Preparation Of Zeolite-based Geopolymer And Its Performance On Curing Strontium

The vigorous development of Nuclear power has produced a significant amount of low and medium radioactive waste liquid.Disposing the nuclear waste safely and effectively has become the key factor restricting the development of nuclear energy.This paper put forward a new technology that realize the adsorption-solidified integration of low and intermediate level radioactive liquid waste.The 4A zeolite loaded strontium after adsorption was prepared into geopolymer in suit to realize the curing of strontium, shorten the process flow and processing time, reduce the solidified body than their capacities.Contrast experiment was used to study the curing performanceof traditional cement solidified body and geopolymer solidified under new technology.For the hysteresis effect brought by the addition of Sr2+, preliminary experiments were carried out by the measurement of resistivity and final setting time.Research shows that optimal parameters for the preparation the zeolite-based geopolymer were:the modulus of sodium silicate between 0.8 and 01.5, the activator ratio 2:3 and5:6,while the metakaolin admixture 20%～80%. The adsorptio mechanism of 4A zeolite for Sr2+ was ion exchange.Among the zeolite-based geopolymer,metakaolin-based geopolymer,zeolite-based cement,and cement, the overall performance of zeolite-basedgeopolymer was best in curing Sr2+ as following reasons:It has high compressive strength without increasing its volume.It has almost the lowest leaching rate and cumulative leaching fraction in four different leaching agent,which are deionized water, sulfuric acid,Acetic acid sodium acetate buffer,Magnesium sulfate.Its high temperature resistant performance is best,and lost minimumstrength after freezing-thawing circulation. The XRD,IR and XPS analysis showed that the Sr2+ took partly place of Na+ of the raw materials,and Sr was also physically sealed by geopolymer gel and that simulated nuclide strontium may be cured through going into the three-dimensional network structure as chemical bonds.In the reaction of geopolymerization,the addition of strontium caused the hysteresis effect and we can predict final setting time by measuring resistivity.Higher content of strontium (3.58%) had shorter final setting time than lower content(1%),because Sr2+ replaced part of the Na+ to charge balance system,while Sr2+ have stronger electrostatic attraction and charge neutralization function make the silicon aluminate polymer gel formation faster.When there is a same content of Sr2+ in the reaction, the experiment using "integration of adsorption-solidified" technology had a longer final setting time because the zeolite adsorption had Sr2+ fixed in its crystal phase structure, so its ion mobility, electrostatic attraction and charge neutralization ability were weaker.