Environmental Engineering Reference
In-Depth Information
(250 cm
3
/g). Vermiculite selectivity for
85
Sr was relatively low in both sodium and
calcium nitrate solutions.
The calcined waste at the Idaho National Engineering and Environmental Lab-
oratory (INEEL) can be reacted to make hydroceramic, an insoluble ceramic of
sodium alumino silicates.
58
Vermiculite was added to enhance the cesium leach
resistance of this waste form. Illite was destroyed in the hydrothermal reaction to
produce hydroceramic and did not enhance the cesium leach resistance.
Heat-treated vermiculite had aqueous distribution ratios of 420, 52, and 11 for
137
Cs,
90
Sr/
90
Y, and
239
Pu, respectively.
59
The ratio ranges for several natural and
synthetic materials were < 5 - 1800, < 5 - 1800, < 5 - 680, respectively, with the
following ranking for
137
Cs ratios:
Ferricyanide NZA > ferricyanide FS-2 > synthetic zeolite > modified morden-
ite > mordenite ≈ clinoptilolite > modified glauconite > glauconite > caoline
> vermiculite > cambria clay > cation exchange resin > modified charcoal >
charcoal > anion exhange resin
Although the synthetic materials exhibited high sorption efficiency, the natural
materials were favored because of their longer working cycle and lower costs.
Combining copper ferricyanide (CFC) with porous media (silica gel, bentonite,
vermiculite, and zeolite) removed cesium from aqueous solutions.
60
The treated
vermiculite and zeolite removed cesium better than treated silica gel or bentonite.
A compound sorbent of CFC and vermiculite was used to increase the cesium
leachability index of solidified borate wastes from around 8 to around 10, with CFC
receiving the most credit for the enhanced leach resistance.
8.3
NON-METALS AND ORGANICS
Simple complexes such as cyanides can often be destroyed by alkaline chlorination,
for example, by using sodium or calcium hypochlorite. Destruction may be pH
sensitive.
The most common application has been for non-metals such as cyanide, hydro-
gen sulfide, and phenol.
18
If organics such as oil and grease are present they will
also consume the oxidizing agent. This may require large quantities of oxidizing
agent, making treatment costly or practically prohibitive.
8.4
ORGANIC STABILIZATION
For waste streams containing low levels of hazardous organic contaminants, useful
sorbents include activated carbon, organoclays (natural clays treated with quaternary
ammonium compounds), rubber particulates, rice hull ash, and other natural miner-
als. In such instances, the purpose of treatment is to sorb and reduce the leaching
of organic contaminants to below regulatory levels. Activated carbon, organoclays,
and rubber particulate are useful with specific contaminants in specific test methods,
but none works best for all. Carbon is effective overall for reduction in TCLP
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