Experimental Study On Preparation And Performance Of Fiber-reinforced Uranium Tailings Geopolymer Solidified Body

A large number of tailings containing uranium series and thorium series radionuclides will be produced in the process of uranium mining.under the influence of complex external conditions,the radioactive elements in uranium tailings are easy to spread and migrate to the surrounding environment.it is a serious threat to the ecological safety around the uranium tailings reservoir and the health of the residents.In this paper,11 kinds of uranium tailings samples were prepared by using water glass and sodium hydroxide as alkali activator,adding polyvinyl alcohol（PVA）fiber,basalt fiber,metakaolin and fly ash.The relationships between microscopic morphology,pore structure,macroscopic physical and mechanical properties and radon exhalation rate and U（Ⅵ）leaching rate of different solidified samples were studied.The main contents and conclusions of this paper are as follows:（1）The pore size distribution of the solidified body was measured by nitrogen adsorption method,and the compressive strength,tensile strength and volume resistivity of the solidified body were tested.The results show that the pore sizes of solidified samples are mainly distributed between 1～50nm,with the largest number of pores around25nm.The compressive strength and volume resistivity of cured samples increased at first and then decreased with the increase of fiber content,while the tensile strength increased gradually with the increase of fiber content.（2）The cumulative radon concentration of solidified samples was measured by closed cavity method,and the radon exhalation rate,radon diffusion length and radon diffusion coefficient were calculated.The results show that the radon exhalation rates of single-sided and double-sided solidified samples decreased at first and then increased with the increase of fiber content,and the radon exhalation rate ranges from0.0397 to 0.0853 Bq·m^-2s^-1,which was lower than the national standard.（3）The concentration of U（Ⅵ）in the leaching solution of solidified samples at different pH values and different soaking ages was measured by spectrophotometry.The results show that the U（Ⅵ）leaching concentration of solidified sample decreases gradually with the increase of pH value,and increases at first and then decreases with the increase of soaking days.U（Ⅵ）the leaching rate is in the shape of"L".When soaked for 42 days,it is between 2.82～4.53×10^-4cm/d,which is lower than the national standard.（4）There is a good positive correlation between the compressive strength and the volume resistivity of the solidified samples with different fiber content and ratio,while the compressive strength has a good negative correlation with radon diffusion coefficient and U（Ⅵ）cumulative leaching fraction.Based on the comprehensive analysis of the physical and mechanical properties,radon exhalation rate and U（Ⅵ）leaching rate of solidified samples,it is considered that basalt fiber is better than PVA fiber as a whole,and the solidification effect is the best when 0.6%basalt fiber is added.