Research On Solidification/Stabilization Of Uranium Contaminated Soil With Geopolymer

Uranium is a relatively active and chemically toxic natural radionuclide.Its enrichment or pollution in the environment poses a serious threat to human health and the ecosystem,and soil is an important medium for uranium.Therefore,it is necessary to study how to safely and efficiently dispose of this uranium-contaminated soil.This dissertation takes the uranium-contaminated soil around a uranium tailings pond in Hunan Province as the research object,respectively investigates the solidification/stabilization effects of coal gangue-based geopolymers and their composite materials on uranium-contaminated soil,and compares and studies the solidified uranium soil He united the mechanical properties,leaching resistance and uranium occurrence form of solidified uranium soil,combined with Visual MINTEQ simulation,microscopic morphology analysis,mineral phase analysis and molecular structure analysis methods,the mechanism of solidification and stabilization of Coal Gangue based geopolymer and hydroxylapatite uranium contaminated soil was discussed.Through single factor experiment and orthogonal experiment,the influence of the content of alkali activator,the modulus and liquid-solid ratio of alkali activator on the compressive strength and fixing effect of uranium soil solidified body and combined uranium soil solidified body is analyzed.Orthogonal experiments show that the addition of nanohydroxyapatite does not have much impact on the mechanical properties of uranium soil solidification.However,the static toxicity leaching experiment of combined uranium soil solidification body has achieved better results.The immobilization efficiency reached 81.73%,which was an increase of 6.10% compared with the solidified uranium soil.The dynamic leaching toxicity test results show that the overall leaching resistance of the combined uranium soil solidified body is better.According to the leaching kinetics,the leaching process of uranium in the solidified body is mainly controlled by the interface reaction.SEM-EDS,XRD,and FTIR combined with toxicity leaching test analysis showed that the solidified uranium soil mainly solidified/stabilized uranium through three-dimensional network structure adsorption,immobilization,and ion exchange.The combined uranium soil solidification body added with nano-hydroxyapatite also has complex precipitation and dissolution-chemical mineralization,thereby achieving more effective solidification/stabilization of uranium-contaminated soil.