Conference Proceedings Paper
STRONTIUM SORPTION OF FLUORINATED CLINOPTILOLITE, CHABAZITE, AND MORDENITE
3rd Canadian Nuclear Waste Management Decommissioning and Environmental Restoration - 2016 Sept. 11-14
S.G. Xu (Canadian Nuclear Laboratories)
Clinoptilolite, chabazite, and mordenite are zeolites commonly used for the removal of radioactive strontium from contaminated water in the environment. However, their strontium removal performances are relatively poor for the treatment of acidic processing wastes, e.g., those generated from the small-scale processing of irradiated fuels and isotopes. Zeolite fluorination, which improves the acidity of the functional groups, has potential for improving strontium sorption onto zeolites under acidic conditions. Fluorinated low-cost zeolites can be more economical for the treatment of small volumes of acidic waste, as compared to multiple- step processes involving pH adjustment, precipitation, and ion exchange on organic resins.
This study prepared fluorinated clinoptilolite, chabazite, and mordenite at fluorine loadings of 4 to 25 mg-F/g-zeolite. The fluorine loading depended on the quantities of Ca2+, Mg2+, and H+ in the zeolites, as fluoride replaced the OH- groups associated with these ions. The fluorinated materials were tested for strontium sorption at pHs of 6.7 and 1.5, the known pHs of contaminated environmental water and hot-cell wastes, respectively. After fluorination, the H- form mordenite and chabazite, which were known to have no strontium sorption in their unmodified form, showed significant strontium sorption capacities at near-neutral pH, but lost the strontium sorption capacities at acidic pH values, relative to their capacity at near-neutral pH. Improvements in strontium removal at acidic but not at neutral pH were observed for the fluorinated Na-form clinoptilolite and chabazite. The improved strontium sorption onto the fluorinated Na-form clinoptilolite and chabazite was caused by the exchange between strontium and aluminium after the fluorination.
Individual Conference-Paper Copies (Electronic Where Available):
- For CNS members, the first 5 copies per calendar year are free, and additional copies are $10 each.
- For non-members, the price is $25 for the first Conference-paper copy in a request, and $10 each for additional copies of papers in the same conference and in the same request.
- Contact the CNS office to order reprints.