极低放废物填埋场土壤对U、Sr的吸附及影响

Adsorption and Effect of Very Low-Level Radioactive Waste Site Soil on U and Sr

  • 摘要: 为了解U、Sr在极低放废物预选场址土壤中的吸附行为,分别以238U和90Sr溶液为示踪剂,用静态吸附法测定吸附分配系数,并研究pH、共存离子、胶体等条件的影响。研究结果表明:场址土壤对U、Sr的最大分配系数分别为11 300和723 mL/g;U、Sr的吸附均符合Fruendlich等温吸附方程;当pH为4~8时,铀的吸附分配比最大,而锶的分配系数最小;Ca2+和Mg2+的引入均能降低土壤对U、Sr的吸附,且对Sr的影响大于对铀的影响;在CO2-3和C2O2-4浓度很低时,能显著降低U的吸附分配系数;而CO2-3的存在能够增大其对Sr的吸附;Fe(OH)3胶体的存在使U、Sr的吸附分配系数显著降低;腐殖酸(HA)的存在使土壤对U的吸附减弱,但能够增大Sr在土壤中的吸附。

     

    Abstract: The adsorption behaviors of uranium and strontium were investigated on soil of very low-level radioactive waste (VLLW) in a preelection site by the static experimental method. The effects of the various experimental conditions such as pH, coexist iron and colloid on the adsorption were investigated with the 238U and 90Sr as indicator respectively. The maximum adsorption distribution coefficient (Kd) of U and Sr on the site’s soil are 11 300 and 723 mL/g, respectively. The concentration relationship in aqueous solutions and the adsorption capacities of U and Sr can be described by the Freundlich adsorption equation. The Kd of U is maximum when the pH is 4-8, however, the Kd of Sr is minimal. It is also noted that the Kd of U and Sr drops obviously when the solution contains Ca2+ or Mg2+, even the influence on Sr is more than U. The Kd of U reduces remarkably when adding in CO2-3 or C2O2-4, but the Kd of Sr increases. The ferric hydroxide colloid would make the Kd of U and Sr drop. The Kd of U decreases while the Kd of Sr increases when the humic acid exists in solution.

     

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