Water-soluble organophosphorus reagents for mineralization of heavy metals

摘要

In this report, we have described the principal stages of a two-step process for211u001ethe in-situ stabilization of actinide ions in the environment. The combination of 211u001ecation exchange and mineralization appears likely to provide a long-term solution 211u001eto environments contaminated with heavy metals. Relying on a naturally occurring 211u001esequestering agent has obvious potential advantages from a regulatory standpoint. 211u001eThere are additional aspects of this technology requiring further elucidation, 211u001eincluding the demonstration of the effect of these treatment protocols on the 211u001egeohydrology of soil columns, further examination of the influence of humates and 211u001eother colloidal species on cation uptake, and microbiological studies of phytate 211u001ehydrolysis. We have learned during the course of this investigation that phytic 211u001eacid is potentially available in large quantities. In the US alone, phytic acid 211u001eis produced at an annual rate of several hundred thousand metric tons as a 211u001ebyproduct of fermentation processes (11). This material presently is not isolated 211u001efor use. Instead, most of the insoluble phyate (as phytin) is being recycled 211u001ealong with the other solid fermentation residues for animal feed. This material 211u001eis in fact considered undesirable in animal feed. The details of possible 211u001eseparation processes for phytate from these residues would have to be worked out 211u001ebefore this untapped resource would be available for application to heavy metal 211u001esequestration. The results described emphasize the behavior of actinide and 211u001etrivalent lanthanide metal ions, as these species are of primary interest to the 211u001eDepartment of Energy for the cleanup of the former nuclear weapons production 211u001ecomplex. While the specific demonstration includes this limited selection of 211u001emetal ions, the technique should be readily applicable to any class of metal ions 211u001ethat form insoluble phosphate compounds under appropriate conditions. Further, 211u001ethough this demonstration has been conducted in the pH 5-8 range, it is 211u001econceivable that the basic concepts would apply equally well for the 211u001estabilization of waste metals in mill tailings piles, wherein conditions can be 211u001emoderately acidic.