfactory from the environmental point of view. Wet air oxidation (WAO) and supercritical water oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but hardly tested for oily wastes. In the case of refractory wastes, WAO process is not efficient enough due to the moderate temperatures used. SCWO is a more powerful process since operating temperatures are usually around 600 degrees C, but the use of severe conditions leads to major disadvantages in the commercialization of the technology. In order to enhance WAO and SCWO efficiency at mild conditions, the use of free radical promoters has been studied in this work. Both normal and promoted hydrothermal oxidation have been tested to treat cutting oil wastes in a continuous flow system operating at 300-500 degrees C. Hydrogen peroxide has been used both as a source of oxygen and as a source of free radicals by introducing it into the reactor with or without previous thermal decomposition, respectively. Organic material is easily oxidized in both cases, obtaining more than 90% TOC reduction in less than 10s at 500 degrees C. At lower temperatures, the use of promoters clearly enhances the oxidation process. Activation energies have been estimated for normal and promoted oxidation processes.
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Heating of fine sand-sized common mineral powders (quartz, feldspar, or calcite) or a soil (from the Department of Energy's Hanford site) up to 1000 degrees C, in contact with sorbed radioisotopes (85Sr, 57Co, 134Cs, or U), markedly increased each isotope's immobilization. A sequential extraction procedure was applied after heating the materials to assess the changes in each isotope's functional form among water-soluble, cation-exchangeable, acid-soluble, and residual phases. The overall immobilization effects were consistent with rapid high temperature ionic diffusion from the initially contaminated surfaces into the mineral matrices; subsequent diffusion out of mineral particles at ambient temperature, as measured by the sequential extraction behavior, would be such a slow process that the radionuclides may be considered sequestered from further potential environmental mobilization. In the Hanford soil, the effect was found to follow an Arrhenius-type relationship with treatment temperature up to 1000 degrees C for 57Co, 85Sr, and U, and immobilization was independent of previous thermal treatment of the materials. Although 134Cs exhibited its largest immobilization in the Hanford soil after heating to 1000 degrees C, the large immobilization of 134Cs at all temperature and even in unheated Hanford soil made it difficult to observe a strong temperature dependence. A general and promising technique for environmental remediation of contaminated soil by high-temperature heating without melting can be extrapolated directly from the empirical leaching information.